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[PATCH v8 1/2] PCI: dwc: Don't poll L2 if QUIRK_NOL2POLL_IN_PM is existing in suspend

Richard Zhu posted 2 patches 1 month ago
There is a newer version of this series
[PATCH v8 1/2] PCI: dwc: Don't poll L2 if QUIRK_NOL2POLL_IN_PM is existing in suspend
Posted by Richard Zhu 1 month ago 
Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management State Flow
Diagram. Both L0 and L2/L3 Ready can be transferred to LDn directly.

It's harmless to let dw_pcie_suspend_noirq() proceed suspend after the
PME_Turn_Off is sent out, whatever the LTSSM state is in L2 or L3 after
a recommended 10ms max wait refer to PCIe r6.0, sec 5.3.3.2.1 PME
Synchronization.

The LTSSM states are inaccessible on i.MX6QP and i.MX7D after the
PME_Turn_Off is sent out.

To support this case, don't poll L2 state and apply a simple delay of
PCIE_PME_TO_L2_TIMEOUT_US(10ms) if the QUIRK_NOL2POLL_IN_PM flag is set
in suspend.

Cc: stable@vger.kernel.org
Fixes: 4774faf854f5 ("PCI: dwc: Implement generic suspend/resume functionality")
Fixes: a528d1a72597 ("PCI: imx6: Use DWC common suspend resume method")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/pci/controller/dwc/pci-imx6.c         |  4 +++
 .../pci/controller/dwc/pcie-designware-host.c | 34 +++++++++++++------
 drivers/pci/controller/dwc/pcie-designware.h  |  4 +++
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 4668fc9648bf..d84bfcd1079c 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -125,6 +125,7 @@ struct imx_pcie_drvdata {
 	enum imx_pcie_variants variant;
 	enum dw_pcie_device_mode mode;
 	u32 flags;
+	u32 quirk;
 	int dbi_length;
 	const char *gpr;
 	const u32 ltssm_off;
@@ -1765,6 +1766,7 @@ static int imx_pcie_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	pci->quirk_flag = imx_pcie->drvdata->quirk;
 	pci->use_parent_dt_ranges = true;
 	if (imx_pcie->drvdata->mode == DW_PCIE_EP_TYPE) {
 		ret = imx_add_pcie_ep(imx_pcie, pdev);
@@ -1849,6 +1851,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.enable_ref_clk = imx6q_pcie_enable_ref_clk,
 		.core_reset = imx6qp_pcie_core_reset,
 		.ops = &imx_pcie_host_ops,
+		.quirk = QUIRK_NOL2POLL_IN_PM,
 	},
 	[IMX7D] = {
 		.variant = IMX7D,
@@ -1860,6 +1863,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
 		.enable_ref_clk = imx7d_pcie_enable_ref_clk,
 		.core_reset = imx7d_pcie_core_reset,
+		.quirk = QUIRK_NOL2POLL_IN_PM,
 	},
 	[IMX8MQ] = {
 		.variant = IMX8MQ,
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 43d091128ef7..06cbfd9e1f1e 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -1179,15 +1179,29 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 			return ret;
 	}
 
-	ret = read_poll_timeout(dw_pcie_get_ltssm, val,
-				val == DW_PCIE_LTSSM_L2_IDLE ||
-				val <= DW_PCIE_LTSSM_DETECT_WAIT,
-				PCIE_PME_TO_L2_TIMEOUT_US/10,
-				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
-	if (ret) {
-		/* Only log message when LTSSM isn't in DETECT or POLL */
-		dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
-		return ret;
+	if (dwc_quirk(pci, QUIRK_NOL2POLL_IN_PM)) {
+		/*
+		 * Add the QUIRK_NOL2_POLL_IN_PM case to avoid the read hang,
+		 * when LTSSM is not powered in L2/L3/LDn properly.
+		 *
+		 * Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management
+		 * State Flow Diagram. Both L0 and L2/L3 Ready can be
+		 * transferred to LDn directly. On the LTSSM states poll broken
+		 * platforms, add a max 10ms delay refer to PCIe r6.0,
+		 * sec 5.3.3.2.1 PME Synchronization.
+		 */
+		mdelay(PCIE_PME_TO_L2_TIMEOUT_US/1000);
+	} else {
+		ret = read_poll_timeout(dw_pcie_get_ltssm, val,
+					val == DW_PCIE_LTSSM_L2_IDLE ||
+					val <= DW_PCIE_LTSSM_DETECT_WAIT,
+					PCIE_PME_TO_L2_TIMEOUT_US/10,
+					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
+		if (ret) {
+			/* Only log message when LTSSM isn't in DETECT or POLL */
+			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
+			return ret;
+		}
 	}
 
 	/*
@@ -1204,7 +1218,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 
 	pci->suspended = true;
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 31685951a080..dd760c17bdcc 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -305,6 +305,9 @@
 /* Default eDMA LLP memory size */
 #define DMA_LLP_MEM_SIZE		PAGE_SIZE
 
+#define QUIRK_NOL2POLL_IN_PM		BIT(0)
+#define dwc_quirk(pci, val)		(pci->quirk_flag & val)
+
 struct dw_pcie;
 struct dw_pcie_rp;
 struct dw_pcie_ep;
@@ -520,6 +523,7 @@ struct dw_pcie {
 	const struct dw_pcie_ops *ops;
 	u32			version;
 	u32			type;
+	u32			quirk_flag;
 	unsigned long		caps;
 	int			num_lanes;
 	int			max_link_speed;
-- 
2.37.1
Re: [PATCH v8 1/2] PCI: dwc: Don't poll L2 if QUIRK_NOL2POLL_IN_PM is existing in suspend
Posted by Manivannan Sadhasivam 3 weeks, 6 days ago 
On Wed, Jan 07, 2026 at 10:45:52AM +0800, Richard Zhu wrote:
> Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management State Flow
> Diagram. Both L0 and L2/L3 Ready can be transferred to LDn directly.
> 
> It's harmless to let dw_pcie_suspend_noirq() proceed suspend after the
> PME_Turn_Off is sent out, whatever the LTSSM state is in L2 or L3 after
> a recommended 10ms max wait refer to PCIe r6.0, sec 5.3.3.2.1 PME
> Synchronization.
> 
> The LTSSM states are inaccessible on i.MX6QP and i.MX7D after the
> PME_Turn_Off is sent out.
> 
> To support this case, don't poll L2 state and apply a simple delay of
> PCIE_PME_TO_L2_TIMEOUT_US(10ms) if the QUIRK_NOL2POLL_IN_PM flag is set
> in suspend.
> 
> Cc: stable@vger.kernel.org
> Fixes: 4774faf854f5 ("PCI: dwc: Implement generic suspend/resume functionality")
> Fixes: a528d1a72597 ("PCI: imx6: Use DWC common suspend resume method")
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c         |  4 +++
>  .../pci/controller/dwc/pcie-designware-host.c | 34 +++++++++++++------
>  drivers/pci/controller/dwc/pcie-designware.h  |  4 +++
>  3 files changed, 32 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 4668fc9648bf..d84bfcd1079c 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -125,6 +125,7 @@ struct imx_pcie_drvdata {
>  	enum imx_pcie_variants variant;
>  	enum dw_pcie_device_mode mode;
>  	u32 flags;
> +	u32 quirk;
>  	int dbi_length;
>  	const char *gpr;
>  	const u32 ltssm_off;
> @@ -1765,6 +1766,7 @@ static int imx_pcie_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	pci->quirk_flag = imx_pcie->drvdata->quirk;
>  	pci->use_parent_dt_ranges = true;
>  	if (imx_pcie->drvdata->mode == DW_PCIE_EP_TYPE) {
>  		ret = imx_add_pcie_ep(imx_pcie, pdev);
> @@ -1849,6 +1851,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.enable_ref_clk = imx6q_pcie_enable_ref_clk,
>  		.core_reset = imx6qp_pcie_core_reset,
>  		.ops = &imx_pcie_host_ops,
> +		.quirk = QUIRK_NOL2POLL_IN_PM,
>  	},
>  	[IMX7D] = {
>  		.variant = IMX7D,
> @@ -1860,6 +1863,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
>  		.enable_ref_clk = imx7d_pcie_enable_ref_clk,
>  		.core_reset = imx7d_pcie_core_reset,
> +		.quirk = QUIRK_NOL2POLL_IN_PM,
>  	},
>  	[IMX8MQ] = {
>  		.variant = IMX8MQ,
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 43d091128ef7..06cbfd9e1f1e 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -1179,15 +1179,29 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  			return ret;
>  	}
>  
> -	ret = read_poll_timeout(dw_pcie_get_ltssm, val,
> -				val == DW_PCIE_LTSSM_L2_IDLE ||
> -				val <= DW_PCIE_LTSSM_DETECT_WAIT,
> -				PCIE_PME_TO_L2_TIMEOUT_US/10,
> -				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> -	if (ret) {
> -		/* Only log message when LTSSM isn't in DETECT or POLL */
> -		dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> -		return ret;
> +	if (dwc_quirk(pci, QUIRK_NOL2POLL_IN_PM)) {
> +		/*
> +		 * Add the QUIRK_NOL2_POLL_IN_PM case to avoid the read hang,
> +		 * when LTSSM is not powered in L2/L3/LDn properly.
> +		 *
> +		 * Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management
> +		 * State Flow Diagram. Both L0 and L2/L3 Ready can be
> +		 * transferred to LDn directly. On the LTSSM states poll broken
> +		 * platforms, add a max 10ms delay refer to PCIe r6.0,
> +		 * sec 5.3.3.2.1 PME Synchronization.
> +		 */
> +		mdelay(PCIE_PME_TO_L2_TIMEOUT_US/1000);
> +	} else {
> +		ret = read_poll_timeout(dw_pcie_get_ltssm, val,
> +					val == DW_PCIE_LTSSM_L2_IDLE ||
> +					val <= DW_PCIE_LTSSM_DETECT_WAIT,
> +					PCIE_PME_TO_L2_TIMEOUT_US/10,
> +					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> +		if (ret) {
> +			/* Only log message when LTSSM isn't in DETECT or POLL */
> +			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> +			return ret;
> +		}
>  	}
>  
>  	/*
> @@ -1204,7 +1218,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  
>  	pci->suspended = true;
>  
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
>  
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 31685951a080..dd760c17bdcc 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -305,6 +305,9 @@
>  /* Default eDMA LLP memory size */
>  #define DMA_LLP_MEM_SIZE		PAGE_SIZE
>  
> +#define QUIRK_NOL2POLL_IN_PM		BIT(0)
> +#define dwc_quirk(pci, val)		(pci->quirk_flag & val)
> +

Though I like this quirk idea, I think at this point a simple flag will do the
job.

>  struct dw_pcie;
>  struct dw_pcie_rp;
>  struct dw_pcie_ep;
> @@ -520,6 +523,7 @@ struct dw_pcie {
>  	const struct dw_pcie_ops *ops;
>  	u32			version;
>  	u32			type;
> +	u32			quirk_flag;

You can just add a flag "skip_l23_wait" in dw_pcie_rp as this is a Root Port
behavior.

- Mani

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