[PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Nadeem Athani]

Cadence controller will not initiate autonomous speed change if strapped
as Gen2. The Retrain Link bit is set as quirk to enable this speed change.
Adding a quirk flag for defective IP. In future IP revisions this will not
be applicable.

Version history:
Changes in v7:
- Changing the commit title of patch 1 in this series.
- Added a return value for function cdns_pcie_retrain().
Changes in v6:
- Move the position of function cdns_pcie_host_wait_for_link to remove
  compilation error. No changes in code. Separate patch for this.
Changes in v5:
- Remove the compatible string based setting of quirk flag.
- Removed additional Link Up Check
- Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c
Changes in v4:
- Added a quirk flag based on a new compatible string.
- Change of api for link up: cdns_pcie_host_wait_for_link().
Changes in v3:
- To set retrain link bit,checking device capability & link status.
- 32bit read in place of 8bit.
- Minor correction in patch comment.
- Change in variable & macro name.
Changes in v2:
- 16bit read in place of 8bit.

Nadeem Athani (2):
  PCI: cadence: Shifting of a function to support new code.
  PCI: cadence: Retrain Link to work around Gen2 training defect.

 drivers/pci/controller/cadence/pci-j721e.c         |  3 +
 drivers/pci/controller/cadence/pcie-cadence-host.c | 70 ++++++++++++++++------
 drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
 3 files changed, 65 insertions(+), 19 deletions(-)

-- 
2.15.0

[PATCH v7 1/2] PCI: cadence: Shifting of a function to support new code.

[Nadeem Athani]

Move the function cdns_pcie_host_wait_for_link() further up in the file,
as it's going to be used by upcoming additional code in the driver.

Signed-off-by: Nadeem Athani <nadeem@cadence.com>
---
 drivers/pci/controller/cadence/pcie-cadence-host.c | 33 +++++++++++-----------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index 811c1cb2e8de..9f7aa718c8d4 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -77,6 +77,22 @@ static struct pci_ops cdns_pcie_host_ops = {
 	.write		= pci_generic_config_write,
 };
 
+static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
+{
+	struct device *dev = pcie->dev;
+	int retries;
+
+	/* Check if the link is up or not */
+	for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
+		if (cdns_pcie_link_up(pcie)) {
+			dev_info(dev, "Link up\n");
+			return 0;
+		}
+		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
+	}
+
+	return -ETIMEDOUT;
+}
 
 static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
 {
@@ -398,23 +414,6 @@ static int cdns_pcie_host_init(struct device *dev,
 	return cdns_pcie_host_init_address_translation(rc);
 }
 
-static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
-{
-	struct device *dev = pcie->dev;
-	int retries;
-
-	/* Check if the link is up or not */
-	for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
-		if (cdns_pcie_link_up(pcie)) {
-			dev_info(dev, "Link up\n");
-			return 0;
-		}
-		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
-	}
-
-	return -ETIMEDOUT;
-}
-
 int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
 {
 	struct device *dev = rc->pcie.dev;
-- 
2.15.0

[PATCH v7 2/2] PCI: cadence: Retrain Link to work around Gen2 training defect.

[Nadeem Athani]

Cadence controller will not initiate autonomous speed change if strapped
as Gen2. The Retrain Link bit is set as quirk to enable this speed change.

Signed-off-by: Nadeem Athani <nadeem@cadence.com>
---
 drivers/pci/controller/cadence/pci-j721e.c         |  3 ++
 drivers/pci/controller/cadence/pcie-cadence-host.c | 37 +++++++++++++++++++++-
 drivers/pci/controller/cadence/pcie-cadence.h      | 11 ++++++-
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index dac1ac8a7615..849f1e416ea5 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -64,6 +64,7 @@ enum j721e_pcie_mode {
 
 struct j721e_pcie_data {
 	enum j721e_pcie_mode	mode;
+	bool quirk_retrain_flag;
 };
 
 static inline u32 j721e_pcie_user_readl(struct j721e_pcie *pcie, u32 offset)
@@ -280,6 +281,7 @@ static struct pci_ops cdns_ti_pcie_host_ops = {
 
 static const struct j721e_pcie_data j721e_pcie_rc_data = {
 	.mode = PCI_MODE_RC,
+	.quirk_retrain_flag = true,
 };
 
 static const struct j721e_pcie_data j721e_pcie_ep_data = {
@@ -388,6 +390,7 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 
 		bridge->ops = &cdns_ti_pcie_host_ops;
 		rc = pci_host_bridge_priv(bridge);
+		rc->quirk_retrain_flag = data->quirk_retrain_flag;
 
 		cdns_pcie = &rc->pcie;
 		cdns_pcie->dev = dev;
diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index 9f7aa718c8d4..f3496588862d 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -94,6 +94,35 @@ static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
 	return -ETIMEDOUT;
 }
 
+static int cdns_pcie_retrain(struct cdns_pcie *pcie)
+{
+	u32 lnk_cap_sls, pcie_cap_off = CDNS_PCIE_RP_CAP_OFFSET;
+	u16 lnk_stat, lnk_ctl;
+	int ret = 0;
+
+	/*
+	 * Set retrain bit if current speed is 2.5 GB/s,
+	 * but the PCIe root port support is > 2.5 GB/s.
+	 */
+
+	lnk_cap_sls = cdns_pcie_readl(pcie, (CDNS_PCIE_RP_BASE + pcie_cap_off +
+					     PCI_EXP_LNKCAP));
+	if ((lnk_cap_sls & PCI_EXP_LNKCAP_SLS) <= PCI_EXP_LNKCAP_SLS_2_5GB)
+		return ret;
+
+	lnk_stat = cdns_pcie_rp_readw(pcie, pcie_cap_off + PCI_EXP_LNKSTA);
+	if ((lnk_stat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
+		lnk_ctl = cdns_pcie_rp_readw(pcie,
+					     pcie_cap_off + PCI_EXP_LNKCTL);
+		lnk_ctl |= PCI_EXP_LNKCTL_RL;
+		cdns_pcie_rp_writew(pcie, pcie_cap_off + PCI_EXP_LNKCTL,
+				    lnk_ctl);
+
+		ret = cdns_pcie_host_wait_for_link(pcie);
+	}
+	return ret;
+}
+
 static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
 {
 	struct cdns_pcie *pcie = &rc->pcie;
@@ -457,8 +486,14 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
 	}
 
 	ret = cdns_pcie_host_wait_for_link(pcie);
-	if (ret)
+	if (ret) {
 		dev_dbg(dev, "PCIe link never came up\n");
+	} else {
+		if (rc->quirk_retrain_flag) {
+			if (cdns_pcie_retrain(pcie))
+				dev_dbg(dev, "PCIe link never came up\n");
+		}
+	}
 
 	for (bar = RP_BAR0; bar <= RP_NO_BAR; bar++)
 		rc->avail_ib_bar[bar] = true;
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index 30eba6cafe2c..0f29128a5d0a 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -119,7 +119,7 @@
  * Root Port Registers (PCI configuration space for the root port function)
  */
 #define CDNS_PCIE_RP_BASE	0x00200000
-
+#define CDNS_PCIE_RP_CAP_OFFSET 0xc0
 
 /*
  * Address Translation Registers
@@ -291,6 +291,7 @@ struct cdns_pcie {
  * @device_id: PCI device ID
  * @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
  */
 struct cdns_pcie_rc {
 	struct cdns_pcie	pcie;
@@ -299,6 +300,7 @@ struct cdns_pcie_rc {
 	u32			vendor_id;
 	u32			device_id;
 	bool			avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
+	bool			quirk_retrain_flag;
 };
 
 /**
@@ -414,6 +416,13 @@ static inline void cdns_pcie_rp_writew(struct cdns_pcie *pcie,
 	cdns_pcie_write_sz(addr, 0x2, value);
 }
 
+static inline u16 cdns_pcie_rp_readw(struct cdns_pcie *pcie, u32 reg)
+{
+	void __iomem *addr = pcie->reg_base + CDNS_PCIE_RP_BASE + reg;
+
+	return cdns_pcie_read_sz(addr, 0x2);
+}
+
 /* Endpoint Function register access */
 static inline void cdns_pcie_ep_fn_writeb(struct cdns_pcie *pcie, u8 fn,
 					  u32 reg, u8 value)
-- 
2.15.0

RE: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Athani Nadeem Ladkhan]

Hello,

Requesting to provide review comments.

Thanks & Regards,
Nadeem Athani

> -----Original Message-----
> From: Nadeem Athani <nadeem@cadence.com>
> Sent: Wednesday, December 30, 2020 5:35 PM
> To: Tom Joseph <tjoseph@cadence.com>; lorenzo.pieralisi@arm.com;
> robh@kernel.org; bhelgaas@google.com; kishon@ti.com; linux-
> omap@vger.kernel.org; linux-pci@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Cc: Athani Nadeem Ladkhan <nadeem@cadence.com>; Milind Parab
> <mparab@cadence.com>; Swapnil Kashinath Jakhade
> <sjakhade@cadence.com>; Parshuram Raju Thombare
> <pthombar@cadence.com>
> Subject: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2
> 
> Cadence controller will not initiate autonomous speed change if strapped as
> Gen2. The Retrain Link bit is set as quirk to enable this speed change.
> Adding a quirk flag for defective IP. In future IP revisions this will not be
> applicable.
> 
> Version history:
> Changes in v7:
> - Changing the commit title of patch 1 in this series.
> - Added a return value for function cdns_pcie_retrain().
> Changes in v6:
> - Move the position of function cdns_pcie_host_wait_for_link to remove
>   compilation error. No changes in code. Separate patch for this.
> Changes in v5:
> - Remove the compatible string based setting of quirk flag.
> - Removed additional Link Up Check
> - Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c Changes
> in v4:
> - Added a quirk flag based on a new compatible string.
> - Change of api for link up: cdns_pcie_host_wait_for_link().
> Changes in v3:
> - To set retrain link bit,checking device capability & link status.
> - 32bit read in place of 8bit.
> - Minor correction in patch comment.
> - Change in variable & macro name.
> Changes in v2:
> - 16bit read in place of 8bit.
> 
> Nadeem Athani (2):
>   PCI: cadence: Shifting of a function to support new code.
>   PCI: cadence: Retrain Link to work around Gen2 training defect.
> 
>  drivers/pci/controller/cadence/pci-j721e.c         |  3 +
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 70 ++++++++++++++++-
> -----
>  drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
>  3 files changed, 65 insertions(+), 19 deletions(-)
> 
> --
> 2.15.0

Re: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Kishon Vijay Abraham I]

On 30/12/20 5:35 pm, Nadeem Athani wrote:
> Cadence controller will not initiate autonomous speed change if strapped
> as Gen2. The Retrain Link bit is set as quirk to enable this speed change.
> Adding a quirk flag for defective IP. In future IP revisions this will not
> be applicable.
> 
> Version history:
> Changes in v7:
> - Changing the commit title of patch 1 in this series.
> - Added a return value for function cdns_pcie_retrain().
> Changes in v6:
> - Move the position of function cdns_pcie_host_wait_for_link to remove
>   compilation error. No changes in code. Separate patch for this.
> Changes in v5:
> - Remove the compatible string based setting of quirk flag.
> - Removed additional Link Up Check
> - Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c
> Changes in v4:
> - Added a quirk flag based on a new compatible string.
> - Change of api for link up: cdns_pcie_host_wait_for_link().
> Changes in v3:
> - To set retrain link bit,checking device capability & link status.
> - 32bit read in place of 8bit.
> - Minor correction in patch comment.
> - Change in variable & macro name.
> Changes in v2:
> - 16bit read in place of 8bit.

Could get GEN2 card enumerated in GEN2 mode in J7ES EVM.

Tested-by: Kishon Vijay Abraham I <kishon@ti.com>

Thanks
Kishon
> 
> Nadeem Athani (2):
>   PCI: cadence: Shifting of a function to support new code.
>   PCI: cadence: Retrain Link to work around Gen2 training defect.
> 
>  drivers/pci/controller/cadence/pci-j721e.c         |  3 +
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 70 ++++++++++++++++------
>  drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
>  3 files changed, 65 insertions(+), 19 deletions(-)
> 

RE: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Athani Nadeem Ladkhan]

Hi Rob / Thomas,

Requesting to provide your reviews.

Thanks & Regards,
Nadeem Athani

> -----Original Message-----
> From: Kishon Vijay Abraham I <kishon@ti.com>
> Sent: Tuesday, January 12, 2021 12:46 PM
> To: Athani Nadeem Ladkhan <nadeem@cadence.com>; Tom Joseph
> <tjoseph@cadence.com>; lorenzo.pieralisi@arm.com; robh@kernel.org;
> bhelgaas@google.com; linux-omap@vger.kernel.org; linux-
> pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org
> Cc: Milind Parab <mparab@cadence.com>; Swapnil Kashinath Jakhade
> <sjakhade@cadence.com>; Parshuram Raju Thombare
> <pthombar@cadence.com>
> Subject: Re: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2
> 
> EXTERNAL MAIL
> 
> 
> 
> 
> On 30/12/20 5:35 pm, Nadeem Athani wrote:
> > Cadence controller will not initiate autonomous speed change if
> > strapped as Gen2. The Retrain Link bit is set as quirk to enable this speed
> change.
> > Adding a quirk flag for defective IP. In future IP revisions this will
> > not be applicable.
> >
> > Version history:
> > Changes in v7:
> > - Changing the commit title of patch 1 in this series.
> > - Added a return value for function cdns_pcie_retrain().
> > Changes in v6:
> > - Move the position of function cdns_pcie_host_wait_for_link to remove
> >   compilation error. No changes in code. Separate patch for this.
> > Changes in v5:
> > - Remove the compatible string based setting of quirk flag.
> > - Removed additional Link Up Check
> > - Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c
> > Changes in v4:
> > - Added a quirk flag based on a new compatible string.
> > - Change of api for link up: cdns_pcie_host_wait_for_link().
> > Changes in v3:
> > - To set retrain link bit,checking device capability & link status.
> > - 32bit read in place of 8bit.
> > - Minor correction in patch comment.
> > - Change in variable & macro name.
> > Changes in v2:
> > - 16bit read in place of 8bit.
> 
> Could get GEN2 card enumerated in GEN2 mode in J7ES EVM.
> 
> Tested-by: Kishon Vijay Abraham I <kishon@ti.com>
> 
> Thanks
> Kishon
> >
> > Nadeem Athani (2):
> >   PCI: cadence: Shifting of a function to support new code.
> >   PCI: cadence: Retrain Link to work around Gen2 training defect.
> >
> >  drivers/pci/controller/cadence/pci-j721e.c         |  3 +
> >  drivers/pci/controller/cadence/pcie-cadence-host.c | 70
> ++++++++++++++++------
> >  drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
> >  3 files changed, 65 insertions(+), 19 deletions(-)
> >

RE: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Tom Joseph]

> -----Original Message-----
> From: Nadeem Athani <nadeem@cadence.com>
> Sent: 30 December 2020 12:05
> To: Tom Joseph <tjoseph@cadence.com>; lorenzo.pieralisi@arm.com;
> robh@kernel.org; bhelgaas@google.com; kishon@ti.com; linux-
> omap@vger.kernel.org; linux-pci@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Cc: Athani Nadeem Ladkhan <nadeem@cadence.com>; Milind Parab
> <mparab@cadence.com>; Swapnil Kashinath Jakhade
> <sjakhade@cadence.com>; Parshuram Raju Thombare
> <pthombar@cadence.com>
> Subject: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2
> 
> Cadence controller will not initiate autonomous speed change if strapped
> as Gen2. The Retrain Link bit is set as quirk to enable this speed change.
> Adding a quirk flag for defective IP. In future IP revisions this will not
> be applicable.
> 
> Version history:
> Changes in v7:
> - Changing the commit title of patch 1 in this series.
> - Added a return value for function cdns_pcie_retrain().
> Changes in v6:
> - Move the position of function cdns_pcie_host_wait_for_link to remove
>   compilation error. No changes in code. Separate patch for this.
> Changes in v5:
> - Remove the compatible string based setting of quirk flag.
> - Removed additional Link Up Check
> - Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c
> Changes in v4:
> - Added a quirk flag based on a new compatible string.
> - Change of api for link up: cdns_pcie_host_wait_for_link().
> Changes in v3:
> - To set retrain link bit,checking device capability & link status.
> - 32bit read in place of 8bit.
> - Minor correction in patch comment.
> - Change in variable & macro name.
> Changes in v2:
> - 16bit read in place of 8bit.
> 
> Nadeem Athani (2):
>   PCI: cadence: Shifting of a function to support new code.
>   PCI: cadence: Retrain Link to work around Gen2 training defect.
> 
>  drivers/pci/controller/cadence/pci-j721e.c         |  3 +
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 70
> ++++++++++++++++------
>  drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
>  3 files changed, 65 insertions(+), 19 deletions(-)

Reviewed-by: Tom Joseph <tjoseph@cadence.com>


Thanks,
Tom

Re: [PATCH v7 0/2] PCI: cadence: Retrain Link to work around Gen2

[Kishon Vijay Abraham I]

Hi Lorenzo, Rob,

On 12/01/21 12:45 pm, Kishon Vijay Abraham I wrote:
> 
> 
> On 30/12/20 5:35 pm, Nadeem Athani wrote:
>> Cadence controller will not initiate autonomous speed change if strapped
>> as Gen2. The Retrain Link bit is set as quirk to enable this speed change.
>> Adding a quirk flag for defective IP. In future IP revisions this will not
>> be applicable.
>>
>> Version history:
>> Changes in v7:
>> - Changing the commit title of patch 1 in this series.
>> - Added a return value for function cdns_pcie_retrain().
>> Changes in v6:
>> - Move the position of function cdns_pcie_host_wait_for_link to remove
>>   compilation error. No changes in code. Separate patch for this.
>> Changes in v5:
>> - Remove the compatible string based setting of quirk flag.
>> - Removed additional Link Up Check
>> - Removed quirk from pcie-cadence-plat.c and added in pci-j721e.c
>> Changes in v4:
>> - Added a quirk flag based on a new compatible string.
>> - Change of api for link up: cdns_pcie_host_wait_for_link().
>> Changes in v3:
>> - To set retrain link bit,checking device capability & link status.
>> - 32bit read in place of 8bit.
>> - Minor correction in patch comment.
>> - Change in variable & macro name.
>> Changes in v2:
>> - 16bit read in place of 8bit.
> 
> Could get GEN2 card enumerated in GEN2 mode in J7ES EVM.
> 
> Tested-by: Kishon Vijay Abraham I <kishon@ti.com>

Can this series be merged?

Thanks
Kishon

> 
> Thanks
> Kishon
>>
>> Nadeem Athani (2):
>>   PCI: cadence: Shifting of a function to support new code.
>>   PCI: cadence: Retrain Link to work around Gen2 training defect.
>>
>>  drivers/pci/controller/cadence/pci-j721e.c         |  3 +
>>  drivers/pci/controller/cadence/pcie-cadence-host.c | 70 ++++++++++++++++------
>>  drivers/pci/controller/cadence/pcie-cadence.h      | 11 +++-
>>  3 files changed, 65 insertions(+), 19 deletions(-)
>>

Re: [PATCH v7 2/2] PCI: cadence: Retrain Link to work around Gen2 training defect.

[Lorenzo Pieralisi]

On Wed, Dec 30, 2020 at 01:05:15PM +0100, Nadeem Athani wrote:
> Cadence controller will not initiate autonomous speed change if strapped
> as Gen2. The Retrain Link bit is set as quirk to enable this speed change.
> 
> Signed-off-by: Nadeem Athani <nadeem@cadence.com>
> ---
>  drivers/pci/controller/cadence/pci-j721e.c         |  3 ++
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 37 +++++++++++++++++++++-
>  drivers/pci/controller/cadence/pcie-cadence.h      | 11 ++++++-
>  3 files changed, 49 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> index dac1ac8a7615..849f1e416ea5 100644
> --- a/drivers/pci/controller/cadence/pci-j721e.c
> +++ b/drivers/pci/controller/cadence/pci-j721e.c
> @@ -64,6 +64,7 @@ enum j721e_pcie_mode {
>  
>  struct j721e_pcie_data {
>  	enum j721e_pcie_mode	mode;
> +	bool quirk_retrain_flag;
>  };
>  
>  static inline u32 j721e_pcie_user_readl(struct j721e_pcie *pcie, u32 offset)
> @@ -280,6 +281,7 @@ static struct pci_ops cdns_ti_pcie_host_ops = {
>  
>  static const struct j721e_pcie_data j721e_pcie_rc_data = {
>  	.mode = PCI_MODE_RC,
> +	.quirk_retrain_flag = true,
>  };
>  
>  static const struct j721e_pcie_data j721e_pcie_ep_data = {
> @@ -388,6 +390,7 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>  
>  		bridge->ops = &cdns_ti_pcie_host_ops;
>  		rc = pci_host_bridge_priv(bridge);
> +		rc->quirk_retrain_flag = data->quirk_retrain_flag;
>  
>  		cdns_pcie = &rc->pcie;
>  		cdns_pcie->dev = dev;
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index 9f7aa718c8d4..f3496588862d 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -94,6 +94,35 @@ static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
>  	return -ETIMEDOUT;
>  }
>  
> +static int cdns_pcie_retrain(struct cdns_pcie *pcie)
> +{
> +	u32 lnk_cap_sls, pcie_cap_off = CDNS_PCIE_RP_CAP_OFFSET;
> +	u16 lnk_stat, lnk_ctl;
> +	int ret = 0;
> +
> +	/*
> +	 * Set retrain bit if current speed is 2.5 GB/s,
> +	 * but the PCIe root port support is > 2.5 GB/s.
> +	 */
> +
> +	lnk_cap_sls = cdns_pcie_readl(pcie, (CDNS_PCIE_RP_BASE + pcie_cap_off +
> +					     PCI_EXP_LNKCAP));
> +	if ((lnk_cap_sls & PCI_EXP_LNKCAP_SLS) <= PCI_EXP_LNKCAP_SLS_2_5GB)
> +		return ret;
> +
> +	lnk_stat = cdns_pcie_rp_readw(pcie, pcie_cap_off + PCI_EXP_LNKSTA);
> +	if ((lnk_stat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
> +		lnk_ctl = cdns_pcie_rp_readw(pcie,
> +					     pcie_cap_off + PCI_EXP_LNKCTL);
> +		lnk_ctl |= PCI_EXP_LNKCTL_RL;
> +		cdns_pcie_rp_writew(pcie, pcie_cap_off + PCI_EXP_LNKCTL,
> +				    lnk_ctl);
> +
> +		ret = cdns_pcie_host_wait_for_link(pcie);
> +	}
> +	return ret;
> +}
> +
>  static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
>  {
>  	struct cdns_pcie *pcie = &rc->pcie;
> @@ -457,8 +486,14 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
>  	}
>  
>  	ret = cdns_pcie_host_wait_for_link(pcie);
> -	if (ret)
> +	if (ret) {
>  		dev_dbg(dev, "PCIe link never came up\n");
> +	} else {
> +		if (rc->quirk_retrain_flag) {
> +			if (cdns_pcie_retrain(pcie))
> +				dev_dbg(dev, "PCIe link never came up\n");

I'd move this whole if/else in a function cdns_pcie_host_start_link(),
IMO that's cleaner.

static int cdns_pcie_host_start_link(struct cdns_pcie_rc *rc)
{
	struct cdns_pcie *pcie = &rc->pcie;
	int ret;

	ret = cdns_pcie_host_wait_for_link(pcie);
	/*
	 * PLS ADD A COMMENT HERE
	 */
	if (!ret && rc->quirk_retrain_flag)
		ret = cdns_pcie_retrain(pcie);

	return ret;
}