[PATCH v6 0/3] Add root port reset to support link recovery

[PATCH v6 0/3] Add root port reset to support link recovery

[hongxing.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] [PATCH v8 0/5] 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 v6:
- Use conditional constraints (if/then schema) to specify that these three
optional interrupts are only valid for the i.MX95 variant, while other
variants like imx6q should not have them.
- Change lnk_intr data type from u32 to int to properly handle negative
error codes returned by platform_get_irq_byname_optional().
- Replace platform_get_irq_byname() with platform_get_irq_byname_optional()
to suppress unnecessary error messages when the optional link event IRQ is
not present in the device tree.
- To avoid inadvertently clear the pending W1C status bit, clear the W1C
bit firstly, then do the regmap_clear_bits().

Changes in v5:
- Update the commit message of the first dt-binding patch for clarity.
- Add explicit comment explaining that writing 1 to IMX95_LINK_DOWN_INT_STS
clears the bit

Changes in v4:
- Set these new added three interrupts as optional interrupt.

Changes in v3:
- Don't add a new if:block; Drop the maxItems constraint of the interrupts
  property for i.MX95 PCIe.
- Add constraints for the interrupts property for other variants.
- Regarding the ABI break: add descriptions explaining why these new
  interrupts are mandatory and required by i.MX95 PCIe.

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


[PATCH v6 1/3] dt-bindings: imx6q-pcie: Add optional intr/aer/pme
[PATCH v6 2/3] arm64: dts: imx95: Add dma, intr, aer and pme
[PATCH v6 3/3] PCI: imx6: Add root port reset to support link

Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml |  29 +++++++++++++++++++++
arch/arm64/boot/dts/freescale/imx95.dtsi                  |  16 +++++++++---
drivers/pci/controller/dwc/pci-imx6.c                     | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 164 insertions(+), 4 deletions(-)

[PATCH v6 1/3] dt-bindings: imx6q-pcie: Add optional intr/aer/pme interrupts for i.MX95

[hongxing.zhu]

From: Richard Zhu <hongxing.zhu@nxp.com>

The i.MX95 PCIe controller introduces three additional dedicated hardware
interrupt lines for specific events:
- intr: general controller events
- aer: Advanced Error Reporting events
- pme: Power Management Events

These interrupts are optional on i.MX95. PCIe basic functionality
(enumeration, configuration, and data transfer) works correctly without
them, as the controller can operate using only the existing msi interrupt.

Earlier i.MX PCIe variants (imx6q, imx6sx, imx6qp, imx7d, imx8mm, imx8mp,
imx8mq, imx8q) do not have these three dedicated interrupt lines.

Update the binding to allow up to 5 interrupts for i.MX95, while
restricting earlier variants to a maximum of 2 interrupts using
conditional constraints (if/then schema). This ensures the schema
accurately reflects the hardware capabilities of each SoC variant.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---
 .../bindings/pci/fsl,imx6q-pcie.yaml          | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
index e8b8131f5f23..9b5d4e59dfff 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 interrupt line.
+      - description: builtin PME SPI standalone interrupt line.
 
   interrupt-names:
     minItems: 1
     items:
       - const: msi
       - const: dma
+      - const: intr
+      - const: aer
+      - const: pme
 
   reset-gpio:
     deprecated: true
@@ -248,6 +254,29 @@ allOf:
             - const: pcie_aux
             - const: ref
             - const: extref  # Optional
+        interrupts:
+          maxItems: 5
+        interrupt-names:
+          maxItems: 5
+
+  - if:
+      properties:
+        compatible:
+          enum:
+            - fsl,imx6q-pcie
+            - fsl,imx6sx-pcie
+            - fsl,imx6qp-pcie
+            - fsl,imx7d-pcie
+            - fsl,imx8mm-pcie
+            - fsl,imx8mp-pcie
+            - fsl,imx8mq-pcie
+            - fsl,imx8q-pcie
+    then:
+      properties:
+        interrupts:
+          maxItems: 2
+        interrupt-names:
+          maxItems: 2
 
 unevaluatedProperties: false
 
-- 
2.34.1

Re: [PATCH v6 1/3] dt-bindings: imx6q-pcie: Add optional intr/aer/pme interrupts for i.MX95

[Rob Herring]

On Wed, Jun 03, 2026 at 02:25:08PM +0800, hongxing.zhu@oss.nxp.com wrote:
> From: Richard Zhu <hongxing.zhu@nxp.com>
> 
> The i.MX95 PCIe controller introduces three additional dedicated hardware
> interrupt lines for specific events:
> - intr: general controller events
> - aer: Advanced Error Reporting events
> - pme: Power Management Events
> 
> These interrupts are optional on i.MX95. PCIe basic functionality
> (enumeration, configuration, and data transfer) works correctly without
> them, as the controller can operate using only the existing msi interrupt.
> 
> Earlier i.MX PCIe variants (imx6q, imx6sx, imx6qp, imx7d, imx8mm, imx8mp,
> imx8mq, imx8q) do not have these three dedicated interrupt lines.
> 
> Update the binding to allow up to 5 interrupts for i.MX95, while
> restricting earlier variants to a maximum of 2 interrupts using
> conditional constraints (if/then schema). This ensures the schema
> accurately reflects the hardware capabilities of each SoC variant.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
>  .../bindings/pci/fsl,imx6q-pcie.yaml          | 29 +++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> index e8b8131f5f23..9b5d4e59dfff 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 interrupt line.
> +      - description: builtin PME SPI standalone interrupt line.
>  
>    interrupt-names:
>      minItems: 1
>      items:
>        - const: msi
>        - const: dma
> +      - const: intr
> +      - const: aer
> +      - const: pme
>  
>    reset-gpio:
>      deprecated: true
> @@ -248,6 +254,29 @@ allOf:
>              - const: pcie_aux
>              - const: ref
>              - const: extref  # Optional
> +        interrupts:
> +          maxItems: 5
> +        interrupt-names:
> +          maxItems: 5

5 is already the max.

> +
> +  - if:
> +      properties:
> +        compatible:
> +          enum:
> +            - fsl,imx6q-pcie
> +            - fsl,imx6sx-pcie
> +            - fsl,imx6qp-pcie
> +            - fsl,imx7d-pcie
> +            - fsl,imx8mm-pcie
> +            - fsl,imx8mp-pcie
> +            - fsl,imx8mq-pcie
> +            - fsl,imx8q-pcie
> +    then:
> +      properties:
> +        interrupts:
> +          maxItems: 2
> +        interrupt-names:
> +          maxItems: 2
>  
>  unevaluatedProperties: false
>  
> -- 
> 2.34.1
> 

[PATCH v6 2/3] arm64: dts: imx95: Add dma, intr, aer and pme interrupts for PCIe

[hongxing.zhu]

From: Richard Zhu <hongxing.zhu@nxp.com>

The current PCIe device tree configuration only defines the MSI
interrupt, which is sufficient for basic PCIe operation but limits
advanced functionality.

Add the following interrupt lines to pcie0 and pcie1 nodes:
- dma: DMA interrupt for PCIe DMA operations
- intr: General controller events and link state changes
- aer: Advanced Error Reporting interrupt
- pme: Power Management Event interrupt

This enables enhanced PCIe features and capabilities that were
previously unavailable due to missing interrupt definitions.

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 3e35c956a4d7..1a9803f96790 100644
--- a/arch/arm64/boot/dts/freescale/imx95.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx95.dtsi
@@ -1945,8 +1945,12 @@ 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>,
@@ -2020,8 +2024,12 @@ 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>,
-- 
2.34.1

[PATCH v6 3/3] PCI: imx6: Add root port reset to support link recovery

[hongxing.zhu]

From: Richard Zhu <hongxing.zhu@nxp.com>

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.

When a link down event occurs, reset the root port by: uninitializing the
PCIe controller, re-initializing it, and restarting the link.

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 773ab65b2afa..aa5c90be23df 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -79,6 +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)
 
@@ -126,6 +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 +164,7 @@ struct imx_pcie {
 	bool			supports_clkreq;
 	bool			enable_ext_refclk;
 	struct regmap		*iomuxc_gpr;
+	int			lnk_intr;
 	u16			msi_ctrl;
 	u32			controller_id;
 	struct reset_control	*pciephy_reset;
@@ -1394,6 +1401,13 @@ 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:
@@ -1661,6 +1675,9 @@ 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 > 0)
+		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);
@@ -1711,6 +1728,9 @@ 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 > 0)
+		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				IMX95_LINK_DOWN_INT_EN);
 
 	return 0;
 }
@@ -1720,6 +1740,85 @@ 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");
+		/* Clear link down interrupt status by writing 1b'1 to it */
+		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				IMX95_LINK_DOWN_INT_STS);
+		regmap_clear_bits(imx_pcie->iomuxc_gpr, IMX95_LINK_INT_CTRL_STS,
+				  IMX95_LINK_DOWN_INT_EN);
+
+		return IRQ_WAKE_THREAD;
+	}
+
+	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;
@@ -1919,9 +2018,33 @@ 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_optional(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)
-- 
2.34.1