diff mbox series

[v10,1/2] scsi: ufs: Enable power management for wlun

Message ID 0576d6eae15486740c25767e2d8805f7e94eb79d.1614725302.git.asutoshd@codeaurora.org (mailing list archive)
State New
Headers show
Series Enable power management for ufs wlun | expand

Commit Message

Asutosh Das March 2, 2021, 10:52 p.m. UTC
During runtime-suspend of ufs host, the scsi devices are
already suspended and so are the queues associated with them.
But the ufs host sends SSU to wlun during its runtime-suspend.
During the process blk_queue_enter checks if the queue is not in
suspended state. If so, it waits for the queue to resume, and never
comes out of it.
The commit
(d55d15a33: scsi: block: Do not accept any requests while suspended)
adds the check if the queue is in suspended state in blk_queue_enter().

Call trace:
 __switch_to+0x174/0x2c4
 __schedule+0x478/0x764
 schedule+0x9c/0xe0
 blk_queue_enter+0x158/0x228
 blk_mq_alloc_request+0x40/0xa4
 blk_get_request+0x2c/0x70
 __scsi_execute+0x60/0x1c4
 ufshcd_set_dev_pwr_mode+0x124/0x1e4
 ufshcd_suspend+0x208/0x83c
 ufshcd_runtime_suspend+0x40/0x154
 ufshcd_pltfrm_runtime_suspend+0x14/0x20
 pm_generic_runtime_suspend+0x28/0x3c
 __rpm_callback+0x80/0x2a4
 rpm_suspend+0x308/0x614
 rpm_idle+0x158/0x228
 pm_runtime_work+0x84/0xac
 process_one_work+0x1f0/0x470
 worker_thread+0x26c/0x4c8
 kthread+0x13c/0x320
 ret_from_fork+0x10/0x18

Fix this by registering ufs device wlun as a scsi driver and
registering it for block runtime-pm. Also make this as a
supplier for all other luns. That way, this device wlun
suspends after all the consumers and resumes after
hba resumes.

Co-developed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
---
 drivers/scsi/ufs/cdns-pltfrm.c     |   2 +
 drivers/scsi/ufs/tc-dwc-g210-pci.c |   2 +
 drivers/scsi/ufs/ufs-exynos.c      |   2 +
 drivers/scsi/ufs/ufs-hisi.c        |   2 +
 drivers/scsi/ufs/ufs-mediatek.c    |   2 +
 drivers/scsi/ufs/ufs-qcom.c        |   2 +
 drivers/scsi/ufs/ufs_bsg.c         |   6 +-
 drivers/scsi/ufs/ufshcd-pci.c      |  32 +-
 drivers/scsi/ufs/ufshcd.c          | 583 +++++++++++++++++++++++++++----------
 drivers/scsi/ufs/ufshcd.h          |   7 +
 include/trace/events/ufs.h         |  20 ++
 11 files changed, 478 insertions(+), 182 deletions(-)

Comments

Adrian Hunter March 4, 2021, 3:35 p.m. UTC | #1
On 3/03/21 12:52 am, Asutosh Das wrote:
> During runtime-suspend of ufs host, the scsi devices are
> already suspended and so are the queues associated with them.
> But the ufs host sends SSU to wlun during its runtime-suspend.
> During the process blk_queue_enter checks if the queue is not in
> suspended state. If so, it waits for the queue to resume, and never
> comes out of it.
> The commit
> (d55d15a33: scsi: block: Do not accept any requests while suspended)
> adds the check if the queue is in suspended state in blk_queue_enter().
> 
> Call trace:
>  __switch_to+0x174/0x2c4
>  __schedule+0x478/0x764
>  schedule+0x9c/0xe0
>  blk_queue_enter+0x158/0x228
>  blk_mq_alloc_request+0x40/0xa4
>  blk_get_request+0x2c/0x70
>  __scsi_execute+0x60/0x1c4
>  ufshcd_set_dev_pwr_mode+0x124/0x1e4
>  ufshcd_suspend+0x208/0x83c
>  ufshcd_runtime_suspend+0x40/0x154
>  ufshcd_pltfrm_runtime_suspend+0x14/0x20
>  pm_generic_runtime_suspend+0x28/0x3c
>  __rpm_callback+0x80/0x2a4
>  rpm_suspend+0x308/0x614
>  rpm_idle+0x158/0x228
>  pm_runtime_work+0x84/0xac
>  process_one_work+0x1f0/0x470
>  worker_thread+0x26c/0x4c8
>  kthread+0x13c/0x320
>  ret_from_fork+0x10/0x18
> 
> Fix this by registering ufs device wlun as a scsi driver and
> registering it for block runtime-pm. Also make this as a
> supplier for all other luns. That way, this device wlun
> suspends after all the consumers and resumes after
> hba resumes.
> 
> Co-developed-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>

It looks good, but still a few further comments below.

Also, do you think ufshcd_err_handling_prepare()/unprepare()
need changes?  And ufshcd_recover_pm_error()?

And maybe ufshcd_auto_hibern8_update() when it is called from ufs_sysfs.c?

> ---
>  drivers/scsi/ufs/cdns-pltfrm.c     |   2 +
>  drivers/scsi/ufs/tc-dwc-g210-pci.c |   2 +
>  drivers/scsi/ufs/ufs-exynos.c      |   2 +
>  drivers/scsi/ufs/ufs-hisi.c        |   2 +
>  drivers/scsi/ufs/ufs-mediatek.c    |   2 +
>  drivers/scsi/ufs/ufs-qcom.c        |   2 +
>  drivers/scsi/ufs/ufs_bsg.c         |   6 +-
>  drivers/scsi/ufs/ufshcd-pci.c      |  32 +-
>  drivers/scsi/ufs/ufshcd.c          | 583 +++++++++++++++++++++++++++----------
>  drivers/scsi/ufs/ufshcd.h          |   7 +
>  include/trace/events/ufs.h         |  20 ++
>  11 files changed, 478 insertions(+), 182 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/cdns-pltfrm.c b/drivers/scsi/ufs/cdns-pltfrm.c
> index 149391f..3e70c23 100644
> --- a/drivers/scsi/ufs/cdns-pltfrm.c
> +++ b/drivers/scsi/ufs/cdns-pltfrm.c
> @@ -319,6 +319,8 @@ static const struct dev_pm_ops cdns_ufs_dev_pm_ops = {
>  	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>  	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>  	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static struct platform_driver cdns_ufs_pltfrm_driver = {
> diff --git a/drivers/scsi/ufs/tc-dwc-g210-pci.c b/drivers/scsi/ufs/tc-dwc-g210-pci.c
> index 67a6a61..b01db12 100644
> --- a/drivers/scsi/ufs/tc-dwc-g210-pci.c
> +++ b/drivers/scsi/ufs/tc-dwc-g210-pci.c
> @@ -148,6 +148,8 @@ static const struct dev_pm_ops tc_dwc_g210_pci_pm_ops = {
>  	.runtime_suspend = tc_dwc_g210_pci_runtime_suspend,
>  	.runtime_resume  = tc_dwc_g210_pci_runtime_resume,
>  	.runtime_idle    = tc_dwc_g210_pci_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static const struct pci_device_id tc_dwc_g210_pci_tbl[] = {
> diff --git a/drivers/scsi/ufs/ufs-exynos.c b/drivers/scsi/ufs/ufs-exynos.c
> index 267943a1..45c0b02 100644
> --- a/drivers/scsi/ufs/ufs-exynos.c
> +++ b/drivers/scsi/ufs/ufs-exynos.c
> @@ -1268,6 +1268,8 @@ static const struct dev_pm_ops exynos_ufs_pm_ops = {
>  	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>  	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>  	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static struct platform_driver exynos_ufs_pltform = {
> diff --git a/drivers/scsi/ufs/ufs-hisi.c b/drivers/scsi/ufs/ufs-hisi.c
> index 0aa5813..d463b44 100644
> --- a/drivers/scsi/ufs/ufs-hisi.c
> +++ b/drivers/scsi/ufs/ufs-hisi.c
> @@ -574,6 +574,8 @@ static const struct dev_pm_ops ufs_hisi_pm_ops = {
>  	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>  	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>  	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static struct platform_driver ufs_hisi_pltform = {
> diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
> index c55202b..df1eabb 100644
> --- a/drivers/scsi/ufs/ufs-mediatek.c
> +++ b/drivers/scsi/ufs/ufs-mediatek.c
> @@ -1097,6 +1097,8 @@ static const struct dev_pm_ops ufs_mtk_pm_ops = {
>  	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>  	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>  	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static struct platform_driver ufs_mtk_pltform = {
> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> index f97d7b0..9aa098a 100644
> --- a/drivers/scsi/ufs/ufs-qcom.c
> +++ b/drivers/scsi/ufs/ufs-qcom.c
> @@ -1546,6 +1546,8 @@ static const struct dev_pm_ops ufs_qcom_pm_ops = {
>  	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>  	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>  	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
> +	.prepare	 = ufshcd_suspend_prepare,
> +	.complete	= ufshcd_resume_complete,
>  };
>  
>  static struct platform_driver ufs_qcom_pltform = {
> diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
> index 5b2bc1a..cbb5a90 100644
> --- a/drivers/scsi/ufs/ufs_bsg.c
> +++ b/drivers/scsi/ufs/ufs_bsg.c
> @@ -97,7 +97,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>  
>  	bsg_reply->reply_payload_rcv_len = 0;
>  
> -	pm_runtime_get_sync(hba->dev);
> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>  
>  	msgcode = bsg_request->msgcode;
>  	switch (msgcode) {
> @@ -106,7 +106,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>  		ret = ufs_bsg_alloc_desc_buffer(hba, job, &desc_buff,
>  						&desc_len, desc_op);
>  		if (ret) {
> -			pm_runtime_put_sync(hba->dev);
> +			scsi_autopm_put_device(hba->sdev_ufs_device);
>  			goto out;
>  		}
>  
> @@ -138,7 +138,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>  		break;
>  	}
>  
> -	pm_runtime_put_sync(hba->dev);
> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>  
>  	if (!desc_buff)
>  		goto out;
> diff --git a/drivers/scsi/ufs/ufshcd-pci.c b/drivers/scsi/ufs/ufshcd-pci.c
> index fadd566..50f84bf 100644
> --- a/drivers/scsi/ufs/ufshcd-pci.c
> +++ b/drivers/scsi/ufs/ufshcd-pci.c
> @@ -247,29 +247,6 @@ static int ufshcd_pci_resume(struct device *dev)
>  	return ufshcd_system_resume(dev_get_drvdata(dev));
>  }
>  
> -/**
> - * ufshcd_pci_poweroff - suspend-to-disk poweroff function
> - * @dev: pointer to PCI device handle
> - *
> - * Returns 0 if successful
> - * Returns non-zero otherwise
> - */
> -static int ufshcd_pci_poweroff(struct device *dev)
> -{
> -	struct ufs_hba *hba = dev_get_drvdata(dev);
> -	int spm_lvl = hba->spm_lvl;
> -	int ret;
> -
> -	/*
> -	 * For poweroff we need to set the UFS device to PowerDown mode.
> -	 * Force spm_lvl to ensure that.
> -	 */
> -	hba->spm_lvl = 5;
> -	ret = ufshcd_system_suspend(hba);
> -	hba->spm_lvl = spm_lvl;
> -	return ret;
> -}
> -
>  #endif /* !CONFIG_PM_SLEEP */
>  
>  #ifdef CONFIG_PM
> @@ -366,12 +343,9 @@ ufshcd_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  
>  static const struct dev_pm_ops ufshcd_pci_pm_ops = {
>  #ifdef CONFIG_PM_SLEEP
> -	.suspend	= ufshcd_pci_suspend,
> -	.resume		= ufshcd_pci_resume,
> -	.freeze		= ufshcd_pci_suspend,
> -	.thaw		= ufshcd_pci_resume,
> -	.poweroff	= ufshcd_pci_poweroff,
> -	.restore	= ufshcd_pci_resume,
> +	.prepare	 = ufshcd_suspend_prepare,

Please remove extra space before =

> +	.complete	= ufshcd_resume_complete,
> +	SET_SYSTEM_SLEEP_PM_OPS(ufshcd_pci_suspend, ufshcd_pci_resume)

Would you mind putting SET_SYSTEM_SLEEP_PM_OPS above
#ifdef CONFIG_PM_SLEEP

>  #endif
>  	SET_RUNTIME_PM_OPS(ufshcd_pci_runtime_suspend,
>  			   ufshcd_pci_runtime_resume,
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 45624c7..32139dd 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -16,6 +16,7 @@
>  #include <linux/bitfield.h>
>  #include <linux/blk-pm.h>
>  #include <linux/blkdev.h>
> +#include <scsi/scsi_driver.h>
>  #include "ufshcd.h"
>  #include "ufs_quirks.h"
>  #include "unipro.h"
> @@ -78,6 +79,8 @@
>  /* Polling time to wait for fDeviceInit */
>  #define FDEVICEINIT_COMPL_TIMEOUT 1500 /* millisecs */
>  
> +#define wlun_dev_to_hba(dv) shost_priv(to_scsi_device(dv)->host)
> +
>  #define ufshcd_toggle_vreg(_dev, _vreg, _on)				\
>  	({                                                              \
>  		int _ret;                                               \
> @@ -1556,7 +1559,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>  	if (value == hba->clk_scaling.is_enabled)
>  		goto out;
>  
> -	pm_runtime_get_sync(hba->dev);
> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>  	ufshcd_hold(hba, false);
>  
>  	hba->clk_scaling.is_enabled = value;
> @@ -1572,7 +1575,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>  	}
>  
>  	ufshcd_release(hba);
> -	pm_runtime_put_sync(hba->dev);
> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>  out:
>  	up(&hba->host_sem);
>  	return err ? err : count;
> @@ -2572,6 +2575,17 @@ static inline u16 ufshcd_upiu_wlun_to_scsi_wlun(u8 upiu_wlun_id)
>  	return (upiu_wlun_id & ~UFS_UPIU_WLUN_ID) | SCSI_W_LUN_BASE;
>  }
>  
> +static inline bool is_rpmb_wlun(struct scsi_device *sdev)
> +{
> +	return (sdev->lun == ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_RPMB_WLUN));
> +}
> +
> +static inline bool is_device_wlun(struct scsi_device *sdev)
> +{
> +	return (sdev->lun ==
> +		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_UFS_DEVICE_WLUN));
> +}
> +
>  static void ufshcd_init_lrb(struct ufs_hba *hba, struct ufshcd_lrb *lrb, int i)
>  {
>  	struct utp_transfer_cmd_desc *cmd_descp = hba->ucdl_base_addr;
> @@ -4808,6 +4822,41 @@ static inline void ufshcd_get_lu_power_on_wp_status(struct ufs_hba *hba,
>  }
>  
>  /**
> + * ufshcd_setup_links - associate link b/w device wlun and other luns
> + * @sdev: pointer to SCSI device
> + * @hba: pointer to ufs hba
> + */
> +static void ufshcd_setup_links(struct ufs_hba *hba, struct scsi_device *sdev)
> +{
> +	struct device_link *link;
> +
> +	/*
> +	 * device wlun is the supplier & rest of the luns are consumers
> +	 * This ensures that device wlun suspends after all other luns.
> +	 */
> +	if (hba->sdev_ufs_device) {
> +		link = device_link_add(&sdev->sdev_gendev,
> +				       &hba->sdev_ufs_device->sdev_gendev,
> +				       DL_FLAG_PM_RUNTIME);
> +		if (!link) {
> +			dev_err(&sdev->sdev_gendev, "Failed establishing link - %s\n",
> +				dev_name(&hba->sdev_ufs_device->sdev_gendev));
> +			return;
> +		}
> +		hba->luns_avail--;
> +		/* Ignore REPORT_LUN wlun probing */
> +		if (hba->luns_avail != 1)
> +			return;
> +
> +		pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
> +		pm_runtime_mark_last_busy(&hba->sdev_ufs_device->sdev_gendev);

Now that we set zero autosuspend_delay, mark_last_busy has no effect.

> +	} else {
> +		/* device wlun is probed */
> +		hba->luns_avail--;
> +	}
> +}
> +
> +/**
>   * ufshcd_slave_alloc - handle initial SCSI device configurations
>   * @sdev: pointer to SCSI device
>   *
> @@ -4838,6 +4887,8 @@ static int ufshcd_slave_alloc(struct scsi_device *sdev)
>  
>  	ufshcd_get_lu_power_on_wp_status(hba, sdev);
>  
> +	ufshcd_setup_links(hba, sdev);
> +
>  	return 0;
>  }
>  
> @@ -4985,15 +5036,9 @@ ufshcd_transfer_rsp_status(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
>  			 * UFS device needs urgent BKOPs.
>  			 */
>  			if (!hba->pm_op_in_progress &&
> -			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr) &&
> -			    schedule_work(&hba->eeh_work)) {
> -				/*
> -				 * Prevent suspend once eeh_work is scheduled
> -				 * to avoid deadlock between ufshcd_suspend
> -				 * and exception event handler.
> -				 */
> -				pm_runtime_get_noresume(hba->dev);
> -			}
> +			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
> +				/* Flushed in suspend */
> +				schedule_work(&hba->eeh_work);
>  			break;
>  		case UPIU_TRANSACTION_REJECT_UPIU:
>  			/* TODO: handle Reject UPIU Response */
> @@ -5589,8 +5634,8 @@ static void ufshcd_rpm_dev_flush_recheck_work(struct work_struct *work)
>  	 * after a certain delay to recheck the threshold by next runtime
>  	 * suspend.
>  	 */
> -	pm_runtime_get_sync(hba->dev);
> -	pm_runtime_put_sync(hba->dev);
> +	scsi_autopm_get_device(hba->sdev_ufs_device);
> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>  }
>  
>  /**
> @@ -5607,7 +5652,6 @@ static void ufshcd_exception_event_handler(struct work_struct *work)
>  	u32 status = 0;
>  	hba = container_of(work, struct ufs_hba, eeh_work);
>  
> -	pm_runtime_get_sync(hba->dev);
>  	ufshcd_scsi_block_requests(hba);
>  	err = ufshcd_get_ee_status(hba, &status);
>  	if (err) {
> @@ -5623,14 +5667,6 @@ static void ufshcd_exception_event_handler(struct work_struct *work)
>  
>  out:
>  	ufshcd_scsi_unblock_requests(hba);
> -	/*
> -	 * pm_runtime_get_noresume is called while scheduling
> -	 * eeh_work to avoid suspend racing with exception work.
> -	 * Hence decrement usage counter using pm_runtime_put_noidle
> -	 * to allow suspend on completion of exception event handler.
> -	 */
> -	pm_runtime_put_noidle(hba->dev);
> -	pm_runtime_put(hba->dev);
>  	return;
>  }
>  
> @@ -7207,11 +7243,12 @@ static void ufshcd_set_active_icc_lvl(struct ufs_hba *hba)
>  
>  static inline void ufshcd_blk_pm_runtime_init(struct scsi_device *sdev)
>  {
> +	int dly = is_device_wlun(sdev) ? 0:RPM_AUTOSUSPEND_DELAY_MS;
> +
>  	scsi_autopm_get_device(sdev);
>  	blk_pm_runtime_init(sdev->request_queue, &sdev->sdev_gendev);
>  	if (sdev->rpm_autosuspend)
> -		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev,
> -						 RPM_AUTOSUSPEND_DELAY_MS);
> +		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev, dly);
>  	scsi_autopm_put_device(sdev);
>  }
>  
> @@ -7254,6 +7291,15 @@ static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
>  		goto out;
>  	}
>  	ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device);
> +	/*
> +	 * A pm_runtime_put_sync is invoked when this device enables blk_pm_runtime
> +	 * & would suspend the device-wlun upon timer expiry.
> +	 * But suspending device wlun _may_ put the ufs device in the pre-defined
> +	 * low power mode (SSU <rpm_lvl>). Probing of other luns may fail then.
> +	 * Don't allow this suspend until all the luns have been probed.
> +	 * See pm_runtime_mark_last_busy in ufshcd_setup_links.
> +	 */
> +	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
>  	scsi_device_put(hba->sdev_ufs_device);
>  
>  	hba->sdev_rpmb = __scsi_add_device(hba->host, 0, 0,
> @@ -7417,6 +7463,9 @@ static int ufs_get_device_desc(struct ufs_hba *hba)
>  		goto out;
>  	}
>  
> +	hba->luns_avail = desc_buf[DEVICE_DESC_PARAM_NUM_LU] +
> +		desc_buf[DEVICE_DESC_PARAM_NUM_WLU];
> +
>  	ufs_fixup_device_setup(hba);
>  
>  	ufshcd_wb_probe(hba, desc_buf);
> @@ -7892,6 +7941,7 @@ static int ufshcd_probe_hba(struct ufs_hba *hba, bool async)
>  	ufshcd_set_ufs_dev_active(hba);
>  	ufshcd_force_reset_auto_bkops(hba);
>  	hba->wlun_dev_clr_ua = true;
> +	hba->wlun_rpmb_clr_ua = true;
>  
>  	/* Gear up to HS gear if supported */
>  	if (hba->max_pwr_info.is_valid) {
> @@ -7964,6 +8014,7 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
>  		pm_runtime_put_sync(hba->dev);
>  		ufshcd_hba_exit(hba);
>  	}
> +	hba->init_done = true;
>  }
>  
>  static const struct attribute_group *ufshcd_driver_groups[] = {
> @@ -8475,7 +8526,8 @@ static int ufshcd_set_dev_pwr_mode(struct ufs_hba *hba,
>  	 * handling context.
>  	 */
>  	hba->host->eh_noresume = 1;
> -	ufshcd_clear_ua_wluns(hba);
> +	if (hba->wlun_dev_clr_ua)
> +		ufshcd_clear_ua_wlun(hba, UFS_UPIU_UFS_DEVICE_WLUN);
>  
>  	cmd[4] = pwr_mode << 4;
>  
> @@ -8650,23 +8702,7 @@ static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba)
>  		ufshcd_setup_hba_vreg(hba, true);
>  }
>  
> -/**
> - * ufshcd_suspend - helper function for suspend operations
> - * @hba: per adapter instance
> - * @pm_op: desired low power operation type
> - *
> - * This function will try to put the UFS device and link into low power
> - * mode based on the "rpm_lvl" (Runtime PM level) or "spm_lvl"
> - * (System PM level).
> - *
> - * If this function is called during shutdown, it will make sure that
> - * both UFS device and UFS link is powered off.
> - *
> - * NOTE: UFS device & link must be active before we enter in this function.
> - *
> - * Returns 0 for success and non-zero for failure
> - */
> -static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
> +static int __ufshcd_wl_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  {
>  	int ret = 0;
>  	int check_for_bkops;
> @@ -8674,7 +8710,13 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	enum ufs_dev_pwr_mode req_dev_pwr_mode;
>  	enum uic_link_state req_link_state;
>  
> -	hba->pm_op_in_progress = 1;
> +	/*
> +	 * Is invoked when the device wlun is added to sysfs
> +	 * But by then hba->sdev_ufs_device may not be initialized.
> +	 */
> +	if (!hba->init_done)

There is a pm_runtime_get_noresume() when sdev_ufs_device is created, and the
corresponding pm_runtime_put_noidle() after the last of the device links is
created, so it is not obvious what initialization may not have been done.
Can you explain a bit more?

> +		return 0;
> +	hba->pm_op_in_progress = true;
>  	if (!ufshcd_is_shutdown_pm(pm_op)) {
>  		pm_lvl = ufshcd_is_runtime_pm(pm_op) ?
>  			 hba->rpm_lvl : hba->spm_lvl;
> @@ -8697,17 +8739,17 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  
>  	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
>  			req_link_state == UIC_LINK_ACTIVE_STATE) {
> -		goto disable_clks;
> +		goto enable_scaling;
>  	}
>  
>  	if ((req_dev_pwr_mode == hba->curr_dev_pwr_mode) &&
>  	    (req_link_state == hba->uic_link_state))
> -		goto enable_gating;
> +		goto enable_scaling;
>  
>  	/* UFS device & link must be active before we enter in this function */
>  	if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba)) {
>  		ret = -EINVAL;
> -		goto enable_gating;
> +		goto enable_scaling;
>  	}
>  
>  	if (ufshcd_is_runtime_pm(pm_op)) {
> @@ -8719,7 +8761,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  			 */
>  			ret = ufshcd_urgent_bkops(hba);
>  			if (ret)
> -				goto enable_gating;
> +				goto enable_scaling;
>  		} else {
>  			/* make sure that auto bkops is disabled */
>  			ufshcd_disable_auto_bkops(hba);
> @@ -8747,7 +8789,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  		if (!hba->dev_info.b_rpm_dev_flush_capable) {
>  			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
>  			if (ret)
> -				goto enable_gating;
> +				goto enable_scaling;
>  		}
>  	}
>  
> @@ -8760,7 +8802,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	if (ret)
>  		goto set_dev_active;
>  
> -disable_clks:
>  	/*
>  	 * Call vendor specific suspend callback. As these callbacks may access
>  	 * vendor specific host controller register space call them before the
> @@ -8769,28 +8810,9 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	ret = ufshcd_vops_suspend(hba, pm_op);
>  	if (ret)
>  		goto set_link_active;
> -	/*
> -	 * Disable the host irq as host controller as there won't be any
> -	 * host controller transaction expected till resume.
> -	 */
> -	ufshcd_disable_irq(hba);
> -
> -	ufshcd_setup_clocks(hba, false);
> -
> -	if (ufshcd_is_clkgating_allowed(hba)) {
> -		hba->clk_gating.state = CLKS_OFF;
> -		trace_ufshcd_clk_gating(dev_name(hba->dev),
> -					hba->clk_gating.state);
> -	}
> -
> -	ufshcd_vreg_set_lpm(hba);
> -
> -	/* Put the host controller in low power mode if possible */
> -	ufshcd_hba_vreg_set_lpm(hba);
>  	goto out;
>  
>  set_link_active:
> -	ufshcd_vreg_set_hpm(hba);
>  	/*
>  	 * Device hardware reset is required to exit DeepSleep. Also, for
>  	 * DeepSleep, the link is off so host reset and restore will be done
> @@ -8812,57 +8834,35 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	}
>  	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
>  		ufshcd_disable_auto_bkops(hba);
> -enable_gating:
> +enable_scaling:
>  	if (ufshcd_is_clkscaling_supported(hba))
>  		ufshcd_clk_scaling_suspend(hba, false);
>  
> -	hba->clk_gating.is_suspended = false;
>  	hba->dev_info.b_rpm_dev_flush_capable = false;
> -	ufshcd_clear_ua_wluns(hba);
> -	ufshcd_release(hba);
>  out:
>  	if (hba->dev_info.b_rpm_dev_flush_capable) {
>  		schedule_delayed_work(&hba->rpm_dev_flush_recheck_work,
>  			msecs_to_jiffies(RPM_DEV_FLUSH_RECHECK_WORK_DELAY_MS));
>  	}
>  
> -	hba->pm_op_in_progress = 0;
> -
> -	if (ret)
> -		ufshcd_update_evt_hist(hba, UFS_EVT_SUSPEND_ERR, (u32)ret);
> +	if (ret) {
> +		ufshcd_update_evt_hist(hba, UFS_EVT_WL_SUSP_ERR, (u32)ret);
> +		hba->clk_gating.is_suspended = false;
> +		ufshcd_release(hba);
> +	}
> +	hba->pm_op_in_progress = false;
>  	return ret;
>  }
>  
> -/**
> - * ufshcd_resume - helper function for resume operations
> - * @hba: per adapter instance
> - * @pm_op: runtime PM or system PM
> - *
> - * This function basically brings the UFS device, UniPro link and controller
> - * to active state.
> - *
> - * Returns 0 for success and non-zero for failure
> - */
> -static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
> +static int __ufshcd_wl_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  {
>  	int ret;
> -	enum uic_link_state old_link_state;
> -
> -	hba->pm_op_in_progress = 1;
> -	old_link_state = hba->uic_link_state;
> -
> -	ufshcd_hba_vreg_set_hpm(hba);
> -	ret = ufshcd_vreg_set_hpm(hba);
> -	if (ret)
> -		goto out;
> +	enum uic_link_state old_link_state = hba->uic_link_state;
>  
> -	/* Make sure clocks are enabled before accessing controller */
> -	ret = ufshcd_setup_clocks(hba, true);
> -	if (ret)
> -		goto disable_vreg;
> +	if (!hba->init_done)
> +		return 0;
>  
> -	/* enable the host irq as host controller would be active soon */
> -	ufshcd_enable_irq(hba);
> +	hba->pm_op_in_progress = true;
>  
>  	/*
>  	 * Call vendor specific resume callback. As these callbacks may access
> @@ -8871,7 +8871,7 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	 */
>  	ret = ufshcd_vops_resume(hba, pm_op);
>  	if (ret)
> -		goto disable_irq_and_vops_clks;
> +		goto out;
>  
>  	/* For DeepSleep, the only supported option is to have the link off */
>  	WARN_ON(ufshcd_is_ufs_dev_deepsleep(hba) && !ufshcd_is_link_off(hba));
> @@ -8916,31 +8916,147 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  		 */
>  		ufshcd_urgent_bkops(hba);
>  
> -	hba->clk_gating.is_suspended = false;
> -
> -	if (ufshcd_is_clkscaling_supported(hba))
> -		ufshcd_clk_scaling_suspend(hba, false);
> -
> -	/* Enable Auto-Hibernate if configured */
> -	ufshcd_auto_hibern8_enable(hba);
> +	if (hba->clk_scaling.is_allowed)
> +		ufshcd_resume_clkscaling(hba);
>  
>  	if (hba->dev_info.b_rpm_dev_flush_capable) {
>  		hba->dev_info.b_rpm_dev_flush_capable = false;
>  		cancel_delayed_work(&hba->rpm_dev_flush_recheck_work);
>  	}
>  
> -	ufshcd_clear_ua_wluns(hba);
> -
> -	/* Schedule clock gating in case of no access to UFS device yet */
> -	ufshcd_release(hba);
> -
> +	/* Enable Auto-Hibernate if configured */
> +	ufshcd_auto_hibern8_enable(hba);
>  	goto out;
>  
>  set_old_link_state:
>  	ufshcd_link_state_transition(hba, old_link_state, 0);
>  vendor_suspend:
>  	ufshcd_vops_suspend(hba, pm_op);
> -disable_irq_and_vops_clks:
> +out:
> +	if (ret)
> +		ufshcd_update_evt_hist(hba, UFS_EVT_WL_RES_ERR, (u32)ret);
> +	hba->clk_gating.is_suspended = false;
> +	ufshcd_release(hba);
> +	hba->pm_op_in_progress = false;
> +	return ret;
> +}
> +
> +static int ufshcd_wl_runtime_suspend(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +	int ret;
> +	ktime_t start = ktime_get();
> +
> +	hba = shost_priv(sdev->host);
> +
> +	ret = __ufshcd_wl_suspend(hba, UFS_RUNTIME_PM);
> +	if (ret)
> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
> +
> +	trace_ufshcd_wl_runtime_suspend(dev_name(dev), ret,
> +		ktime_to_us(ktime_sub(ktime_get(), start)),
> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
> +
> +	return ret;
> +}
> +
> +static int ufshcd_wl_runtime_resume(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +	int ret = 0;
> +	ktime_t start = ktime_get();
> +
> +	hba = shost_priv(sdev->host);
> +
> +	ret = __ufshcd_wl_resume(hba, UFS_RUNTIME_PM);
> +	if (ret)
> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
> +
> +	trace_ufshcd_wl_runtime_resume(dev_name(dev), ret,
> +		ktime_to_us(ktime_sub(ktime_get(), start)),
> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
> +
> +	return ret;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int ufshcd_wl_suspend(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +	int ret;
> +	ktime_t start = ktime_get();
> +
> +	hba = shost_priv(sdev->host);
> +	ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
> +	if (ret)
> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
> +
> +	trace_ufshcd_wl_suspend(dev_name(dev), ret,
> +		ktime_to_us(ktime_sub(ktime_get(), start)),
> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
> +
> +	return ret;
> +}
> +
> +static int ufshcd_wl_resume(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +	int ret = 0;
> +	ktime_t start = ktime_get();
> +
> +	if (pm_runtime_suspended(dev))
> +		return 0;
> +	hba = shost_priv(sdev->host);
> +
> +	ret = __ufshcd_wl_resume(hba, UFS_SYSTEM_PM);
> +	if (ret)
> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
> +
> +	trace_ufshcd_wl_resume(dev_name(dev), ret,
> +		ktime_to_us(ktime_sub(ktime_get(), start)),
> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
> +
> +	return ret;
> +}
> +#endif
> +
> +static void ufshcd_wl_shutdown(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +
> +	hba = shost_priv(sdev->host);
> +	/* Turn on everything while shutting down */
> +	scsi_autopm_get_device(sdev);
> +	scsi_device_quiesce(sdev);
> +	shost_for_each_device(sdev, hba->host) {
> +		if (sdev == hba->sdev_ufs_device)
> +			continue;
> +		scsi_device_quiesce(sdev);
> +	}
> +	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
> +}
> +
> +/**
> + * ufshcd_suspend - helper function for suspend operations
> + * @hba: per adapter instance
> + *
> + * This function will put disable irqs, turn off clocks
> + * and set vreg and hba-vreg in lpm mode.
> + * Also check the description of __ufshcd_wl_suspend().
> + */
> +static void ufshcd_suspend(struct ufs_hba *hba)
> +{
> +	hba->pm_op_in_progress = 1;
> +
> +	/*
> +	 * Disable the host irq as host controller as there won't be any
> +	 * host controller transaction expected till resume.
> +	 */
>  	ufshcd_disable_irq(hba);
>  	ufshcd_setup_clocks(hba, false);
>  	if (ufshcd_is_clkgating_allowed(hba)) {
> @@ -8948,6 +9064,43 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  		trace_ufshcd_clk_gating(dev_name(hba->dev),
>  					hba->clk_gating.state);
>  	}
> +
> +	ufshcd_vreg_set_lpm(hba);
> +	/* Put the host controller in low power mode if possible */
> +	ufshcd_hba_vreg_set_lpm(hba);
> +	hba->pm_op_in_progress = 0;
> +}
> +
> +/**
> + * ufshcd_resume - helper function for resume operations
> + * @hba: per adapter instance
> + *
> + * This function basically turns on the regulators, clocks and
> + * irqs of the hba.
> + * Also check the description of __ufshcd_wl_resume().
> + *
> + * Returns 0 for success and non-zero for failure
> + */
> +static int ufshcd_resume(struct ufs_hba *hba)
> +{
> +	int ret;
> +
> +	hba->pm_op_in_progress = 1;
> +
> +	ufshcd_hba_vreg_set_hpm(hba);
> +	ret = ufshcd_vreg_set_hpm(hba);
> +	if (ret)
> +		goto out;
> +
> +	/* Make sure clocks are enabled before accessing controller */
> +	ret = ufshcd_setup_clocks(hba, true);
> +	if (ret)
> +		goto disable_vreg;
> +
> +	/* enable the host irq as host controller would be active soon */
> +	ufshcd_enable_irq(hba);
> +	goto out;
> +
>  disable_vreg:
>  	ufshcd_vreg_set_lpm(hba);
>  out:
> @@ -8962,6 +9115,7 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   * @hba: per adapter instance
>   *
>   * Check the description of ufshcd_suspend() function for more details.
> + * Also check the description of __ufshcd_wl_suspend().
>   *
>   * Returns 0 for success and non-zero for failure
>   */
> @@ -9001,7 +9155,7 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
	if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) ==
	     hba->curr_dev_pwr_mode) &&
	    (ufs_get_pm_lvl_to_link_pwr_state(hba->spm_lvl) ==
	     hba->uic_link_state) &&
	     !hba->dev_info.b_rpm_dev_flush_capable)
		goto out;

	if (pm_runtime_suspended(hba->dev)) {
		/*
		 * UFS device and/or UFS link low power states during runtime
		 * suspend seems to be different than what is expected during
		 * system suspend. Hence runtime resume the devic & link and
		 * let the system suspend low power states to take effect.
		 * TODO: If resume takes longer time, we might have optimize
		 * it in future by not resuming everything if possible.
		 */
		ret = ufshcd_runtime_resume(hba);
		if (ret)
>  			goto out;
>  	}

The logic above does not belong anymore.

>  
> -	ret = ufshcd_suspend(hba, UFS_SYSTEM_PM);
> +	ufshcd_suspend(hba);
>  out:
>  	trace_ufshcd_system_suspend(dev_name(hba->dev), ret,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),
> @@ -9023,7 +9177,6 @@ EXPORT_SYMBOL(ufshcd_system_suspend);
>  
>  int ufshcd_system_resume(struct ufs_hba *hba)
>  {
> -	int ret = 0;
>  	ktime_t start = ktime_get();
>  
>  	if (!hba)
> @@ -9041,15 +9194,15 @@ int ufshcd_system_resume(struct ufs_hba *hba)
>  		 */
>  		goto out;
>  	else
> -		ret = ufshcd_resume(hba, UFS_SYSTEM_PM);
> +		ufshcd_resume(hba);
>  out:
> -	trace_ufshcd_system_resume(dev_name(hba->dev), ret,
> +	trace_ufshcd_system_resume(dev_name(hba->dev), 0,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),
>  		hba->curr_dev_pwr_mode, hba->uic_link_state);
> -	if (!ret)
> -		hba->is_sys_suspended = false;
> +
> +	hba->is_sys_suspended = false;
>  	up(&hba->host_sem);
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL(ufshcd_system_resume);
>  
> @@ -9058,12 +9211,12 @@ EXPORT_SYMBOL(ufshcd_system_resume);
>   * @hba: per adapter instance
>   *
>   * Check the description of ufshcd_suspend() function for more details.
> + * Also check the description of __ufshcd_wl_suspend().
>   *
>   * Returns 0 for success and non-zero for failure
>   */
>  int ufshcd_runtime_suspend(struct ufs_hba *hba)
>  {
> -	int ret = 0;
>  	ktime_t start = ktime_get();
>  
>  	if (!hba)
> @@ -9072,12 +9225,12 @@ int ufshcd_runtime_suspend(struct ufs_hba *hba)
>  	if (!hba->is_powered)
>  		goto out;
>  	else
> -		ret = ufshcd_suspend(hba, UFS_RUNTIME_PM);
> +		ufshcd_suspend(hba);
>  out:
> -	trace_ufshcd_runtime_suspend(dev_name(hba->dev), ret,
> +	trace_ufshcd_runtime_suspend(dev_name(hba->dev), 0,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),
>  		hba->curr_dev_pwr_mode, hba->uic_link_state);
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL(ufshcd_runtime_suspend);
>  
> @@ -9085,26 +9238,14 @@ EXPORT_SYMBOL(ufshcd_runtime_suspend);
>   * ufshcd_runtime_resume - runtime resume routine
>   * @hba: per adapter instance
>   *
> - * This function basically brings the UFS device, UniPro link and controller
> + * This function basically brings controller
>   * to active state. Following operations are done in this function:
>   *
>   * 1. Turn on all the controller related clocks
> - * 2. Bring the UniPro link out of Hibernate state
> - * 3. If UFS device is in sleep state, turn ON VCC rail and bring the UFS device
> - *    to active state.
> - * 4. If auto-bkops is enabled on the device, disable it.
> - *
> - * So following would be the possible power state after this function return
> - * successfully:
> - *	S1: UFS device in Active state with VCC rail ON
> - *	    UniPro link in Active state
> - *	    All the UFS/UniPro controller clocks are ON
> - *
> - * Returns 0 for success and non-zero for failure
> + * 2. Turn ON VCC rail
>   */
>  int ufshcd_runtime_resume(struct ufs_hba *hba)
>  {
> -	int ret = 0;
>  	ktime_t start = ktime_get();
>  
>  	if (!hba)
> @@ -9113,12 +9254,12 @@ int ufshcd_runtime_resume(struct ufs_hba *hba)
>  	if (!hba->is_powered)
>  		goto out;
>  	else
> -		ret = ufshcd_resume(hba, UFS_RUNTIME_PM);
> +		ufshcd_resume(hba);
>  out:
> -	trace_ufshcd_runtime_resume(dev_name(hba->dev), ret,
> +	trace_ufshcd_runtime_resume(dev_name(hba->dev), 0,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),
>  		hba->curr_dev_pwr_mode, hba->uic_link_state);
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL(ufshcd_runtime_resume);
>  
> @@ -9132,14 +9273,13 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
>   * ufshcd_shutdown - shutdown routine
>   * @hba: per adapter instance
>   *
> - * This function would power off both UFS device and UFS link.
> + * This function would turn off both UFS device and UFS hba
> + * regulators. It would also disable clocks.
>   *
>   * Returns 0 always to allow force shutdown even in case of errors.
>   */
>  int ufshcd_shutdown(struct ufs_hba *hba)
>  {
> -	int ret = 0;
> -
>  	down(&hba->host_sem);
>  	hba->shutting_down = true;
>  	up(&hba->host_sem);
> @@ -9152,10 +9292,8 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>  
>  	pm_runtime_get_sync(hba->dev);
>  
> -	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> +	ufshcd_suspend(hba);
>  out:
> -	if (ret)
> -		dev_err(hba->dev, "%s failed, err %d\n", __func__, ret);
>  	hba->is_powered = false;
>  	/* allow force shutdown even in case of errors */
>  	return 0;
> @@ -9477,15 +9615,160 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>  }
>  EXPORT_SYMBOL_GPL(ufshcd_init);
>  
> +void ufshcd_resume_complete(struct device *dev)
> +{
> +	struct ufs_hba *hba = dev_get_drvdata(dev);
> +
> +	pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
> +}
> +EXPORT_SYMBOL_GPL(ufshcd_resume_complete);
> +
> +int ufshcd_suspend_prepare(struct device *dev)
> +{
> +	struct ufs_hba *hba = dev_get_drvdata(dev);
> +
> +	/*
> +	 * SCSI assumes that runtime-pm and system-pm for scsi drivers
> +	 * are same. And it doesn't wake up the device for system-suspend
> +	 * if it's runtime suspended. But ufs doesn't follow that.
> +	 * The rpm-lvl and spm-lvl can be different in ufs.
> +	 * Force it to honor system-suspend.
> +	 */
> +	scsi_autopm_get_device(hba->sdev_ufs_device);
> +	/* Refer ufshcd_resume_complete() */
> +	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
> +	scsi_autopm_put_device(hba->sdev_ufs_device);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(ufshcd_suspend_prepare);
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int ufshcd_wl_poweroff(struct device *dev)
> +{
> +	ufshcd_wl_shutdown(dev);
> +	return 0;
> +}
> +#endif
> +
> +static int ufshcd_wl_probe(struct device *dev)
> +{
> +	return is_device_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
> +}
> +
> +static int ufshcd_wl_remove(struct device *dev)
> +{
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops ufshcd_wl_pm_ops = {
> +#ifdef CONFIG_PM_SLEEP
> +	.suspend = ufshcd_wl_suspend,
> +	.resume = ufshcd_wl_resume,
> +	.freeze = ufshcd_wl_suspend,
> +	.thaw = ufshcd_wl_resume,
> +	.poweroff = ufshcd_wl_poweroff,
> +	.restore = ufshcd_wl_resume,
> +#endif
> +	SET_RUNTIME_PM_OPS(ufshcd_wl_runtime_suspend, ufshcd_wl_runtime_resume, NULL)
> +};
> +
> +/**
> + * ufs_dev_wlun_template - describes ufs device wlun
> + * ufs-device wlun - used to send pm commands
> + * All luns are consumers of ufs-device wlun.
> + *
> + * Currently, no sd driver is present for wluns.
> + * Hence the no specific pm operations are performed.
> + * With ufs design, SSU should be sent to ufs-device wlun.
> + * Hence register a scsi driver for ufs wluns only.
> + */
> +static struct scsi_driver ufs_dev_wlun_template = {
> +	.gendrv = {
> +		.name = "ufs_device_wlun",
> +		.owner = THIS_MODULE,
> +		.probe = ufshcd_wl_probe,
> +		.remove = ufshcd_wl_remove,
> +		.pm = &ufshcd_wl_pm_ops,
> +		.shutdown = ufshcd_wl_shutdown,
> +	},
> +};
> +
> +static int ufshcd_rpmb_probe(struct device *dev)
> +{
> +	return is_rpmb_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
> +}
> +
> +static inline int ufshcd_clear_rpmb_uac(struct ufs_hba *hba)
> +{
> +	int ret = 0;
> +
> +	if (!hba->wlun_rpmb_clr_ua)
> +		return 0;
> +	ret = ufshcd_clear_ua_wlun(hba, UFS_UPIU_RPMB_WLUN);
> +	if (!ret)
> +		hba->wlun_rpmb_clr_ua = 0;
> +	return ret;
> +}
> +
> +static int ufshcd_rpmb_runtime_resume(struct device *dev)
> +{
> +	struct ufs_hba *hba = wlun_dev_to_hba(dev);
> +
> +	if (hba->sdev_rpmb)
> +		return ufshcd_clear_rpmb_uac(hba);
> +	return 0;
> +}
> +
> +static int ufshcd_rpmb_resume(struct device *dev)
> +{
> +	struct ufs_hba *hba = wlun_dev_to_hba(dev);
> +
> +	if (hba->sdev_rpmb && !pm_runtime_suspended(dev))
> +		return ufshcd_clear_rpmb_uac(hba);
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops ufs_rpmb_pm_ops = {
> +	SET_RUNTIME_PM_OPS(NULL, ufshcd_rpmb_runtime_resume, NULL)
> +	SET_SYSTEM_SLEEP_PM_OPS(NULL, ufshcd_rpmb_resume)
> +};
> +
> +/**
> + * Describes the ufs rpmb wlun.
> + * Used only to send uac.
> + */
> +static struct scsi_driver ufs_rpmb_wlun_template = {
> +	.gendrv = {
> +		.name = "ufs_rpmb_wlun",
> +		.owner = THIS_MODULE,
> +		.probe = ufshcd_rpmb_probe,
> +		.pm = &ufs_rpmb_pm_ops,
> +	},
> +};
> +
>  static int __init ufshcd_core_init(void)
>  {
> +	int ret;
> +
>  	ufs_debugfs_init();
> +
> +	ret = scsi_register_driver(&ufs_dev_wlun_template.gendrv);
> +	if (ret)

I should have noticed before, but the error path needs ufs_debugfs_exit()

> +		return ret;
> +
> +	ret = scsi_register_driver(&ufs_rpmb_wlun_template.gendrv);
> +	if (ret) {
> +		scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);

Error path needs ufs_debugfs_exit()

> +		return ret;
> +	}
>  	return 0;
>  }
>  
>  static void __exit ufshcd_core_exit(void)
>  {
>  	ufs_debugfs_exit();
> +	scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);
> +	scsi_unregister_driver(&ufs_rpmb_wlun_template.gendrv);
>  }
>  
>  module_init(ufshcd_core_init);
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index ee61f82..e246ec3 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -72,6 +72,8 @@ enum ufs_event_type {
>  	UFS_EVT_LINK_STARTUP_FAIL,
>  	UFS_EVT_RESUME_ERR,
>  	UFS_EVT_SUSPEND_ERR,
> +	UFS_EVT_WL_SUSP_ERR,
> +	UFS_EVT_WL_RES_ERR,
>  
>  	/* abnormal events */
>  	UFS_EVT_DEV_RESET,
> @@ -804,6 +806,7 @@ struct ufs_hba {
>  	struct list_head clk_list_head;
>  
>  	bool wlun_dev_clr_ua;
> +	bool wlun_rpmb_clr_ua;
>  
>  	/* Number of requests aborts */
>  	int req_abort_count;
> @@ -841,6 +844,8 @@ struct ufs_hba {
>  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *debugfs_root;
>  #endif
> +	bool init_done;
> +	u32 luns_avail;
>  };
>  
>  /* Returns true if clocks can be gated. Otherwise false */
> @@ -1100,6 +1105,8 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
>  			     enum query_opcode desc_op);
>  
>  int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable);
> +int ufshcd_suspend_prepare(struct device *dev);
> +void ufshcd_resume_complete(struct device *dev);
>  
>  /* Wrapper functions for safely calling variant operations */
>  static inline const char *ufshcd_get_var_name(struct ufs_hba *hba)
> diff --git a/include/trace/events/ufs.h b/include/trace/events/ufs.h
> index e151477..d9d233b 100644
> --- a/include/trace/events/ufs.h
> +++ b/include/trace/events/ufs.h
> @@ -246,6 +246,26 @@ DEFINE_EVENT(ufshcd_template, ufshcd_init,
>  		      int dev_state, int link_state),
>  	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>  
> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_suspend,
> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
> +		      int dev_state, int link_state),
> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
> +
> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_resume,
> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
> +		      int dev_state, int link_state),
> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
> +
> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_suspend,
> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
> +		      int dev_state, int link_state),
> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
> +
> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_resume,
> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
> +		      int dev_state, int link_state),
> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
> +
>  TRACE_EVENT(ufshcd_command,
>  	TP_PROTO(const char *dev_name, enum ufs_trace_str_t str_t,
>  		 unsigned int tag, u32 doorbell, int transfer_len, u32 intr,
>
Asutosh Das March 6, 2021, 2:54 a.m. UTC | #2
On 3/4/2021 7:35 AM, Adrian Hunter wrote:
> On 3/03/21 12:52 am, Asutosh Das wrote:
>> During runtime-suspend of ufs host, the scsi devices are
>> already suspended and so are the queues associated with them.
>> But the ufs host sends SSU to wlun during its runtime-suspend.
>> During the process blk_queue_enter checks if the queue is not in
>> suspended state. If so, it waits for the queue to resume, and never
>> comes out of it.
>> The commit
>> (d55d15a33: scsi: block: Do not accept any requests while suspended)
>> adds the check if the queue is in suspended state in blk_queue_enter().
>>
>> Call trace:
>>   __switch_to+0x174/0x2c4
>>   __schedule+0x478/0x764
>>   schedule+0x9c/0xe0
>>   blk_queue_enter+0x158/0x228
>>   blk_mq_alloc_request+0x40/0xa4
>>   blk_get_request+0x2c/0x70
>>   __scsi_execute+0x60/0x1c4
>>   ufshcd_set_dev_pwr_mode+0x124/0x1e4
>>   ufshcd_suspend+0x208/0x83c
>>   ufshcd_runtime_suspend+0x40/0x154
>>   ufshcd_pltfrm_runtime_suspend+0x14/0x20
>>   pm_generic_runtime_suspend+0x28/0x3c
>>   __rpm_callback+0x80/0x2a4
>>   rpm_suspend+0x308/0x614
>>   rpm_idle+0x158/0x228
>>   pm_runtime_work+0x84/0xac
>>   process_one_work+0x1f0/0x470
>>   worker_thread+0x26c/0x4c8
>>   kthread+0x13c/0x320
>>   ret_from_fork+0x10/0x18
>>
>> Fix this by registering ufs device wlun as a scsi driver and
>> registering it for block runtime-pm. Also make this as a
>> supplier for all other luns. That way, this device wlun
>> suspends after all the consumers and resumes after
>> hba resumes.
>>
>> Co-developed-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> 
> It looks good, but still a few further comments below.
> 
> Also, do you think ufshcd_err_handling_prepare()/unprepare()
> need changes?  And ufshcd_recover_pm_error()?
> 
> And maybe ufshcd_auto_hibern8_update() when it is called from ufs_sysfs.c?

Hi Adrian
Sure, I'll fix it in the next version.

Now during my testing I see a weird issue sometimes (1 in 7).
Scenario - bootups

Issue:
The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend 
even when one/more of its consumers are in RPM_ACTIVE state.

*Log:
[   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
[   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
[   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
[   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
[   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
[   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
[   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache

/** Printing all the consumer nodes of supplier **/
[   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ 
suspend: 0 <-- this is the usage_count
[   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
[   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
[   11.005453][    T5] sd 0:0:0:0: PM state - 2
[   11.009958][    T5] sd 0:0:0:1: PM state - 2
[   11.014469][    T5] sd 0:0:0:2: PM state - 2
[   11.019072][    T5] sd 0:0:0:3: PM state - 2
[   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
[   11.353298][    T5] sd 0:0:0:5: PM state - 2
[   11.357726][    T5] sd 0:0:0:6: PM state - 2
[   11.362155][    T5] sd 0:0:0:7: PM state - 2
[   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
[   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend 
- (0) has rpm_active flags
[   11.383376][    T5] ufs_device_wlun 0:0:0:49488: 
ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
[   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache

And the the suspend of sde is stuck now:
schedule+0x9c/0xe0
schedule_timeout+0x40/0x128
io_schedule_timeout+0x44/0x68
wait_for_common_io+0x7c/0x100
wait_for_completion_io+0x14/0x20
blk_execute_rq+0x90/0xcc
__scsi_execute+0x104/0x1c4
sd_sync_cache+0xf8/0x2a0
sd_suspend_common+0x74/0x11c
sd_suspend_runtime+0x14/0x20
scsi_runtime_suspend+0x64/0x94
__rpm_callback+0x80/0x2a4
rpm_suspend+0x308/0x614
pm_runtime_work+0x98/0xa8

I added 'DL_FLAG_RPM_ACTIVE' while creating links.
       if (hba->sdev_ufs_device) {
               link = device_link_add(&sdev->sdev_gendev,
                                   &hba->sdev_ufs_device->sdev_gendev,
                                  DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
I didn't expect this to resolve the issue anyway and it didn't.

Another interesting point here is when I resume any of the above 
suspended consumers, it all goes back to normal, which is kind of 
expected. I tried resuming the consumer and the supplier is resumed and 
the supplier is suspended when all the consumers are suspended.

Any pointers on this issue please?

@Bart/@Alan - Do you've any pointers please?

Thanks,
AsutoshD


> 
>> ---
>>   drivers/scsi/ufs/cdns-pltfrm.c     |   2 +
>>   drivers/scsi/ufs/tc-dwc-g210-pci.c |   2 +
>>   drivers/scsi/ufs/ufs-exynos.c      |   2 +
>>   drivers/scsi/ufs/ufs-hisi.c        |   2 +
>>   drivers/scsi/ufs/ufs-mediatek.c    |   2 +
>>   drivers/scsi/ufs/ufs-qcom.c        |   2 +
>>   drivers/scsi/ufs/ufs_bsg.c         |   6 +-
>>   drivers/scsi/ufs/ufshcd-pci.c      |  32 +-
>>   drivers/scsi/ufs/ufshcd.c          | 583 +++++++++++++++++++++++++++----------
>>   drivers/scsi/ufs/ufshcd.h          |   7 +
>>   include/trace/events/ufs.h         |  20 ++
>>   11 files changed, 478 insertions(+), 182 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/cdns-pltfrm.c b/drivers/scsi/ufs/cdns-pltfrm.c
>> index 149391f..3e70c23 100644
>> --- a/drivers/scsi/ufs/cdns-pltfrm.c
>> +++ b/drivers/scsi/ufs/cdns-pltfrm.c
>> @@ -319,6 +319,8 @@ static const struct dev_pm_ops cdns_ufs_dev_pm_ops = {
>>   	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>>   	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>>   	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static struct platform_driver cdns_ufs_pltfrm_driver = {
>> diff --git a/drivers/scsi/ufs/tc-dwc-g210-pci.c b/drivers/scsi/ufs/tc-dwc-g210-pci.c
>> index 67a6a61..b01db12 100644
>> --- a/drivers/scsi/ufs/tc-dwc-g210-pci.c
>> +++ b/drivers/scsi/ufs/tc-dwc-g210-pci.c
>> @@ -148,6 +148,8 @@ static const struct dev_pm_ops tc_dwc_g210_pci_pm_ops = {
>>   	.runtime_suspend = tc_dwc_g210_pci_runtime_suspend,
>>   	.runtime_resume  = tc_dwc_g210_pci_runtime_resume,
>>   	.runtime_idle    = tc_dwc_g210_pci_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static const struct pci_device_id tc_dwc_g210_pci_tbl[] = {
>> diff --git a/drivers/scsi/ufs/ufs-exynos.c b/drivers/scsi/ufs/ufs-exynos.c
>> index 267943a1..45c0b02 100644
>> --- a/drivers/scsi/ufs/ufs-exynos.c
>> +++ b/drivers/scsi/ufs/ufs-exynos.c
>> @@ -1268,6 +1268,8 @@ static const struct dev_pm_ops exynos_ufs_pm_ops = {
>>   	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>>   	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>>   	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static struct platform_driver exynos_ufs_pltform = {
>> diff --git a/drivers/scsi/ufs/ufs-hisi.c b/drivers/scsi/ufs/ufs-hisi.c
>> index 0aa5813..d463b44 100644
>> --- a/drivers/scsi/ufs/ufs-hisi.c
>> +++ b/drivers/scsi/ufs/ufs-hisi.c
>> @@ -574,6 +574,8 @@ static const struct dev_pm_ops ufs_hisi_pm_ops = {
>>   	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>>   	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>>   	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static struct platform_driver ufs_hisi_pltform = {
>> diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
>> index c55202b..df1eabb 100644
>> --- a/drivers/scsi/ufs/ufs-mediatek.c
>> +++ b/drivers/scsi/ufs/ufs-mediatek.c
>> @@ -1097,6 +1097,8 @@ static const struct dev_pm_ops ufs_mtk_pm_ops = {
>>   	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>>   	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>>   	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static struct platform_driver ufs_mtk_pltform = {
>> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> index f97d7b0..9aa098a 100644
>> --- a/drivers/scsi/ufs/ufs-qcom.c
>> +++ b/drivers/scsi/ufs/ufs-qcom.c
>> @@ -1546,6 +1546,8 @@ static const struct dev_pm_ops ufs_qcom_pm_ops = {
>>   	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
>>   	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
>>   	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
>> +	.prepare	 = ufshcd_suspend_prepare,
>> +	.complete	= ufshcd_resume_complete,
>>   };
>>   
>>   static struct platform_driver ufs_qcom_pltform = {
>> diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
>> index 5b2bc1a..cbb5a90 100644
>> --- a/drivers/scsi/ufs/ufs_bsg.c
>> +++ b/drivers/scsi/ufs/ufs_bsg.c
>> @@ -97,7 +97,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>>   
>>   	bsg_reply->reply_payload_rcv_len = 0;
>>   
>> -	pm_runtime_get_sync(hba->dev);
>> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>>   
>>   	msgcode = bsg_request->msgcode;
>>   	switch (msgcode) {
>> @@ -106,7 +106,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>>   		ret = ufs_bsg_alloc_desc_buffer(hba, job, &desc_buff,
>>   						&desc_len, desc_op);
>>   		if (ret) {
>> -			pm_runtime_put_sync(hba->dev);
>> +			scsi_autopm_put_device(hba->sdev_ufs_device);
>>   			goto out;
>>   		}
>>   
>> @@ -138,7 +138,7 @@ static int ufs_bsg_request(struct bsg_job *job)
>>   		break;
>>   	}
>>   
>> -	pm_runtime_put_sync(hba->dev);
>> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>>   
>>   	if (!desc_buff)
>>   		goto out;
>> diff --git a/drivers/scsi/ufs/ufshcd-pci.c b/drivers/scsi/ufs/ufshcd-pci.c
>> index fadd566..50f84bf 100644
>> --- a/drivers/scsi/ufs/ufshcd-pci.c
>> +++ b/drivers/scsi/ufs/ufshcd-pci.c
>> @@ -247,29 +247,6 @@ static int ufshcd_pci_resume(struct device *dev)
>>   	return ufshcd_system_resume(dev_get_drvdata(dev));
>>   }
>>   
>> -/**
>> - * ufshcd_pci_poweroff - suspend-to-disk poweroff function
>> - * @dev: pointer to PCI device handle
>> - *
>> - * Returns 0 if successful
>> - * Returns non-zero otherwise
>> - */
>> -static int ufshcd_pci_poweroff(struct device *dev)
>> -{
>> -	struct ufs_hba *hba = dev_get_drvdata(dev);
>> -	int spm_lvl = hba->spm_lvl;
>> -	int ret;
>> -
>> -	/*
>> -	 * For poweroff we need to set the UFS device to PowerDown mode.
>> -	 * Force spm_lvl to ensure that.
>> -	 */
>> -	hba->spm_lvl = 5;
>> -	ret = ufshcd_system_suspend(hba);
>> -	hba->spm_lvl = spm_lvl;
>> -	return ret;
>> -}
>> -
>>   #endif /* !CONFIG_PM_SLEEP */
>>   
>>   #ifdef CONFIG_PM
>> @@ -366,12 +343,9 @@ ufshcd_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>>   
>>   static const struct dev_pm_ops ufshcd_pci_pm_ops = {
>>   #ifdef CONFIG_PM_SLEEP
>> -	.suspend	= ufshcd_pci_suspend,
>> -	.resume		= ufshcd_pci_resume,
>> -	.freeze		= ufshcd_pci_suspend,
>> -	.thaw		= ufshcd_pci_resume,
>> -	.poweroff	= ufshcd_pci_poweroff,
>> -	.restore	= ufshcd_pci_resume,
>> +	.prepare	 = ufshcd_suspend_prepare,
> 
> Please remove extra space before =
> 
>> +	.complete	= ufshcd_resume_complete,
>> +	SET_SYSTEM_SLEEP_PM_OPS(ufshcd_pci_suspend, ufshcd_pci_resume)
> 
> Would you mind putting SET_SYSTEM_SLEEP_PM_OPS above
> #ifdef CONFIG_PM_SLEEP
> 
>>   #endif
>>   	SET_RUNTIME_PM_OPS(ufshcd_pci_runtime_suspend,
>>   			   ufshcd_pci_runtime_resume,
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 45624c7..32139dd 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -16,6 +16,7 @@
>>   #include <linux/bitfield.h>
>>   #include <linux/blk-pm.h>
>>   #include <linux/blkdev.h>
>> +#include <scsi/scsi_driver.h>
>>   #include "ufshcd.h"
>>   #include "ufs_quirks.h"
>>   #include "unipro.h"
>> @@ -78,6 +79,8 @@
>>   /* Polling time to wait for fDeviceInit */
>>   #define FDEVICEINIT_COMPL_TIMEOUT 1500 /* millisecs */
>>   
>> +#define wlun_dev_to_hba(dv) shost_priv(to_scsi_device(dv)->host)
>> +
>>   #define ufshcd_toggle_vreg(_dev, _vreg, _on)				\
>>   	({                                                              \
>>   		int _ret;                                               \
>> @@ -1556,7 +1559,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>>   	if (value == hba->clk_scaling.is_enabled)
>>   		goto out;
>>   
>> -	pm_runtime_get_sync(hba->dev);
>> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>>   	ufshcd_hold(hba, false);
>>   
>>   	hba->clk_scaling.is_enabled = value;
>> @@ -1572,7 +1575,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>>   	}
>>   
>>   	ufshcd_release(hba);
>> -	pm_runtime_put_sync(hba->dev);
>> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>>   out:
>>   	up(&hba->host_sem);
>>   	return err ? err : count;
>> @@ -2572,6 +2575,17 @@ static inline u16 ufshcd_upiu_wlun_to_scsi_wlun(u8 upiu_wlun_id)
>>   	return (upiu_wlun_id & ~UFS_UPIU_WLUN_ID) | SCSI_W_LUN_BASE;
>>   }
>>   
>> +static inline bool is_rpmb_wlun(struct scsi_device *sdev)
>> +{
>> +	return (sdev->lun == ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_RPMB_WLUN));
>> +}
>> +
>> +static inline bool is_device_wlun(struct scsi_device *sdev)
>> +{
>> +	return (sdev->lun ==
>> +		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_UFS_DEVICE_WLUN));
>> +}
>> +
>>   static void ufshcd_init_lrb(struct ufs_hba *hba, struct ufshcd_lrb *lrb, int i)
>>   {
>>   	struct utp_transfer_cmd_desc *cmd_descp = hba->ucdl_base_addr;
>> @@ -4808,6 +4822,41 @@ static inline void ufshcd_get_lu_power_on_wp_status(struct ufs_hba *hba,
>>   }
>>   
>>   /**
>> + * ufshcd_setup_links - associate link b/w device wlun and other luns
>> + * @sdev: pointer to SCSI device
>> + * @hba: pointer to ufs hba
>> + */
>> +static void ufshcd_setup_links(struct ufs_hba *hba, struct scsi_device *sdev)
>> +{
>> +	struct device_link *link;
>> +
>> +	/*
>> +	 * device wlun is the supplier & rest of the luns are consumers
>> +	 * This ensures that device wlun suspends after all other luns.
>> +	 */
>> +	if (hba->sdev_ufs_device) {
>> +		link = device_link_add(&sdev->sdev_gendev,
>> +				       &hba->sdev_ufs_device->sdev_gendev,
>> +				       DL_FLAG_PM_RUNTIME);
>> +		if (!link) {
>> +			dev_err(&sdev->sdev_gendev, "Failed establishing link - %s\n",
>> +				dev_name(&hba->sdev_ufs_device->sdev_gendev));
>> +			return;
>> +		}
>> +		hba->luns_avail--;
>> +		/* Ignore REPORT_LUN wlun probing */
>> +		if (hba->luns_avail != 1)
>> +			return;
>> +
>> +		pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
>> +		pm_runtime_mark_last_busy(&hba->sdev_ufs_device->sdev_gendev);
> 
> Now that we set zero autosuspend_delay, mark_last_busy has no effect.
> 
>> +	} else {
>> +		/* device wlun is probed */
>> +		hba->luns_avail--;
>> +	}
>> +}
>> +
>> +/**
>>    * ufshcd_slave_alloc - handle initial SCSI device configurations
>>    * @sdev: pointer to SCSI device
>>    *
>> @@ -4838,6 +4887,8 @@ static int ufshcd_slave_alloc(struct scsi_device *sdev)
>>   
>>   	ufshcd_get_lu_power_on_wp_status(hba, sdev);
>>   
>> +	ufshcd_setup_links(hba, sdev);
>> +
>>   	return 0;
>>   }
>>   
>> @@ -4985,15 +5036,9 @@ ufshcd_transfer_rsp_status(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
>>   			 * UFS device needs urgent BKOPs.
>>   			 */
>>   			if (!hba->pm_op_in_progress &&
>> -			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr) &&
>> -			    schedule_work(&hba->eeh_work)) {
>> -				/*
>> -				 * Prevent suspend once eeh_work is scheduled
>> -				 * to avoid deadlock between ufshcd_suspend
>> -				 * and exception event handler.
>> -				 */
>> -				pm_runtime_get_noresume(hba->dev);
>> -			}
>> +			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
>> +				/* Flushed in suspend */
>> +				schedule_work(&hba->eeh_work);
>>   			break;
>>   		case UPIU_TRANSACTION_REJECT_UPIU:
>>   			/* TODO: handle Reject UPIU Response */
>> @@ -5589,8 +5634,8 @@ static void ufshcd_rpm_dev_flush_recheck_work(struct work_struct *work)
>>   	 * after a certain delay to recheck the threshold by next runtime
>>   	 * suspend.
>>   	 */
>> -	pm_runtime_get_sync(hba->dev);
>> -	pm_runtime_put_sync(hba->dev);
>> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>>   }
>>   
>>   /**
>> @@ -5607,7 +5652,6 @@ static void ufshcd_exception_event_handler(struct work_struct *work)
>>   	u32 status = 0;
>>   	hba = container_of(work, struct ufs_hba, eeh_work);
>>   
>> -	pm_runtime_get_sync(hba->dev);
>>   	ufshcd_scsi_block_requests(hba);
>>   	err = ufshcd_get_ee_status(hba, &status);
>>   	if (err) {
>> @@ -5623,14 +5667,6 @@ static void ufshcd_exception_event_handler(struct work_struct *work)
>>   
>>   out:
>>   	ufshcd_scsi_unblock_requests(hba);
>> -	/*
>> -	 * pm_runtime_get_noresume is called while scheduling
>> -	 * eeh_work to avoid suspend racing with exception work.
>> -	 * Hence decrement usage counter using pm_runtime_put_noidle
>> -	 * to allow suspend on completion of exception event handler.
>> -	 */
>> -	pm_runtime_put_noidle(hba->dev);
>> -	pm_runtime_put(hba->dev);
>>   	return;
>>   }
>>   
>> @@ -7207,11 +7243,12 @@ static void ufshcd_set_active_icc_lvl(struct ufs_hba *hba)
>>   
>>   static inline void ufshcd_blk_pm_runtime_init(struct scsi_device *sdev)
>>   {
>> +	int dly = is_device_wlun(sdev) ? 0:RPM_AUTOSUSPEND_DELAY_MS;
>> +
>>   	scsi_autopm_get_device(sdev);
>>   	blk_pm_runtime_init(sdev->request_queue, &sdev->sdev_gendev);
>>   	if (sdev->rpm_autosuspend)
>> -		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev,
>> -						 RPM_AUTOSUSPEND_DELAY_MS);
>> +		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev, dly);
>>   	scsi_autopm_put_device(sdev);
>>   }
>>   
>> @@ -7254,6 +7291,15 @@ static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
>>   		goto out;
>>   	}
>>   	ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device);
>> +	/*
>> +	 * A pm_runtime_put_sync is invoked when this device enables blk_pm_runtime
>> +	 * & would suspend the device-wlun upon timer expiry.
>> +	 * But suspending device wlun _may_ put the ufs device in the pre-defined
>> +	 * low power mode (SSU <rpm_lvl>). Probing of other luns may fail then.
>> +	 * Don't allow this suspend until all the luns have been probed.
>> +	 * See pm_runtime_mark_last_busy in ufshcd_setup_links.
>> +	 */
>> +	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
>>   	scsi_device_put(hba->sdev_ufs_device);
>>   
>>   	hba->sdev_rpmb = __scsi_add_device(hba->host, 0, 0,
>> @@ -7417,6 +7463,9 @@ static int ufs_get_device_desc(struct ufs_hba *hba)
>>   		goto out;
>>   	}
>>   
>> +	hba->luns_avail = desc_buf[DEVICE_DESC_PARAM_NUM_LU] +
>> +		desc_buf[DEVICE_DESC_PARAM_NUM_WLU];
>> +
>>   	ufs_fixup_device_setup(hba);
>>   
>>   	ufshcd_wb_probe(hba, desc_buf);
>> @@ -7892,6 +7941,7 @@ static int ufshcd_probe_hba(struct ufs_hba *hba, bool async)
>>   	ufshcd_set_ufs_dev_active(hba);
>>   	ufshcd_force_reset_auto_bkops(hba);
>>   	hba->wlun_dev_clr_ua = true;
>> +	hba->wlun_rpmb_clr_ua = true;
>>   
>>   	/* Gear up to HS gear if supported */
>>   	if (hba->max_pwr_info.is_valid) {
>> @@ -7964,6 +8014,7 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
>>   		pm_runtime_put_sync(hba->dev);
>>   		ufshcd_hba_exit(hba);
>>   	}
>> +	hba->init_done = true;
>>   }
>>   
>>   static const struct attribute_group *ufshcd_driver_groups[] = {
>> @@ -8475,7 +8526,8 @@ static int ufshcd_set_dev_pwr_mode(struct ufs_hba *hba,
>>   	 * handling context.
>>   	 */
>>   	hba->host->eh_noresume = 1;
>> -	ufshcd_clear_ua_wluns(hba);
>> +	if (hba->wlun_dev_clr_ua)
>> +		ufshcd_clear_ua_wlun(hba, UFS_UPIU_UFS_DEVICE_WLUN);
>>   
>>   	cmd[4] = pwr_mode << 4;
>>   
>> @@ -8650,23 +8702,7 @@ static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba)
>>   		ufshcd_setup_hba_vreg(hba, true);
>>   }
>>   
>> -/**
>> - * ufshcd_suspend - helper function for suspend operations
>> - * @hba: per adapter instance
>> - * @pm_op: desired low power operation type
>> - *
>> - * This function will try to put the UFS device and link into low power
>> - * mode based on the "rpm_lvl" (Runtime PM level) or "spm_lvl"
>> - * (System PM level).
>> - *
>> - * If this function is called during shutdown, it will make sure that
>> - * both UFS device and UFS link is powered off.
>> - *
>> - * NOTE: UFS device & link must be active before we enter in this function.
>> - *
>> - * Returns 0 for success and non-zero for failure
>> - */
>> -static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>> +static int __ufshcd_wl_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   {
>>   	int ret = 0;
>>   	int check_for_bkops;
>> @@ -8674,7 +8710,13 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   	enum ufs_dev_pwr_mode req_dev_pwr_mode;
>>   	enum uic_link_state req_link_state;
>>   
>> -	hba->pm_op_in_progress = 1;
>> +	/*
>> +	 * Is invoked when the device wlun is added to sysfs
>> +	 * But by then hba->sdev_ufs_device may not be initialized.
>> +	 */
>> +	if (!hba->init_done)
> 
> There is a pm_runtime_get_noresume() when sdev_ufs_device is created, and the
> corresponding pm_runtime_put_noidle() after the last of the device links is
> created, so it is not obvious what initialization may not have been done.
> Can you explain a bit more?
> 
>> +		return 0;
>> +	hba->pm_op_in_progress = true;
>>   	if (!ufshcd_is_shutdown_pm(pm_op)) {
>>   		pm_lvl = ufshcd_is_runtime_pm(pm_op) ?
>>   			 hba->rpm_lvl : hba->spm_lvl;
>> @@ -8697,17 +8739,17 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   
>>   	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
>>   			req_link_state == UIC_LINK_ACTIVE_STATE) {
>> -		goto disable_clks;
>> +		goto enable_scaling;
>>   	}
>>   
>>   	if ((req_dev_pwr_mode == hba->curr_dev_pwr_mode) &&
>>   	    (req_link_state == hba->uic_link_state))
>> -		goto enable_gating;
>> +		goto enable_scaling;
>>   
>>   	/* UFS device & link must be active before we enter in this function */
>>   	if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba)) {
>>   		ret = -EINVAL;
>> -		goto enable_gating;
>> +		goto enable_scaling;
>>   	}
>>   
>>   	if (ufshcd_is_runtime_pm(pm_op)) {
>> @@ -8719,7 +8761,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   			 */
>>   			ret = ufshcd_urgent_bkops(hba);
>>   			if (ret)
>> -				goto enable_gating;
>> +				goto enable_scaling;
>>   		} else {
>>   			/* make sure that auto bkops is disabled */
>>   			ufshcd_disable_auto_bkops(hba);
>> @@ -8747,7 +8789,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   		if (!hba->dev_info.b_rpm_dev_flush_capable) {
>>   			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
>>   			if (ret)
>> -				goto enable_gating;
>> +				goto enable_scaling;
>>   		}
>>   	}
>>   
>> @@ -8760,7 +8802,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   	if (ret)
>>   		goto set_dev_active;
>>   
>> -disable_clks:
>>   	/*
>>   	 * Call vendor specific suspend callback. As these callbacks may access
>>   	 * vendor specific host controller register space call them before the
>> @@ -8769,28 +8810,9 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   	ret = ufshcd_vops_suspend(hba, pm_op);
>>   	if (ret)
>>   		goto set_link_active;
>> -	/*
>> -	 * Disable the host irq as host controller as there won't be any
>> -	 * host controller transaction expected till resume.
>> -	 */
>> -	ufshcd_disable_irq(hba);
>> -
>> -	ufshcd_setup_clocks(hba, false);
>> -
>> -	if (ufshcd_is_clkgating_allowed(hba)) {
>> -		hba->clk_gating.state = CLKS_OFF;
>> -		trace_ufshcd_clk_gating(dev_name(hba->dev),
>> -					hba->clk_gating.state);
>> -	}
>> -
>> -	ufshcd_vreg_set_lpm(hba);
>> -
>> -	/* Put the host controller in low power mode if possible */
>> -	ufshcd_hba_vreg_set_lpm(hba);
>>   	goto out;
>>   
>>   set_link_active:
>> -	ufshcd_vreg_set_hpm(hba);
>>   	/*
>>   	 * Device hardware reset is required to exit DeepSleep. Also, for
>>   	 * DeepSleep, the link is off so host reset and restore will be done
>> @@ -8812,57 +8834,35 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   	}
>>   	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
>>   		ufshcd_disable_auto_bkops(hba);
>> -enable_gating:
>> +enable_scaling:
>>   	if (ufshcd_is_clkscaling_supported(hba))
>>   		ufshcd_clk_scaling_suspend(hba, false);
>>   
>> -	hba->clk_gating.is_suspended = false;
>>   	hba->dev_info.b_rpm_dev_flush_capable = false;
>> -	ufshcd_clear_ua_wluns(hba);
>> -	ufshcd_release(hba);
>>   out:
>>   	if (hba->dev_info.b_rpm_dev_flush_capable) {
>>   		schedule_delayed_work(&hba->rpm_dev_flush_recheck_work,
>>   			msecs_to_jiffies(RPM_DEV_FLUSH_RECHECK_WORK_DELAY_MS));
>>   	}
>>   
>> -	hba->pm_op_in_progress = 0;
>> -
>> -	if (ret)
>> -		ufshcd_update_evt_hist(hba, UFS_EVT_SUSPEND_ERR, (u32)ret);
>> +	if (ret) {
>> +		ufshcd_update_evt_hist(hba, UFS_EVT_WL_SUSP_ERR, (u32)ret);
>> +		hba->clk_gating.is_suspended = false;
>> +		ufshcd_release(hba);
>> +	}
>> +	hba->pm_op_in_progress = false;
>>   	return ret;
>>   }
>>   
>> -/**
>> - * ufshcd_resume - helper function for resume operations
>> - * @hba: per adapter instance
>> - * @pm_op: runtime PM or system PM
>> - *
>> - * This function basically brings the UFS device, UniPro link and controller
>> - * to active state.
>> - *
>> - * Returns 0 for success and non-zero for failure
>> - */
>> -static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>> +static int __ufshcd_wl_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   {
>>   	int ret;
>> -	enum uic_link_state old_link_state;
>> -
>> -	hba->pm_op_in_progress = 1;
>> -	old_link_state = hba->uic_link_state;
>> -
>> -	ufshcd_hba_vreg_set_hpm(hba);
>> -	ret = ufshcd_vreg_set_hpm(hba);
>> -	if (ret)
>> -		goto out;
>> +	enum uic_link_state old_link_state = hba->uic_link_state;
>>   
>> -	/* Make sure clocks are enabled before accessing controller */
>> -	ret = ufshcd_setup_clocks(hba, true);
>> -	if (ret)
>> -		goto disable_vreg;
>> +	if (!hba->init_done)
>> +		return 0;
>>   
>> -	/* enable the host irq as host controller would be active soon */
>> -	ufshcd_enable_irq(hba);
>> +	hba->pm_op_in_progress = true;
>>   
>>   	/*
>>   	 * Call vendor specific resume callback. As these callbacks may access
>> @@ -8871,7 +8871,7 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   	 */
>>   	ret = ufshcd_vops_resume(hba, pm_op);
>>   	if (ret)
>> -		goto disable_irq_and_vops_clks;
>> +		goto out;
>>   
>>   	/* For DeepSleep, the only supported option is to have the link off */
>>   	WARN_ON(ufshcd_is_ufs_dev_deepsleep(hba) && !ufshcd_is_link_off(hba));
>> @@ -8916,31 +8916,147 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   		 */
>>   		ufshcd_urgent_bkops(hba);
>>   
>> -	hba->clk_gating.is_suspended = false;
>> -
>> -	if (ufshcd_is_clkscaling_supported(hba))
>> -		ufshcd_clk_scaling_suspend(hba, false);
>> -
>> -	/* Enable Auto-Hibernate if configured */
>> -	ufshcd_auto_hibern8_enable(hba);
>> +	if (hba->clk_scaling.is_allowed)
>> +		ufshcd_resume_clkscaling(hba);
>>   
>>   	if (hba->dev_info.b_rpm_dev_flush_capable) {
>>   		hba->dev_info.b_rpm_dev_flush_capable = false;
>>   		cancel_delayed_work(&hba->rpm_dev_flush_recheck_work);
>>   	}
>>   
>> -	ufshcd_clear_ua_wluns(hba);
>> -
>> -	/* Schedule clock gating in case of no access to UFS device yet */
>> -	ufshcd_release(hba);
>> -
>> +	/* Enable Auto-Hibernate if configured */
>> +	ufshcd_auto_hibern8_enable(hba);
>>   	goto out;
>>   
>>   set_old_link_state:
>>   	ufshcd_link_state_transition(hba, old_link_state, 0);
>>   vendor_suspend:
>>   	ufshcd_vops_suspend(hba, pm_op);
>> -disable_irq_and_vops_clks:
>> +out:
>> +	if (ret)
>> +		ufshcd_update_evt_hist(hba, UFS_EVT_WL_RES_ERR, (u32)ret);
>> +	hba->clk_gating.is_suspended = false;
>> +	ufshcd_release(hba);
>> +	hba->pm_op_in_progress = false;
>> +	return ret;
>> +}
>> +
>> +static int ufshcd_wl_runtime_suspend(struct device *dev)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct ufs_hba *hba;
>> +	int ret;
>> +	ktime_t start = ktime_get();
>> +
>> +	hba = shost_priv(sdev->host);
>> +
>> +	ret = __ufshcd_wl_suspend(hba, UFS_RUNTIME_PM);
>> +	if (ret)
>> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
>> +
>> +	trace_ufshcd_wl_runtime_suspend(dev_name(dev), ret,
>> +		ktime_to_us(ktime_sub(ktime_get(), start)),
>> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> +
>> +	return ret;
>> +}
>> +
>> +static int ufshcd_wl_runtime_resume(struct device *dev)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct ufs_hba *hba;
>> +	int ret = 0;
>> +	ktime_t start = ktime_get();
>> +
>> +	hba = shost_priv(sdev->host);
>> +
>> +	ret = __ufshcd_wl_resume(hba, UFS_RUNTIME_PM);
>> +	if (ret)
>> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
>> +
>> +	trace_ufshcd_wl_runtime_resume(dev_name(dev), ret,
>> +		ktime_to_us(ktime_sub(ktime_get(), start)),
>> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> +
>> +	return ret;
>> +}
>> +
>> +#ifdef CONFIG_PM_SLEEP
>> +static int ufshcd_wl_suspend(struct device *dev)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct ufs_hba *hba;
>> +	int ret;
>> +	ktime_t start = ktime_get();
>> +
>> +	hba = shost_priv(sdev->host);
>> +	ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
>> +	if (ret)
>> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
>> +
>> +	trace_ufshcd_wl_suspend(dev_name(dev), ret,
>> +		ktime_to_us(ktime_sub(ktime_get(), start)),
>> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> +
>> +	return ret;
>> +}
>> +
>> +static int ufshcd_wl_resume(struct device *dev)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct ufs_hba *hba;
>> +	int ret = 0;
>> +	ktime_t start = ktime_get();
>> +
>> +	if (pm_runtime_suspended(dev))
>> +		return 0;
>> +	hba = shost_priv(sdev->host);
>> +
>> +	ret = __ufshcd_wl_resume(hba, UFS_SYSTEM_PM);
>> +	if (ret)
>> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
>> +
>> +	trace_ufshcd_wl_resume(dev_name(dev), ret,
>> +		ktime_to_us(ktime_sub(ktime_get(), start)),
>> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> +
>> +	return ret;
>> +}
>> +#endif
>> +
>> +static void ufshcd_wl_shutdown(struct device *dev)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct ufs_hba *hba;
>> +
>> +	hba = shost_priv(sdev->host);
>> +	/* Turn on everything while shutting down */
>> +	scsi_autopm_get_device(sdev);
>> +	scsi_device_quiesce(sdev);
>> +	shost_for_each_device(sdev, hba->host) {
>> +		if (sdev == hba->sdev_ufs_device)
>> +			continue;
>> +		scsi_device_quiesce(sdev);
>> +	}
>> +	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
>> +}
>> +
>> +/**
>> + * ufshcd_suspend - helper function for suspend operations
>> + * @hba: per adapter instance
>> + *
>> + * This function will put disable irqs, turn off clocks
>> + * and set vreg and hba-vreg in lpm mode.
>> + * Also check the description of __ufshcd_wl_suspend().
>> + */
>> +static void ufshcd_suspend(struct ufs_hba *hba)
>> +{
>> +	hba->pm_op_in_progress = 1;
>> +
>> +	/*
>> +	 * Disable the host irq as host controller as there won't be any
>> +	 * host controller transaction expected till resume.
>> +	 */
>>   	ufshcd_disable_irq(hba);
>>   	ufshcd_setup_clocks(hba, false);
>>   	if (ufshcd_is_clkgating_allowed(hba)) {
>> @@ -8948,6 +9064,43 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>   		trace_ufshcd_clk_gating(dev_name(hba->dev),
>>   					hba->clk_gating.state);
>>   	}
>> +
>> +	ufshcd_vreg_set_lpm(hba);
>> +	/* Put the host controller in low power mode if possible */
>> +	ufshcd_hba_vreg_set_lpm(hba);
>> +	hba->pm_op_in_progress = 0;
>> +}
>> +
>> +/**
>> + * ufshcd_resume - helper function for resume operations
>> + * @hba: per adapter instance
>> + *
>> + * This function basically turns on the regulators, clocks and
>> + * irqs of the hba.
>> + * Also check the description of __ufshcd_wl_resume().
>> + *
>> + * Returns 0 for success and non-zero for failure
>> + */
>> +static int ufshcd_resume(struct ufs_hba *hba)
>> +{
>> +	int ret;
>> +
>> +	hba->pm_op_in_progress = 1;
>> +
>> +	ufshcd_hba_vreg_set_hpm(hba);
>> +	ret = ufshcd_vreg_set_hpm(hba);
>> +	if (ret)
>> +		goto out;
>> +
>> +	/* Make sure clocks are enabled before accessing controller */
>> +	ret = ufshcd_setup_clocks(hba, true);
>> +	if (ret)
>> +		goto disable_vreg;
>> +
>> +	/* enable the host irq as host controller would be active soon */
>> +	ufshcd_enable_irq(hba);
>> +	goto out;
>> +
>>   disable_vreg:
>>   	ufshcd_vreg_set_lpm(hba);
>>   out:
>> @@ -8962,6 +9115,7 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>    * @hba: per adapter instance
>>    *
>>    * Check the description of ufshcd_suspend() function for more details.
>> + * Also check the description of __ufshcd_wl_suspend().
>>    *
>>    * Returns 0 for success and non-zero for failure
>>    */
>> @@ -9001,7 +9155,7 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
> 	if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) ==
> 	     hba->curr_dev_pwr_mode) &&
> 	    (ufs_get_pm_lvl_to_link_pwr_state(hba->spm_lvl) ==
> 	     hba->uic_link_state) &&
> 	     !hba->dev_info.b_rpm_dev_flush_capable)
> 		goto out;
> 
> 	if (pm_runtime_suspended(hba->dev)) {
> 		/*
> 		 * UFS device and/or UFS link low power states during runtime
> 		 * suspend seems to be different than what is expected during
> 		 * system suspend. Hence runtime resume the devic & link and
> 		 * let the system suspend low power states to take effect.
> 		 * TODO: If resume takes longer time, we might have optimize
> 		 * it in future by not resuming everything if possible.
> 		 */
> 		ret = ufshcd_runtime_resume(hba);
> 		if (ret)
>>   			goto out;
>>   	}
> 
> The logic above does not belong anymore.
> 
>>   
>> -	ret = ufshcd_suspend(hba, UFS_SYSTEM_PM);
>> +	ufshcd_suspend(hba);
>>   out:
>>   	trace_ufshcd_system_suspend(dev_name(hba->dev), ret,
>>   		ktime_to_us(ktime_sub(ktime_get(), start)),
>> @@ -9023,7 +9177,6 @@ EXPORT_SYMBOL(ufshcd_system_suspend);
>>   
>>   int ufshcd_system_resume(struct ufs_hba *hba)
>>   {
>> -	int ret = 0;
>>   	ktime_t start = ktime_get();
>>   
>>   	if (!hba)
>> @@ -9041,15 +9194,15 @@ int ufshcd_system_resume(struct ufs_hba *hba)
>>   		 */
>>   		goto out;
>>   	else
>> -		ret = ufshcd_resume(hba, UFS_SYSTEM_PM);
>> +		ufshcd_resume(hba);
>>   out:
>> -	trace_ufshcd_system_resume(dev_name(hba->dev), ret,
>> +	trace_ufshcd_system_resume(dev_name(hba->dev), 0,
>>   		ktime_to_us(ktime_sub(ktime_get(), start)),
>>   		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> -	if (!ret)
>> -		hba->is_sys_suspended = false;
>> +
>> +	hba->is_sys_suspended = false;
>>   	up(&hba->host_sem);
>> -	return ret;
>> +	return 0;
>>   }
>>   EXPORT_SYMBOL(ufshcd_system_resume);
>>   
>> @@ -9058,12 +9211,12 @@ EXPORT_SYMBOL(ufshcd_system_resume);
>>    * @hba: per adapter instance
>>    *
>>    * Check the description of ufshcd_suspend() function for more details.
>> + * Also check the description of __ufshcd_wl_suspend().
>>    *
>>    * Returns 0 for success and non-zero for failure
>>    */
>>   int ufshcd_runtime_suspend(struct ufs_hba *hba)
>>   {
>> -	int ret = 0;
>>   	ktime_t start = ktime_get();
>>   
>>   	if (!hba)
>> @@ -9072,12 +9225,12 @@ int ufshcd_runtime_suspend(struct ufs_hba *hba)
>>   	if (!hba->is_powered)
>>   		goto out;
>>   	else
>> -		ret = ufshcd_suspend(hba, UFS_RUNTIME_PM);
>> +		ufshcd_suspend(hba);
>>   out:
>> -	trace_ufshcd_runtime_suspend(dev_name(hba->dev), ret,
>> +	trace_ufshcd_runtime_suspend(dev_name(hba->dev), 0,
>>   		ktime_to_us(ktime_sub(ktime_get(), start)),
>>   		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> -	return ret;
>> +	return 0;
>>   }
>>   EXPORT_SYMBOL(ufshcd_runtime_suspend);
>>   
>> @@ -9085,26 +9238,14 @@ EXPORT_SYMBOL(ufshcd_runtime_suspend);
>>    * ufshcd_runtime_resume - runtime resume routine
>>    * @hba: per adapter instance
>>    *
>> - * This function basically brings the UFS device, UniPro link and controller
>> + * This function basically brings controller
>>    * to active state. Following operations are done in this function:
>>    *
>>    * 1. Turn on all the controller related clocks
>> - * 2. Bring the UniPro link out of Hibernate state
>> - * 3. If UFS device is in sleep state, turn ON VCC rail and bring the UFS device
>> - *    to active state.
>> - * 4. If auto-bkops is enabled on the device, disable it.
>> - *
>> - * So following would be the possible power state after this function return
>> - * successfully:
>> - *	S1: UFS device in Active state with VCC rail ON
>> - *	    UniPro link in Active state
>> - *	    All the UFS/UniPro controller clocks are ON
>> - *
>> - * Returns 0 for success and non-zero for failure
>> + * 2. Turn ON VCC rail
>>    */
>>   int ufshcd_runtime_resume(struct ufs_hba *hba)
>>   {
>> -	int ret = 0;
>>   	ktime_t start = ktime_get();
>>   
>>   	if (!hba)
>> @@ -9113,12 +9254,12 @@ int ufshcd_runtime_resume(struct ufs_hba *hba)
>>   	if (!hba->is_powered)
>>   		goto out;
>>   	else
>> -		ret = ufshcd_resume(hba, UFS_RUNTIME_PM);
>> +		ufshcd_resume(hba);
>>   out:
>> -	trace_ufshcd_runtime_resume(dev_name(hba->dev), ret,
>> +	trace_ufshcd_runtime_resume(dev_name(hba->dev), 0,
>>   		ktime_to_us(ktime_sub(ktime_get(), start)),
>>   		hba->curr_dev_pwr_mode, hba->uic_link_state);
>> -	return ret;
>> +	return 0;
>>   }
>>   EXPORT_SYMBOL(ufshcd_runtime_resume);
>>   
>> @@ -9132,14 +9273,13 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
>>    * ufshcd_shutdown - shutdown routine
>>    * @hba: per adapter instance
>>    *
>> - * This function would power off both UFS device and UFS link.
>> + * This function would turn off both UFS device and UFS hba
>> + * regulators. It would also disable clocks.
>>    *
>>    * Returns 0 always to allow force shutdown even in case of errors.
>>    */
>>   int ufshcd_shutdown(struct ufs_hba *hba)
>>   {
>> -	int ret = 0;
>> -
>>   	down(&hba->host_sem);
>>   	hba->shutting_down = true;
>>   	up(&hba->host_sem);
>> @@ -9152,10 +9292,8 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>>   
>>   	pm_runtime_get_sync(hba->dev);
>>   
>> -	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
>> +	ufshcd_suspend(hba);
>>   out:
>> -	if (ret)
>> -		dev_err(hba->dev, "%s failed, err %d\n", __func__, ret);
>>   	hba->is_powered = false;
>>   	/* allow force shutdown even in case of errors */
>>   	return 0;
>> @@ -9477,15 +9615,160 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>>   }
>>   EXPORT_SYMBOL_GPL(ufshcd_init);
>>   
>> +void ufshcd_resume_complete(struct device *dev)
>> +{
>> +	struct ufs_hba *hba = dev_get_drvdata(dev);
>> +
>> +	pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
>> +}
>> +EXPORT_SYMBOL_GPL(ufshcd_resume_complete);
>> +
>> +int ufshcd_suspend_prepare(struct device *dev)
>> +{
>> +	struct ufs_hba *hba = dev_get_drvdata(dev);
>> +
>> +	/*
>> +	 * SCSI assumes that runtime-pm and system-pm for scsi drivers
>> +	 * are same. And it doesn't wake up the device for system-suspend
>> +	 * if it's runtime suspended. But ufs doesn't follow that.
>> +	 * The rpm-lvl and spm-lvl can be different in ufs.
>> +	 * Force it to honor system-suspend.
>> +	 */
>> +	scsi_autopm_get_device(hba->sdev_ufs_device);
>> +	/* Refer ufshcd_resume_complete() */
>> +	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
>> +	scsi_autopm_put_device(hba->sdev_ufs_device);
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(ufshcd_suspend_prepare);
>> +
>> +#ifdef CONFIG_PM_SLEEP
>> +static int ufshcd_wl_poweroff(struct device *dev)
>> +{
>> +	ufshcd_wl_shutdown(dev);
>> +	return 0;
>> +}
>> +#endif
>> +
>> +static int ufshcd_wl_probe(struct device *dev)
>> +{
>> +	return is_device_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
>> +}
>> +
>> +static int ufshcd_wl_remove(struct device *dev)
>> +{
>> +	return 0;
>> +}
>> +
>> +static const struct dev_pm_ops ufshcd_wl_pm_ops = {
>> +#ifdef CONFIG_PM_SLEEP
>> +	.suspend = ufshcd_wl_suspend,
>> +	.resume = ufshcd_wl_resume,
>> +	.freeze = ufshcd_wl_suspend,
>> +	.thaw = ufshcd_wl_resume,
>> +	.poweroff = ufshcd_wl_poweroff,
>> +	.restore = ufshcd_wl_resume,
>> +#endif
>> +	SET_RUNTIME_PM_OPS(ufshcd_wl_runtime_suspend, ufshcd_wl_runtime_resume, NULL)
>> +};
>> +
>> +/**
>> + * ufs_dev_wlun_template - describes ufs device wlun
>> + * ufs-device wlun - used to send pm commands
>> + * All luns are consumers of ufs-device wlun.
>> + *
>> + * Currently, no sd driver is present for wluns.
>> + * Hence the no specific pm operations are performed.
>> + * With ufs design, SSU should be sent to ufs-device wlun.
>> + * Hence register a scsi driver for ufs wluns only.
>> + */
>> +static struct scsi_driver ufs_dev_wlun_template = {
>> +	.gendrv = {
>> +		.name = "ufs_device_wlun",
>> +		.owner = THIS_MODULE,
>> +		.probe = ufshcd_wl_probe,
>> +		.remove = ufshcd_wl_remove,
>> +		.pm = &ufshcd_wl_pm_ops,
>> +		.shutdown = ufshcd_wl_shutdown,
>> +	},
>> +};
>> +
>> +static int ufshcd_rpmb_probe(struct device *dev)
>> +{
>> +	return is_rpmb_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
>> +}
>> +
>> +static inline int ufshcd_clear_rpmb_uac(struct ufs_hba *hba)
>> +{
>> +	int ret = 0;
>> +
>> +	if (!hba->wlun_rpmb_clr_ua)
>> +		return 0;
>> +	ret = ufshcd_clear_ua_wlun(hba, UFS_UPIU_RPMB_WLUN);
>> +	if (!ret)
>> +		hba->wlun_rpmb_clr_ua = 0;
>> +	return ret;
>> +}
>> +
>> +static int ufshcd_rpmb_runtime_resume(struct device *dev)
>> +{
>> +	struct ufs_hba *hba = wlun_dev_to_hba(dev);
>> +
>> +	if (hba->sdev_rpmb)
>> +		return ufshcd_clear_rpmb_uac(hba);
>> +	return 0;
>> +}
>> +
>> +static int ufshcd_rpmb_resume(struct device *dev)
>> +{
>> +	struct ufs_hba *hba = wlun_dev_to_hba(dev);
>> +
>> +	if (hba->sdev_rpmb && !pm_runtime_suspended(dev))
>> +		return ufshcd_clear_rpmb_uac(hba);
>> +	return 0;
>> +}
>> +
>> +static const struct dev_pm_ops ufs_rpmb_pm_ops = {
>> +	SET_RUNTIME_PM_OPS(NULL, ufshcd_rpmb_runtime_resume, NULL)
>> +	SET_SYSTEM_SLEEP_PM_OPS(NULL, ufshcd_rpmb_resume)
>> +};
>> +
>> +/**
>> + * Describes the ufs rpmb wlun.
>> + * Used only to send uac.
>> + */
>> +static struct scsi_driver ufs_rpmb_wlun_template = {
>> +	.gendrv = {
>> +		.name = "ufs_rpmb_wlun",
>> +		.owner = THIS_MODULE,
>> +		.probe = ufshcd_rpmb_probe,
>> +		.pm = &ufs_rpmb_pm_ops,
>> +	},
>> +};
>> +
>>   static int __init ufshcd_core_init(void)
>>   {
>> +	int ret;
>> +
>>   	ufs_debugfs_init();
>> +
>> +	ret = scsi_register_driver(&ufs_dev_wlun_template.gendrv);
>> +	if (ret)
> 
> I should have noticed before, but the error path needs ufs_debugfs_exit()
> 
>> +		return ret;
>> +
>> +	ret = scsi_register_driver(&ufs_rpmb_wlun_template.gendrv);
>> +	if (ret) {
>> +		scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);
> 
> Error path needs ufs_debugfs_exit()
> 
>> +		return ret;
>> +	}
>>   	return 0;
>>   }
>>   
>>   static void __exit ufshcd_core_exit(void)
>>   {
>>   	ufs_debugfs_exit();
>> +	scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);
>> +	scsi_unregister_driver(&ufs_rpmb_wlun_template.gendrv);
>>   }
>>   
>>   module_init(ufshcd_core_init);
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index ee61f82..e246ec3 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -72,6 +72,8 @@ enum ufs_event_type {
>>   	UFS_EVT_LINK_STARTUP_FAIL,
>>   	UFS_EVT_RESUME_ERR,
>>   	UFS_EVT_SUSPEND_ERR,
>> +	UFS_EVT_WL_SUSP_ERR,
>> +	UFS_EVT_WL_RES_ERR,
>>   
>>   	/* abnormal events */
>>   	UFS_EVT_DEV_RESET,
>> @@ -804,6 +806,7 @@ struct ufs_hba {
>>   	struct list_head clk_list_head;
>>   
>>   	bool wlun_dev_clr_ua;
>> +	bool wlun_rpmb_clr_ua;
>>   
>>   	/* Number of requests aborts */
>>   	int req_abort_count;
>> @@ -841,6 +844,8 @@ struct ufs_hba {
>>   #ifdef CONFIG_DEBUG_FS
>>   	struct dentry *debugfs_root;
>>   #endif
>> +	bool init_done;
>> +	u32 luns_avail;
>>   };
>>   
>>   /* Returns true if clocks can be gated. Otherwise false */
>> @@ -1100,6 +1105,8 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
>>   			     enum query_opcode desc_op);
>>   
>>   int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable);
>> +int ufshcd_suspend_prepare(struct device *dev);
>> +void ufshcd_resume_complete(struct device *dev);
>>   
>>   /* Wrapper functions for safely calling variant operations */
>>   static inline const char *ufshcd_get_var_name(struct ufs_hba *hba)
>> diff --git a/include/trace/events/ufs.h b/include/trace/events/ufs.h
>> index e151477..d9d233b 100644
>> --- a/include/trace/events/ufs.h
>> +++ b/include/trace/events/ufs.h
>> @@ -246,6 +246,26 @@ DEFINE_EVENT(ufshcd_template, ufshcd_init,
>>   		      int dev_state, int link_state),
>>   	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>>   
>> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_suspend,
>> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
>> +		      int dev_state, int link_state),
>> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>> +
>> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_resume,
>> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
>> +		      int dev_state, int link_state),
>> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>> +
>> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_suspend,
>> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
>> +		      int dev_state, int link_state),
>> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>> +
>> +DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_resume,
>> +	     TP_PROTO(const char *dev_name, int err, s64 usecs,
>> +		      int dev_state, int link_state),
>> +	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
>> +
>>   TRACE_EVENT(ufshcd_command,
>>   	TP_PROTO(const char *dev_name, enum ufs_trace_str_t str_t,
>>   		 unsigned int tag, u32 doorbell, int transfer_len, u32 intr,
>>
>
Alan Stern March 6, 2021, 4:16 p.m. UTC | #3
On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:

> Now during my testing I see a weird issue sometimes (1 in 7).
> Scenario - bootups
> 
> Issue:
> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> when one/more of its consumers are in RPM_ACTIVE state.
> 
> *Log:
> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> 
> /** Printing all the consumer nodes of supplier **/
> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> <-- this is the usage_count
> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> (0) has rpm_active flags
> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> 
> And the the suspend of sde is stuck now:
> schedule+0x9c/0xe0
> schedule_timeout+0x40/0x128
> io_schedule_timeout+0x44/0x68
> wait_for_common_io+0x7c/0x100
> wait_for_completion_io+0x14/0x20
> blk_execute_rq+0x90/0xcc
> __scsi_execute+0x104/0x1c4
> sd_sync_cache+0xf8/0x2a0
> sd_suspend_common+0x74/0x11c
> sd_suspend_runtime+0x14/0x20
> scsi_runtime_suspend+0x64/0x94
> __rpm_callback+0x80/0x2a4
> rpm_suspend+0x308/0x614
> pm_runtime_work+0x98/0xa8
> 
> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>       if (hba->sdev_ufs_device) {
>               link = device_link_add(&sdev->sdev_gendev,
>                                   &hba->sdev_ufs_device->sdev_gendev,
>                                  DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> I didn't expect this to resolve the issue anyway and it didn't.
> 
> Another interesting point here is when I resume any of the above suspended
> consumers, it all goes back to normal, which is kind of expected. I tried
> resuming the consumer and the supplier is resumed and the supplier is
> suspended when all the consumers are suspended.
> 
> Any pointers on this issue please?
> 
> @Bart/@Alan - Do you've any pointers please?

It's very noticeable that although you seem to have isolated a bug in
the power management subsystem (supplier goes into runtime suspend
even when one of its consumers is still active), you did not CC the
power management maintainer or mailing list.

I have added the appropriate CC's.

Alan Stern
Rafael J. Wysocki March 8, 2021, 4:21 p.m. UTC | #4
On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>
> > Now during my testing I see a weird issue sometimes (1 in 7).
> > Scenario - bootups
> >
> > Issue:
> > The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> > when one/more of its consumers are in RPM_ACTIVE state.
> >
> > *Log:
> > [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> > [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> > [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> > [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> > [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> > [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> > [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> >
> > /** Printing all the consumer nodes of supplier **/
> > [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> > <-- this is the usage_count
> > [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> > [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> > [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> > [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> > [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> > [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> > [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> > [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> > [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> > [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> > [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> > [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> > (0) has rpm_active flags

Do you mean that rpm_active of the link between the consumer and the
supplier is greater than 0 at this point and the consumer is
RPM_ACTIVE, but the supplier suspends successfully nevertheless?

> > [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> > ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> > [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >
> > And the the suspend of sde is stuck now:
> > schedule+0x9c/0xe0
> > schedule_timeout+0x40/0x128
> > io_schedule_timeout+0x44/0x68
> > wait_for_common_io+0x7c/0x100
> > wait_for_completion_io+0x14/0x20
> > blk_execute_rq+0x90/0xcc
> > __scsi_execute+0x104/0x1c4
> > sd_sync_cache+0xf8/0x2a0
> > sd_suspend_common+0x74/0x11c
> > sd_suspend_runtime+0x14/0x20
> > scsi_runtime_suspend+0x64/0x94
> > __rpm_callback+0x80/0x2a4
> > rpm_suspend+0x308/0x614
> > pm_runtime_work+0x98/0xa8
> >
> > I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> >       if (hba->sdev_ufs_device) {
> >               link = device_link_add(&sdev->sdev_gendev,
> >                                   &hba->sdev_ufs_device->sdev_gendev,
> >                                  DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> > I didn't expect this to resolve the issue anyway and it didn't.
> >
> > Another interesting point here is when I resume any of the above suspended
> > consumers, it all goes back to normal, which is kind of expected. I tried
> > resuming the consumer and the supplier is resumed and the supplier is
> > suspended when all the consumers are suspended.
> >
> > Any pointers on this issue please?
> >
> > @Bart/@Alan - Do you've any pointers please?
>
> It's very noticeable that although you seem to have isolated a bug in
> the power management subsystem (supplier goes into runtime suspend
> even when one of its consumers is still active), you did not CC the
> power management maintainer or mailing list.
>
> I have added the appropriate CC's.

Thanks Alan!
Rafael J. Wysocki March 8, 2021, 5:17 p.m. UTC | #5
On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> >
> > On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
> >
> > > Now during my testing I see a weird issue sometimes (1 in 7).
> > > Scenario - bootups
> > >
> > > Issue:
> > > The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> > > when one/more of its consumers are in RPM_ACTIVE state.
> > >
> > > *Log:
> > > [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> > > [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> > > [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> > > [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> > > [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> > > [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> > > [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> > >
> > > /** Printing all the consumer nodes of supplier **/
> > > [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> > > <-- this is the usage_count
> > > [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> > > [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> > > [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> > > [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> > > [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> > > [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> > > [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> > > [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> > > [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> > > [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> > > [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> > > [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> > > (0) has rpm_active flags
>
> Do you mean that rpm_active of the link between the consumer and the
> supplier is greater than 0 at this point and the consumer is

I mean is rpm_active of the link greater than 1 (because 1 means "no
active references to the supplier")?

> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>
> > > [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> > > ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> > > [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> > >
> > > And the the suspend of sde is stuck now:
> > > schedule+0x9c/0xe0
> > > schedule_timeout+0x40/0x128
> > > io_schedule_timeout+0x44/0x68
> > > wait_for_common_io+0x7c/0x100
> > > wait_for_completion_io+0x14/0x20
> > > blk_execute_rq+0x90/0xcc
> > > __scsi_execute+0x104/0x1c4
> > > sd_sync_cache+0xf8/0x2a0
> > > sd_suspend_common+0x74/0x11c
> > > sd_suspend_runtime+0x14/0x20
> > > scsi_runtime_suspend+0x64/0x94
> > > __rpm_callback+0x80/0x2a4
> > > rpm_suspend+0x308/0x614
> > > pm_runtime_work+0x98/0xa8
> > >
> > > I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> > >       if (hba->sdev_ufs_device) {
> > >               link = device_link_add(&sdev->sdev_gendev,
> > >                                   &hba->sdev_ufs_device->sdev_gendev,
> > >                                  DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> > > I didn't expect this to resolve the issue anyway and it didn't.
> > >
> > > Another interesting point here is when I resume any of the above suspended
> > > consumers, it all goes back to normal, which is kind of expected. I tried
> > > resuming the consumer and the supplier is resumed and the supplier is
> > > suspended when all the consumers are suspended.
> > >
> > > Any pointers on this issue please?
> > >
> > > @Bart/@Alan - Do you've any pointers please?
> >
> > It's very noticeable that although you seem to have isolated a bug in
> > the power management subsystem (supplier goes into runtime suspend
> > even when one of its consumers is still active), you did not CC the
> > power management maintainer or mailing list.
> >
> > I have added the appropriate CC's.
>
> Thanks Alan!
Asutosh Das March 9, 2021, 3:56 p.m. UTC | #6
On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>
>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>
>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>
>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>> Scenario - bootups
>>>>
>>>> Issue:
>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>
>>>> *Log:
>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>
>>>> /** Printing all the consumer nodes of supplier **/
>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>> <-- this is the usage_count
>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>> (0) has rpm_active flags
>>
>> Do you mean that rpm_active of the link between the consumer and the
>> supplier is greater than 0 at this point and the consumer is
> 
> I mean is rpm_active of the link greater than 1 (because 1 means "no
> active references to the supplier")?
Hi Rafael:
No - it is not greater than 1.

I'm trying to understand what's going on in it; will update when I've 
something.

> 
>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>
>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>
>>>> And the the suspend of sde is stuck now:
>>>> schedule+0x9c/0xe0
>>>> schedule_timeout+0x40/0x128
>>>> io_schedule_timeout+0x44/0x68
>>>> wait_for_common_io+0x7c/0x100
>>>> wait_for_completion_io+0x14/0x20
>>>> blk_execute_rq+0x90/0xcc
>>>> __scsi_execute+0x104/0x1c4
>>>> sd_sync_cache+0xf8/0x2a0
>>>> sd_suspend_common+0x74/0x11c
>>>> sd_suspend_runtime+0x14/0x20
>>>> scsi_runtime_suspend+0x64/0x94
>>>> __rpm_callback+0x80/0x2a4
>>>> rpm_suspend+0x308/0x614
>>>> pm_runtime_work+0x98/0xa8
>>>>
>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>        if (hba->sdev_ufs_device) {
>>>>                link = device_link_add(&sdev->sdev_gendev,
>>>>                                    &hba->sdev_ufs_device->sdev_gendev,
>>>>                                   DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>
>>>> Another interesting point here is when I resume any of the above suspended
>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>> suspended when all the consumers are suspended.
>>>>
>>>> Any pointers on this issue please?
>>>>
>>>> @Bart/@Alan - Do you've any pointers please?
>>>
>>> It's very noticeable that although you seem to have isolated a bug in
>>> the power management subsystem (supplier goes into runtime suspend
>>> even when one of its consumers is still active), you did not CC the
>>> power management maintainer or mailing list.
>>>
>>> I have added the appropriate CC's.
>>
>> Thanks Alan!
Asutosh Das March 10, 2021, 3:04 a.m. UTC | #7
On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> 
>> wrote:
>>>
>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> 
>>> wrote:
>>>>
>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>
>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>> Scenario - bootups
>>>>>
>>>>> Issue:
>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime 
>>>>> suspend even
>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>
>>>>> *Log:
>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>
>>>>> /** Printing all the consumer nodes of supplier **/
>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ 
>>>>> suspend: 0
>>>>> <-- this is the usage_count
>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: 
>>>>> __ufshcd_wl_suspend - 8709
>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: 
>>>>> __ufshcd_wl_suspend -
>>>>> (0) has rpm_active flags
>>>
>>> Do you mean that rpm_active of the link between the consumer and the
>>> supplier is greater than 0 at this point and the consumer is
>>
>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>> active references to the supplier")?
> Hi Rafael:
> No - it is not greater than 1.
> 
> I'm trying to understand what's going on in it; will update when I've 
> something.
> 
>>
>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>
>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>
>>>>> And the the suspend of sde is stuck now:
>>>>> schedule+0x9c/0xe0
>>>>> schedule_timeout+0x40/0x128
>>>>> io_schedule_timeout+0x44/0x68
>>>>> wait_for_common_io+0x7c/0x100
>>>>> wait_for_completion_io+0x14/0x20
>>>>> blk_execute_rq+0x90/0xcc
>>>>> __scsi_execute+0x104/0x1c4
>>>>> sd_sync_cache+0xf8/0x2a0
>>>>> sd_suspend_common+0x74/0x11c
>>>>> sd_suspend_runtime+0x14/0x20
>>>>> scsi_runtime_suspend+0x64/0x94
>>>>> __rpm_callback+0x80/0x2a4
>>>>> rpm_suspend+0x308/0x614
>>>>> pm_runtime_work+0x98/0xa8
>>>>>
>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>        if (hba->sdev_ufs_device) {
>>>>>                link = device_link_add(&sdev->sdev_gendev,
>>>>>                                    &hba->sdev_ufs_device->sdev_gendev,
>>>>>                                   
>>>>> DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>
>>>>> Another interesting point here is when I resume any of the above 
>>>>> suspended
>>>>> consumers, it all goes back to normal, which is kind of expected. I 
>>>>> tried
>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>> suspended when all the consumers are suspended.
>>>>>
>>>>> Any pointers on this issue please?
>>>>>
>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>
>>>> It's very noticeable that although you seem to have isolated a bug in
>>>> the power management subsystem (supplier goes into runtime suspend
>>>> even when one of its consumers is still active), you did not CC the
>>>> power management maintainer or mailing list.
>>>>
>>>> I have added the appropriate CC's.
>>>
>>> Thanks Alan!
> 
> 

Hello
I & Can (thanks CanG) debugged this further:

Looks like this issue can occur if the sd probe is asynchronous.

Essentially, the sd_probe() is done asynchronously and 
driver_probe_device() invokes pm_runtime_get_suppliers() before invoking 
sd_probe().

But scsi_probe_and_add_lun() runs in a separate context.
So the scsi_autopm_put_device() invoked from scsi_scan_host() context 
reduces the link->rpm_active to 1. And sd_probe() invokes 
scsi_autopm_put_device() and starts a timer. And then 
driver_probe_device() invoked from __device_attach_async_helper context 
reduces the link->rpm_active to 1 thus enabling the supplier to suspend 
before the consumer suspends.

So if:
Context T1:
[1] scsi_probe_and_add_lun()
[2]	|- scsi_autopm_put_device() - reduce the link->rpm_active to 1

Context T2:
__device_attach_async_helper()
	|- driver_probe_device()
		|- sd_probe()
In between [1] and [2] say, driver_probe_device() -> sd_probe() is 
invoked in a separate context from __device_attach_async_helper().
The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would 
reduce link->rpm_active to 1.
Then sd_probe() would invoke rpm_resume() and proceed as is.
When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, 
dev->power.timer_autosuspends = 1.

Now then, pm_runtime_put_suppliers() is invoked from 
driver_probe_device() and that makes the link->rpm_active = 1.
But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state 
= RPM_ACTIVE and link->rpm_active = 1.
At this point of time, all other 'sd dev' (consumers) _may_ be suspended 
or active but would have the link->rpm_active = 1.

Since the supplier has 0 auto-suspend delay, it now suspends!


Context [T1]
Call trace:
dump_backtrace+0x0/0x1d4
show_stack+0x18/0x24
dump_stack+0xc4/0x144
__pm_runtime_idle+0xb4/0x184
scsi_autopm_put_device+0x18/0x24
scsi_sysfs_add_sdev+0x26c/0x278
scsi_probe_and_add_lun+0xbac/0xd48
__scsi_scan_target+0x38c/0x510
scsi_scan_host_selected+0x14c/0x1e4
scsi_scan_host+0x1e0/0x228
ufshcd_async_scan+0x39c/0x408
async_run_entry_fn+0x48/0x128
process_one_work+0x1f0/0x470
worker_thread+0x26c/0x4c8
kthread+0x13c/0x320
ret_from_fork+0x10/0x18


Context [T2]
Call trace:
dump_backtrace+0x0/0x1d4
show_stack+0x18/0x24
dump_stack+0xc4/0x144
rpm_get_suppliers+0x48/0x1ac
__rpm_callback+0x58/0x12c
rpm_resume+0x3a4/0x618
__pm_runtime_resume+0x50/0x80
scsi_autopm_get_device+0x20/0x54
sd_probe+0x40/0x3d0
really_probe+0x1bc/0x4a0
driver_probe_device+0x84/0xf0
__device_attach_driver+0x114/0x138
bus_for_each_drv+0x84/0xd0
__device_attach_async_helper+0x7c/0xf0
async_run_entry_fn+0x48/0x128
process_one_work+0x1f0/0x470
worker_thread+0x26c/0x4c8
kthread+0x13c/0x320
ret_from_fork+0x10/0x18

Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
[    7.574654][  T212] Call trace:
[    7.574657][  T212]  dump_backtrace+0x0/0x1d4
[    7.574661][  T212]  show_stack+0x18/0x24
[    7.574665][  T212]  dump_stack+0xc4/0x144
[    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
[    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
[    7.574675][  T212]  sd_probe+0x314/0x3d0
[    7.574677][  T212]  really_probe+0x1bc/0x4a0
[    7.574680][  T212]  driver_probe_device+0x84/0xf0
[    7.574683][  T212]  __device_attach_driver+0x114/0x138
[    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
[    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
[    7.574692][  T212]  async_run_entry_fn+0x48/0x128
[    7.574695][  T212]  process_one_work+0x1f0/0x470
[    7.574698][  T212]  worker_thread+0x26c/0x4c8
[    7.574700][  T212]  kthread+0x13c/0x320
[    7.574703][  T212]  ret_from_fork+0x10/0x18
[    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
[    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: 
pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 
pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
[    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
[    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: 
pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2

[    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
[    7.574754][  T212] Call trace:
[    7.574758][  T212]  dump_backtrace+0x0/0x1d4
[    7.574761][  T212]  show_stack+0x18/0x24
[    7.574765][  T212]  dump_stack+0xc4/0x144
[    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
[    7.574770][  T212]  driver_probe_device+0x94/0xf0
[    7.574773][  T212]  __device_attach_driver+0x114/0x138
[    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
[    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
[    7.574781][  T212]  async_run_entry_fn+0x48/0x128
[    7.574783][  T212]  process_one_work+0x1f0/0x470
[    7.574786][  T212]  worker_thread+0x26c/0x4c8
[    7.574788][  T212]  kthread+0x13c/0x320
[    7.574791][  T212]  ret_from_fork+0x10/0x18
[    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
[    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: 
pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 
0 usage_count: 0 rpm_status: 0 link-rpm_active:2
[    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: 
rpm_status: 0 link-rpm_active:1
[    7.574866][  T212] sd 0:0:0:4: async probe completed
[    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: 
pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1


So, from the above it looks like when async probe is enabled this is a 
possibility.

I don't see a way around this. Please let me know if you 
(@Alan/@Bart/@Adrian) have any thoughts on this.

Thanks,
-asd
Alan Stern March 10, 2021, 3:14 a.m. UTC | #8
On Tue, Mar 09, 2021 at 07:04:34PM -0800, Asutosh Das (asd) wrote:
> Hello
> I & Can (thanks CanG) debugged this further:
> 
> Looks like this issue can occur if the sd probe is asynchronous.
> 
> Essentially, the sd_probe() is done asynchronously and driver_probe_device()
> invokes pm_runtime_get_suppliers() before invoking sd_probe().
> 
> But scsi_probe_and_add_lun() runs in a separate context.
> So the scsi_autopm_put_device() invoked from scsi_scan_host() context
> reduces the link->rpm_active to 1. And sd_probe() invokes
> scsi_autopm_put_device() and starts a timer. And then driver_probe_device()
> invoked from __device_attach_async_helper context reduces the
> link->rpm_active to 1 thus enabling the supplier to suspend before the
> consumer suspends.

> I don't see a way around this. Please let me know if you
> (@Alan/@Bart/@Adrian) have any thoughts on this.

How about changing the SCSI core so that it does a runtime_get before
starting an async probe, and the async probe routine does a
runtime_put when it is finished?  In other words, don't allow a device
to go into runtime suspend while it is waiting to be probed.

I don't think that would be too intrusive.

Alan Stern
Asutosh Das March 10, 2021, 4:04 a.m. UTC | #9
On 3/9/2021 7:14 PM, Alan Stern wrote:
> On Tue, Mar 09, 2021 at 07:04:34PM -0800, Asutosh Das (asd) wrote:
>> Hello
>> I & Can (thanks CanG) debugged this further:
>>
>> Looks like this issue can occur if the sd probe is asynchronous.
>>
>> Essentially, the sd_probe() is done asynchronously and driver_probe_device()
>> invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>
>> But scsi_probe_and_add_lun() runs in a separate context.
>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context
>> reduces the link->rpm_active to 1. And sd_probe() invokes
>> scsi_autopm_put_device() and starts a timer. And then driver_probe_device()
>> invoked from __device_attach_async_helper context reduces the
>> link->rpm_active to 1 thus enabling the supplier to suspend before the
>> consumer suspends.
> 
>> I don't see a way around this. Please let me know if you
>> (@Alan/@Bart/@Adrian) have any thoughts on this.
> 
> How about changing the SCSI core so that it does a runtime_get before
> starting an async probe, and the async probe routine does a
> runtime_put when it is finished?  In other words, don't allow a device
> to go into runtime suspend while it is waiting to be probed.
> 
> I don't think that would be too intrusive.
> 
> Alan Stern
> 

Hi Alan
Thanks for the suggestion.

Am trying to understand:

Do you mean something like this:

int scsi_sysfs_add_sdev(struct scsi_device *sdev)
{
	
	scsi_autopm_get_device(sdev);
	pm_runtime_get_noresume(&sdev->sdev_gendev);
	[...]
	scsi_autopm_put_device(sdev);
	[...]
}

static int sd_probe(struct device *dev)
{
	[...]
	pm_runtime_put_noidle(dev);
	scsi_autopm_put_device(sdp);
	[...]
}

This may work (I'm limited by my imagination in scsi layer :) ).

But the pm_runtime_put_noidle() would have to be added to all registered 
scsi_driver{}, perhaps? Or may be I can check for sdp->type?

-asd
Alan Stern March 10, 2021, 4:27 p.m. UTC | #10
On Tue, Mar 09, 2021 at 08:04:53PM -0800, Asutosh Das (asd) wrote:
> On 3/9/2021 7:14 PM, Alan Stern wrote:
> > On Tue, Mar 09, 2021 at 07:04:34PM -0800, Asutosh Das (asd) wrote:
> > > Hello
> > > I & Can (thanks CanG) debugged this further:
> > > 
> > > Looks like this issue can occur if the sd probe is asynchronous.
> > > 
> > > Essentially, the sd_probe() is done asynchronously and driver_probe_device()
> > > invokes pm_runtime_get_suppliers() before invoking sd_probe().
> > > 
> > > But scsi_probe_and_add_lun() runs in a separate context.
> > > So the scsi_autopm_put_device() invoked from scsi_scan_host() context
> > > reduces the link->rpm_active to 1. And sd_probe() invokes
> > > scsi_autopm_put_device() and starts a timer. And then driver_probe_device()
> > > invoked from __device_attach_async_helper context reduces the
> > > link->rpm_active to 1 thus enabling the supplier to suspend before the
> > > consumer suspends.
> > 
> > > I don't see a way around this. Please let me know if you
> > > (@Alan/@Bart/@Adrian) have any thoughts on this.
> > 
> > How about changing the SCSI core so that it does a runtime_get before
> > starting an async probe, and the async probe routine does a
> > runtime_put when it is finished?  In other words, don't allow a device
> > to go into runtime suspend while it is waiting to be probed.
> > 
> > I don't think that would be too intrusive.
> > 
> > Alan Stern
> > 
> 
> Hi Alan
> Thanks for the suggestion.
> 
> Am trying to understand:
> 
> Do you mean something like this:
> 
> int scsi_sysfs_add_sdev(struct scsi_device *sdev)
> {
> 	
> 	scsi_autopm_get_device(sdev);
> 	pm_runtime_get_noresume(&sdev->sdev_gendev);
> 	[...]
> 	scsi_autopm_put_device(sdev);
> 	[...]
> }
> 
> static int sd_probe(struct device *dev)
> {
> 	[...]
> 	pm_runtime_put_noidle(dev);
> 	scsi_autopm_put_device(sdp);
> 	[...]
> }
> 
> This may work (I'm limited by my imagination in scsi layer :) ).

I'm not sure about this.  To be honest, I did not read the entirety of 
your last message; it had way too much detail.  THere's a time and place 
for that, but when you're brainstorming to figure out the underlying 
cause of a problem and come up with a strategy to fix it, you want to 
concentrate on the overall picture, not the details.

As I understand the situation, you've get a SCSI target with multiple 
logical units, let's say A and B, and you need to make sure that A never 
goes into runtime suspend unless B is already suspended.  In other 
words, B always has to suspend before A and resume after A.

To do this, you register a device link with A as the supplier and B as 
the consumer.  Then the PM core takes care of the ordering for you.

But I don't understand when you set up the device link.  If the timing 
is wrong then, thanks to async SCSI probing, you may have a situation 
where A is registered before B and before the link is set up.  Then 
there's temporarily nothing to stop A from suspending before B.

You also need to prevent each device from suspending before it is 
probed.  That's the easy part I was trying to address before (although 
it may not be so easy if the drivers are in loadable modules and not 
present in the kernel).

You need to think through these issues before proposing actual changes.

> But the pm_runtime_put_noidle() would have to be added to all registered
> scsi_driver{}, perhaps? Or may be I can check for sdp->type?

Like this; it's too early to worry about this sort of thing.

Alan Stern
Asutosh Das March 10, 2021, 4:39 p.m. UTC | #11
On 3/10/2021 8:27 AM, Alan Stern wrote:
> On Tue, Mar 09, 2021 at 08:04:53PM -0800, Asutosh Das (asd) wrote:
>> On 3/9/2021 7:14 PM, Alan Stern wrote:
>>> On Tue, Mar 09, 2021 at 07:04:34PM -0800, Asutosh Das (asd) wrote:
>>>> Hello
>>>> I & Can (thanks CanG) debugged this further:
>>>>
>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>
>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device()
>>>> invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>
>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context
>>>> reduces the link->rpm_active to 1. And sd_probe() invokes
>>>> scsi_autopm_put_device() and starts a timer. And then driver_probe_device()
>>>> invoked from __device_attach_async_helper context reduces the
>>>> link->rpm_active to 1 thus enabling the supplier to suspend before the
>>>> consumer suspends.
>>>
>>>> I don't see a way around this. Please let me know if you
>>>> (@Alan/@Bart/@Adrian) have any thoughts on this.
>>>
>>> How about changing the SCSI core so that it does a runtime_get before
>>> starting an async probe, and the async probe routine does a
>>> runtime_put when it is finished?  In other words, don't allow a device
>>> to go into runtime suspend while it is waiting to be probed.
>>>
>>> I don't think that would be too intrusive.
>>>
>>> Alan Stern
>>>
>>
>> Hi Alan
>> Thanks for the suggestion.
>>
>> Am trying to understand:
>>
>> Do you mean something like this:
>>
>> int scsi_sysfs_add_sdev(struct scsi_device *sdev)
>> {
>> 	
>> 	scsi_autopm_get_device(sdev);
>> 	pm_runtime_get_noresume(&sdev->sdev_gendev);
>> 	[...]
>> 	scsi_autopm_put_device(sdev);
>> 	[...]
>> }
>>
>> static int sd_probe(struct device *dev)
>> {
>> 	[...]
>> 	pm_runtime_put_noidle(dev);
>> 	scsi_autopm_put_device(sdp);
>> 	[...]
>> }
>>
>> This may work (I'm limited by my imagination in scsi layer :) ).
> 
> I'm not sure about this.  To be honest, I did not read the entirety of
> your last message; it had way too much detail.  THere's a time and place
> for that, but when you're brainstorming to figure out the underlying
> cause of a problem and come up with a strategy to fix it, you want to
> concentrate on the overall picture, not the details.
> 
> As I understand the situation, you've get a SCSI target with multiple
> logical units, let's say A and B, and you need to make sure that A never
> goes into runtime suspend unless B is already suspended.  In other
> words, B always has to suspend before A and resume after A.
> 
> To do this, you register a device link with A as the supplier and B as
> the consumer.  Then the PM core takes care of the ordering for you.
> 
> But I don't understand when you set up the device link.  If the timing
> is wrong then, thanks to async SCSI probing, you may have a situation
> where A is registered before B and before the link is set up.  Then
> there's temporarily nothing to stop A from suspending before B.
> 
> You also need to prevent each device from suspending before it is
> probed.  That's the easy part I was trying to address before (although
> it may not be so easy if the drivers are in loadable modules and not
> present in the kernel).
> 
> You need to think through these issues before proposing actual changes.
> 
>> But the pm_runtime_put_noidle() would have to be added to all registered
>> scsi_driver{}, perhaps? Or may be I can check for sdp->type?
> 
> Like this; it's too early to worry about this sort of thing.
> 
> Alan Stern
> 
Hi Alan
Thanks. Understood.

I will check the details and see if I can come up with something.
I'll propose an alternate fix otherwise and drop this change altogether.

Thanks!
-asd
Adrian Hunter March 14, 2021, 9:11 a.m. UTC | #12
On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>
>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>
>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>
>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>> Scenario - bootups
>>>>>>
>>>>>> Issue:
>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>
>>>>>> *Log:
>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>
>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>> <-- this is the usage_count
>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>> (0) has rpm_active flags
>>>>
>>>> Do you mean that rpm_active of the link between the consumer and the
>>>> supplier is greater than 0 at this point and the consumer is
>>>
>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>> active references to the supplier")?
>> Hi Rafael:
>> No - it is not greater than 1.
>>
>> I'm trying to understand what's going on in it; will update when I've something.
>>
>>>
>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>
>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>
>>>>>> And the the suspend of sde is stuck now:
>>>>>> schedule+0x9c/0xe0
>>>>>> schedule_timeout+0x40/0x128
>>>>>> io_schedule_timeout+0x44/0x68
>>>>>> wait_for_common_io+0x7c/0x100
>>>>>> wait_for_completion_io+0x14/0x20
>>>>>> blk_execute_rq+0x90/0xcc
>>>>>> __scsi_execute+0x104/0x1c4
>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>> sd_suspend_common+0x74/0x11c
>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>> __rpm_callback+0x80/0x2a4
>>>>>> rpm_suspend+0x308/0x614
>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>
>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>        if (hba->sdev_ufs_device) {
>>>>>>                link = device_link_add(&sdev->sdev_gendev,
>>>>>>                                    &hba->sdev_ufs_device->sdev_gendev,
>>>>>>                                   DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>
>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>> suspended when all the consumers are suspended.
>>>>>>
>>>>>> Any pointers on this issue please?
>>>>>>
>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>
>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>> even when one of its consumers is still active), you did not CC the
>>>>> power management maintainer or mailing list.
>>>>>
>>>>> I have added the appropriate CC's.
>>>>
>>>> Thanks Alan!
>>
>>
> 
> Hello
> I & Can (thanks CanG) debugged this further:
> 
> Looks like this issue can occur if the sd probe is asynchronous.
> 
> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
> 
> But scsi_probe_and_add_lun() runs in a separate context.
> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
> 
> So if:
> Context T1:
> [1] scsi_probe_and_add_lun()
> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
> 
> Context T2:
> __device_attach_async_helper()
>     |- driver_probe_device()
>         |- sd_probe()
> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
> Then sd_probe() would invoke rpm_resume() and proceed as is.
> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
> 
> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.

Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
consumers have link->rpm_active = 2 and also have incremented
the supplier's usage_count?

Another outstanding issue that comes to mind, is to ensure
hba->sdev_ufs_device does not runtime suspend before it is probed.
I suggest changing ufshcd_slave_configure() so it does not set
sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
ufshcd_wl_remove() respectively.

However we still want to stop hba->sdev_ufs_device runtime
suspending while consumers are being added.  With that in mind,
I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
in ufshcd_scsi_add_wlus() to come *before*
ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
be more logical to make it, pm_runtime_get_sync() since we require
hba->sdev_ufs_device to be active at that point.


> 
> Since the supplier has 0 auto-suspend delay, it now suspends!
> 
> 
> Context [T1]
> Call trace:
> dump_backtrace+0x0/0x1d4
> show_stack+0x18/0x24
> dump_stack+0xc4/0x144
> __pm_runtime_idle+0xb4/0x184
> scsi_autopm_put_device+0x18/0x24
> scsi_sysfs_add_sdev+0x26c/0x278
> scsi_probe_and_add_lun+0xbac/0xd48
> __scsi_scan_target+0x38c/0x510
> scsi_scan_host_selected+0x14c/0x1e4
> scsi_scan_host+0x1e0/0x228
> ufshcd_async_scan+0x39c/0x408
> async_run_entry_fn+0x48/0x128
> process_one_work+0x1f0/0x470
> worker_thread+0x26c/0x4c8
> kthread+0x13c/0x320
> ret_from_fork+0x10/0x18
> 
> 
> Context [T2]
> Call trace:
> dump_backtrace+0x0/0x1d4
> show_stack+0x18/0x24
> dump_stack+0xc4/0x144
> rpm_get_suppliers+0x48/0x1ac
> __rpm_callback+0x58/0x12c
> rpm_resume+0x3a4/0x618
> __pm_runtime_resume+0x50/0x80
> scsi_autopm_get_device+0x20/0x54
> sd_probe+0x40/0x3d0
> really_probe+0x1bc/0x4a0
> driver_probe_device+0x84/0xf0
> __device_attach_driver+0x114/0x138
> bus_for_each_drv+0x84/0xd0
> __device_attach_async_helper+0x7c/0xf0
> async_run_entry_fn+0x48/0x128
> process_one_work+0x1f0/0x470
> worker_thread+0x26c/0x4c8
> kthread+0x13c/0x320
> ret_from_fork+0x10/0x18
> 
> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
> [    7.574654][  T212] Call trace:
> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
> [    7.574661][  T212]  show_stack+0x18/0x24
> [    7.574665][  T212]  dump_stack+0xc4/0x144
> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
> [    7.574675][  T212]  sd_probe+0x314/0x3d0
> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
> [    7.574695][  T212]  process_one_work+0x1f0/0x470
> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
> [    7.574700][  T212]  kthread+0x13c/0x320
> [    7.574703][  T212]  ret_from_fork+0x10/0x18
> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> 
> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
> [    7.574754][  T212] Call trace:
> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
> [    7.574761][  T212]  show_stack+0x18/0x24
> [    7.574765][  T212]  dump_stack+0xc4/0x144
> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
> [    7.574783][  T212]  process_one_work+0x1f0/0x470
> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
> [    7.574788][  T212]  kthread+0x13c/0x320
> [    7.574791][  T212]  ret_from_fork+0x10/0x18
> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
> [    7.574866][  T212] sd 0:0:0:4: async probe completed
> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
> 
> 
> So, from the above it looks like when async probe is enabled this is a possibility.
> 
> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
> 
> Thanks,
> -asd
>
Asutosh Das March 15, 2021, 10:22 p.m. UTC | #13
On 3/14/2021 1:11 AM, Adrian Hunter wrote:
> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>
>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>
>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>
>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>> Scenario - bootups
>>>>>>>
>>>>>>> Issue:
>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>
>>>>>>> *Log:
>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>
>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>> <-- this is the usage_count
>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>> (0) has rpm_active flags
>>>>>
>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>> supplier is greater than 0 at this point and the consumer is
>>>>
>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>> active references to the supplier")?
>>> Hi Rafael:
>>> No - it is not greater than 1.
>>>
>>> I'm trying to understand what's going on in it; will update when I've something.
>>>
>>>>
>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>
>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>
>>>>>>> And the the suspend of sde is stuck now:
>>>>>>> schedule+0x9c/0xe0
>>>>>>> schedule_timeout+0x40/0x128
>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>> rpm_suspend+0x308/0x614
>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>
>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>         if (hba->sdev_ufs_device) {
>>>>>>>                 link = device_link_add(&sdev->sdev_gendev,
>>>>>>>                                     &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>                                    DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>
>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>> suspended when all the consumers are suspended.
>>>>>>>
>>>>>>> Any pointers on this issue please?
>>>>>>>
>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>
>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>> power management maintainer or mailing list.
>>>>>>
>>>>>> I have added the appropriate CC's.
>>>>>
>>>>> Thanks Alan!
>>>
>>>
>>
>> Hello
>> I & Can (thanks CanG) debugged this further:
>>
>> Looks like this issue can occur if the sd probe is asynchronous.
>>
>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>
>> But scsi_probe_and_add_lun() runs in a separate context.
>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>
>> So if:
>> Context T1:
>> [1] scsi_probe_and_add_lun()
>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>
>> Context T2:
>> __device_attach_async_helper()
>>      |- driver_probe_device()
>>          |- sd_probe()
>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>
>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
> 
> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
> consumers have link->rpm_active = 2 and also have incremented
> the supplier's usage_count?
> 
> Another outstanding issue that comes to mind, is to ensure
> hba->sdev_ufs_device does not runtime suspend before it is probed.
> I suggest changing ufshcd_slave_configure() so it does not set
> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
> ufshcd_wl_remove() respectively.
> 
> However we still want to stop hba->sdev_ufs_device runtime
> suspending while consumers are being added.  With that in mind,
> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
> in ufshcd_scsi_add_wlus() to come *before*
> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
> be more logical to make it, pm_runtime_get_sync() since we require
> hba->sdev_ufs_device to be active at that point.
> 
> 

Hi Adrian,
I think the v11 that I pushed can handle this.
runtime-suspend is forbidden at probe and is re-enabled after probe is 
done. Please take a look and let me know if I'm missing something.

>>
>> Since the supplier has 0 auto-suspend delay, it now suspends!
>>
>>
>> Context [T1]
>> Call trace:
>> dump_backtrace+0x0/0x1d4
>> show_stack+0x18/0x24
>> dump_stack+0xc4/0x144
>> __pm_runtime_idle+0xb4/0x184
>> scsi_autopm_put_device+0x18/0x24
>> scsi_sysfs_add_sdev+0x26c/0x278
>> scsi_probe_and_add_lun+0xbac/0xd48
>> __scsi_scan_target+0x38c/0x510
>> scsi_scan_host_selected+0x14c/0x1e4
>> scsi_scan_host+0x1e0/0x228
>> ufshcd_async_scan+0x39c/0x408
>> async_run_entry_fn+0x48/0x128
>> process_one_work+0x1f0/0x470
>> worker_thread+0x26c/0x4c8
>> kthread+0x13c/0x320
>> ret_from_fork+0x10/0x18
>>
>>
>> Context [T2]
>> Call trace:
>> dump_backtrace+0x0/0x1d4
>> show_stack+0x18/0x24
>> dump_stack+0xc4/0x144
>> rpm_get_suppliers+0x48/0x1ac
>> __rpm_callback+0x58/0x12c
>> rpm_resume+0x3a4/0x618
>> __pm_runtime_resume+0x50/0x80
>> scsi_autopm_get_device+0x20/0x54
>> sd_probe+0x40/0x3d0
>> really_probe+0x1bc/0x4a0
>> driver_probe_device+0x84/0xf0
>> __device_attach_driver+0x114/0x138
>> bus_for_each_drv+0x84/0xd0
>> __device_attach_async_helper+0x7c/0xf0
>> async_run_entry_fn+0x48/0x128
>> process_one_work+0x1f0/0x470
>> worker_thread+0x26c/0x4c8
>> kthread+0x13c/0x320
>> ret_from_fork+0x10/0x18
>>
>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
>> [    7.574654][  T212] Call trace:
>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
>> [    7.574661][  T212]  show_stack+0x18/0x24
>> [    7.574665][  T212]  dump_stack+0xc4/0x144
>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
>> [    7.574700][  T212]  kthread+0x13c/0x320
>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>
>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
>> [    7.574754][  T212] Call trace:
>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
>> [    7.574761][  T212]  show_stack+0x18/0x24
>> [    7.574765][  T212]  dump_stack+0xc4/0x144
>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
>> [    7.574788][  T212]  kthread+0x13c/0x320
>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
>>
>>
>> So, from the above it looks like when async probe is enabled this is a possibility.
>>
>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
>>
>> Thanks,
>> -asd
>>
>
Adrian Hunter March 16, 2021, 7:48 a.m. UTC | #14
On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>
>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>
>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>
>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>> Scenario - bootups
>>>>>>>>
>>>>>>>> Issue:
>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>
>>>>>>>> *Log:
>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>
>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>> <-- this is the usage_count
>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>> (0) has rpm_active flags
>>>>>>
>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>
>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>> active references to the supplier")?
>>>> Hi Rafael:
>>>> No - it is not greater than 1.
>>>>
>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>
>>>>>
>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>
>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>
>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>> schedule+0x9c/0xe0
>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>
>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>         if (hba->sdev_ufs_device) {
>>>>>>>>                 link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>                                     &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>                                    DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>
>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>
>>>>>>>> Any pointers on this issue please?
>>>>>>>>
>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>
>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>> power management maintainer or mailing list.
>>>>>>>
>>>>>>> I have added the appropriate CC's.
>>>>>>
>>>>>> Thanks Alan!
>>>>
>>>>
>>>
>>> Hello
>>> I & Can (thanks CanG) debugged this further:
>>>
>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>
>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>
>>> But scsi_probe_and_add_lun() runs in a separate context.
>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>
>>> So if:
>>> Context T1:
>>> [1] scsi_probe_and_add_lun()
>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>
>>> Context T2:
>>> __device_attach_async_helper()
>>>      |- driver_probe_device()
>>>          |- sd_probe()
>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>
>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>
>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>> consumers have link->rpm_active = 2 and also have incremented
>> the supplier's usage_count?
>>
>> Another outstanding issue that comes to mind, is to ensure
>> hba->sdev_ufs_device does not runtime suspend before it is probed.
>> I suggest changing ufshcd_slave_configure() so it does not set
>> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
>> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
>> ufshcd_wl_remove() respectively.
>>
>> However we still want to stop hba->sdev_ufs_device runtime
>> suspending while consumers are being added.  With that in mind,
>> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
>> in ufshcd_scsi_add_wlus() to come *before*
>> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
>> be more logical to make it, pm_runtime_get_sync() since we require
>> hba->sdev_ufs_device to be active at that point.
>>
>>
> 
> Hi Adrian,
> I think the v11 that I pushed can handle this.
> runtime-suspend is forbidden at probe and is re-enabled after probe is done. Please take a look and let me know if I'm missing something.

If the PM APIs are being used correctly, the usage and active
counts should never be wrong.  If they were, then that would
be an issue for the PM framework.

However, it is hard to tell what the issues are until all the
UFS driver changes have been completed, such as the ones I
suggested above above.

v11 could be hiding issues rather than fixing them.

> 
>>>
>>> Since the supplier has 0 auto-suspend delay, it now suspends!
>>>
>>>
>>> Context [T1]
>>> Call trace:
>>> dump_backtrace+0x0/0x1d4
>>> show_stack+0x18/0x24
>>> dump_stack+0xc4/0x144
>>> __pm_runtime_idle+0xb4/0x184
>>> scsi_autopm_put_device+0x18/0x24
>>> scsi_sysfs_add_sdev+0x26c/0x278
>>> scsi_probe_and_add_lun+0xbac/0xd48
>>> __scsi_scan_target+0x38c/0x510
>>> scsi_scan_host_selected+0x14c/0x1e4
>>> scsi_scan_host+0x1e0/0x228
>>> ufshcd_async_scan+0x39c/0x408
>>> async_run_entry_fn+0x48/0x128
>>> process_one_work+0x1f0/0x470
>>> worker_thread+0x26c/0x4c8
>>> kthread+0x13c/0x320
>>> ret_from_fork+0x10/0x18
>>>
>>>
>>> Context [T2]
>>> Call trace:
>>> dump_backtrace+0x0/0x1d4
>>> show_stack+0x18/0x24
>>> dump_stack+0xc4/0x144
>>> rpm_get_suppliers+0x48/0x1ac
>>> __rpm_callback+0x58/0x12c
>>> rpm_resume+0x3a4/0x618
>>> __pm_runtime_resume+0x50/0x80
>>> scsi_autopm_get_device+0x20/0x54
>>> sd_probe+0x40/0x3d0
>>> really_probe+0x1bc/0x4a0
>>> driver_probe_device+0x84/0xf0
>>> __device_attach_driver+0x114/0x138
>>> bus_for_each_drv+0x84/0xd0
>>> __device_attach_async_helper+0x7c/0xf0
>>> async_run_entry_fn+0x48/0x128
>>> process_one_work+0x1f0/0x470
>>> worker_thread+0x26c/0x4c8
>>> kthread+0x13c/0x320
>>> ret_from_fork+0x10/0x18
>>>
>>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
>>> [    7.574654][  T212] Call trace:
>>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
>>> [    7.574661][  T212]  show_stack+0x18/0x24
>>> [    7.574665][  T212]  dump_stack+0xc4/0x144
>>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
>>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
>>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
>>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
>>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
>>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
>>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
>>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
>>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
>>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
>>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
>>> [    7.574700][  T212]  kthread+0x13c/0x320
>>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
>>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
>>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
>>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>
>>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
>>> [    7.574754][  T212] Call trace:
>>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
>>> [    7.574761][  T212]  show_stack+0x18/0x24
>>> [    7.574765][  T212]  dump_stack+0xc4/0x144
>>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
>>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
>>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
>>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
>>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
>>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
>>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
>>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
>>> [    7.574788][  T212]  kthread+0x13c/0x320
>>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
>>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
>>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
>>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
>>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
>>>
>>>
>>> So, from the above it looks like when async probe is enabled this is a possibility.
>>>
>>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
>>>
>>> Thanks,
>>> -asd
>>>
>>
> 
>
Asutosh Das March 16, 2021, 8:35 p.m. UTC | #15
On 3/16/2021 12:48 AM, Adrian Hunter wrote:
> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>
>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>
>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>
>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>> Scenario - bootups
>>>>>>>>>
>>>>>>>>> Issue:
>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>
>>>>>>>>> *Log:
>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>
>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>> <-- this is the usage_count
>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>> (0) has rpm_active flags
>>>>>>>
>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>
>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>> active references to the supplier")?
>>>>> Hi Rafael:
>>>>> No - it is not greater than 1.
>>>>>
>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>
>>>>>>
>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>
>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>
>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>
>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>          if (hba->sdev_ufs_device) {
>>>>>>>>>                  link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>                                      &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>                                     DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>
>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>
>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>
>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>
>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>> power management maintainer or mailing list.
>>>>>>>>
>>>>>>>> I have added the appropriate CC's.
>>>>>>>
>>>>>>> Thanks Alan!
>>>>>
>>>>>
>>>>
>>>> Hello
>>>> I & Can (thanks CanG) debugged this further:
>>>>
>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>
>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>
>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>
>>>> So if:
>>>> Context T1:
>>>> [1] scsi_probe_and_add_lun()
>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>
>>>> Context T2:
>>>> __device_attach_async_helper()
>>>>       |- driver_probe_device()
>>>>           |- sd_probe()
>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>
>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>
>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>> consumers have link->rpm_active = 2 and also have incremented
>>> the supplier's usage_count?

Yes this is with DL_FLAG_RPM_ACTIVE.

Please let me share a log here:
BEF means - Before, AFT means After.

[    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779: 
  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
[    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: 
(0:0:0:49488): supp: usage_count: 5 rpm_active: 4

In the above log, T7 is the context in which this scsi device is being 
added - scsi_sysfs_add_sdev()

[    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: 
ufshcd_rpmb_probe:9692: invoked
[    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4

[    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: 
(0:0:0:49488) [BEF] usage_count: 5
[    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: 
(0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3

[    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp 
(0:0:0:49488) usage_count: 4 rpm_active: 3

------ T196 Context comes in while T7 is running ----------
[    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: 
(0:0:0:49488): supp: usage_count: 5 rpm_active: 4
--------------------------------------------------------------

[    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp 
(0:0:0:49488) usage_count: 2 rpm_active: 1
Adrian Hunter March 17, 2021, 6:37 a.m. UTC | #16
On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>>
>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>>
>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>>
>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>>> Scenario - bootups
>>>>>>>>>>
>>>>>>>>>> Issue:
>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>>
>>>>>>>>>> *Log:
>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>>
>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>>> <-- this is the usage_count
>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>>> (0) has rpm_active flags
>>>>>>>>
>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>>
>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>>> active references to the supplier")?
>>>>>> Hi Rafael:
>>>>>> No - it is not greater than 1.
>>>>>>
>>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>>
>>>>>>>
>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>>
>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>>
>>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>>
>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>>          if (hba->sdev_ufs_device) {
>>>>>>>>>>                  link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>>                                      &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>>                                     DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>>
>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>>
>>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>>
>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>>
>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>>> power management maintainer or mailing list.
>>>>>>>>>
>>>>>>>>> I have added the appropriate CC's.
>>>>>>>>
>>>>>>>> Thanks Alan!
>>>>>>
>>>>>>
>>>>>
>>>>> Hello
>>>>> I & Can (thanks CanG) debugged this further:
>>>>>
>>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>>
>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>>
>>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>>
>>>>> So if:
>>>>> Context T1:
>>>>> [1] scsi_probe_and_add_lun()
>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>>
>>>>> Context T2:
>>>>> __device_attach_async_helper()
>>>>>       |- driver_probe_device()
>>>>>           |- sd_probe()
>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>>
>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>>
>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>>> consumers have link->rpm_active = 2 and also have incremented
>>>> the supplier's usage_count?
> 
> Yes this is with DL_FLAG_RPM_ACTIVE.
> 
> Please let me share a log here:
> BEF means - Before, AFT means After.
> 
> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> 
> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
> 
> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
> 
> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
> 
> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
> 
> ------ T196 Context comes in while T7 is running ----------
> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> --------------------------------------------------------------
> 
> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1



> 
> -- 
> 
> T196 is the context in which sd_probe() is invoked for this scsi device.
> 
> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
> 
> The reference to the link is released after sd_probe() is completed.
> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
> 
> In this log, the usage_count of supplier becomes 0 here:
> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
> 
> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:

If that is the case, then it is an error in PM not UFS.

A second look at the code around rpm_put_suppliers() does look
potentially racy, since there does not appear to be anything
stopping the runtime_status changing between
spin_unlock_irq(&dev->power.lock) and device_links_read_lock().

Rafael, can you comment?

	/*
	 * If the device is suspending and the callback has returned success,
	 * drop the usage counters of the suppliers that have been reference
	 * counted on its resume.
	 *
	 * Do that if the resume fails too.
	 */
	put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
	if (put)
		__update_runtime_status(dev, RPM_SUSPENDED);
	else
		put = get && retval;

	if (put) {
		spin_unlock_irq(&dev->power.lock);

		idx = device_links_read_lock();

fail:
		rpm_put_suppliers(dev);

		device_links_read_unlock(idx);

		spin_lock_irq(&dev->power.lock);
	}




> [   12.002792][  T117] scsi 0:0:0:49456: rpm_status - 2
> [   12.002806][  T117] sd 0:0:0:0: rpm_status - 2
> [   12.002834][  T117] sd 0:0:0:1: rpm_status - 2
> [   12.017730][  T117] sd 0:0:0:2: rpm_status - 2
> [   12.041317][  T117] sd 0:0:0:3: rpm_status - 2
> [   12.045953][  T117] sd 0:0:0:4: rpm_status - 0
> 
> And sd 0:0:0:4 tries to suspend here:
> [   15.465914][  T117] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> 
>>>>
>>>> Another outstanding issue that comes to mind, is to ensure
>>>> hba->sdev_ufs_device does not runtime suspend before it is probed.
>>>> I suggest changing ufshcd_slave_configure() so it does not set
>>>> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
>>>> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
>>>> ufshcd_wl_remove() respectively.
>>>>
> If pm_runtime_allow() is invoked from ufshcd_wl_probe() it'd invoke runtime_suspend on hba->sdev_ufs_device before exiting scsi_sysfs_add_sdev(). So I think pm_runtime_allow() should be invoked in ufshcd_scsi_add_wlus().
> 
>>>> However we still want to stop hba->sdev_ufs_device runtime
>>>> suspending while consumers are being added.  With that in mind,
>>>> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
>>>> in ufshcd_scsi_add_wlus() to come *before*
>>>> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
>>>> be more logical to make it, pm_runtime_get_sync() since we require
>>>> hba->sdev_ufs_device to be active at that point.
>>>>
> Correct, scsi_autopm_get_device(hba->sdev_ufs_device) should be invoked before ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).
> Now a corresponding scsi_autopm_put_device(hba->sdev_ufs_device) is invoked after the consumers are added in ufshcd_setup_links().
> Even then I think this issue would still pop up.
> 
>>>>
>>>
>>> Hi Adrian,
>>> I think the v11 that I pushed can handle this.
>>> runtime-suspend is forbidden at probe and is re-enabled after probe is done. Please take a look and let me know if I'm missing something.
>>
>> If the PM APIs are being used correctly, the usage and active
>> counts should never be wrong.  If they were, then that would
>> be an issue for the PM framework.
>> It is more likely that I'm using it incorrectly :).
> 
>> However, it is hard to tell what the issues are until all the
>> UFS driver changes have been completed, such as the ones I
>> suggested above above.
>>
> Ok, understood.
> 
>> v11 could be hiding issues rather than fixing them.
>>
> Based on the logs, in v11, I tried to forbid any runtime-suspend until sd_probe() is done.
> I could be misunderstanding the whole thing though.
> 
> Having said that, I will make the changes as per your suggestions and push a v12. I will test with v12 as well and see if this issue is seen.
> 
>>>
>>>>>
>>>>> Since the supplier has 0 auto-suspend delay, it now suspends!
>>>>>
>>>>>
>>>>> Context [T1]
>>>>> Call trace:
>>>>> dump_backtrace+0x0/0x1d4
>>>>> show_stack+0x18/0x24
>>>>> dump_stack+0xc4/0x144
>>>>> __pm_runtime_idle+0xb4/0x184
>>>>> scsi_autopm_put_device+0x18/0x24
>>>>> scsi_sysfs_add_sdev+0x26c/0x278
>>>>> scsi_probe_and_add_lun+0xbac/0xd48
>>>>> __scsi_scan_target+0x38c/0x510
>>>>> scsi_scan_host_selected+0x14c/0x1e4
>>>>> scsi_scan_host+0x1e0/0x228
>>>>> ufshcd_async_scan+0x39c/0x408
>>>>> async_run_entry_fn+0x48/0x128
>>>>> process_one_work+0x1f0/0x470
>>>>> worker_thread+0x26c/0x4c8
>>>>> kthread+0x13c/0x320
>>>>> ret_from_fork+0x10/0x18
>>>>>
>>>>>
>>>>> Context [T2]
>>>>> Call trace:
>>>>> dump_backtrace+0x0/0x1d4
>>>>> show_stack+0x18/0x24
>>>>> dump_stack+0xc4/0x144
>>>>> rpm_get_suppliers+0x48/0x1ac
>>>>> __rpm_callback+0x58/0x12c
>>>>> rpm_resume+0x3a4/0x618
>>>>> __pm_runtime_resume+0x50/0x80
>>>>> scsi_autopm_get_device+0x20/0x54
>>>>> sd_probe+0x40/0x3d0
>>>>> really_probe+0x1bc/0x4a0
>>>>> driver_probe_device+0x84/0xf0
>>>>> __device_attach_driver+0x114/0x138
>>>>> bus_for_each_drv+0x84/0xd0
>>>>> __device_attach_async_helper+0x7c/0xf0
>>>>> async_run_entry_fn+0x48/0x128
>>>>> process_one_work+0x1f0/0x470
>>>>> worker_thread+0x26c/0x4c8
>>>>> kthread+0x13c/0x320
>>>>> ret_from_fork+0x10/0x18
>>>>>
>>>>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
>>>>> [    7.574654][  T212] Call trace:
>>>>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
>>>>> [    7.574661][  T212]  show_stack+0x18/0x24
>>>>> [    7.574665][  T212]  dump_stack+0xc4/0x144
>>>>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
>>>>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
>>>>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
>>>>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
>>>>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
>>>>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
>>>>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
>>>>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
>>>>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
>>>>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
>>>>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
>>>>> [    7.574700][  T212]  kthread+0x13c/0x320
>>>>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
>>>>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
>>>>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
>>>>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>>
>>>>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
>>>>> [    7.574754][  T212] Call trace:
>>>>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
>>>>> [    7.574761][  T212]  show_stack+0x18/0x24
>>>>> [    7.574765][  T212]  dump_stack+0xc4/0x144
>>>>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
>>>>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
>>>>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
>>>>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
>>>>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
>>>>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
>>>>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
>>>>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
>>>>> [    7.574788][  T212]  kthread+0x13c/0x320
>>>>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
>>>>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
>>>>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
>>>>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
>>>>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
>>>>>
>>>>>
>>>>> So, from the above it looks like when async probe is enabled this is a possibility.
>>>>>
>>>>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
>>>>>
>>>>> Thanks,
>>>>> -asd
>>>>>
>>>>
>>>
>>>
>>
> 
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> Linux Foundation Collaborative Project
Rafael J. Wysocki March 18, 2021, 2 p.m. UTC | #17
On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
> > On 3/16/2021 12:48 AM, Adrian Hunter wrote:
> >> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
> >>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
> >>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
> >>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
> >>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
> >>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >>>>>>>>
> >>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> >>>>>>>>>
> >>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
> >>>>>>>>>
> >>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
> >>>>>>>>>> Scenario - bootups
> >>>>>>>>>>
> >>>>>>>>>> Issue:
> >>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> >>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
> >>>>>>>>>>
> >>>>>>>>>> *Log:
> >>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> >>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> >>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> >>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> >>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> >>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> >>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> >>>>>>>>>>
> >>>>>>>>>> /** Printing all the consumer nodes of supplier **/
> >>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> >>>>>>>>>> <-- this is the usage_count
> >>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> >>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> >>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> >>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> >>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> >>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> >>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> >>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> >>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> >>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> >>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> >>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> >>>>>>>>>> (0) has rpm_active flags
> >>>>>>>>
> >>>>>>>> Do you mean that rpm_active of the link between the consumer and the
> >>>>>>>> supplier is greater than 0 at this point and the consumer is
> >>>>>>>
> >>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
> >>>>>>> active references to the supplier")?
> >>>>>> Hi Rafael:
> >>>>>> No - it is not greater than 1.
> >>>>>>
> >>>>>> I'm trying to understand what's going on in it; will update when I've something.
> >>>>>>
> >>>>>>>
> >>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
> >>>>>>>>
> >>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> >>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> >>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >>>>>>>>>>
> >>>>>>>>>> And the the suspend of sde is stuck now:
> >>>>>>>>>> schedule+0x9c/0xe0
> >>>>>>>>>> schedule_timeout+0x40/0x128
> >>>>>>>>>> io_schedule_timeout+0x44/0x68
> >>>>>>>>>> wait_for_common_io+0x7c/0x100
> >>>>>>>>>> wait_for_completion_io+0x14/0x20
> >>>>>>>>>> blk_execute_rq+0x90/0xcc
> >>>>>>>>>> __scsi_execute+0x104/0x1c4
> >>>>>>>>>> sd_sync_cache+0xf8/0x2a0
> >>>>>>>>>> sd_suspend_common+0x74/0x11c
> >>>>>>>>>> sd_suspend_runtime+0x14/0x20
> >>>>>>>>>> scsi_runtime_suspend+0x64/0x94
> >>>>>>>>>> __rpm_callback+0x80/0x2a4
> >>>>>>>>>> rpm_suspend+0x308/0x614
> >>>>>>>>>> pm_runtime_work+0x98/0xa8
> >>>>>>>>>>
> >>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> >>>>>>>>>>          if (hba->sdev_ufs_device) {
> >>>>>>>>>>                  link = device_link_add(&sdev->sdev_gendev,
> >>>>>>>>>>                                      &hba->sdev_ufs_device->sdev_gendev,
> >>>>>>>>>>                                     DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> >>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
> >>>>>>>>>>
> >>>>>>>>>> Another interesting point here is when I resume any of the above suspended
> >>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
> >>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
> >>>>>>>>>> suspended when all the consumers are suspended.
> >>>>>>>>>>
> >>>>>>>>>> Any pointers on this issue please?
> >>>>>>>>>>
> >>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
> >>>>>>>>>
> >>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
> >>>>>>>>> the power management subsystem (supplier goes into runtime suspend
> >>>>>>>>> even when one of its consumers is still active), you did not CC the
> >>>>>>>>> power management maintainer or mailing list.
> >>>>>>>>>
> >>>>>>>>> I have added the appropriate CC's.
> >>>>>>>>
> >>>>>>>> Thanks Alan!
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> Hello
> >>>>> I & Can (thanks CanG) debugged this further:
> >>>>>
> >>>>> Looks like this issue can occur if the sd probe is asynchronous.
> >>>>>
> >>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
> >>>>>
> >>>>> But scsi_probe_and_add_lun() runs in a separate context.
> >>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
> >>>>>
> >>>>> So if:
> >>>>> Context T1:
> >>>>> [1] scsi_probe_and_add_lun()
> >>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
> >>>>>
> >>>>> Context T2:
> >>>>> __device_attach_async_helper()
> >>>>>       |- driver_probe_device()
> >>>>>           |- sd_probe()
> >>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
> >>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
> >>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
> >>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
> >>>>>
> >>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
> >>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
> >>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
> >>>>
> >>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
> >>>> consumers have link->rpm_active = 2 and also have incremented
> >>>> the supplier's usage_count?
> >
> > Yes this is with DL_FLAG_RPM_ACTIVE.
> >
> > Please let me share a log here:
> > BEF means - Before, AFT means After.
> >
> > [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
> > [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> >
> > In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
> >
> > [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
> > [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
> >
> > [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
> > [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
> >
> > [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
> >
> > ------ T196 Context comes in while T7 is running ----------
> > [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> > --------------------------------------------------------------
> >
> > [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>
>
>
> >
> > --
> >
> > T196 is the context in which sd_probe() is invoked for this scsi device.
> >
> > [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
> > [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
> > [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
> > [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
> >
> > The reference to the link is released after sd_probe() is completed.
> > At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
> >
> > In this log, the usage_count of supplier becomes 0 here:
> > [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
> > [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
> >
> > However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>
> If that is the case, then it is an error in PM not UFS.
>
> A second look at the code around rpm_put_suppliers() does look
> potentially racy, since there does not appear to be anything
> stopping the runtime_status changing between
> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>
> Rafael, can you comment?

Indeed, if the device is suspending, changing its PM-runtime status to
RPM_SUSPENDED and dropping its power.lock allows a concurrent
rpm_resume() to run and resume the device before the suppliers can be
suspended.

That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
runtime: Update device status before letting suppliers suspend").

It is probably better to revert that commit and address the original
issue in a different way.

>         /*
>          * If the device is suspending and the callback has returned success,
>          * drop the usage counters of the suppliers that have been reference
>          * counted on its resume.
>          *
>          * Do that if the resume fails too.
>          */
>         put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
>         if (put)
>                 __update_runtime_status(dev, RPM_SUSPENDED);
>         else
>                 put = get && retval;
>
>         if (put) {
>                 spin_unlock_irq(&dev->power.lock);
>
>                 idx = device_links_read_lock();
>
> fail:
>                 rpm_put_suppliers(dev);
>
>                 device_links_read_unlock(idx);
>
>                 spin_lock_irq(&dev->power.lock);
>         }
>
>
>
>
> > [   12.002792][  T117] scsi 0:0:0:49456: rpm_status - 2
> > [   12.002806][  T117] sd 0:0:0:0: rpm_status - 2
> > [   12.002834][  T117] sd 0:0:0:1: rpm_status - 2
> > [   12.017730][  T117] sd 0:0:0:2: rpm_status - 2
> > [   12.041317][  T117] sd 0:0:0:3: rpm_status - 2
> > [   12.045953][  T117] sd 0:0:0:4: rpm_status - 0
> >
> > And sd 0:0:0:4 tries to suspend here:
> > [   15.465914][  T117] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >
> >>>>
> >>>> Another outstanding issue that comes to mind, is to ensure
> >>>> hba->sdev_ufs_device does not runtime suspend before it is probed.
> >>>> I suggest changing ufshcd_slave_configure() so it does not set
> >>>> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
> >>>> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
> >>>> ufshcd_wl_remove() respectively.
> >>>>
> > If pm_runtime_allow() is invoked from ufshcd_wl_probe() it'd invoke runtime_suspend on hba->sdev_ufs_device before exiting scsi_sysfs_add_sdev(). So I think pm_runtime_allow() should be invoked in ufshcd_scsi_add_wlus().
> >
> >>>> However we still want to stop hba->sdev_ufs_device runtime
> >>>> suspending while consumers are being added.  With that in mind,
> >>>> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
> >>>> in ufshcd_scsi_add_wlus() to come *before*
> >>>> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
> >>>> be more logical to make it, pm_runtime_get_sync() since we require
> >>>> hba->sdev_ufs_device to be active at that point.
> >>>>
> > Correct, scsi_autopm_get_device(hba->sdev_ufs_device) should be invoked before ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).
> > Now a corresponding scsi_autopm_put_device(hba->sdev_ufs_device) is invoked after the consumers are added in ufshcd_setup_links().
> > Even then I think this issue would still pop up.
> >
> >>>>
> >>>
> >>> Hi Adrian,
> >>> I think the v11 that I pushed can handle this.
> >>> runtime-suspend is forbidden at probe and is re-enabled after probe is done. Please take a look and let me know if I'm missing something.
> >>
> >> If the PM APIs are being used correctly, the usage and active
> >> counts should never be wrong.  If they were, then that would
> >> be an issue for the PM framework.
> >> It is more likely that I'm using it incorrectly :).
> >
> >> However, it is hard to tell what the issues are until all the
> >> UFS driver changes have been completed, such as the ones I
> >> suggested above above.
> >>
> > Ok, understood.
> >
> >> v11 could be hiding issues rather than fixing them.
> >>
> > Based on the logs, in v11, I tried to forbid any runtime-suspend until sd_probe() is done.
> > I could be misunderstanding the whole thing though.
> >
> > Having said that, I will make the changes as per your suggestions and push a v12. I will test with v12 as well and see if this issue is seen.
> >
> >>>
> >>>>>
> >>>>> Since the supplier has 0 auto-suspend delay, it now suspends!
> >>>>>
> >>>>>
> >>>>> Context [T1]
> >>>>> Call trace:
> >>>>> dump_backtrace+0x0/0x1d4
> >>>>> show_stack+0x18/0x24
> >>>>> dump_stack+0xc4/0x144
> >>>>> __pm_runtime_idle+0xb4/0x184
> >>>>> scsi_autopm_put_device+0x18/0x24
> >>>>> scsi_sysfs_add_sdev+0x26c/0x278
> >>>>> scsi_probe_and_add_lun+0xbac/0xd48
> >>>>> __scsi_scan_target+0x38c/0x510
> >>>>> scsi_scan_host_selected+0x14c/0x1e4
> >>>>> scsi_scan_host+0x1e0/0x228
> >>>>> ufshcd_async_scan+0x39c/0x408
> >>>>> async_run_entry_fn+0x48/0x128
> >>>>> process_one_work+0x1f0/0x470
> >>>>> worker_thread+0x26c/0x4c8
> >>>>> kthread+0x13c/0x320
> >>>>> ret_from_fork+0x10/0x18
> >>>>>
> >>>>>
> >>>>> Context [T2]
> >>>>> Call trace:
> >>>>> dump_backtrace+0x0/0x1d4
> >>>>> show_stack+0x18/0x24
> >>>>> dump_stack+0xc4/0x144
> >>>>> rpm_get_suppliers+0x48/0x1ac
> >>>>> __rpm_callback+0x58/0x12c
> >>>>> rpm_resume+0x3a4/0x618
> >>>>> __pm_runtime_resume+0x50/0x80
> >>>>> scsi_autopm_get_device+0x20/0x54
> >>>>> sd_probe+0x40/0x3d0
> >>>>> really_probe+0x1bc/0x4a0
> >>>>> driver_probe_device+0x84/0xf0
> >>>>> __device_attach_driver+0x114/0x138
> >>>>> bus_for_each_drv+0x84/0xd0
> >>>>> __device_attach_async_helper+0x7c/0xf0
> >>>>> async_run_entry_fn+0x48/0x128
> >>>>> process_one_work+0x1f0/0x470
> >>>>> worker_thread+0x26c/0x4c8
> >>>>> kthread+0x13c/0x320
> >>>>> ret_from_fork+0x10/0x18
> >>>>>
> >>>>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
> >>>>> [    7.574654][  T212] Call trace:
> >>>>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
> >>>>> [    7.574661][  T212]  show_stack+0x18/0x24
> >>>>> [    7.574665][  T212]  dump_stack+0xc4/0x144
> >>>>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
> >>>>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
> >>>>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
> >>>>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
> >>>>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
> >>>>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
> >>>>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
> >>>>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
> >>>>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
> >>>>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
> >>>>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
> >>>>> [    7.574700][  T212]  kthread+0x13c/0x320
> >>>>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
> >>>>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
> >>>>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
> >>>>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>>
> >>>>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
> >>>>> [    7.574754][  T212] Call trace:
> >>>>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
> >>>>> [    7.574761][  T212]  show_stack+0x18/0x24
> >>>>> [    7.574765][  T212]  dump_stack+0xc4/0x144
> >>>>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
> >>>>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
> >>>>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
> >>>>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
> >>>>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
> >>>>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
> >>>>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
> >>>>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
> >>>>> [    7.574788][  T212]  kthread+0x13c/0x320
> >>>>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
> >>>>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
> >>>>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
> >>>>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
> >>>>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
> >>>>>
> >>>>>
> >>>>> So, from the above it looks like when async probe is enabled this is a possibility.
> >>>>>
> >>>>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
> >>>>>
> >>>>> Thanks,
> >>>>> -asd
> >>>>>
> >>>>
> >>>
> >>>
> >>
> >
> >
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > Linux Foundation Collaborative Project
>
Asutosh Das March 18, 2021, 5:27 p.m. UTC | #18
On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
> On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
>>> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
>>>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>>>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>>>>
>>>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>>>>
>>>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>>>>> Scenario - bootups
>>>>>>>>>>>>
>>>>>>>>>>>> Issue:
>>>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>>>>
>>>>>>>>>>>> *Log:
>>>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>>>>
>>>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>>>>> <-- this is the usage_count
>>>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>>>>> (0) has rpm_active flags
>>>>>>>>>>
>>>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>>>>
>>>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>>>>> active references to the supplier")?
>>>>>>>> Hi Rafael:
>>>>>>>> No - it is not greater than 1.
>>>>>>>>
>>>>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>>>>
>>>>>>>>>
>>>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>>>>
>>>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>>>>
>>>>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>>>>
>>>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>>>>           if (hba->sdev_ufs_device) {
>>>>>>>>>>>>                   link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>>>>                                       &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>>>>                                      DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>>>>
>>>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>>>>
>>>>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>>>>
>>>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>>>>
>>>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>>>>> power management maintainer or mailing list.
>>>>>>>>>>>
>>>>>>>>>>> I have added the appropriate CC's.
>>>>>>>>>>
>>>>>>>>>> Thanks Alan!
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> Hello
>>>>>>> I & Can (thanks CanG) debugged this further:
>>>>>>>
>>>>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>>>>
>>>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>>>>
>>>>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>>>>
>>>>>>> So if:
>>>>>>> Context T1:
>>>>>>> [1] scsi_probe_and_add_lun()
>>>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>>>>
>>>>>>> Context T2:
>>>>>>> __device_attach_async_helper()
>>>>>>>        |- driver_probe_device()
>>>>>>>            |- sd_probe()
>>>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>>>>
>>>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>>>>
>>>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>>>>> consumers have link->rpm_active = 2 and also have incremented
>>>>>> the supplier's usage_count?
>>>
>>> Yes this is with DL_FLAG_RPM_ACTIVE.
>>>
>>> Please let me share a log here:
>>> BEF means - Before, AFT means After.
>>>
>>> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
>>> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>
>>> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
>>>
>>> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
>>>
>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
>>> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
>>>
>>> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
>>>
>>> ------ T196 Context comes in while T7 is running ----------
>>> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>> --------------------------------------------------------------
>>>
>>> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>>
>>
>>
>>>
>>> --
>>>
>>> T196 is the context in which sd_probe() is invoked for this scsi device.
>>>
>>> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
>>> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
>>> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
>>> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
>>>
>>> The reference to the link is released after sd_probe() is completed.
>>> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
>>>
>>> In this log, the usage_count of supplier becomes 0 here:
>>> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
>>> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
>>>
>>> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>>
>> If that is the case, then it is an error in PM not UFS.
>>
>> A second look at the code around rpm_put_suppliers() does look
>> potentially racy, since there does not appear to be anything
>> stopping the runtime_status changing between
>> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>>
>> Rafael, can you comment?
> 
> Indeed, if the device is suspending, changing its PM-runtime status to
> RPM_SUSPENDED and dropping its power.lock allows a concurrent
> rpm_resume() to run and resume the device before the suppliers can be
> suspended.
> 
> That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
> runtime: Update device status before letting suppliers suspend").
> 
> It is probably better to revert that commit and address the original
> issue in a different way.
> 
Hello,
One approach to address the original issue could be to prevent the scsi 
devices from suspending until the probe is completed, perhaps?

Please let me know if there's a better way to handle this.
Else I'd address all other comments from Adrian and push a change with 
the above approach.

>>          /*
>>           * If the device is suspending and the callback has returned success,
>>           * drop the usage counters of the suppliers that have been reference
>>           * counted on its resume.
>>           *
>>           * Do that if the resume fails too.
>>           */
>>          put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
>>          if (put)
>>                  __update_runtime_status(dev, RPM_SUSPENDED);
>>          else
>>                  put = get && retval;
>>
>>          if (put) {
>>                  spin_unlock_irq(&dev->power.lock);
>>
>>                  idx = device_links_read_lock();
>>
>> fail:
>>                  rpm_put_suppliers(dev);
>>
>>                  device_links_read_unlock(idx);
>>
>>                  spin_lock_irq(&dev->power.lock);
>>          }
>>
>>
>>
>>
>>> [   12.002792][  T117] scsi 0:0:0:49456: rpm_status - 2
>>> [   12.002806][  T117] sd 0:0:0:0: rpm_status - 2
>>> [   12.002834][  T117] sd 0:0:0:1: rpm_status - 2
>>> [   12.017730][  T117] sd 0:0:0:2: rpm_status - 2
>>> [   12.041317][  T117] sd 0:0:0:3: rpm_status - 2
>>> [   12.045953][  T117] sd 0:0:0:4: rpm_status - 0
>>>
>>> And sd 0:0:0:4 tries to suspend here:
>>> [   15.465914][  T117] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>
>>>>>>
>>>>>> Another outstanding issue that comes to mind, is to ensure
>>>>>> hba->sdev_ufs_device does not runtime suspend before it is probed.
>>>>>> I suggest changing ufshcd_slave_configure() so it does not set
>>>>>> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
>>>>>> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
>>>>>> ufshcd_wl_remove() respectively.
>>>>>>
>>> If pm_runtime_allow() is invoked from ufshcd_wl_probe() it'd invoke runtime_suspend on hba->sdev_ufs_device before exiting scsi_sysfs_add_sdev(). So I think pm_runtime_allow() should be invoked in ufshcd_scsi_add_wlus().
>>>
>>>>>> However we still want to stop hba->sdev_ufs_device runtime
>>>>>> suspending while consumers are being added.  With that in mind,
>>>>>> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
>>>>>> in ufshcd_scsi_add_wlus() to come *before*
>>>>>> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
>>>>>> be more logical to make it, pm_runtime_get_sync() since we require
>>>>>> hba->sdev_ufs_device to be active at that point.
>>>>>>
>>> Correct, scsi_autopm_get_device(hba->sdev_ufs_device) should be invoked before ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).
>>> Now a corresponding scsi_autopm_put_device(hba->sdev_ufs_device) is invoked after the consumers are added in ufshcd_setup_links().
>>> Even then I think this issue would still pop up.
>>>
>>>>>>
>>>>>
>>>>> Hi Adrian,
>>>>> I think the v11 that I pushed can handle this.
>>>>> runtime-suspend is forbidden at probe and is re-enabled after probe is done. Please take a look and let me know if I'm missing something.
>>>>
>>>> If the PM APIs are being used correctly, the usage and active
>>>> counts should never be wrong.  If they were, then that would
>>>> be an issue for the PM framework.
>>>> It is more likely that I'm using it incorrectly :).
>>>
>>>> However, it is hard to tell what the issues are until all the
>>>> UFS driver changes have been completed, such as the ones I
>>>> suggested above above.
>>>>
>>> Ok, understood.
>>>
>>>> v11 could be hiding issues rather than fixing them.
>>>>
>>> Based on the logs, in v11, I tried to forbid any runtime-suspend until sd_probe() is done.
>>> I could be misunderstanding the whole thing though.
>>>
>>> Having said that, I will make the changes as per your suggestions and push a v12. I will test with v12 as well and see if this issue is seen.
>>>
>>>>>
>>>>>>>
>>>>>>> Since the supplier has 0 auto-suspend delay, it now suspends!
>>>>>>>
>>>>>>>
>>>>>>> Context [T1]
>>>>>>> Call trace:
>>>>>>> dump_backtrace+0x0/0x1d4
>>>>>>> show_stack+0x18/0x24
>>>>>>> dump_stack+0xc4/0x144
>>>>>>> __pm_runtime_idle+0xb4/0x184
>>>>>>> scsi_autopm_put_device+0x18/0x24
>>>>>>> scsi_sysfs_add_sdev+0x26c/0x278
>>>>>>> scsi_probe_and_add_lun+0xbac/0xd48
>>>>>>> __scsi_scan_target+0x38c/0x510
>>>>>>> scsi_scan_host_selected+0x14c/0x1e4
>>>>>>> scsi_scan_host+0x1e0/0x228
>>>>>>> ufshcd_async_scan+0x39c/0x408
>>>>>>> async_run_entry_fn+0x48/0x128
>>>>>>> process_one_work+0x1f0/0x470
>>>>>>> worker_thread+0x26c/0x4c8
>>>>>>> kthread+0x13c/0x320
>>>>>>> ret_from_fork+0x10/0x18
>>>>>>>
>>>>>>>
>>>>>>> Context [T2]
>>>>>>> Call trace:
>>>>>>> dump_backtrace+0x0/0x1d4
>>>>>>> show_stack+0x18/0x24
>>>>>>> dump_stack+0xc4/0x144
>>>>>>> rpm_get_suppliers+0x48/0x1ac
>>>>>>> __rpm_callback+0x58/0x12c
>>>>>>> rpm_resume+0x3a4/0x618
>>>>>>> __pm_runtime_resume+0x50/0x80
>>>>>>> scsi_autopm_get_device+0x20/0x54
>>>>>>> sd_probe+0x40/0x3d0
>>>>>>> really_probe+0x1bc/0x4a0
>>>>>>> driver_probe_device+0x84/0xf0
>>>>>>> __device_attach_driver+0x114/0x138
>>>>>>> bus_for_each_drv+0x84/0xd0
>>>>>>> __device_attach_async_helper+0x7c/0xf0
>>>>>>> async_run_entry_fn+0x48/0x128
>>>>>>> process_one_work+0x1f0/0x470
>>>>>>> worker_thread+0x26c/0x4c8
>>>>>>> kthread+0x13c/0x320
>>>>>>> ret_from_fork+0x10/0x18
>>>>>>>
>>>>>>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
>>>>>>> [    7.574654][  T212] Call trace:
>>>>>>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
>>>>>>> [    7.574661][  T212]  show_stack+0x18/0x24
>>>>>>> [    7.574665][  T212]  dump_stack+0xc4/0x144
>>>>>>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
>>>>>>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
>>>>>>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
>>>>>>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
>>>>>>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
>>>>>>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
>>>>>>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
>>>>>>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
>>>>>>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
>>>>>>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
>>>>>>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
>>>>>>> [    7.574700][  T212]  kthread+0x13c/0x320
>>>>>>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
>>>>>>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
>>>>>>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>>>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
>>>>>>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>>>>
>>>>>>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
>>>>>>> [    7.574754][  T212] Call trace:
>>>>>>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
>>>>>>> [    7.574761][  T212]  show_stack+0x18/0x24
>>>>>>> [    7.574765][  T212]  dump_stack+0xc4/0x144
>>>>>>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
>>>>>>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
>>>>>>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
>>>>>>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
>>>>>>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
>>>>>>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
>>>>>>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
>>>>>>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
>>>>>>> [    7.574788][  T212]  kthread+0x13c/0x320
>>>>>>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
>>>>>>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
>>>>>>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
>>>>>>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
>>>>>>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
>>>>>>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
>>>>>>>
>>>>>>>
>>>>>>> So, from the above it looks like when async probe is enabled this is a possibility.
>>>>>>>
>>>>>>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> -asd
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>>> Linux Foundation Collaborative Project
>>
Rafael J. Wysocki March 18, 2021, 5:54 p.m. UTC | #19
On Thu, Mar 18, 2021 at 6:33 PM Asutosh Das (asd)
<asutoshd@codeaurora.org> wrote:
>
> On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
> > On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >>
> >> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
> >>> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
> >>>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
> >>>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
> >>>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
> >>>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
> >>>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
> >>>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >>>>>>>>>>
> >>>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
> >>>>>>>>>>>> Scenario - bootups
> >>>>>>>>>>>>
> >>>>>>>>>>>> Issue:
> >>>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> >>>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
> >>>>>>>>>>>>
> >>>>>>>>>>>> *Log:
> >>>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> >>>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> >>>>>>>>>>>>
> >>>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
> >>>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> >>>>>>>>>>>> <-- this is the usage_count
> >>>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> >>>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> >>>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> >>>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> >>>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> >>>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> >>>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> >>>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> >>>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> >>>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> >>>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> >>>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> >>>>>>>>>>>> (0) has rpm_active flags
> >>>>>>>>>>
> >>>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
> >>>>>>>>>> supplier is greater than 0 at this point and the consumer is
> >>>>>>>>>
> >>>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
> >>>>>>>>> active references to the supplier")?
> >>>>>>>> Hi Rafael:
> >>>>>>>> No - it is not greater than 1.
> >>>>>>>>
> >>>>>>>> I'm trying to understand what's going on in it; will update when I've something.
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
> >>>>>>>>>>
> >>>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> >>>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> >>>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >>>>>>>>>>>>
> >>>>>>>>>>>> And the the suspend of sde is stuck now:
> >>>>>>>>>>>> schedule+0x9c/0xe0
> >>>>>>>>>>>> schedule_timeout+0x40/0x128
> >>>>>>>>>>>> io_schedule_timeout+0x44/0x68
> >>>>>>>>>>>> wait_for_common_io+0x7c/0x100
> >>>>>>>>>>>> wait_for_completion_io+0x14/0x20
> >>>>>>>>>>>> blk_execute_rq+0x90/0xcc
> >>>>>>>>>>>> __scsi_execute+0x104/0x1c4
> >>>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
> >>>>>>>>>>>> sd_suspend_common+0x74/0x11c
> >>>>>>>>>>>> sd_suspend_runtime+0x14/0x20
> >>>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
> >>>>>>>>>>>> __rpm_callback+0x80/0x2a4
> >>>>>>>>>>>> rpm_suspend+0x308/0x614
> >>>>>>>>>>>> pm_runtime_work+0x98/0xa8
> >>>>>>>>>>>>
> >>>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> >>>>>>>>>>>>           if (hba->sdev_ufs_device) {
> >>>>>>>>>>>>                   link = device_link_add(&sdev->sdev_gendev,
> >>>>>>>>>>>>                                       &hba->sdev_ufs_device->sdev_gendev,
> >>>>>>>>>>>>                                      DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> >>>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
> >>>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
> >>>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
> >>>>>>>>>>>> suspended when all the consumers are suspended.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Any pointers on this issue please?
> >>>>>>>>>>>>
> >>>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
> >>>>>>>>>>>
> >>>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
> >>>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
> >>>>>>>>>>> even when one of its consumers is still active), you did not CC the
> >>>>>>>>>>> power management maintainer or mailing list.
> >>>>>>>>>>>
> >>>>>>>>>>> I have added the appropriate CC's.
> >>>>>>>>>>
> >>>>>>>>>> Thanks Alan!
> >>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>> Hello
> >>>>>>> I & Can (thanks CanG) debugged this further:
> >>>>>>>
> >>>>>>> Looks like this issue can occur if the sd probe is asynchronous.
> >>>>>>>
> >>>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
> >>>>>>>
> >>>>>>> But scsi_probe_and_add_lun() runs in a separate context.
> >>>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
> >>>>>>>
> >>>>>>> So if:
> >>>>>>> Context T1:
> >>>>>>> [1] scsi_probe_and_add_lun()
> >>>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
> >>>>>>>
> >>>>>>> Context T2:
> >>>>>>> __device_attach_async_helper()
> >>>>>>>        |- driver_probe_device()
> >>>>>>>            |- sd_probe()
> >>>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
> >>>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
> >>>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
> >>>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
> >>>>>>>
> >>>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
> >>>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
> >>>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
> >>>>>>
> >>>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
> >>>>>> consumers have link->rpm_active = 2 and also have incremented
> >>>>>> the supplier's usage_count?
> >>>
> >>> Yes this is with DL_FLAG_RPM_ACTIVE.
> >>>
> >>> Please let me share a log here:
> >>> BEF means - Before, AFT means After.
> >>>
> >>> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
> >>> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> >>>
> >>> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
> >>>
> >>> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
> >>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
> >>>
> >>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
> >>> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
> >>>
> >>> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
> >>>
> >>> ------ T196 Context comes in while T7 is running ----------
> >>> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> >>> --------------------------------------------------------------
> >>>
> >>> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
> >>
> >>
> >>
> >>>
> >>> --
> >>>
> >>> T196 is the context in which sd_probe() is invoked for this scsi device.
> >>>
> >>> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
> >>> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
> >>> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
> >>> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
> >>>
> >>> The reference to the link is released after sd_probe() is completed.
> >>> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
> >>>
> >>> In this log, the usage_count of supplier becomes 0 here:
> >>> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
> >>> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
> >>>
> >>> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
> >>
> >> If that is the case, then it is an error in PM not UFS.
> >>
> >> A second look at the code around rpm_put_suppliers() does look
> >> potentially racy, since there does not appear to be anything
> >> stopping the runtime_status changing between
> >> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
> >>
> >> Rafael, can you comment?
> >
> > Indeed, if the device is suspending, changing its PM-runtime status to
> > RPM_SUSPENDED and dropping its power.lock allows a concurrent
> > rpm_resume() to run and resume the device before the suppliers can be
> > suspended.
> >
> > That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
> > runtime: Update device status before letting suppliers suspend").
> >
> > It is probably better to revert that commit and address the original
> > issue in a different way.
> >
> Hello,
> One approach to address the original issue could be to prevent the scsi
> devices from suspending until the probe is completed, perhaps?

I was talking about the original issue that commit 44cc89f76464
attempted to address.

I'm not sure if and how it is related to the issue you have been debugging.
Asutosh Das March 18, 2021, 5:58 p.m. UTC | #20
On 3/18/2021 10:54 AM, Rafael J. Wysocki wrote:
> On Thu, Mar 18, 2021 at 6:33 PM Asutosh Das (asd)
> <asutoshd@codeaurora.org> wrote:
>>
>> On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
>>> On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>
>>>> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
>>>>> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
>>>>>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>>>>>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>>>>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>>>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>>>>>>> Scenario - bootups
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Issue:
>>>>>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> *Log:
>>>>>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>>>>>>> <-- this is the usage_count
>>>>>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>>>>>>> (0) has rpm_active flags
>>>>>>>>>>>>
>>>>>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>>>>>>
>>>>>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>>>>>>> active references to the supplier")?
>>>>>>>>>> Hi Rafael:
>>>>>>>>>> No - it is not greater than 1.
>>>>>>>>>>
>>>>>>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>>>>>>
>>>>>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>>>>>>            if (hba->sdev_ufs_device) {
>>>>>>>>>>>>>>                    link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>>>>>>                                        &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>>>>>>                                       DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>>>>>>
>>>>>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>>>>>>> power management maintainer or mailing list.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I have added the appropriate CC's.
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks Alan!
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hello
>>>>>>>>> I & Can (thanks CanG) debugged this further:
>>>>>>>>>
>>>>>>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>>>>>>
>>>>>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>>>>>>
>>>>>>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>>>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>>>>>>
>>>>>>>>> So if:
>>>>>>>>> Context T1:
>>>>>>>>> [1] scsi_probe_and_add_lun()
>>>>>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>>>>>>
>>>>>>>>> Context T2:
>>>>>>>>> __device_attach_async_helper()
>>>>>>>>>         |- driver_probe_device()
>>>>>>>>>             |- sd_probe()
>>>>>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>>>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>>>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>>>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>>>>>>
>>>>>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>>>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>>>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>>>>>>
>>>>>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>>>>>>> consumers have link->rpm_active = 2 and also have incremented
>>>>>>>> the supplier's usage_count?
>>>>>
>>>>> Yes this is with DL_FLAG_RPM_ACTIVE.
>>>>>
>>>>> Please let me share a log here:
>>>>> BEF means - Before, AFT means After.
>>>>>
>>>>> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
>>>>> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>>
>>>>> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
>>>>>
>>>>> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
>>>>>
>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
>>>>> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
>>>>>
>>>>> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
>>>>>
>>>>> ------ T196 Context comes in while T7 is running ----------
>>>>> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>> --------------------------------------------------------------
>>>>>
>>>>> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>>>>
>>>>
>>>>
>>>>>
>>>>> --
>>>>>
>>>>> T196 is the context in which sd_probe() is invoked for this scsi device.
>>>>>
>>>>> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
>>>>> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
>>>>> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
>>>>> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
>>>>>
>>>>> The reference to the link is released after sd_probe() is completed.
>>>>> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
>>>>>
>>>>> In this log, the usage_count of supplier becomes 0 here:
>>>>> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
>>>>> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
>>>>>
>>>>> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>>>>
>>>> If that is the case, then it is an error in PM not UFS.
>>>>
>>>> A second look at the code around rpm_put_suppliers() does look
>>>> potentially racy, since there does not appear to be anything
>>>> stopping the runtime_status changing between
>>>> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>>>>
>>>> Rafael, can you comment?
>>>
>>> Indeed, if the device is suspending, changing its PM-runtime status to
>>> RPM_SUSPENDED and dropping its power.lock allows a concurrent
>>> rpm_resume() to run and resume the device before the suppliers can be
>>> suspended.
>>>
>>> That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
>>> runtime: Update device status before letting suppliers suspend").
>>>
>>> It is probably better to revert that commit and address the original
>>> issue in a different way.
>>>
>> Hello,
>> One approach to address the original issue could be to prevent the scsi
>> devices from suspending until the probe is completed, perhaps?
> 
> I was talking about the original issue that commit 44cc89f76464
> attempted to address.
> 
> I'm not sure if and how it is related to the issue you have been debugging.
> 
Hi Rafael
Thanks for clarifying that.
Understood.
I was referring to the issue that I've been discussing with Adrian.

-asd
Adrian Hunter March 18, 2021, 7:16 p.m. UTC | #21
On 18/03/21 7:58 pm, Asutosh Das (asd) wrote:
> On 3/18/2021 10:54 AM, Rafael J. Wysocki wrote:
>> On Thu, Mar 18, 2021 at 6:33 PM Asutosh Das (asd)
>> <asutoshd@codeaurora.org> wrote:
>>>
>>> On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
>>>> On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>>
>>>>> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
>>>>>> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
>>>>>>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>>>>>>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>>>>>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>>>>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>>>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>>>>>>>> Scenario - bootups
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Issue:
>>>>>>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> *Log:
>>>>>>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>>>>>>>> <-- this is the usage_count
>>>>>>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>>>>>>>> (0) has rpm_active flags
>>>>>>>>>>>>>
>>>>>>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>>>>>>>
>>>>>>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>>>>>>>> active references to the supplier")?
>>>>>>>>>>> Hi Rafael:
>>>>>>>>>>> No - it is not greater than 1.
>>>>>>>>>>>
>>>>>>>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>>>>>>>
>>>>>>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>>>>>>>            if (hba->sdev_ufs_device) {
>>>>>>>>>>>>>>>                    link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>>>>>>>                                        &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>>>>>>>                                       DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>>>>>>>> power management maintainer or mailing list.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I have added the appropriate CC's.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks Alan!
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Hello
>>>>>>>>>> I & Can (thanks CanG) debugged this further:
>>>>>>>>>>
>>>>>>>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>>>>>>>
>>>>>>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>>>>>>>
>>>>>>>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>>>>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>>>>>>>
>>>>>>>>>> So if:
>>>>>>>>>> Context T1:
>>>>>>>>>> [1] scsi_probe_and_add_lun()
>>>>>>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>>>>>>>
>>>>>>>>>> Context T2:
>>>>>>>>>> __device_attach_async_helper()
>>>>>>>>>>         |- driver_probe_device()
>>>>>>>>>>             |- sd_probe()
>>>>>>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>>>>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>>>>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>>>>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>>>>>>>
>>>>>>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>>>>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>>>>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>>>>>>>
>>>>>>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>>>>>>>> consumers have link->rpm_active = 2 and also have incremented
>>>>>>>>> the supplier's usage_count?
>>>>>>
>>>>>> Yes this is with DL_FLAG_RPM_ACTIVE.
>>>>>>
>>>>>> Please let me share a log here:
>>>>>> BEF means - Before, AFT means After.
>>>>>>
>>>>>> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
>>>>>> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>>>
>>>>>> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
>>>>>>
>>>>>> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
>>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
>>>>>>
>>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
>>>>>> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
>>>>>>
>>>>>> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
>>>>>>
>>>>>> ------ T196 Context comes in while T7 is running ----------
>>>>>> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>>> --------------------------------------------------------------
>>>>>>
>>>>>> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> -- 
>>>>>>
>>>>>> T196 is the context in which sd_probe() is invoked for this scsi device.
>>>>>>
>>>>>> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
>>>>>> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
>>>>>> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
>>>>>> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
>>>>>>
>>>>>> The reference to the link is released after sd_probe() is completed.
>>>>>> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
>>>>>>
>>>>>> In this log, the usage_count of supplier becomes 0 here:
>>>>>> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
>>>>>> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
>>>>>>
>>>>>> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>>>>>
>>>>> If that is the case, then it is an error in PM not UFS.
>>>>>
>>>>> A second look at the code around rpm_put_suppliers() does look
>>>>> potentially racy, since there does not appear to be anything
>>>>> stopping the runtime_status changing between
>>>>> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>>>>>
>>>>> Rafael, can you comment?
>>>>
>>>> Indeed, if the device is suspending, changing its PM-runtime status to
>>>> RPM_SUSPENDED and dropping its power.lock allows a concurrent
>>>> rpm_resume() to run and resume the device before the suppliers can be
>>>> suspended.
>>>>
>>>> That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
>>>> runtime: Update device status before letting suppliers suspend").
>>>>
>>>> It is probably better to revert that commit and address the original
>>>> issue in a different way.
>>>>
>>> Hello,
>>> One approach to address the original issue could be to prevent the scsi
>>> devices from suspending until the probe is completed, perhaps?
>>
>> I was talking about the original issue that commit 44cc89f76464
>> attempted to address.
>>
>> I'm not sure if and how it is related to the issue you have been debugging.
>>
> Hi Rafael
> Thanks for clarifying that.
> Understood.
> I was referring to the issue that I've been discussing with Adrian.

For test purposes, you could try reverting 44cc89f76464, making the
other changes to the UFS driver, and see if the device_links issue
goes away.
Asutosh Das March 19, 2021, 12:40 a.m. UTC | #22
On 3/18/2021 12:16 PM, Adrian Hunter wrote:
> On 18/03/21 7:58 pm, Asutosh Das (asd) wrote:
>> On 3/18/2021 10:54 AM, Rafael J. Wysocki wrote:
>>> On Thu, Mar 18, 2021 at 6:33 PM Asutosh Das (asd)
>>> <asutoshd@codeaurora.org> wrote:
>>>>
>>>> On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
>>>>> On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>>>
>>>>>> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
>>>>>>> On 3/16/2021 12:48 AM, Adrian Hunter wrote:
>>>>>>>> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
>>>>>>>>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
>>>>>>>>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
>>>>>>>>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
>>>>>>>>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
>>>>>>>>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
>>>>>>>>>>>>>>>> Scenario - bootups
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Issue:
>>>>>>>>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
>>>>>>>>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> *Log:
>>>>>>>>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
>>>>>>>>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> /** Printing all the consumer nodes of supplier **/
>>>>>>>>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
>>>>>>>>>>>>>>>> <-- this is the usage_count
>>>>>>>>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
>>>>>>>>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
>>>>>>>>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
>>>>>>>>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
>>>>>>>>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
>>>>>>>>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
>>>>>>>>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
>>>>>>>>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
>>>>>>>>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
>>>>>>>>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
>>>>>>>>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
>>>>>>>>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
>>>>>>>>>>>>>>>> (0) has rpm_active flags
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Do you mean that rpm_active of the link between the consumer and the
>>>>>>>>>>>>>> supplier is greater than 0 at this point and the consumer is
>>>>>>>>>>>>>
>>>>>>>>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
>>>>>>>>>>>>> active references to the supplier")?
>>>>>>>>>>>> Hi Rafael:
>>>>>>>>>>>> No - it is not greater than 1.
>>>>>>>>>>>>
>>>>>>>>>>>> I'm trying to understand what's going on in it; will update when I've something.
>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
>>>>>>>>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
>>>>>>>>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> And the the suspend of sde is stuck now:
>>>>>>>>>>>>>>>> schedule+0x9c/0xe0
>>>>>>>>>>>>>>>> schedule_timeout+0x40/0x128
>>>>>>>>>>>>>>>> io_schedule_timeout+0x44/0x68
>>>>>>>>>>>>>>>> wait_for_common_io+0x7c/0x100
>>>>>>>>>>>>>>>> wait_for_completion_io+0x14/0x20
>>>>>>>>>>>>>>>> blk_execute_rq+0x90/0xcc
>>>>>>>>>>>>>>>> __scsi_execute+0x104/0x1c4
>>>>>>>>>>>>>>>> sd_sync_cache+0xf8/0x2a0
>>>>>>>>>>>>>>>> sd_suspend_common+0x74/0x11c
>>>>>>>>>>>>>>>> sd_suspend_runtime+0x14/0x20
>>>>>>>>>>>>>>>> scsi_runtime_suspend+0x64/0x94
>>>>>>>>>>>>>>>> __rpm_callback+0x80/0x2a4
>>>>>>>>>>>>>>>> rpm_suspend+0x308/0x614
>>>>>>>>>>>>>>>> pm_runtime_work+0x98/0xa8
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
>>>>>>>>>>>>>>>>             if (hba->sdev_ufs_device) {
>>>>>>>>>>>>>>>>                     link = device_link_add(&sdev->sdev_gendev,
>>>>>>>>>>>>>>>>                                         &hba->sdev_ufs_device->sdev_gendev,
>>>>>>>>>>>>>>>>                                        DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
>>>>>>>>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Another interesting point here is when I resume any of the above suspended
>>>>>>>>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
>>>>>>>>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
>>>>>>>>>>>>>>>> suspended when all the consumers are suspended.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Any pointers on this issue please?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
>>>>>>>>>>>>>>> the power management subsystem (supplier goes into runtime suspend
>>>>>>>>>>>>>>> even when one of its consumers is still active), you did not CC the
>>>>>>>>>>>>>>> power management maintainer or mailing list.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I have added the appropriate CC's.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks Alan!
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Hello
>>>>>>>>>>> I & Can (thanks CanG) debugged this further:
>>>>>>>>>>>
>>>>>>>>>>> Looks like this issue can occur if the sd probe is asynchronous.
>>>>>>>>>>>
>>>>>>>>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
>>>>>>>>>>>
>>>>>>>>>>> But scsi_probe_and_add_lun() runs in a separate context.
>>>>>>>>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
>>>>>>>>>>>
>>>>>>>>>>> So if:
>>>>>>>>>>> Context T1:
>>>>>>>>>>> [1] scsi_probe_and_add_lun()
>>>>>>>>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
>>>>>>>>>>>
>>>>>>>>>>> Context T2:
>>>>>>>>>>> __device_attach_async_helper()
>>>>>>>>>>>          |- driver_probe_device()
>>>>>>>>>>>              |- sd_probe()
>>>>>>>>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
>>>>>>>>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
>>>>>>>>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
>>>>>>>>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
>>>>>>>>>>>
>>>>>>>>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
>>>>>>>>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
>>>>>>>>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
>>>>>>>>>>
>>>>>>>>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
>>>>>>>>>> consumers have link->rpm_active = 2 and also have incremented
>>>>>>>>>> the supplier's usage_count?
>>>>>>>
>>>>>>> Yes this is with DL_FLAG_RPM_ACTIVE.
>>>>>>>
>>>>>>> Please let me share a log here:
>>>>>>> BEF means - Before, AFT means After.
>>>>>>>
>>>>>>> [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
>>>>>>> [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>>>>
>>>>>>> In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
>>>>>>>
>>>>>>> [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
>>>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
>>>>>>>
>>>>>>> [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
>>>>>>> [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
>>>>>>>
>>>>>>> [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
>>>>>>>
>>>>>>> ------ T196 Context comes in while T7 is running ----------
>>>>>>> [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
>>>>>>> --------------------------------------------------------------
>>>>>>>
>>>>>>> [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> -- 
>>>>>>>
>>>>>>> T196 is the context in which sd_probe() is invoked for this scsi device.
>>>>>>>
>>>>>>> [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
>>>>>>> [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
>>>>>>> [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
>>>>>>> [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
>>>>>>>
>>>>>>> The reference to the link is released after sd_probe() is completed.
>>>>>>> At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
>>>>>>>
>>>>>>> In this log, the usage_count of supplier becomes 0 here:
>>>>>>> [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
>>>>>>> [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
>>>>>>>
>>>>>>> However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>>>>>>
>>>>>> If that is the case, then it is an error in PM not UFS.
>>>>>>
>>>>>> A second look at the code around rpm_put_suppliers() does look
>>>>>> potentially racy, since there does not appear to be anything
>>>>>> stopping the runtime_status changing between
>>>>>> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>>>>>>
>>>>>> Rafael, can you comment?
>>>>>
>>>>> Indeed, if the device is suspending, changing its PM-runtime status to
>>>>> RPM_SUSPENDED and dropping its power.lock allows a concurrent
>>>>> rpm_resume() to run and resume the device before the suppliers can be
>>>>> suspended.
>>>>>
>>>>> That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
>>>>> runtime: Update device status before letting suppliers suspend").
>>>>>
>>>>> It is probably better to revert that commit and address the original
>>>>> issue in a different way.
>>>>>
>>>> Hello,
>>>> One approach to address the original issue could be to prevent the scsi
>>>> devices from suspending until the probe is completed, perhaps?
>>>
>>> I was talking about the original issue that commit 44cc89f76464
>>> attempted to address.
>>>
>>> I'm not sure if and how it is related to the issue you have been debugging.
>>>
>> Hi Rafael
>> Thanks for clarifying that.
>> Understood.
>> I was referring to the issue that I've been discussing with Adrian.
> 
> For test purposes, you could try reverting 44cc89f76464, making the
> other changes to the UFS driver, and see if the device_links issue
> goes away.
> 
Hi Adrian

Thanks for the review and comments.

I addressed the comments and tested it. I still see the device_links 
issue. I've pushed the change that I tested as v12.

# grep -H . /sys/bus/scsi/devices/*/power/runtime_status 
          <
/sys/bus/scsi/devices/0:0:0:0/power/runtime_status:suspending <
/sys/bus/scsi/devices/0:0:0:1/power/runtime_status:suspended
/sys/bus/scsi/devices/0:0:0:2/power/runtime_status:suspended
/sys/bus/scsi/devices/0:0:0:3/power/runtime_status:suspending <
/sys/bus/scsi/devices/0:0:0:4/power/runtime_status:suspending <
/sys/bus/scsi/devices/0:0:0:49456/power/runtime_status:suspended
/sys/bus/scsi/devices/0:0:0:49476/power/runtime_status:suspended
/sys/bus/scsi/devices/0:0:0:49488/power/runtime_status:suspended <

I think it couldn't resolve the issue because we're not stopping the 
scsi devices from suspending after the async probe is scheduled.

-asd
diff mbox series

Patch

diff --git a/drivers/scsi/ufs/cdns-pltfrm.c b/drivers/scsi/ufs/cdns-pltfrm.c
index 149391f..3e70c23 100644
--- a/drivers/scsi/ufs/cdns-pltfrm.c
+++ b/drivers/scsi/ufs/cdns-pltfrm.c
@@ -319,6 +319,8 @@  static const struct dev_pm_ops cdns_ufs_dev_pm_ops = {
 	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
 	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
 	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static struct platform_driver cdns_ufs_pltfrm_driver = {
diff --git a/drivers/scsi/ufs/tc-dwc-g210-pci.c b/drivers/scsi/ufs/tc-dwc-g210-pci.c
index 67a6a61..b01db12 100644
--- a/drivers/scsi/ufs/tc-dwc-g210-pci.c
+++ b/drivers/scsi/ufs/tc-dwc-g210-pci.c
@@ -148,6 +148,8 @@  static const struct dev_pm_ops tc_dwc_g210_pci_pm_ops = {
 	.runtime_suspend = tc_dwc_g210_pci_runtime_suspend,
 	.runtime_resume  = tc_dwc_g210_pci_runtime_resume,
 	.runtime_idle    = tc_dwc_g210_pci_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static const struct pci_device_id tc_dwc_g210_pci_tbl[] = {
diff --git a/drivers/scsi/ufs/ufs-exynos.c b/drivers/scsi/ufs/ufs-exynos.c
index 267943a1..45c0b02 100644
--- a/drivers/scsi/ufs/ufs-exynos.c
+++ b/drivers/scsi/ufs/ufs-exynos.c
@@ -1268,6 +1268,8 @@  static const struct dev_pm_ops exynos_ufs_pm_ops = {
 	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
 	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
 	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static struct platform_driver exynos_ufs_pltform = {
diff --git a/drivers/scsi/ufs/ufs-hisi.c b/drivers/scsi/ufs/ufs-hisi.c
index 0aa5813..d463b44 100644
--- a/drivers/scsi/ufs/ufs-hisi.c
+++ b/drivers/scsi/ufs/ufs-hisi.c
@@ -574,6 +574,8 @@  static const struct dev_pm_ops ufs_hisi_pm_ops = {
 	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
 	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
 	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static struct platform_driver ufs_hisi_pltform = {
diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
index c55202b..df1eabb 100644
--- a/drivers/scsi/ufs/ufs-mediatek.c
+++ b/drivers/scsi/ufs/ufs-mediatek.c
@@ -1097,6 +1097,8 @@  static const struct dev_pm_ops ufs_mtk_pm_ops = {
 	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
 	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
 	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static struct platform_driver ufs_mtk_pltform = {
diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
index f97d7b0..9aa098a 100644
--- a/drivers/scsi/ufs/ufs-qcom.c
+++ b/drivers/scsi/ufs/ufs-qcom.c
@@ -1546,6 +1546,8 @@  static const struct dev_pm_ops ufs_qcom_pm_ops = {
 	.runtime_suspend = ufshcd_pltfrm_runtime_suspend,
 	.runtime_resume  = ufshcd_pltfrm_runtime_resume,
 	.runtime_idle    = ufshcd_pltfrm_runtime_idle,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
 };
 
 static struct platform_driver ufs_qcom_pltform = {
diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
index 5b2bc1a..cbb5a90 100644
--- a/drivers/scsi/ufs/ufs_bsg.c
+++ b/drivers/scsi/ufs/ufs_bsg.c
@@ -97,7 +97,7 @@  static int ufs_bsg_request(struct bsg_job *job)
 
 	bsg_reply->reply_payload_rcv_len = 0;
 
-	pm_runtime_get_sync(hba->dev);
+	scsi_autopm_get_device(hba->sdev_ufs_device);
 
 	msgcode = bsg_request->msgcode;
 	switch (msgcode) {
@@ -106,7 +106,7 @@  static int ufs_bsg_request(struct bsg_job *job)
 		ret = ufs_bsg_alloc_desc_buffer(hba, job, &desc_buff,
 						&desc_len, desc_op);
 		if (ret) {
-			pm_runtime_put_sync(hba->dev);
+			scsi_autopm_put_device(hba->sdev_ufs_device);
 			goto out;
 		}
 
@@ -138,7 +138,7 @@  static int ufs_bsg_request(struct bsg_job *job)
 		break;
 	}
 
-	pm_runtime_put_sync(hba->dev);
+	scsi_autopm_put_device(hba->sdev_ufs_device);
 
 	if (!desc_buff)
 		goto out;
diff --git a/drivers/scsi/ufs/ufshcd-pci.c b/drivers/scsi/ufs/ufshcd-pci.c
index fadd566..50f84bf 100644
--- a/drivers/scsi/ufs/ufshcd-pci.c
+++ b/drivers/scsi/ufs/ufshcd-pci.c
@@ -247,29 +247,6 @@  static int ufshcd_pci_resume(struct device *dev)
 	return ufshcd_system_resume(dev_get_drvdata(dev));
 }
 
-/**
- * ufshcd_pci_poweroff - suspend-to-disk poweroff function
- * @dev: pointer to PCI device handle
- *
- * Returns 0 if successful
- * Returns non-zero otherwise
- */
-static int ufshcd_pci_poweroff(struct device *dev)
-{
-	struct ufs_hba *hba = dev_get_drvdata(dev);
-	int spm_lvl = hba->spm_lvl;
-	int ret;
-
-	/*
-	 * For poweroff we need to set the UFS device to PowerDown mode.
-	 * Force spm_lvl to ensure that.
-	 */
-	hba->spm_lvl = 5;
-	ret = ufshcd_system_suspend(hba);
-	hba->spm_lvl = spm_lvl;
-	return ret;
-}
-
 #endif /* !CONFIG_PM_SLEEP */
 
 #ifdef CONFIG_PM
@@ -366,12 +343,9 @@  ufshcd_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 static const struct dev_pm_ops ufshcd_pci_pm_ops = {
 #ifdef CONFIG_PM_SLEEP
-	.suspend	= ufshcd_pci_suspend,
-	.resume		= ufshcd_pci_resume,
-	.freeze		= ufshcd_pci_suspend,
-	.thaw		= ufshcd_pci_resume,
-	.poweroff	= ufshcd_pci_poweroff,
-	.restore	= ufshcd_pci_resume,
+	.prepare	 = ufshcd_suspend_prepare,
+	.complete	= ufshcd_resume_complete,
+	SET_SYSTEM_SLEEP_PM_OPS(ufshcd_pci_suspend, ufshcd_pci_resume)
 #endif
 	SET_RUNTIME_PM_OPS(ufshcd_pci_runtime_suspend,
 			   ufshcd_pci_runtime_resume,
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 45624c7..32139dd 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -16,6 +16,7 @@ 
 #include <linux/bitfield.h>
 #include <linux/blk-pm.h>
 #include <linux/blkdev.h>
+#include <scsi/scsi_driver.h>
 #include "ufshcd.h"
 #include "ufs_quirks.h"
 #include "unipro.h"
@@ -78,6 +79,8 @@ 
 /* Polling time to wait for fDeviceInit */
 #define FDEVICEINIT_COMPL_TIMEOUT 1500 /* millisecs */
 
+#define wlun_dev_to_hba(dv) shost_priv(to_scsi_device(dv)->host)
+
 #define ufshcd_toggle_vreg(_dev, _vreg, _on)				\
 	({                                                              \
 		int _ret;                                               \
@@ -1556,7 +1559,7 @@  static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 	if (value == hba->clk_scaling.is_enabled)
 		goto out;
 
-	pm_runtime_get_sync(hba->dev);
+	scsi_autopm_get_device(hba->sdev_ufs_device);
 	ufshcd_hold(hba, false);
 
 	hba->clk_scaling.is_enabled = value;
@@ -1572,7 +1575,7 @@  static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 	}
 
 	ufshcd_release(hba);
-	pm_runtime_put_sync(hba->dev);
+	scsi_autopm_put_device(hba->sdev_ufs_device);
 out:
 	up(&hba->host_sem);
 	return err ? err : count;
@@ -2572,6 +2575,17 @@  static inline u16 ufshcd_upiu_wlun_to_scsi_wlun(u8 upiu_wlun_id)
 	return (upiu_wlun_id & ~UFS_UPIU_WLUN_ID) | SCSI_W_LUN_BASE;
 }
 
+static inline bool is_rpmb_wlun(struct scsi_device *sdev)
+{
+	return (sdev->lun == ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_RPMB_WLUN));
+}
+
+static inline bool is_device_wlun(struct scsi_device *sdev)
+{
+	return (sdev->lun ==
+		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_UFS_DEVICE_WLUN));
+}
+
 static void ufshcd_init_lrb(struct ufs_hba *hba, struct ufshcd_lrb *lrb, int i)
 {
 	struct utp_transfer_cmd_desc *cmd_descp = hba->ucdl_base_addr;
@@ -4808,6 +4822,41 @@  static inline void ufshcd_get_lu_power_on_wp_status(struct ufs_hba *hba,
 }
 
 /**
+ * ufshcd_setup_links - associate link b/w device wlun and other luns
+ * @sdev: pointer to SCSI device
+ * @hba: pointer to ufs hba
+ */
+static void ufshcd_setup_links(struct ufs_hba *hba, struct scsi_device *sdev)
+{
+	struct device_link *link;
+
+	/*
+	 * device wlun is the supplier & rest of the luns are consumers
+	 * This ensures that device wlun suspends after all other luns.
+	 */
+	if (hba->sdev_ufs_device) {
+		link = device_link_add(&sdev->sdev_gendev,
+				       &hba->sdev_ufs_device->sdev_gendev,
+				       DL_FLAG_PM_RUNTIME);
+		if (!link) {
+			dev_err(&sdev->sdev_gendev, "Failed establishing link - %s\n",
+				dev_name(&hba->sdev_ufs_device->sdev_gendev));
+			return;
+		}
+		hba->luns_avail--;
+		/* Ignore REPORT_LUN wlun probing */
+		if (hba->luns_avail != 1)
+			return;
+
+		pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
+		pm_runtime_mark_last_busy(&hba->sdev_ufs_device->sdev_gendev);
+	} else {
+		/* device wlun is probed */
+		hba->luns_avail--;
+	}
+}
+
+/**
  * ufshcd_slave_alloc - handle initial SCSI device configurations
  * @sdev: pointer to SCSI device
  *
@@ -4838,6 +4887,8 @@  static int ufshcd_slave_alloc(struct scsi_device *sdev)
 
 	ufshcd_get_lu_power_on_wp_status(hba, sdev);
 
+	ufshcd_setup_links(hba, sdev);
+
 	return 0;
 }
 
@@ -4985,15 +5036,9 @@  ufshcd_transfer_rsp_status(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
 			 * UFS device needs urgent BKOPs.
 			 */
 			if (!hba->pm_op_in_progress &&
-			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr) &&
-			    schedule_work(&hba->eeh_work)) {
-				/*
-				 * Prevent suspend once eeh_work is scheduled
-				 * to avoid deadlock between ufshcd_suspend
-				 * and exception event handler.
-				 */
-				pm_runtime_get_noresume(hba->dev);
-			}
+			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
+				/* Flushed in suspend */
+				schedule_work(&hba->eeh_work);
 			break;
 		case UPIU_TRANSACTION_REJECT_UPIU:
 			/* TODO: handle Reject UPIU Response */
@@ -5589,8 +5634,8 @@  static void ufshcd_rpm_dev_flush_recheck_work(struct work_struct *work)
 	 * after a certain delay to recheck the threshold by next runtime
 	 * suspend.
 	 */
-	pm_runtime_get_sync(hba->dev);
-	pm_runtime_put_sync(hba->dev);
+	scsi_autopm_get_device(hba->sdev_ufs_device);
+	scsi_autopm_put_device(hba->sdev_ufs_device);
 }
 
 /**
@@ -5607,7 +5652,6 @@  static void ufshcd_exception_event_handler(struct work_struct *work)
 	u32 status = 0;
 	hba = container_of(work, struct ufs_hba, eeh_work);
 
-	pm_runtime_get_sync(hba->dev);
 	ufshcd_scsi_block_requests(hba);
 	err = ufshcd_get_ee_status(hba, &status);
 	if (err) {
@@ -5623,14 +5667,6 @@  static void ufshcd_exception_event_handler(struct work_struct *work)
 
 out:
 	ufshcd_scsi_unblock_requests(hba);
-	/*
-	 * pm_runtime_get_noresume is called while scheduling
-	 * eeh_work to avoid suspend racing with exception work.
-	 * Hence decrement usage counter using pm_runtime_put_noidle
-	 * to allow suspend on completion of exception event handler.
-	 */
-	pm_runtime_put_noidle(hba->dev);
-	pm_runtime_put(hba->dev);
 	return;
 }
 
@@ -7207,11 +7243,12 @@  static void ufshcd_set_active_icc_lvl(struct ufs_hba *hba)
 
 static inline void ufshcd_blk_pm_runtime_init(struct scsi_device *sdev)
 {
+	int dly = is_device_wlun(sdev) ? 0:RPM_AUTOSUSPEND_DELAY_MS;
+
 	scsi_autopm_get_device(sdev);
 	blk_pm_runtime_init(sdev->request_queue, &sdev->sdev_gendev);
 	if (sdev->rpm_autosuspend)
-		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev,
-						 RPM_AUTOSUSPEND_DELAY_MS);
+		pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev, dly);
 	scsi_autopm_put_device(sdev);
 }
 
@@ -7254,6 +7291,15 @@  static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
 		goto out;
 	}
 	ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device);
+	/*
+	 * A pm_runtime_put_sync is invoked when this device enables blk_pm_runtime
+	 * & would suspend the device-wlun upon timer expiry.
+	 * But suspending device wlun _may_ put the ufs device in the pre-defined
+	 * low power mode (SSU <rpm_lvl>). Probing of other luns may fail then.
+	 * Don't allow this suspend until all the luns have been probed.
+	 * See pm_runtime_mark_last_busy in ufshcd_setup_links.
+	 */
+	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
 	scsi_device_put(hba->sdev_ufs_device);
 
 	hba->sdev_rpmb = __scsi_add_device(hba->host, 0, 0,
@@ -7417,6 +7463,9 @@  static int ufs_get_device_desc(struct ufs_hba *hba)
 		goto out;
 	}
 
+	hba->luns_avail = desc_buf[DEVICE_DESC_PARAM_NUM_LU] +
+		desc_buf[DEVICE_DESC_PARAM_NUM_WLU];
+
 	ufs_fixup_device_setup(hba);
 
 	ufshcd_wb_probe(hba, desc_buf);
@@ -7892,6 +7941,7 @@  static int ufshcd_probe_hba(struct ufs_hba *hba, bool async)
 	ufshcd_set_ufs_dev_active(hba);
 	ufshcd_force_reset_auto_bkops(hba);
 	hba->wlun_dev_clr_ua = true;
+	hba->wlun_rpmb_clr_ua = true;
 
 	/* Gear up to HS gear if supported */
 	if (hba->max_pwr_info.is_valid) {
@@ -7964,6 +8014,7 @@  static void ufshcd_async_scan(void *data, async_cookie_t cookie)
 		pm_runtime_put_sync(hba->dev);
 		ufshcd_hba_exit(hba);
 	}
+	hba->init_done = true;
 }
 
 static const struct attribute_group *ufshcd_driver_groups[] = {
@@ -8475,7 +8526,8 @@  static int ufshcd_set_dev_pwr_mode(struct ufs_hba *hba,
 	 * handling context.
 	 */
 	hba->host->eh_noresume = 1;
-	ufshcd_clear_ua_wluns(hba);
+	if (hba->wlun_dev_clr_ua)
+		ufshcd_clear_ua_wlun(hba, UFS_UPIU_UFS_DEVICE_WLUN);
 
 	cmd[4] = pwr_mode << 4;
 
@@ -8650,23 +8702,7 @@  static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba)
 		ufshcd_setup_hba_vreg(hba, true);
 }
 
-/**
- * ufshcd_suspend - helper function for suspend operations
- * @hba: per adapter instance
- * @pm_op: desired low power operation type
- *
- * This function will try to put the UFS device and link into low power
- * mode based on the "rpm_lvl" (Runtime PM level) or "spm_lvl"
- * (System PM level).
- *
- * If this function is called during shutdown, it will make sure that
- * both UFS device and UFS link is powered off.
- *
- * NOTE: UFS device & link must be active before we enter in this function.
- *
- * Returns 0 for success and non-zero for failure
- */
-static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
+static int __ufshcd_wl_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	int ret = 0;
 	int check_for_bkops;
@@ -8674,7 +8710,13 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	enum ufs_dev_pwr_mode req_dev_pwr_mode;
 	enum uic_link_state req_link_state;
 
-	hba->pm_op_in_progress = 1;
+	/*
+	 * Is invoked when the device wlun is added to sysfs
+	 * But by then hba->sdev_ufs_device may not be initialized.
+	 */
+	if (!hba->init_done)
+		return 0;
+	hba->pm_op_in_progress = true;
 	if (!ufshcd_is_shutdown_pm(pm_op)) {
 		pm_lvl = ufshcd_is_runtime_pm(pm_op) ?
 			 hba->rpm_lvl : hba->spm_lvl;
@@ -8697,17 +8739,17 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 
 	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
 			req_link_state == UIC_LINK_ACTIVE_STATE) {
-		goto disable_clks;
+		goto enable_scaling;
 	}
 
 	if ((req_dev_pwr_mode == hba->curr_dev_pwr_mode) &&
 	    (req_link_state == hba->uic_link_state))
-		goto enable_gating;
+		goto enable_scaling;
 
 	/* UFS device & link must be active before we enter in this function */
 	if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba)) {
 		ret = -EINVAL;
-		goto enable_gating;
+		goto enable_scaling;
 	}
 
 	if (ufshcd_is_runtime_pm(pm_op)) {
@@ -8719,7 +8761,7 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 			 */
 			ret = ufshcd_urgent_bkops(hba);
 			if (ret)
-				goto enable_gating;
+				goto enable_scaling;
 		} else {
 			/* make sure that auto bkops is disabled */
 			ufshcd_disable_auto_bkops(hba);
@@ -8747,7 +8789,7 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 		if (!hba->dev_info.b_rpm_dev_flush_capable) {
 			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
 			if (ret)
-				goto enable_gating;
+				goto enable_scaling;
 		}
 	}
 
@@ -8760,7 +8802,6 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	if (ret)
 		goto set_dev_active;
 
-disable_clks:
 	/*
 	 * Call vendor specific suspend callback. As these callbacks may access
 	 * vendor specific host controller register space call them before the
@@ -8769,28 +8810,9 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	ret = ufshcd_vops_suspend(hba, pm_op);
 	if (ret)
 		goto set_link_active;
-	/*
-	 * Disable the host irq as host controller as there won't be any
-	 * host controller transaction expected till resume.
-	 */
-	ufshcd_disable_irq(hba);
-
-	ufshcd_setup_clocks(hba, false);
-
-	if (ufshcd_is_clkgating_allowed(hba)) {
-		hba->clk_gating.state = CLKS_OFF;
-		trace_ufshcd_clk_gating(dev_name(hba->dev),
-					hba->clk_gating.state);
-	}
-
-	ufshcd_vreg_set_lpm(hba);
-
-	/* Put the host controller in low power mode if possible */
-	ufshcd_hba_vreg_set_lpm(hba);
 	goto out;
 
 set_link_active:
-	ufshcd_vreg_set_hpm(hba);
 	/*
 	 * Device hardware reset is required to exit DeepSleep. Also, for
 	 * DeepSleep, the link is off so host reset and restore will be done
@@ -8812,57 +8834,35 @@  static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	}
 	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
 		ufshcd_disable_auto_bkops(hba);
-enable_gating:
+enable_scaling:
 	if (ufshcd_is_clkscaling_supported(hba))
 		ufshcd_clk_scaling_suspend(hba, false);
 
-	hba->clk_gating.is_suspended = false;
 	hba->dev_info.b_rpm_dev_flush_capable = false;
-	ufshcd_clear_ua_wluns(hba);
-	ufshcd_release(hba);
 out:
 	if (hba->dev_info.b_rpm_dev_flush_capable) {
 		schedule_delayed_work(&hba->rpm_dev_flush_recheck_work,
 			msecs_to_jiffies(RPM_DEV_FLUSH_RECHECK_WORK_DELAY_MS));
 	}
 
-	hba->pm_op_in_progress = 0;
-
-	if (ret)
-		ufshcd_update_evt_hist(hba, UFS_EVT_SUSPEND_ERR, (u32)ret);
+	if (ret) {
+		ufshcd_update_evt_hist(hba, UFS_EVT_WL_SUSP_ERR, (u32)ret);
+		hba->clk_gating.is_suspended = false;
+		ufshcd_release(hba);
+	}
+	hba->pm_op_in_progress = false;
 	return ret;
 }
 
-/**
- * ufshcd_resume - helper function for resume operations
- * @hba: per adapter instance
- * @pm_op: runtime PM or system PM
- *
- * This function basically brings the UFS device, UniPro link and controller
- * to active state.
- *
- * Returns 0 for success and non-zero for failure
- */
-static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
+static int __ufshcd_wl_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	int ret;
-	enum uic_link_state old_link_state;
-
-	hba->pm_op_in_progress = 1;
-	old_link_state = hba->uic_link_state;
-
-	ufshcd_hba_vreg_set_hpm(hba);
-	ret = ufshcd_vreg_set_hpm(hba);
-	if (ret)
-		goto out;
+	enum uic_link_state old_link_state = hba->uic_link_state;
 
-	/* Make sure clocks are enabled before accessing controller */
-	ret = ufshcd_setup_clocks(hba, true);
-	if (ret)
-		goto disable_vreg;
+	if (!hba->init_done)
+		return 0;
 
-	/* enable the host irq as host controller would be active soon */
-	ufshcd_enable_irq(hba);
+	hba->pm_op_in_progress = true;
 
 	/*
 	 * Call vendor specific resume callback. As these callbacks may access
@@ -8871,7 +8871,7 @@  static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	 */
 	ret = ufshcd_vops_resume(hba, pm_op);
 	if (ret)
-		goto disable_irq_and_vops_clks;
+		goto out;
 
 	/* For DeepSleep, the only supported option is to have the link off */
 	WARN_ON(ufshcd_is_ufs_dev_deepsleep(hba) && !ufshcd_is_link_off(hba));
@@ -8916,31 +8916,147 @@  static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 		 */
 		ufshcd_urgent_bkops(hba);
 
-	hba->clk_gating.is_suspended = false;
-
-	if (ufshcd_is_clkscaling_supported(hba))
-		ufshcd_clk_scaling_suspend(hba, false);
-
-	/* Enable Auto-Hibernate if configured */
-	ufshcd_auto_hibern8_enable(hba);
+	if (hba->clk_scaling.is_allowed)
+		ufshcd_resume_clkscaling(hba);
 
 	if (hba->dev_info.b_rpm_dev_flush_capable) {
 		hba->dev_info.b_rpm_dev_flush_capable = false;
 		cancel_delayed_work(&hba->rpm_dev_flush_recheck_work);
 	}
 
-	ufshcd_clear_ua_wluns(hba);
-
-	/* Schedule clock gating in case of no access to UFS device yet */
-	ufshcd_release(hba);
-
+	/* Enable Auto-Hibernate if configured */
+	ufshcd_auto_hibern8_enable(hba);
 	goto out;
 
 set_old_link_state:
 	ufshcd_link_state_transition(hba, old_link_state, 0);
 vendor_suspend:
 	ufshcd_vops_suspend(hba, pm_op);
-disable_irq_and_vops_clks:
+out:
+	if (ret)
+		ufshcd_update_evt_hist(hba, UFS_EVT_WL_RES_ERR, (u32)ret);
+	hba->clk_gating.is_suspended = false;
+	ufshcd_release(hba);
+	hba->pm_op_in_progress = false;
+	return ret;
+}
+
+static int ufshcd_wl_runtime_suspend(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct ufs_hba *hba;
+	int ret;
+	ktime_t start = ktime_get();
+
+	hba = shost_priv(sdev->host);
+
+	ret = __ufshcd_wl_suspend(hba, UFS_RUNTIME_PM);
+	if (ret)
+		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
+
+	trace_ufshcd_wl_runtime_suspend(dev_name(dev), ret,
+		ktime_to_us(ktime_sub(ktime_get(), start)),
+		hba->curr_dev_pwr_mode, hba->uic_link_state);
+
+	return ret;
+}
+
+static int ufshcd_wl_runtime_resume(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct ufs_hba *hba;
+	int ret = 0;
+	ktime_t start = ktime_get();
+
+	hba = shost_priv(sdev->host);
+
+	ret = __ufshcd_wl_resume(hba, UFS_RUNTIME_PM);
+	if (ret)
+		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
+
+	trace_ufshcd_wl_runtime_resume(dev_name(dev), ret,
+		ktime_to_us(ktime_sub(ktime_get(), start)),
+		hba->curr_dev_pwr_mode, hba->uic_link_state);
+
+	return ret;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int ufshcd_wl_suspend(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct ufs_hba *hba;
+	int ret;
+	ktime_t start = ktime_get();
+
+	hba = shost_priv(sdev->host);
+	ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
+	if (ret)
+		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
+
+	trace_ufshcd_wl_suspend(dev_name(dev), ret,
+		ktime_to_us(ktime_sub(ktime_get(), start)),
+		hba->curr_dev_pwr_mode, hba->uic_link_state);
+
+	return ret;
+}
+
+static int ufshcd_wl_resume(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct ufs_hba *hba;
+	int ret = 0;
+	ktime_t start = ktime_get();
+
+	if (pm_runtime_suspended(dev))
+		return 0;
+	hba = shost_priv(sdev->host);
+
+	ret = __ufshcd_wl_resume(hba, UFS_SYSTEM_PM);
+	if (ret)
+		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
+
+	trace_ufshcd_wl_resume(dev_name(dev), ret,
+		ktime_to_us(ktime_sub(ktime_get(), start)),
+		hba->curr_dev_pwr_mode, hba->uic_link_state);
+
+	return ret;
+}
+#endif
+
+static void ufshcd_wl_shutdown(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct ufs_hba *hba;
+
+	hba = shost_priv(sdev->host);
+	/* Turn on everything while shutting down */
+	scsi_autopm_get_device(sdev);
+	scsi_device_quiesce(sdev);
+	shost_for_each_device(sdev, hba->host) {
+		if (sdev == hba->sdev_ufs_device)
+			continue;
+		scsi_device_quiesce(sdev);
+	}
+	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
+}
+
+/**
+ * ufshcd_suspend - helper function for suspend operations
+ * @hba: per adapter instance
+ *
+ * This function will put disable irqs, turn off clocks
+ * and set vreg and hba-vreg in lpm mode.
+ * Also check the description of __ufshcd_wl_suspend().
+ */
+static void ufshcd_suspend(struct ufs_hba *hba)
+{
+	hba->pm_op_in_progress = 1;
+
+	/*
+	 * Disable the host irq as host controller as there won't be any
+	 * host controller transaction expected till resume.
+	 */
 	ufshcd_disable_irq(hba);
 	ufshcd_setup_clocks(hba, false);
 	if (ufshcd_is_clkgating_allowed(hba)) {
@@ -8948,6 +9064,43 @@  static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 		trace_ufshcd_clk_gating(dev_name(hba->dev),
 					hba->clk_gating.state);
 	}
+
+	ufshcd_vreg_set_lpm(hba);
+	/* Put the host controller in low power mode if possible */
+	ufshcd_hba_vreg_set_lpm(hba);
+	hba->pm_op_in_progress = 0;
+}
+
+/**
+ * ufshcd_resume - helper function for resume operations
+ * @hba: per adapter instance
+ *
+ * This function basically turns on the regulators, clocks and
+ * irqs of the hba.
+ * Also check the description of __ufshcd_wl_resume().
+ *
+ * Returns 0 for success and non-zero for failure
+ */
+static int ufshcd_resume(struct ufs_hba *hba)
+{
+	int ret;
+
+	hba->pm_op_in_progress = 1;
+
+	ufshcd_hba_vreg_set_hpm(hba);
+	ret = ufshcd_vreg_set_hpm(hba);
+	if (ret)
+		goto out;
+
+	/* Make sure clocks are enabled before accessing controller */
+	ret = ufshcd_setup_clocks(hba, true);
+	if (ret)
+		goto disable_vreg;
+
+	/* enable the host irq as host controller would be active soon */
+	ufshcd_enable_irq(hba);
+	goto out;
+
 disable_vreg:
 	ufshcd_vreg_set_lpm(hba);
 out:
@@ -8962,6 +9115,7 @@  static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
  * @hba: per adapter instance
  *
  * Check the description of ufshcd_suspend() function for more details.
+ * Also check the description of __ufshcd_wl_suspend().
  *
  * Returns 0 for success and non-zero for failure
  */
@@ -9001,7 +9155,7 @@  int ufshcd_system_suspend(struct ufs_hba *hba)
 			goto out;
 	}
 
-	ret = ufshcd_suspend(hba, UFS_SYSTEM_PM);
+	ufshcd_suspend(hba);
 out:
 	trace_ufshcd_system_suspend(dev_name(hba->dev), ret,
 		ktime_to_us(ktime_sub(ktime_get(), start)),
@@ -9023,7 +9177,6 @@  EXPORT_SYMBOL(ufshcd_system_suspend);
 
 int ufshcd_system_resume(struct ufs_hba *hba)
 {
-	int ret = 0;
 	ktime_t start = ktime_get();
 
 	if (!hba)
@@ -9041,15 +9194,15 @@  int ufshcd_system_resume(struct ufs_hba *hba)
 		 */
 		goto out;
 	else
-		ret = ufshcd_resume(hba, UFS_SYSTEM_PM);
+		ufshcd_resume(hba);
 out:
-	trace_ufshcd_system_resume(dev_name(hba->dev), ret,
+	trace_ufshcd_system_resume(dev_name(hba->dev), 0,
 		ktime_to_us(ktime_sub(ktime_get(), start)),
 		hba->curr_dev_pwr_mode, hba->uic_link_state);
-	if (!ret)
-		hba->is_sys_suspended = false;
+
+	hba->is_sys_suspended = false;
 	up(&hba->host_sem);
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(ufshcd_system_resume);
 
@@ -9058,12 +9211,12 @@  EXPORT_SYMBOL(ufshcd_system_resume);
  * @hba: per adapter instance
  *
  * Check the description of ufshcd_suspend() function for more details.
+ * Also check the description of __ufshcd_wl_suspend().
  *
  * Returns 0 for success and non-zero for failure
  */
 int ufshcd_runtime_suspend(struct ufs_hba *hba)
 {
-	int ret = 0;
 	ktime_t start = ktime_get();
 
 	if (!hba)
@@ -9072,12 +9225,12 @@  int ufshcd_runtime_suspend(struct ufs_hba *hba)
 	if (!hba->is_powered)
 		goto out;
 	else
-		ret = ufshcd_suspend(hba, UFS_RUNTIME_PM);
+		ufshcd_suspend(hba);
 out:
-	trace_ufshcd_runtime_suspend(dev_name(hba->dev), ret,
+	trace_ufshcd_runtime_suspend(dev_name(hba->dev), 0,
 		ktime_to_us(ktime_sub(ktime_get(), start)),
 		hba->curr_dev_pwr_mode, hba->uic_link_state);
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(ufshcd_runtime_suspend);
 
@@ -9085,26 +9238,14 @@  EXPORT_SYMBOL(ufshcd_runtime_suspend);
  * ufshcd_runtime_resume - runtime resume routine
  * @hba: per adapter instance
  *
- * This function basically brings the UFS device, UniPro link and controller
+ * This function basically brings controller
  * to active state. Following operations are done in this function:
  *
  * 1. Turn on all the controller related clocks
- * 2. Bring the UniPro link out of Hibernate state
- * 3. If UFS device is in sleep state, turn ON VCC rail and bring the UFS device
- *    to active state.
- * 4. If auto-bkops is enabled on the device, disable it.
- *
- * So following would be the possible power state after this function return
- * successfully:
- *	S1: UFS device in Active state with VCC rail ON
- *	    UniPro link in Active state
- *	    All the UFS/UniPro controller clocks are ON
- *
- * Returns 0 for success and non-zero for failure
+ * 2. Turn ON VCC rail
  */
 int ufshcd_runtime_resume(struct ufs_hba *hba)
 {
-	int ret = 0;
 	ktime_t start = ktime_get();
 
 	if (!hba)
@@ -9113,12 +9254,12 @@  int ufshcd_runtime_resume(struct ufs_hba *hba)
 	if (!hba->is_powered)
 		goto out;
 	else
-		ret = ufshcd_resume(hba, UFS_RUNTIME_PM);
+		ufshcd_resume(hba);
 out:
-	trace_ufshcd_runtime_resume(dev_name(hba->dev), ret,
+	trace_ufshcd_runtime_resume(dev_name(hba->dev), 0,
 		ktime_to_us(ktime_sub(ktime_get(), start)),
 		hba->curr_dev_pwr_mode, hba->uic_link_state);
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(ufshcd_runtime_resume);
 
@@ -9132,14 +9273,13 @@  EXPORT_SYMBOL(ufshcd_runtime_idle);
  * ufshcd_shutdown - shutdown routine
  * @hba: per adapter instance
  *
- * This function would power off both UFS device and UFS link.
+ * This function would turn off both UFS device and UFS hba
+ * regulators. It would also disable clocks.
  *
  * Returns 0 always to allow force shutdown even in case of errors.
  */
 int ufshcd_shutdown(struct ufs_hba *hba)
 {
-	int ret = 0;
-
 	down(&hba->host_sem);
 	hba->shutting_down = true;
 	up(&hba->host_sem);
@@ -9152,10 +9292,8 @@  int ufshcd_shutdown(struct ufs_hba *hba)
 
 	pm_runtime_get_sync(hba->dev);
 
-	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
+	ufshcd_suspend(hba);
 out:
-	if (ret)
-		dev_err(hba->dev, "%s failed, err %d\n", __func__, ret);
 	hba->is_powered = false;
 	/* allow force shutdown even in case of errors */
 	return 0;
@@ -9477,15 +9615,160 @@  int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 }
 EXPORT_SYMBOL_GPL(ufshcd_init);
 
+void ufshcd_resume_complete(struct device *dev)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	pm_runtime_put_noidle(&hba->sdev_ufs_device->sdev_gendev);
+}
+EXPORT_SYMBOL_GPL(ufshcd_resume_complete);
+
+int ufshcd_suspend_prepare(struct device *dev)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	/*
+	 * SCSI assumes that runtime-pm and system-pm for scsi drivers
+	 * are same. And it doesn't wake up the device for system-suspend
+	 * if it's runtime suspended. But ufs doesn't follow that.
+	 * The rpm-lvl and spm-lvl can be different in ufs.
+	 * Force it to honor system-suspend.
+	 */
+	scsi_autopm_get_device(hba->sdev_ufs_device);
+	/* Refer ufshcd_resume_complete() */
+	pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev);
+	scsi_autopm_put_device(hba->sdev_ufs_device);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ufshcd_suspend_prepare);
+
+#ifdef CONFIG_PM_SLEEP
+static int ufshcd_wl_poweroff(struct device *dev)
+{
+	ufshcd_wl_shutdown(dev);
+	return 0;
+}
+#endif
+
+static int ufshcd_wl_probe(struct device *dev)
+{
+	return is_device_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
+}
+
+static int ufshcd_wl_remove(struct device *dev)
+{
+	return 0;
+}
+
+static const struct dev_pm_ops ufshcd_wl_pm_ops = {
+#ifdef CONFIG_PM_SLEEP
+	.suspend = ufshcd_wl_suspend,
+	.resume = ufshcd_wl_resume,
+	.freeze = ufshcd_wl_suspend,
+	.thaw = ufshcd_wl_resume,
+	.poweroff = ufshcd_wl_poweroff,
+	.restore = ufshcd_wl_resume,
+#endif
+	SET_RUNTIME_PM_OPS(ufshcd_wl_runtime_suspend, ufshcd_wl_runtime_resume, NULL)
+};
+
+/**
+ * ufs_dev_wlun_template - describes ufs device wlun
+ * ufs-device wlun - used to send pm commands
+ * All luns are consumers of ufs-device wlun.
+ *
+ * Currently, no sd driver is present for wluns.
+ * Hence the no specific pm operations are performed.
+ * With ufs design, SSU should be sent to ufs-device wlun.
+ * Hence register a scsi driver for ufs wluns only.
+ */
+static struct scsi_driver ufs_dev_wlun_template = {
+	.gendrv = {
+		.name = "ufs_device_wlun",
+		.owner = THIS_MODULE,
+		.probe = ufshcd_wl_probe,
+		.remove = ufshcd_wl_remove,
+		.pm = &ufshcd_wl_pm_ops,
+		.shutdown = ufshcd_wl_shutdown,
+	},
+};
+
+static int ufshcd_rpmb_probe(struct device *dev)
+{
+	return is_rpmb_wlun(to_scsi_device(dev)) ? 0 : -ENODEV;
+}
+
+static inline int ufshcd_clear_rpmb_uac(struct ufs_hba *hba)
+{
+	int ret = 0;
+
+	if (!hba->wlun_rpmb_clr_ua)
+		return 0;
+	ret = ufshcd_clear_ua_wlun(hba, UFS_UPIU_RPMB_WLUN);
+	if (!ret)
+		hba->wlun_rpmb_clr_ua = 0;
+	return ret;
+}
+
+static int ufshcd_rpmb_runtime_resume(struct device *dev)
+{
+	struct ufs_hba *hba = wlun_dev_to_hba(dev);
+
+	if (hba->sdev_rpmb)
+		return ufshcd_clear_rpmb_uac(hba);
+	return 0;
+}
+
+static int ufshcd_rpmb_resume(struct device *dev)
+{
+	struct ufs_hba *hba = wlun_dev_to_hba(dev);
+
+	if (hba->sdev_rpmb && !pm_runtime_suspended(dev))
+		return ufshcd_clear_rpmb_uac(hba);
+	return 0;
+}
+
+static const struct dev_pm_ops ufs_rpmb_pm_ops = {
+	SET_RUNTIME_PM_OPS(NULL, ufshcd_rpmb_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(NULL, ufshcd_rpmb_resume)
+};
+
+/**
+ * Describes the ufs rpmb wlun.
+ * Used only to send uac.
+ */
+static struct scsi_driver ufs_rpmb_wlun_template = {
+	.gendrv = {
+		.name = "ufs_rpmb_wlun",
+		.owner = THIS_MODULE,
+		.probe = ufshcd_rpmb_probe,
+		.pm = &ufs_rpmb_pm_ops,
+	},
+};
+
 static int __init ufshcd_core_init(void)
 {
+	int ret;
+
 	ufs_debugfs_init();
+
+	ret = scsi_register_driver(&ufs_dev_wlun_template.gendrv);
+	if (ret)
+		return ret;
+
+	ret = scsi_register_driver(&ufs_rpmb_wlun_template.gendrv);
+	if (ret) {
+		scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);
+		return ret;
+	}
 	return 0;
 }
 
 static void __exit ufshcd_core_exit(void)
 {
 	ufs_debugfs_exit();
+	scsi_unregister_driver(&ufs_dev_wlun_template.gendrv);
+	scsi_unregister_driver(&ufs_rpmb_wlun_template.gendrv);
 }
 
 module_init(ufshcd_core_init);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index ee61f82..e246ec3 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -72,6 +72,8 @@  enum ufs_event_type {
 	UFS_EVT_LINK_STARTUP_FAIL,
 	UFS_EVT_RESUME_ERR,
 	UFS_EVT_SUSPEND_ERR,
+	UFS_EVT_WL_SUSP_ERR,
+	UFS_EVT_WL_RES_ERR,
 
 	/* abnormal events */
 	UFS_EVT_DEV_RESET,
@@ -804,6 +806,7 @@  struct ufs_hba {
 	struct list_head clk_list_head;
 
 	bool wlun_dev_clr_ua;
+	bool wlun_rpmb_clr_ua;
 
 	/* Number of requests aborts */
 	int req_abort_count;
@@ -841,6 +844,8 @@  struct ufs_hba {
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs_root;
 #endif
+	bool init_done;
+	u32 luns_avail;
 };
 
 /* Returns true if clocks can be gated. Otherwise false */
@@ -1100,6 +1105,8 @@  int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
 			     enum query_opcode desc_op);
 
 int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable);
+int ufshcd_suspend_prepare(struct device *dev);
+void ufshcd_resume_complete(struct device *dev);
 
 /* Wrapper functions for safely calling variant operations */
 static inline const char *ufshcd_get_var_name(struct ufs_hba *hba)
diff --git a/include/trace/events/ufs.h b/include/trace/events/ufs.h
index e151477..d9d233b 100644
--- a/include/trace/events/ufs.h
+++ b/include/trace/events/ufs.h
@@ -246,6 +246,26 @@  DEFINE_EVENT(ufshcd_template, ufshcd_init,
 		      int dev_state, int link_state),
 	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
 
+DEFINE_EVENT(ufshcd_template, ufshcd_wl_suspend,
+	     TP_PROTO(const char *dev_name, int err, s64 usecs,
+		      int dev_state, int link_state),
+	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
+
+DEFINE_EVENT(ufshcd_template, ufshcd_wl_resume,
+	     TP_PROTO(const char *dev_name, int err, s64 usecs,
+		      int dev_state, int link_state),
+	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
+
+DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_suspend,
+	     TP_PROTO(const char *dev_name, int err, s64 usecs,
+		      int dev_state, int link_state),
+	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
+
+DEFINE_EVENT(ufshcd_template, ufshcd_wl_runtime_resume,
+	     TP_PROTO(const char *dev_name, int err, s64 usecs,
+		      int dev_state, int link_state),
+	     TP_ARGS(dev_name, err, usecs, dev_state, link_state));
+
 TRACE_EVENT(ufshcd_command,
 	TP_PROTO(const char *dev_name, enum ufs_trace_str_t str_t,
 		 unsigned int tag, u32 doorbell, int transfer_len, u32 intr,