diff mbox series

[v2] PCI: cadence: Set LTSSM Detect Quiet state minimum delay as workaround for training defect.

Message ID 20210528155626.21793-1-nadeem@cadence.com (mailing list archive)
State New
Delegated to: Lorenzo Pieralisi
Headers show
Series [v2] PCI: cadence: Set LTSSM Detect Quiet state minimum delay as workaround for training defect. | expand

Commit Message

Nadeem Athani May 28, 2021, 3:56 p.m. UTC
PCIe fails to link up if SERDES lanes not used by PCIe are assigned to
another protocol. For example, link training fails if lanes 2 and 3 are
assigned to another protocol while lanes 0 and 1 are used for PCIe to
form a two lane link. This failure is due to an incorrect tie-off on an
internal status signal indicating electrical idle.

Status signals going from SERDES to PCIe Controller are tied-off when a
lane is not assigned to PCIe. Signal indicating electrical idle is
incorrectly tied-off to a state that indicates non-idle. As a result,
PCIe sees unused lanes to be out of electrical idle and this causes
LTSSM to exit Detect.Quiet state without waiting for 12ms timeout to
occur. If a receiver is not detected on the first receiver detection
attempt in Detect.Active state, LTSSM goes back to Detect.Quiet and
again moves forward to Detect.Active state without waiting for 12ms as
required by PCIe base specification. Since wait time in Detect.Quiet is
skipped, multiple receiver detect operations are performed back-to-back
without allowing time for capacitance on the transmit lines to
discharge. This causes subsequent receiver detection to always fail even
if a receiver gets connected eventually.

Adding a quirk flag "quirk_detect_quiet_flag" to program the minimum
time that LTSSM waits on entering Detect.Quiet state.
Setting this to 2ms for specific TI j7200 SOC as a workaround to resolve
a link training issue in IP.
In future revisions this setting will not be required.

As per PCIe specification, all Receivers must meet the Z-RX-DC
specification for 2.5 GT/s within 1ms of entering Detect.Quiet LTSSM
substate. The LTSSM must stay in this substate until the ZRXDC
specification for 2.5 GT/s is met.

00 : 0 minimum wait time in Detect.Quiet state.
01 : 100us minimum wait time in Detect.Quiet state.
10 : 1ms minimum wait time in Detect.Quiet state.
11 : 2ms minimum wait time in Detect.Quiet state.

Changes in v2:
1. Adding the function cdns_pcie_detect_quiet_min_delay_set in
pcie-cadence.c and invoking it from host and endpoint driver file.

Signed-off-by: Nadeem Athani <nadeem@cadence.com>
---
 drivers/pci/controller/cadence/pcie-cadence-ep.c   |  4 ++++
 drivers/pci/controller/cadence/pcie-cadence-host.c |  3 +++
 drivers/pci/controller/cadence/pcie-cadence.c      | 17 +++++++++++++++++
 drivers/pci/controller/cadence/pcie-cadence.h      | 15 +++++++++++++++
 4 files changed, 39 insertions(+)

Comments

Bjorn Helgaas June 4, 2021, 9:22 p.m. UTC | #1
On Fri, May 28, 2021 at 05:56:26PM +0200, Nadeem Athani wrote:
> PCIe fails to link up if SERDES lanes not used by PCIe are assigned to
> another protocol. For example, link training fails if lanes 2 and 3 are
> assigned to another protocol while lanes 0 and 1 are used for PCIe to
> form a two lane link. This failure is due to an incorrect tie-off on an
> internal status signal indicating electrical idle.
> 
> Status signals going from SERDES to PCIe Controller are tied-off when a
> lane is not assigned to PCIe. Signal indicating electrical idle is
> incorrectly tied-off to a state that indicates non-idle. As a result,
> PCIe sees unused lanes to be out of electrical idle and this causes
> LTSSM to exit Detect.Quiet state without waiting for 12ms timeout to
> occur. If a receiver is not detected on the first receiver detection
> attempt in Detect.Active state, LTSSM goes back to Detect.Quiet and
> again moves forward to Detect.Active state without waiting for 12ms as
> required by PCIe base specification. Since wait time in Detect.Quiet is
> skipped, multiple receiver detect operations are performed back-to-back
> without allowing time for capacitance on the transmit lines to
> discharge. This causes subsequent receiver detection to always fail even
> if a receiver gets connected eventually.
> 
> Adding a quirk flag "quirk_detect_quiet_flag" to program the minimum
> time that LTSSM waits on entering Detect.Quiet state.
> Setting this to 2ms for specific TI j7200 SOC as a workaround to resolve
> a link training issue in IP.
> In future revisions this setting will not be required.
> 
> As per PCIe specification, all Receivers must meet the Z-RX-DC
> specification for 2.5 GT/s within 1ms of entering Detect.Quiet LTSSM
> substate. The LTSSM must stay in this substate until the ZRXDC
> specification for 2.5 GT/s is met.
> 
> 00 : 0 minimum wait time in Detect.Quiet state.
> 01 : 100us minimum wait time in Detect.Quiet state.
> 10 : 1ms minimum wait time in Detect.Quiet state.
> 11 : 2ms minimum wait time in Detect.Quiet state.
> 
> Changes in v2:
> 1. Adding the function cdns_pcie_detect_quiet_min_delay_set in
> pcie-cadence.c and invoking it from host and endpoint driver file.
> 
> Signed-off-by: Nadeem Athani <nadeem@cadence.com>
> ---
>  drivers/pci/controller/cadence/pcie-cadence-ep.c   |  4 ++++
>  drivers/pci/controller/cadence/pcie-cadence-host.c |  3 +++
>  drivers/pci/controller/cadence/pcie-cadence.c      | 17 +++++++++++++++++
>  drivers/pci/controller/cadence/pcie-cadence.h      | 15 +++++++++++++++
>  4 files changed, 39 insertions(+)
> 
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> index 897cdde02bd8..dd7df1ac7fda 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> @@ -623,6 +623,10 @@ int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
>  	ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
>  	/* Reserve region 0 for IRQs */
>  	set_bit(0, &ep->ob_region_map);
> +
> +	if (ep->quirk_detect_quiet_flag)
> +		cdns_pcie_detect_quiet_min_delay_set(&ep->pcie);
> +
>  	spin_lock_init(&ep->lock);
>  
>  	return 0;
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index ae1c55503513..fb96d37a135c 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -498,6 +498,9 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
>  		return PTR_ERR(rc->cfg_base);
>  	rc->cfg_res = res;
>  
> +	if (rc->quirk_detect_quiet_flag)
> +		cdns_pcie_detect_quiet_min_delay_set(&rc->pcie);
> +
>  	ret = cdns_pcie_start_link(pcie);
>  	if (ret) {
>  		dev_err(dev, "Failed to start link\n");
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
> index 3c3646502d05..65b6c8bed0d4 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence.c
> @@ -7,6 +7,23 @@
>  
>  #include "pcie-cadence.h"
>  
> +void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie)
> +{
> +	u32 delay = 0x3;
> +	u32 ltssm_control_cap;
> +
> +	/*
> +	 * Set the LTSSM Detect Quiet state min. delay to 2ms.
> +	 */
> +
> +	ltssm_control_cap = cdns_pcie_readl(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP);
> +	ltssm_control_cap = ((ltssm_control_cap &
> +			    ~CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK) |
> +			    CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay));
> +
> +	cdns_pcie_writel(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP, ltssm_control_cap);
> +}
> +
>  void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
>  				   u32 r, bool is_io,
>  				   u64 cpu_addr, u64 pci_addr, size_t size)
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
> index 254d2570f8c9..ccdf9cee9dde 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.h
> +++ b/drivers/pci/controller/cadence/pcie-cadence.h
> @@ -189,6 +189,14 @@
>  /* AXI link down register */
>  #define CDNS_PCIE_AT_LINKDOWN (CDNS_PCIE_AT_BASE + 0x0824)
>  
> +/* LTSSM Capabilities register */
> +#define CDNS_PCIE_LTSSM_CONTROL_CAP             (CDNS_PCIE_LM_BASE + 0x0054)
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK  GENMASK(2, 1)
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT 1
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay) \
> +	 (((delay) << CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT) & \
> +	 CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK)
> +
>  enum cdns_pcie_rp_bar {
>  	RP_BAR_UNDEFINED = -1,
>  	RP_BAR0,
> @@ -292,6 +300,7 @@ struct cdns_pcie {
>   * @avail_ib_bar: Satus of RP_BAR0, RP_BAR1 and	RP_NO_BAR if it's free or
>   *                available
>   * @quirk_retrain_flag: Retrain link as quirk for PCIe Gen2
> + * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
>   */
>  struct cdns_pcie_rc {
>  	struct cdns_pcie	pcie;
> @@ -301,6 +310,7 @@ struct cdns_pcie_rc {
>  	u32			device_id;
>  	bool			avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
>  	bool                    quirk_retrain_flag;
> +	bool                    quirk_detect_quiet_flag;
>  };
>  
>  /**
> @@ -331,6 +341,7 @@ struct cdns_pcie_epf {
>   *        registers fields (RMW) accessible by both remote RC and EP to
>   *        minimize time between read and write
>   * @epf: Structure to hold info about endpoint function
> + * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
>   */
>  struct cdns_pcie_ep {
>  	struct cdns_pcie	pcie;
> @@ -345,6 +356,7 @@ struct cdns_pcie_ep {
>  	/* protect writing to PCI_STATUS while raising legacy interrupts */
>  	spinlock_t		lock;
>  	struct cdns_pcie_epf	*epf;
> +	bool                    quirk_detect_quiet_flag;

1) I don't see this being set anywhere.  Are there follow-on patches
that set it?  We try not to merge things until they are actually used.

2) I typically use "unsigned int foo:1" in structures for this ancient
reason [1].  But it's not always practical, e.g., with the
avail_ib_bar[] array above, and I do see that this follows the
existing style in the file, which is good.

[1] https://lore.kernel.org/linux-fsdevel/CA+55aFzKQ6Pj18TB8p4Yr0M4t+S+BsiHH=BJNmn=76-NcjTj-g@mail.gmail.com/

>  };
>  
>  
> @@ -505,6 +517,9 @@ static inline int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
>  	return 0;
>  }
>  #endif
> +
> +void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
> +
>  void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
>  				   u32 r, bool is_io,
>  				   u64 cpu_addr, u64 pci_addr, size_t size);
> -- 
> 2.15.0
>
Lorenzo Pieralisi June 21, 2021, 5:18 p.m. UTC | #2
Subjects should not end with a period, remove it.

On Fri, May 28, 2021 at 05:56:26PM +0200, Nadeem Athani wrote:
> PCIe fails to link up if SERDES lanes not used by PCIe are assigned to
> another protocol. For example, link training fails if lanes 2 and 3 are
> assigned to another protocol while lanes 0 and 1 are used for PCIe to
> form a two lane link. This failure is due to an incorrect tie-off on an
> internal status signal indicating electrical idle.
> 
> Status signals going from SERDES to PCIe Controller are tied-off when a
> lane is not assigned to PCIe. Signal indicating electrical idle is
> incorrectly tied-off to a state that indicates non-idle. As a result,
> PCIe sees unused lanes to be out of electrical idle and this causes
> LTSSM to exit Detect.Quiet state without waiting for 12ms timeout to
> occur. If a receiver is not detected on the first receiver detection
> attempt in Detect.Active state, LTSSM goes back to Detect.Quiet and
> again moves forward to Detect.Active state without waiting for 12ms as
> required by PCIe base specification. Since wait time in Detect.Quiet is
> skipped, multiple receiver detect operations are performed back-to-back
> without allowing time for capacitance on the transmit lines to
> discharge. This causes subsequent receiver detection to always fail even
> if a receiver gets connected eventually.
> 
> Adding a quirk flag "quirk_detect_quiet_flag" to program the minimum
> time that LTSSM waits on entering Detect.Quiet state.
> Setting this to 2ms for specific TI j7200 SOC as a workaround to resolve
> a link training issue in IP.
> In future revisions this setting will not be required.
> 
> As per PCIe specification, all Receivers must meet the Z-RX-DC
> specification for 2.5 GT/s within 1ms of entering Detect.Quiet LTSSM
> substate. The LTSSM must stay in this substate until the ZRXDC
> specification for 2.5 GT/s is met.
> 
> 00 : 0 minimum wait time in Detect.Quiet state.
> 01 : 100us minimum wait time in Detect.Quiet state.
> 10 : 1ms minimum wait time in Detect.Quiet state.
> 11 : 2ms minimum wait time in Detect.Quiet state.
> 
> Changes in v2:
> 1. Adding the function cdns_pcie_detect_quiet_min_delay_set in
> pcie-cadence.c and invoking it from host and endpoint driver file.
> 
> Signed-off-by: Nadeem Athani <nadeem@cadence.com>
> ---
>  drivers/pci/controller/cadence/pcie-cadence-ep.c   |  4 ++++
>  drivers/pci/controller/cadence/pcie-cadence-host.c |  3 +++
>  drivers/pci/controller/cadence/pcie-cadence.c      | 17 +++++++++++++++++
>  drivers/pci/controller/cadence/pcie-cadence.h      | 15 +++++++++++++++
>  4 files changed, 39 insertions(+)

Can you tell me please what's the status of these patches ?

https://patchwork.kernel.org/user/todo/linux-pci/?series=&submitter=194539&state=&q=&archive=

Are they all solving the same problem so I only have to review:

https://patchwork.kernel.org/project/linux-pci/patch/20210528155626.21793-1-nadeem@cadence.com

?

I am asking because the "first" posting was a two-patch series and then it
became one, I lost track of versions in between.

Thanks,
Lorenzo

> diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> index 897cdde02bd8..dd7df1ac7fda 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> @@ -623,6 +623,10 @@ int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
>  	ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
>  	/* Reserve region 0 for IRQs */
>  	set_bit(0, &ep->ob_region_map);
> +
> +	if (ep->quirk_detect_quiet_flag)
> +		cdns_pcie_detect_quiet_min_delay_set(&ep->pcie);
> +
>  	spin_lock_init(&ep->lock);
>  
>  	return 0;
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index ae1c55503513..fb96d37a135c 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -498,6 +498,9 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
>  		return PTR_ERR(rc->cfg_base);
>  	rc->cfg_res = res;
>  
> +	if (rc->quirk_detect_quiet_flag)
> +		cdns_pcie_detect_quiet_min_delay_set(&rc->pcie);
> +
>  	ret = cdns_pcie_start_link(pcie);
>  	if (ret) {
>  		dev_err(dev, "Failed to start link\n");
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
> index 3c3646502d05..65b6c8bed0d4 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence.c
> @@ -7,6 +7,23 @@
>  
>  #include "pcie-cadence.h"
>  
> +void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie)
> +{
> +	u32 delay = 0x3;
> +	u32 ltssm_control_cap;
> +
> +	/*
> +	 * Set the LTSSM Detect Quiet state min. delay to 2ms.
> +	 */
> +
> +	ltssm_control_cap = cdns_pcie_readl(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP);
> +	ltssm_control_cap = ((ltssm_control_cap &
> +			    ~CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK) |
> +			    CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay));
> +
> +	cdns_pcie_writel(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP, ltssm_control_cap);
> +}
> +
>  void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
>  				   u32 r, bool is_io,
>  				   u64 cpu_addr, u64 pci_addr, size_t size)
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
> index 254d2570f8c9..ccdf9cee9dde 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.h
> +++ b/drivers/pci/controller/cadence/pcie-cadence.h
> @@ -189,6 +189,14 @@
>  /* AXI link down register */
>  #define CDNS_PCIE_AT_LINKDOWN (CDNS_PCIE_AT_BASE + 0x0824)
>  
> +/* LTSSM Capabilities register */
> +#define CDNS_PCIE_LTSSM_CONTROL_CAP             (CDNS_PCIE_LM_BASE + 0x0054)
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK  GENMASK(2, 1)
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT 1
> +#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay) \
> +	 (((delay) << CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT) & \
> +	 CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK)
> +
>  enum cdns_pcie_rp_bar {
>  	RP_BAR_UNDEFINED = -1,
>  	RP_BAR0,
> @@ -292,6 +300,7 @@ struct cdns_pcie {
>   * @avail_ib_bar: Satus of RP_BAR0, RP_BAR1 and	RP_NO_BAR if it's free or
>   *                available
>   * @quirk_retrain_flag: Retrain link as quirk for PCIe Gen2
> + * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
>   */
>  struct cdns_pcie_rc {
>  	struct cdns_pcie	pcie;
> @@ -301,6 +310,7 @@ struct cdns_pcie_rc {
>  	u32			device_id;
>  	bool			avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
>  	bool                    quirk_retrain_flag;
> +	bool                    quirk_detect_quiet_flag;
>  };
>  
>  /**
> @@ -331,6 +341,7 @@ struct cdns_pcie_epf {
>   *        registers fields (RMW) accessible by both remote RC and EP to
>   *        minimize time between read and write
>   * @epf: Structure to hold info about endpoint function
> + * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
>   */
>  struct cdns_pcie_ep {
>  	struct cdns_pcie	pcie;
> @@ -345,6 +356,7 @@ struct cdns_pcie_ep {
>  	/* protect writing to PCI_STATUS while raising legacy interrupts */
>  	spinlock_t		lock;
>  	struct cdns_pcie_epf	*epf;
> +	bool                    quirk_detect_quiet_flag;
>  };
>  
>  
> @@ -505,6 +517,9 @@ static inline int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
>  	return 0;
>  }
>  #endif
> +
> +void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
> +
>  void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
>  				   u32 r, bool is_io,
>  				   u64 cpu_addr, u64 pci_addr, size_t size);
> -- 
> 2.15.0
>
diff mbox series

Patch

diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
index 897cdde02bd8..dd7df1ac7fda 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
@@ -623,6 +623,10 @@  int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
 	ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
 	/* Reserve region 0 for IRQs */
 	set_bit(0, &ep->ob_region_map);
+
+	if (ep->quirk_detect_quiet_flag)
+		cdns_pcie_detect_quiet_min_delay_set(&ep->pcie);
+
 	spin_lock_init(&ep->lock);
 
 	return 0;
diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index ae1c55503513..fb96d37a135c 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -498,6 +498,9 @@  int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
 		return PTR_ERR(rc->cfg_base);
 	rc->cfg_res = res;
 
+	if (rc->quirk_detect_quiet_flag)
+		cdns_pcie_detect_quiet_min_delay_set(&rc->pcie);
+
 	ret = cdns_pcie_start_link(pcie);
 	if (ret) {
 		dev_err(dev, "Failed to start link\n");
diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
index 3c3646502d05..65b6c8bed0d4 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.c
+++ b/drivers/pci/controller/cadence/pcie-cadence.c
@@ -7,6 +7,23 @@ 
 
 #include "pcie-cadence.h"
 
+void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie)
+{
+	u32 delay = 0x3;
+	u32 ltssm_control_cap;
+
+	/*
+	 * Set the LTSSM Detect Quiet state min. delay to 2ms.
+	 */
+
+	ltssm_control_cap = cdns_pcie_readl(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP);
+	ltssm_control_cap = ((ltssm_control_cap &
+			    ~CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK) |
+			    CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay));
+
+	cdns_pcie_writel(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP, ltssm_control_cap);
+}
+
 void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
 				   u32 r, bool is_io,
 				   u64 cpu_addr, u64 pci_addr, size_t size)
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index 254d2570f8c9..ccdf9cee9dde 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -189,6 +189,14 @@ 
 /* AXI link down register */
 #define CDNS_PCIE_AT_LINKDOWN (CDNS_PCIE_AT_BASE + 0x0824)
 
+/* LTSSM Capabilities register */
+#define CDNS_PCIE_LTSSM_CONTROL_CAP             (CDNS_PCIE_LM_BASE + 0x0054)
+#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK  GENMASK(2, 1)
+#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT 1
+#define  CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay) \
+	 (((delay) << CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT) & \
+	 CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK)
+
 enum cdns_pcie_rp_bar {
 	RP_BAR_UNDEFINED = -1,
 	RP_BAR0,
@@ -292,6 +300,7 @@  struct cdns_pcie {
  * @avail_ib_bar: Satus of RP_BAR0, RP_BAR1 and	RP_NO_BAR if it's free or
  *                available
  * @quirk_retrain_flag: Retrain link as quirk for PCIe Gen2
+ * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
  */
 struct cdns_pcie_rc {
 	struct cdns_pcie	pcie;
@@ -301,6 +310,7 @@  struct cdns_pcie_rc {
 	u32			device_id;
 	bool			avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
 	bool                    quirk_retrain_flag;
+	bool                    quirk_detect_quiet_flag;
 };
 
 /**
@@ -331,6 +341,7 @@  struct cdns_pcie_epf {
  *        registers fields (RMW) accessible by both remote RC and EP to
  *        minimize time between read and write
  * @epf: Structure to hold info about endpoint function
+ * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
  */
 struct cdns_pcie_ep {
 	struct cdns_pcie	pcie;
@@ -345,6 +356,7 @@  struct cdns_pcie_ep {
 	/* protect writing to PCI_STATUS while raising legacy interrupts */
 	spinlock_t		lock;
 	struct cdns_pcie_epf	*epf;
+	bool                    quirk_detect_quiet_flag;
 };
 
 
@@ -505,6 +517,9 @@  static inline int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
 	return 0;
 }
 #endif
+
+void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
+
 void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
 				   u32 r, bool is_io,
 				   u64 cpu_addr, u64 pci_addr, size_t size);