| Message ID | 20200529092310.1106-2-stanley.chu@mediatek.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | scsi: ufs-mediatek: Fix clk-gating and introduce low-power mode for vccq2 | expand |
> > Currently ref-clk control timeout is implemented by Jiffies. However > jiffies is not accurate enough thus "false timeout" may happen. > > Use more accurate delay mechanism instead, for example, ktime. > > Signed-off-by: Stanley Chu <stanley.chu@mediatek.com> > Reviewed-by: Andy Teng <andy.teng@mediatek.com> Reviewed-by: Avri Altman <avri.altman@wdc.com> > --- > drivers/scsi/ufs/ufs-mediatek.c | 7 ++++--- > drivers/scsi/ufs/ufs-mediatek.h | 2 +- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c > index d56ce8d97d4e..523ee5573921 100644 > --- a/drivers/scsi/ufs/ufs-mediatek.c > +++ b/drivers/scsi/ufs/ufs-mediatek.c > @@ -120,7 +120,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, > bool on) > { > struct ufs_mtk_host *host = ufshcd_get_variant(hba); > struct arm_smccc_res res; > - unsigned long timeout; > + ktime_t timeout, time_checked; > u32 value; > > if (host->ref_clk_enabled == on) > @@ -135,8 +135,9 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, > bool on) > } > > /* Wait for ack */ > - timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS); > + timeout = ktime_add_us(ktime_get(), REFCLK_REQ_TIMEOUT_US); > do { > + time_checked = ktime_get(); > value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL); > > /* Wait until ack bit equals to req bit */ > @@ -144,7 +145,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, > bool on) > goto out; > > usleep_range(100, 200); > - } while (time_before(jiffies, timeout)); > + } while (ktime_before(time_checked, timeout)); Nit: you could get rid of time_checked if you would use ktime_compare(ktime_get(), timeout) > 0 Thanks, Avri > > dev_err(hba->dev, "missing ack of refclk req, reg: 0x%x\n", value); > > diff --git a/drivers/scsi/ufs/ufs-mediatek.h b/drivers/scsi/ufs/ufs-mediatek.h > index 5bbd3e9cbae2..fc42dcbfd800 100644 > --- a/drivers/scsi/ufs/ufs-mediatek.h > +++ b/drivers/scsi/ufs/ufs-mediatek.h > @@ -28,7 +28,7 @@ > #define REFCLK_REQUEST BIT(0) > #define REFCLK_ACK BIT(1) > > -#define REFCLK_REQ_TIMEOUT_MS 3 > +#define REFCLK_REQ_TIMEOUT_US 3000 > > /* > * Vendor specific pre-defined parameters > -- > 2.18.0
Hi Avri, On Sun, 2020-05-31 at 07:10 +0000, Avri Altman wrote: > > > > Currently ref-clk control timeout is implemented by Jiffies. However > > jiffies is not accurate enough thus "false timeout" may happen. > > > > Use more accurate delay mechanism instead, for example, ktime. > > > > Signed-off-by: Stanley Chu <stanley.chu@mediatek.com> > > Reviewed-by: Andy Teng <andy.teng@mediatek.com> > Reviewed-by: Avri Altman <avri.altman@wdc.com> > Thanks for your review. > > > > /* Wait for ack */ > > - timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS); > > + timeout = ktime_add_us(ktime_get(), REFCLK_REQ_TIMEOUT_US); > > do { > > + time_checked = ktime_get(); > > value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL); > > > > /* Wait until ack bit equals to req bit */ > > @@ -144,7 +145,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, > > bool on) > > goto out; > > > > usleep_range(100, 200); > > - } while (time_before(jiffies, timeout)); > > + } while (ktime_before(time_checked, timeout)); > Nit: you could get rid of time_checked if you would use ktime_compare(ktime_get(), timeout) > 0 > > Thanks, > Avri If this context is preempted and scheduled out between ufshcd_readl() and ktime_compare(ktime_get(), timeout), then the ktime_get() may get a "timed-out" time even though the last ufshcd_readl() is actually executed before the "timed-out" time. In this case, false alarm will show up. Using "time_checked" here could solve above issue. Thanks, Stanley Chu
diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c index d56ce8d97d4e..523ee5573921 100644 --- a/drivers/scsi/ufs/ufs-mediatek.c +++ b/drivers/scsi/ufs/ufs-mediatek.c @@ -120,7 +120,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on) { struct ufs_mtk_host *host = ufshcd_get_variant(hba); struct arm_smccc_res res; - unsigned long timeout; + ktime_t timeout, time_checked; u32 value; if (host->ref_clk_enabled == on) @@ -135,8 +135,9 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on) } /* Wait for ack */ - timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS); + timeout = ktime_add_us(ktime_get(), REFCLK_REQ_TIMEOUT_US); do { + time_checked = ktime_get(); value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL); /* Wait until ack bit equals to req bit */ @@ -144,7 +145,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on) goto out; usleep_range(100, 200); - } while (time_before(jiffies, timeout)); + } while (ktime_before(time_checked, timeout)); dev_err(hba->dev, "missing ack of refclk req, reg: 0x%x\n", value); diff --git a/drivers/scsi/ufs/ufs-mediatek.h b/drivers/scsi/ufs/ufs-mediatek.h index 5bbd3e9cbae2..fc42dcbfd800 100644 --- a/drivers/scsi/ufs/ufs-mediatek.h +++ b/drivers/scsi/ufs/ufs-mediatek.h @@ -28,7 +28,7 @@ #define REFCLK_REQUEST BIT(0) #define REFCLK_ACK BIT(1) -#define REFCLK_REQ_TIMEOUT_MS 3 +#define REFCLK_REQ_TIMEOUT_US 3000 /* * Vendor specific pre-defined parameters