diff mbox series

[v5] PCI: j721e: Delay T_PVPERL+TPERST_CLK before PERST# inactive

Message ID 20230817093619.1079267-1-a-verma1@ti.com (mailing list archive)
State New, archived
Headers show
Series [v5] PCI: j721e: Delay T_PVPERL+TPERST_CLK before PERST# inactive | expand

Commit Message

Achal Verma Aug. 17, 2023, 9:36 a.m. UTC
As per the PCIe Card Electromechanical specification REV. 5.0, PERST#
signal should be de-asserted after minimum 100ms from the time power-rails
achieve specified operating limits and 100us after reference clock gets
stable.

From PCIe Card Electromechanical specification REV. 5.0 section 2.9.2:
TPVPERL: Power stable to PERST# inactive - 100ms
TPERST_CLK: REFCLK stable before PERST# inactive - 100us

Fixes: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver")
Signed-off-by: Achal Verma <a-verma1@ti.com>
---
 drivers/pci/controller/cadence/pci-j721e.c | 30 +++++++++++-----------
 drivers/pci/pci.h                          |  3 +++
 2 files changed, 18 insertions(+), 15 deletions(-)

Comments

Siddharth Vadapalli Dec. 1, 2023, 10:52 a.m. UTC | #1
Hello Lorenzo, Bjorn,

On 17/08/23 15:06, Achal Verma wrote:
> As per the PCIe Card Electromechanical specification REV. 5.0, PERST#
> signal should be de-asserted after minimum 100ms from the time power-rails
> achieve specified operating limits and 100us after reference clock gets
> stable.
> 
> From PCIe Card Electromechanical specification REV. 5.0 section 2.9.2:
> TPVPERL: Power stable to PERST# inactive - 100ms
> TPERST_CLK: REFCLK stable before PERST# inactive - 100us
> 
> Fixes: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver")
> Signed-off-by: Achal Verma <a-verma1@ti.com>
> ---
>  drivers/pci/controller/cadence/pci-j721e.c | 30 +++++++++++-----------
>  drivers/pci/pci.h                          |  3 +++
>  2 files changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> index e70213c9060a..b09924b010ab 100644
> --- a/drivers/pci/controller/cadence/pci-j721e.c
> +++ b/drivers/pci/controller/cadence/pci-j721e.c
> @@ -34,6 +34,8 @@
>  #define J721E_PCIE_USER_LINKSTATUS	0x14
>  #define LINK_STATUS			GENMASK(1, 0)
>  
> +#define PERST_INACTIVE_US (PCIE_TPVPERL_MS*USEC_PER_MSEC + PCIE_TPERST_CLK_US)

This implementation appears incorrect to me since T_PVPERL already accounts for
T_PERST-CLK according to Figure 2-3 of PCI Express Card Electromechanical
Specification Revision 5.1:
https://members.pcisig.com/wg/PCI-SIG/document/19922

Could you please share your opinion since I wish to post a v6 for this patch,
rebasing it to the latest tree which has the commit:
164f66be0c25 PCI: Add T_PVPERL macro
The macro can be used in the current patch, instead of the PERST_INACTIVE_US macro.

> +
>  enum link_status {
>  	NO_RECEIVERS_DETECTED,
>  	LINK_TRAINING_IN_PROGRESS,
> @@ -359,7 +361,7 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>  	struct j721e_pcie *pcie;
>  	struct cdns_pcie_rc *rc = NULL;
>  	struct cdns_pcie_ep *ep = NULL;
> -	struct gpio_desc *gpiod;
> +	struct gpio_desc *perst_gpiod;
>  	void __iomem *base;
>  	struct clk *clk;
>  	u32 num_lanes;
> @@ -468,11 +470,10 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>  
>  	switch (mode) {
>  	case PCI_MODE_RC:
> -		gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> -		if (IS_ERR(gpiod)) {
> -			ret = PTR_ERR(gpiod);
> -			if (ret != -EPROBE_DEFER)
> -				dev_err(dev, "Failed to get reset GPIO\n");
> +		perst_gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +		if (IS_ERR(perst_gpiod)) {
> +			ret = PTR_ERR(perst_gpiod);
> +			dev_err(dev, "Failed to get reset GPIO\n");
>  			goto err_get_sync;
>  		}
>  
> @@ -498,16 +499,15 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>  
>  		/*
>  		 * "Power Sequencing and Reset Signal Timings" table in
> -		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0
> -		 * indicates PERST# should be deasserted after minimum of 100us
> -		 * once REFCLK is stable. The REFCLK to the connector in RC
> -		 * mode is selected while enabling the PHY. So deassert PERST#
> -		 * after 100 us.
> +		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 5.0
> +		 * indicates PERST# should be deasserted after minimum of 100ms
> +		 * after power rails achieve specified operating limits and
> +		 * 100us after reference clock gets stable.
> +		 * PERST_INACTIVE_US accounts for both delays.
>  		 */
> -		if (gpiod) {
> -			usleep_range(100, 200);
> -			gpiod_set_value_cansleep(gpiod, 1);
> -		}
> +
> +		fsleep(PERST_INACTIVE_US);
> +		gpiod_set_value_cansleep(perst_gpiod, 1);
>  
>  		ret = cdns_pcie_host_setup(rc);
>  		if (ret < 0) {
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index a4c397434057..80d520be34e6 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -13,6 +13,9 @@
>  
>  #define PCIE_LINK_RETRAIN_TIMEOUT_MS	1000
>  
> +#define PCIE_TPVPERL_MS		100	/* see PCIe CEM r5.0, sec 2.9.2 */
> +#define PCIE_TPERST_CLK_US	100
> +
>  extern const unsigned char pcie_link_speed[];
>  extern bool pci_early_dump;
>
diff mbox series

Patch

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index e70213c9060a..b09924b010ab 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -34,6 +34,8 @@ 
 #define J721E_PCIE_USER_LINKSTATUS	0x14
 #define LINK_STATUS			GENMASK(1, 0)
 
+#define PERST_INACTIVE_US (PCIE_TPVPERL_MS*USEC_PER_MSEC + PCIE_TPERST_CLK_US)
+
 enum link_status {
 	NO_RECEIVERS_DETECTED,
 	LINK_TRAINING_IN_PROGRESS,
@@ -359,7 +361,7 @@  static int j721e_pcie_probe(struct platform_device *pdev)
 	struct j721e_pcie *pcie;
 	struct cdns_pcie_rc *rc = NULL;
 	struct cdns_pcie_ep *ep = NULL;
-	struct gpio_desc *gpiod;
+	struct gpio_desc *perst_gpiod;
 	void __iomem *base;
 	struct clk *clk;
 	u32 num_lanes;
@@ -468,11 +470,10 @@  static int j721e_pcie_probe(struct platform_device *pdev)
 
 	switch (mode) {
 	case PCI_MODE_RC:
-		gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
-		if (IS_ERR(gpiod)) {
-			ret = PTR_ERR(gpiod);
-			if (ret != -EPROBE_DEFER)
-				dev_err(dev, "Failed to get reset GPIO\n");
+		perst_gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+		if (IS_ERR(perst_gpiod)) {
+			ret = PTR_ERR(perst_gpiod);
+			dev_err(dev, "Failed to get reset GPIO\n");
 			goto err_get_sync;
 		}
 
@@ -498,16 +499,15 @@  static int j721e_pcie_probe(struct platform_device *pdev)
 
 		/*
 		 * "Power Sequencing and Reset Signal Timings" table in
-		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0
-		 * indicates PERST# should be deasserted after minimum of 100us
-		 * once REFCLK is stable. The REFCLK to the connector in RC
-		 * mode is selected while enabling the PHY. So deassert PERST#
-		 * after 100 us.
+		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 5.0
+		 * indicates PERST# should be deasserted after minimum of 100ms
+		 * after power rails achieve specified operating limits and
+		 * 100us after reference clock gets stable.
+		 * PERST_INACTIVE_US accounts for both delays.
 		 */
-		if (gpiod) {
-			usleep_range(100, 200);
-			gpiod_set_value_cansleep(gpiod, 1);
-		}
+
+		fsleep(PERST_INACTIVE_US);
+		gpiod_set_value_cansleep(perst_gpiod, 1);
 
 		ret = cdns_pcie_host_setup(rc);
 		if (ret < 0) {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a4c397434057..80d520be34e6 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -13,6 +13,9 @@ 
 
 #define PCIE_LINK_RETRAIN_TIMEOUT_MS	1000
 
+#define PCIE_TPVPERL_MS		100	/* see PCIe CEM r5.0, sec 2.9.2 */
+#define PCIE_TPERST_CLK_US	100
+
 extern const unsigned char pcie_link_speed[];
 extern bool pci_early_dump;