linux-kernel - [PATCH 2/2] PCI: amd-mdb: Add support for PCIe RP PERST# signal

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Message-ID: <20250326041507.98232-3-sai.krishna.musham@amd.com>
Date: Wed, 26 Mar 2025 09:45:07 +0530
From: Sai Krishna Musham <sai.krishna.musham@....com>
To: <bhelgaas@...gle.com>, <lpieralisi@...nel.org>, <kw@...ux.com>,
	<manivannan.sadhasivam@...aro.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
	<conor+dt@...nel.org>, <cassel@...nel.org>
CC: <linux-pci@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <michal.simek@....com>,
	<bharat.kumar.gogada@....com>, <thippeswamy.havalige@....com>,
	<sai.krishna.musham@....com>
Subject: [PATCH 2/2] PCI: amd-mdb: Add support for PCIe RP PERST# signal

Add PERST# signal handling via I2C GPIO expander for AMD Versal2
MDB PCIe Root Port.

Signed-off-by: Sai Krishna Musham <sai.krishna.musham@....com>
---
 drivers/pci/controller/dwc/pcie-amd-mdb.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-amd-mdb.c b/drivers/pci/controller/dwc/pcie-amd-mdb.c
index 4eb2a4e8189d..4eea53e9e197 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
@@ -408,6 +409,7 @@ static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
 	struct dw_pcie *pci = &pcie->pci;
 	struct dw_pcie_rp *pp = &pci->pp;
 	struct device *dev = &pdev->dev;
+	struct gpio_desc *reset_gpio;
 	int err;
 
 	pcie->slcr = devm_platform_ioremap_resource_byname(pdev, "slcr");
@@ -426,6 +428,24 @@ static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
 
 	pp->ops = &amd_mdb_pcie_host_ops;
 
+	/* Request the GPIO for PCIe reset signal and assert */
+	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(reset_gpio)) {
+		if (PTR_ERR(reset_gpio) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		dev_err(dev, "Failed to request reset GPIO\n");
+		return PTR_ERR(reset_gpio);
+	}
+
+	if (reset_gpio) {
+		/* Controller specific delay */
+		udelay(50);
+
+		/* Deassert the reset signal */
+		gpiod_set_value_cansleep(reset_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);
-- 
2.31.1