Add support for handling the AMD Versal Gen 2 MDB PCIe Root Port PERST#
signal via a GPIO by parsing the new PCIe bridge node to acquire the
reset GPIO.

As part of this, update the interrupt controller node parsing to use
of_get_child_by_name() instead of of_get_next_child(), since the PCIe
node now has multiple children. This ensures the correct node is
selected during initialization.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506241020.rPD1a2Vr-lkp@intel.com/
Signed-off-by: Sai Krishna Musham <sai.krishna.musham@amd.com>
---
Changes in v4:
- Resolve kernel test robot warning.
https://lore.kernel.org/oe-kbuild-all/202506241020.rPD1a2Vr-lkp@intel.com/
- Update commit message.

Changes in v3:
- Implement amd_mdb_parse_pcie_port to parse bridge node for reset-gpios property.

Changes in v2:
- Change delay to PCIE_T_PVPERL_MS

v3 https://lore.kernel.org/r/20250618080931.2472366-1-sai.krishna.musham@amd.com/
v2 https://lore.kernel.org/r/20250429090046.1512000-1-sai.krishna.musham@amd.com/
v1 https://lore.kernel.org/r/20250326041507.98232-1-sai.krishna.musham@amd.com/
---
 drivers/pci/controller/dwc/pcie-amd-mdb.c | 46 ++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-amd-mdb.c b/drivers/pci/controller/dwc/pcie-amd-mdb.c
index 9f7251a16d32..f011a83550b9 100644
--- a/drivers/pci/controller/dwc/pcie-amd-mdb.c
+++ b/drivers/pci/controller/dwc/pcie-amd-mdb.c
@@ -18,6 +18,7 @@
 #include <linux/resource.h>
 #include <linux/types.h>
 
+#include "../../pci.h"
 #include "pcie-designware.h"
 
 #define AMD_MDB_TLP_IR_STATUS_MISC		0x4C0
@@ -56,6 +57,7 @@
  * @slcr: MDB System Level Control and Status Register (SLCR) base
  * @intx_domain: INTx IRQ domain pointer
  * @mdb_domain: MDB IRQ domain pointer
+ * @perst_gpio: GPIO descriptor for PERST# signal handling
  * @intx_irq: INTx IRQ interrupt number
  */
 struct amd_mdb_pcie {
@@ -63,6 +65,7 @@ struct amd_mdb_pcie {
 	void __iomem			*slcr;
 	struct irq_domain		*intx_domain;
 	struct irq_domain		*mdb_domain;
+	struct gpio_desc		*perst_gpio;
 	int				intx_irq;
 };
 
@@ -284,7 +287,7 @@ static int amd_mdb_pcie_init_irq_domains(struct amd_mdb_pcie *pcie,
 	struct device_node *pcie_intc_node;
 	int err;
 
-	pcie_intc_node = of_get_next_child(node, NULL);
+	pcie_intc_node = of_get_child_by_name(node, "interrupt-controller");
 	if (!pcie_intc_node) {
 		dev_err(dev, "No PCIe Intc node found\n");
 		return -ENODEV;
@@ -402,6 +405,34 @@ static int amd_mdb_setup_irq(struct amd_mdb_pcie *pcie,
 	return 0;
 }
 
+static int amd_mdb_parse_pcie_port(struct amd_mdb_pcie *pcie)
+{
+	struct device *dev = pcie->pci.dev;
+	struct device_node *pcie_port_node;
+
+	pcie_port_node = of_get_next_child_with_prefix(dev->of_node, NULL, "pcie");
+	if (!pcie_port_node) {
+		dev_err(dev, "No PCIe Bridge node found\n");
+		return -ENODEV;
+	}
+
+	/* Request the GPIO for PCIe reset signal and assert */
+	pcie->perst_gpio = devm_fwnode_gpiod_get(dev, of_fwnode_handle(pcie_port_node),
+						 "reset", GPIOD_OUT_HIGH, NULL);
+	if (IS_ERR(pcie->perst_gpio)) {
+		if (PTR_ERR(pcie->perst_gpio) != -ENOENT) {
+			of_node_put(pcie_port_node);
+			return dev_err_probe(dev, PTR_ERR(pcie->perst_gpio),
+					     "Failed to request reset GPIO\n");
+		}
+		pcie->perst_gpio = NULL;
+	}
+
+	of_node_put(pcie_port_node);
+
+	return 0;
+}
+
 static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
 				 struct platform_device *pdev)
 {
@@ -426,6 +457,14 @@ static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
 
 	pp->ops = &amd_mdb_pcie_host_ops;
 
+	if (pcie->perst_gpio) {
+		mdelay(PCIE_T_PVPERL_MS);
+
+		/* Deassert the reset signal */
+		gpiod_set_value_cansleep(pcie->perst_gpio, 0);
+		mdelay(PCIE_T_RRS_READY_MS);
+	}
+
 	err = dw_pcie_host_init(pp);
 	if (err) {
 		dev_err(dev, "Failed to initialize host, err=%d\n", err);
@@ -444,6 +483,7 @@ static int amd_mdb_pcie_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct amd_mdb_pcie *pcie;
 	struct dw_pcie *pci;
+	int ret;
 
 	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
 	if (!pcie)
@@ -454,6 +494,10 @@ static int amd_mdb_pcie_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, pcie);
 
+	ret = amd_mdb_parse_pcie_port(pcie);
+	if (ret)
+		return ret;
+
 	return amd_mdb_add_pcie_port(pcie, pdev);
 }
 
-- 
2.44.1

On Thu, Jun 26, 2025 at 11:19:06AM +0530, Sai Krishna Musham wrote:
> Add support for handling the AMD Versal Gen 2 MDB PCIe Root Port PERST#
> signal via a GPIO by parsing the new PCIe bridge node to acquire the
> reset GPIO.
> 
> As part of this, update the interrupt controller node parsing to use
> of_get_child_by_name() instead of of_get_next_child(), since the PCIe
> node now has multiple children. This ensures the correct node is
> selected during initialization.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202506241020.rPD1a2Vr-lkp@intel.com/

Omit these tags.  This kernel test robot report is basically a code
review comment that doesn't need to be acknowledged here (the robot's
report says:

  If you fix the issue in a separate patch/commit (i.e. not just a new
  version of the same patch/commit), kindly add following tags ...

IIUC this is just a new version of the same patch, so doesn't need the
tags.

> Signed-off-by: Sai Krishna Musham <sai.krishna.musham@amd.com>
> ---
> Changes in v4:
> - Resolve kernel test robot warning.
> https://lore.kernel.org/oe-kbuild-all/202506241020.rPD1a2Vr-lkp@intel.com/
> - Update commit message.
> 
> Changes in v3:
> - Implement amd_mdb_parse_pcie_port to parse bridge node for reset-gpios property.
> 
> Changes in v2:
> - Change delay to PCIE_T_PVPERL_MS
> 
> v3 https://lore.kernel.org/r/20250618080931.2472366-1-sai.krishna.musham@amd.com/
> v2 https://lore.kernel.org/r/20250429090046.1512000-1-sai.krishna.musham@amd.com/
> v1 https://lore.kernel.org/r/20250326041507.98232-1-sai.krishna.musham@amd.com/
> ---
>  drivers/pci/controller/dwc/pcie-amd-mdb.c | 46 ++++++++++++++++++++++-
>  1 file changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-amd-mdb.c b/drivers/pci/controller/dwc/pcie-amd-mdb.c
> index 9f7251a16d32..f011a83550b9 100644
> --- a/drivers/pci/controller/dwc/pcie-amd-mdb.c
> +++ b/drivers/pci/controller/dwc/pcie-amd-mdb.c
> @@ -18,6 +18,7 @@
>  #include <linux/resource.h>
>  #include <linux/types.h>
>  
> +#include "../../pci.h"
>  #include "pcie-designware.h"
>  
>  #define AMD_MDB_TLP_IR_STATUS_MISC		0x4C0
> @@ -56,6 +57,7 @@
>   * @slcr: MDB System Level Control and Status Register (SLCR) base
>   * @intx_domain: INTx IRQ domain pointer
>   * @mdb_domain: MDB IRQ domain pointer
> + * @perst_gpio: GPIO descriptor for PERST# signal handling
>   * @intx_irq: INTx IRQ interrupt number
>   */
>  struct amd_mdb_pcie {
> @@ -63,6 +65,7 @@ struct amd_mdb_pcie {
>  	void __iomem			*slcr;
>  	struct irq_domain		*intx_domain;
>  	struct irq_domain		*mdb_domain;
> +	struct gpio_desc		*perst_gpio;
>  	int				intx_irq;
>  };
>  
> @@ -284,7 +287,7 @@ static int amd_mdb_pcie_init_irq_domains(struct amd_mdb_pcie *pcie,
>  	struct device_node *pcie_intc_node;
>  	int err;
>  
> -	pcie_intc_node = of_get_next_child(node, NULL);
> +	pcie_intc_node = of_get_child_by_name(node, "interrupt-controller");
>  	if (!pcie_intc_node) {
>  		dev_err(dev, "No PCIe Intc node found\n");
>  		return -ENODEV;
> @@ -402,6 +405,34 @@ static int amd_mdb_setup_irq(struct amd_mdb_pcie *pcie,
>  	return 0;
>  }
>  
> +static int amd_mdb_parse_pcie_port(struct amd_mdb_pcie *pcie)
> +{
> +	struct device *dev = pcie->pci.dev;
> +	struct device_node *pcie_port_node;
> +
> +	pcie_port_node = of_get_next_child_with_prefix(dev->of_node, NULL, "pcie");
> +	if (!pcie_port_node) {
> +		dev_err(dev, "No PCIe Bridge node found\n");
> +		return -ENODEV;
> +	}
> +
> +	/* Request the GPIO for PCIe reset signal and assert */
> +	pcie->perst_gpio = devm_fwnode_gpiod_get(dev, of_fwnode_handle(pcie_port_node),
> +						 "reset", GPIOD_OUT_HIGH, NULL);
> +	if (IS_ERR(pcie->perst_gpio)) {
> +		if (PTR_ERR(pcie->perst_gpio) != -ENOENT) {
> +			of_node_put(pcie_port_node);
> +			return dev_err_probe(dev, PTR_ERR(pcie->perst_gpio),
> +					     "Failed to request reset GPIO\n");
> +		}
> +		pcie->perst_gpio = NULL;
> +	}
> +
> +	of_node_put(pcie_port_node);
> +
> +	return 0;
> +}
> +
>  static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
>  				 struct platform_device *pdev)
>  {
> @@ -426,6 +457,14 @@ static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
>  
>  	pp->ops = &amd_mdb_pcie_host_ops;
>  
> +	if (pcie->perst_gpio) {
> +		mdelay(PCIE_T_PVPERL_MS);
> +
> +		/* Deassert the reset signal */
> +		gpiod_set_value_cansleep(pcie->perst_gpio, 0);
> +		mdelay(PCIE_T_RRS_READY_MS);
> +	}
> +
>  	err = dw_pcie_host_init(pp);
>  	if (err) {
>  		dev_err(dev, "Failed to initialize host, err=%d\n", err);
> @@ -444,6 +483,7 @@ static int amd_mdb_pcie_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct amd_mdb_pcie *pcie;
>  	struct dw_pcie *pci;
> +	int ret;
>  
>  	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
>  	if (!pcie)
> @@ -454,6 +494,10 @@ static int amd_mdb_pcie_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, pcie);
>  
> +	ret = amd_mdb_parse_pcie_port(pcie);
> +	if (ret)
> +		return ret;

I'm not a DT expert, but doesn't this break if you run
amd_mdb_parse_pcie_port() on a system with an existing DT that lacks
the pcie@0,0 stanza you added to the binding in patch [1/2]?

I.e., amd_mdb_parse_pcie_port() will return -ENODEV in that case, and
the probe will now fail?

It's good to add new functionality, but if the driver runs with a DT
that doesn't describe the new functionality, it should fall back to
the previous behavior (without the new functionality) instead of
failing completely.

>  	return amd_mdb_add_pcie_port(pcie, pdev);
>  }
>  
> -- 
> 2.44.1
>