[PATCH v2 0/3] Add root port reset to support link recovery

[PATCH v2 0/3] Add root port reset to support link recovery

[Richard Zhu]

Based on the following patch-set[1] issued by Mani.
Add support for resetting the Root Port for i.MX PCIe to enable link recovery.

[1] [v7,0/4] PCI: Add support for resetting the Root Ports in a platform specific way

PCIe links can go down due to various unexpected circumstances. This patch series
adds root port reset support for link recovery on i.MX PCIe controllers when the
optional "intr" interrupt is present.

When a link down event is detected, the root port reset uninitializes and
reinitializes the PCIe controller, then restarts the PCIe link.

On i.MX95 platforms, link events and PME share the same interrupt line.
Link event interrupts cannot use only an IRQ thread handler because the PME
driver uses request_irq() to bind the PME interrupt directly with only the
IRQF_SHARED flag set.

To address this, we register one handler with IRQF_SHARED for link event
interrupts and manipulate the enable bits of link events to ensure the same
interrupt source is triggered only once at a time.

Additionally, this series adds 'intr', 'aer', and 'pme' interrupt entries to
the i.MX6Q PCIe binding to support PCIe event-based interrupts for general
controller events, Advanced Error Reporting, and Power Management Events
respectively.

Changes in v2:
- Constrain the new added three interrupt entries to be valid only for the
i.MX95 variant using conditional schemas

[PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme
[PATCH v2 2/3] arm64: dts: imx95: Add dma, intr, aer and pme
[PATCH v2 3/3] PCI: imx6: Add root port reset to support link

Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml |  21 ++++++++++++++++
arch/arm64/boot/dts/freescale/imx95.dtsi                  |  16 +++++++++---
drivers/pci/controller/dwc/pci-imx6.c                     | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 156 insertions(+), 4 deletions(-)

[PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme interrupts

[Richard Zhu]

Add 'intr', 'aer', and 'pme' interrupt entries to the i.MX6Q PCIe
binding to support PCIe event-based interrupts for general controller
events, Advanced Error Reporting, and Power Management Events
respectively.

These interrupts are optional for most variants but required for
fsl,imx95-pcie, which must specify all 5 interrupts (msi, dma, intr,
aer, pme).

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
---
 .../bindings/pci/fsl,imx6q-pcie.yaml          | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
index 9d1349855b422..0913c3312ed26 100644
--- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
+++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
@@ -58,12 +58,18 @@ properties:
     items:
       - description: builtin MSI controller.
       - description: builtin DMA controller.
+      - description: PCIe event interrupt.
+      - description: builtin AER SPI standalone interrupter line.
+      - description: builtin PME SPI standalone interrupter line.
 
   interrupt-names:
     minItems: 1
     items:
       - const: msi
       - const: dma
+      - const: intr
+      - const: aer
+      - const: pme
 
   reset-gpio:
     description: Should specify the GPIO for controlling the PCI bus device
@@ -231,6 +237,21 @@ allOf:
             - const: ref
             - const: extref  # Optional
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - fsl,imx95-pcie
+    then:
+      properties:
+        interrupts:
+          minItems: 5
+          maxItems: 5
+        interrupt-names:
+          minItems: 5
+          maxItems: 5
+
 unevaluatedProperties: false
 
 examples:
-- 
2.37.1

[PATCH v2 2/3] arm64: dts: imx95: Add dma, intr, aer and pme interrupters for pcie{0,1}

[Richard Zhu]

Add dma, intr, aer and pme interrupters for pcie{0,1}.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
---
 arch/arm64/boot/dts/freescale/imx95.dtsi | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx95.dtsi b/arch/arm64/boot/dts/freescale/imx95.dtsi
index 71394871d8dd0..6896d9c15bf53 100644
--- a/arch/arm64/boot/dts/freescale/imx95.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx95.dtsi
@@ -1861,8 +1861,12 @@ pcie0: pcie@4c300000 {
 			bus-range = <0x00 0xff>;
 			num-lanes = <1>;
 			num-viewport = <8>;
-			interrupts = <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>;
-			interrupt-names = "msi";
+			interrupts = <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 311 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>;
+			interrupt-names = "msi", "dma", "intr", "aer", "pme";
 			#interrupt-cells = <1>;
 			interrupt-map-mask = <0 0 0 0x7>;
 			interrupt-map = <0 0 0 1 &gic 0 0 GIC_SPI 306 IRQ_TYPE_LEVEL_HIGH>,
@@ -1936,8 +1940,12 @@ pcie1: pcie@4c380000 {
 			bus-range = <0x00 0xff>;
 			num-lanes = <1>;
 			num-viewport = <8>;
-			interrupts = <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>;
-			interrupt-names = "msi";
+			interrupts = <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 317 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>;
+			interrupt-names = "msi", "dma", "intr", "aer", "pme";
 			#interrupt-cells = <1>;
 			interrupt-map-mask = <0 0 0 0x7>;
 			interrupt-map = <0 0 0 1 &gic 0 0 GIC_SPI 312 IRQ_TYPE_LEVEL_HIGH>,
-- 
2.37.1

[PATCH v2 3/3] PCI: imx6: Add root port reset to support link recovery

[Richard Zhu]

The PCIe link can go down due to various unexpected circumstances. Add
root port reset support to enable link recovery for the i.MX PCIe
controller when the optional "intr" interrupt is present.

Reset root port to uninitialize, initialize the PCIe controller, and
restart the PCIe link at end when a link down event happens.

On i.MX95 platforms, link events and PME share the same interrupt line.
The link event interrupt cannot use a threaded-only IRQ handler because
the PME driver uses request_irq() with only the IRQF_SHARED flag set,
which requires a primary handler.

To handle this shared interrupt scenario, register a primary interrupt
handler with IRQF_SHARED for link events and manipulate the link event
enable bits to ensure the shared interrupt source triggers only one
handler at a time.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 123 ++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index e35044cc52185..38e0a16655092 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -34,6 +34,7 @@
 #include <linux/pm_runtime.h>
 
 #include "../../pci.h"
+#include "../pci-host-common.h"
 #include "pcie-designware.h"
 
 #define IMX8MQ_GPR_PCIE_REF_USE_PAD		BIT(9)
@@ -78,6 +79,10 @@
 #define IMX95_SID_MASK				GENMASK(5, 0)
 #define IMX95_MAX_LUT				32
 
+#define IMX95_LINK_INT_CTRL_STS			0x1040
+#define IMX95_LINK_DOWN_INT_STS			BIT(11)
+#define IMX95_LINK_DOWN_INT_EN			BIT(10)
+
 #define IMX95_PCIE_RST_CTRL			0x3010
 #define IMX95_PCIE_COLD_RST			BIT(0)
 
@@ -125,6 +130,8 @@ enum imx_pcie_variants {
 #define IMX_PCIE_MAX_INSTANCES	2
 
 struct imx_pcie;
+static int imx_pcie_reset_root_port(struct pci_host_bridge *bridge,
+				    struct pci_dev *pdev);
 
 struct imx_pcie_drvdata {
 	enum imx_pcie_variants variant;
@@ -158,6 +165,7 @@ struct imx_pcie {
 	bool			supports_clkreq;
 	bool			enable_ext_refclk;
 	struct regmap		*iomuxc_gpr;
+	u32			lnk_intr;
 	u16			msi_ctrl;
 	u32			controller_id;
 	struct reset_control	*pciephy_reset;
@@ -1306,6 +1314,13 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)
 
 	imx_setup_phy_mpll(imx_pcie);
 
+	/*
+	 * Callback invoked by PCI core when link down is detected and
+	 * recovery is needed.
+	 */
+	if (pp->bridge)
+		pp->bridge->reset_root_port = imx_pcie_reset_root_port;
+
 	return 0;
 
 err_phy_off:
@@ -1573,6 +1588,9 @@ static int imx_pcie_suspend_noirq(struct device *dev)
 	if (!(imx_pcie->drvdata->flags & IMX_PCIE_FLAG_SUPPORTS_SUSPEND))
 		return 0;
 
+	if (imx_pcie->lnk_intr)
+		regmap_clear_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				  IMX95_LINK_DOWN_INT_EN);
 	imx_pcie_msi_save_restore(imx_pcie, true);
 	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
 		imx_pcie_lut_save(imx_pcie);
@@ -1623,6 +1641,9 @@ static int imx_pcie_resume_noirq(struct device *dev)
 	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
 		imx_pcie_lut_restore(imx_pcie);
 	imx_pcie_msi_save_restore(imx_pcie, false);
+	if (imx_pcie->lnk_intr)
+		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				IMX95_LINK_DOWN_INT_EN);
 
 	return 0;
 }
@@ -1632,6 +1653,84 @@ static const struct dev_pm_ops imx_pcie_pm_ops = {
 				  imx_pcie_resume_noirq)
 };
 
+static irqreturn_t imx_pcie_lnk_irq_isr(int irq, void *priv)
+{
+	struct imx_pcie *imx_pcie = priv;
+	struct dw_pcie *pci = imx_pcie->pci;
+	struct device *dev = pci->dev;
+	u32 val;
+
+	regmap_read(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS, &val);
+	if (val & IMX95_LINK_DOWN_INT_STS) {
+		dev_dbg(dev, "PCIe link down detected, initiating recovery\n");
+		regmap_clear_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				  IMX95_LINK_DOWN_INT_EN);
+		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				IMX95_LINK_DOWN_INT_STS);
+
+		return IRQ_WAKE_THREAD;
+	} else {
+		return IRQ_NONE;
+	}
+}
+
+static irqreturn_t imx_pcie_lnk_irq_thread(int irq, void *priv)
+{
+	struct imx_pcie *imx_pcie = priv;
+	struct dw_pcie *pci = imx_pcie->pci;
+	struct dw_pcie_rp *pp = &pci->pp;
+	struct pci_dev *port;
+
+	for_each_pci_bridge(port, pp->bridge->bus)
+		if (pci_pcie_type(port) == PCI_EXP_TYPE_ROOT_PORT)
+			pci_host_handle_link_down(port);
+
+	regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+			IMX95_LINK_DOWN_INT_EN);
+
+	return IRQ_HANDLED;
+}
+
+static int imx_pcie_reset_root_port(struct pci_host_bridge *bridge,
+				    struct pci_dev *pdev)
+{
+	struct pci_bus *bus = bridge->bus;
+	struct dw_pcie_rp *pp = bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
+	int ret;
+
+	imx_pcie_msi_save_restore(imx_pcie, true);
+	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
+		imx_pcie_lut_save(imx_pcie);
+	imx_pcie_stop_link(pci);
+	imx_pcie_host_exit(pp);
+
+	ret = imx_pcie_host_init(pp);
+	if (ret) {
+		dev_err(pci->dev, "Failed to re-init PCIe\n");
+		return ret;
+	}
+	ret = dw_pcie_setup_rc(pp);
+	if (ret)
+		goto err_host_deinit;
+
+	imx_pcie_start_link(pci);
+	dw_pcie_wait_for_link(pci);
+
+	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
+		imx_pcie_lut_restore(imx_pcie);
+	imx_pcie_msi_save_restore(imx_pcie, false);
+
+	dev_dbg(pci->dev, "Root port reset completed\n");
+	return 0;
+
+err_host_deinit:
+	imx_pcie_host_exit(pp);
+
+	return ret;
+}
+
 static int imx_pcie_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1834,9 +1933,33 @@ static int imx_pcie_probe(struct platform_device *pdev)
 			val |= PCI_MSI_FLAGS_ENABLE;
 			dw_pcie_writew_dbi(pci, offset + PCI_MSI_FLAGS, val);
 		}
+
+		/* Get link event irq if it is present */
+		imx_pcie->lnk_intr = platform_get_irq_byname(pdev, "intr");
+		if (imx_pcie->lnk_intr > 0) {
+			ret = devm_request_threaded_irq(dev, imx_pcie->lnk_intr,
+							imx_pcie_lnk_irq_isr,
+							imx_pcie_lnk_irq_thread,
+							IRQF_SHARED,
+							"lnk", imx_pcie);
+			if (ret) {
+				dev_err_probe(dev, ret,
+					      "unable to request LNK IRQ\n");
+				goto err_host_deinit;
+			}
+
+			regmap_set_bits(imx_pcie->iomuxc_gpr,
+					IMX95_LINK_INT_CTRL_STS,
+					IMX95_LINK_DOWN_INT_EN);
+		}
 	}
 
 	return 0;
+
+err_host_deinit:
+	dw_pcie_host_deinit(&pci->pp);
+
+	return ret;
 }
 
 static void imx_pcie_shutdown(struct platform_device *pdev)
-- 
2.37.1

RE: [PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme interrupts

[Hongxing Zhu]

Hi Frank:
I didn't include your "Reviewed-by: Frank Li Frank.Li@nxp.com" tag in the v2
patch-set because there were some changes made in v2. If you don't mind, I
would add your reviewed-by tag in the next version (v3) if you don't have
suggestions on the changes.

Best Regards
Richard Zhu

> -----Original Message-----
> From: Hongxing Zhu <hongxing.zhu@nxp.com>
> Sent: Tuesday, April 28, 2026 3:50 PM
> To: robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
> bhelgaas@google.com; Frank Li <frank.li@nxp.com>; l.stach@pengutronix.de;
> lpieralisi@kernel.org; kwilczynski@kernel.org; mani@kernel.org;
> s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com
> Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> devicetree@vger.kernel.org; imx@lists.linux.dev; linux-kernel@vger.kernel.org;
> Hongxing Zhu <hongxing.zhu@nxp.com>
> Subject: [PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme
> interrupts
> 
> Add 'intr', 'aer', and 'pme' interrupt entries to the i.MX6Q PCIe binding to support
> PCIe event-based interrupts for general controller events, Advanced Error
> Reporting, and Power Management Events respectively.
> 
> These interrupts are optional for most variants but required for fsl,imx95-pcie,
> which must specify all 5 interrupts (msi, dma, intr, aer, pme).
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> ---
>  .../bindings/pci/fsl,imx6q-pcie.yaml          | 21 +++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> index 9d1349855b422..0913c3312ed26 100644
> --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> @@ -58,12 +58,18 @@ properties:
>      items:
>        - description: builtin MSI controller.
>        - description: builtin DMA controller.
> +      - description: PCIe event interrupt.
> +      - description: builtin AER SPI standalone interrupter line.
> +      - description: builtin PME SPI standalone interrupter line.
> 
>    interrupt-names:
>      minItems: 1
>      items:
>        - const: msi
>        - const: dma
> +      - const: intr
> +      - const: aer
> +      - const: pme
> 
>    reset-gpio:
>      description: Should specify the GPIO for controlling the PCI bus device @@ -
> 231,6 +237,21 @@ allOf:
>              - const: ref
>              - const: extref  # Optional
> 
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - fsl,imx95-pcie
> +    then:
> +      properties:
> +        interrupts:
> +          minItems: 5
> +          maxItems: 5
> +        interrupt-names:
> +          minItems: 5
> +          maxItems: 5
> +
>  unevaluatedProperties: false
> 
>  examples:
> --
> 2.37.1

Re: [PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme interrupts

[Krzysztof Kozlowski]

On Tue, Apr 28, 2026 at 03:50:28PM +0800, Richard Zhu wrote:
> Add 'intr', 'aer', and 'pme' interrupt entries to the i.MX6Q PCIe
> binding to support PCIe event-based interrupts for general controller
> events, Advanced Error Reporting, and Power Management Events
> respectively.
> 
> These interrupts are optional for most variants but required for
> fsl,imx95-pcie, which must specify all 5 interrupts (msi, dma, intr,
> aer, pme).
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> ---
>  .../bindings/pci/fsl,imx6q-pcie.yaml          | 21 +++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> index 9d1349855b422..0913c3312ed26 100644
> --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> @@ -58,12 +58,18 @@ properties:
>      items:
>        - description: builtin MSI controller.
>        - description: builtin DMA controller.
> +      - description: PCIe event interrupt.
> +      - description: builtin AER SPI standalone interrupter line.
> +      - description: builtin PME SPI standalone interrupter line.
>  
>    interrupt-names:
>      minItems: 1
>      items:
>        - const: msi
>        - const: dma
> +      - const: intr
> +      - const: aer
> +      - const: pme
>  
>    reset-gpio:
>      description: Should specify the GPIO for controlling the PCI bus device
> @@ -231,6 +237,21 @@ allOf:
>              - const: ref
>              - const: extref  # Optional
>  
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - fsl,imx95-pcie

Why do you need another if: block? Why can't it be part of existing one?

> +    then:
> +      properties:
> +        interrupts:
> +          minItems: 5
> +          maxItems: 5

Drop maxItems. You need also constraints for all other variants.

> +        interrupt-names:

Best regards,
Krzysztof

Re: [PATCH v2 1/3] dt-bindings: PCI: imx6q-pcie: Add intr, aer and pme interrupts

[Krzysztof Kozlowski]

On 29/04/2026 09:29, Krzysztof Kozlowski wrote:
> On Tue, Apr 28, 2026 at 03:50:28PM +0800, Richard Zhu wrote:
>> Add 'intr', 'aer', and 'pme' interrupt entries to the i.MX6Q PCIe
>> binding to support PCIe event-based interrupts for general controller
>> events, Advanced Error Reporting, and Power Management Events
>> respectively.
>>
>> These interrupts are optional for most variants but required for
>> fsl,imx95-pcie, which must specify all 5 interrupts (msi, dma, intr,
>> aer, pme).

And that's also ABI break, so you must say WHY they are required.

Best regards,
Krzysztof