linux-kernel - [PATCH v2 3/3] pcie-xilinx: Support reset GPIO for PERST#

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Message-ID: <20250325071832.21229-3-mike.looijmans@topic.nl>
Date: Tue, 25 Mar 2025 08:18:27 +0100
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org
CC: Mike Looijmans <mike.looijmans@...ic.nl>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Michal Simek <michal.simek@....com>,
	Rob Herring <robh@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] pcie-xilinx: Support reset GPIO for PERST#

Support providing the PERST# reset signal through a devicetree binding.
Thus the system no longer relies on external components to perform the
bus reset.

Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
---

Changes in v2:
Split into "reset GPIO" and "wait for link" patches
Handle GPIO defer and/or errors

 drivers/pci/controller/pcie-xilinx.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/controller/pcie-xilinx.c b/drivers/pci/controller/pcie-xilinx.c
index 2e59b91f43e0..e191ab95d669 100644
--- a/drivers/pci/controller/pcie-xilinx.c
+++ b/drivers/pci/controller/pcie-xilinx.c
@@ -18,6 +18,7 @@
 #include <linux/iopoll.h>
 #include <linux/msi.h>
 #include <linux/of_address.h>
+#include <linux/of_gpio.h>
 #include <linux/of_pci.h>
 #include <linux/of_platform.h>
 #include <linux/of_irq.h>
@@ -577,11 +578,17 @@ static int xilinx_pcie_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct xilinx_pcie *pcie;
 	struct pci_host_bridge *bridge;
+	struct gpio_desc *perst_gpio;
 	int err;
 
 	if (!dev->of_node)
 		return -ENODEV;
 
+	perst_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(perst_gpio))
+		return dev_err_probe(dev, PTR_ERR(perst_gpio),
+				     "reset-gpios request failed\n");
+
 	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*pcie));
 	if (!bridge)
 		return -ENODEV;
@@ -596,6 +603,13 @@ static int xilinx_pcie_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	if (perst_gpio) {
+		usleep_range(10, 20); /* Assert the reset for ~10 us */
+		gpiod_set_value_cansleep(perst_gpio, 0);
+		/* Initial delay to provide endpoint time to restart */
+		usleep_range(1000, 2000);
+	}
+
 	xilinx_pcie_init_port(pcie);
 
 	err = xilinx_pcie_init_irq_domain(pcie);
-- 
2.43.0


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


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