[PATCH v2 4/9] PCI: aardvark: issue PERST via GPIO

[Marek Behún <marek.behun@xxxxxx>]

From: Pali Rohár <pali@xxxxxxxxxx>

Add support for issuing PERST via GPIO specified in 'reset-gpios'
property (as described in PCI device tree bindings).

Some buggy cards (e.g. Compex WLE900VX or WLE1216) are not detected
after reboot when PERST is not issued during driver initialization.

Tested on Turris MOX.

Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
---
 drivers/pci/controller/pci-aardvark.c | 32 +++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 606bae1e7a88..e2d18094d8ca 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/delay.h>
+#include <linux/gpio.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
@@ -18,6 +19,7 @@
 #include <linux/platform_device.h>
 #include <linux/msi.h>
 #include <linux/of_address.h>
+#include <linux/of_gpio.h>
 #include <linux/of_pci.h>
 
 #include "../pci.h"
@@ -204,6 +206,7 @@ struct advk_pcie {
 	int root_bus_nr;
 	int link_gen;
 	struct pci_bridge_emul bridge;
+	struct gpio_desc *reset_gpio;
 };
 
 static inline void advk_writel(struct advk_pcie *pcie, u32 val, u64 reg)
@@ -329,10 +332,23 @@ static void advk_pcie_train_link(struct advk_pcie *pcie)
 	dev_err(dev, "link never came up\n");
 }
 
+static void advk_pcie_issue_perst(struct advk_pcie *pcie)
+{
+	if (!pcie->reset_gpio)
+		return;
+
+	dev_info(&pcie->pdev->dev, "issuing PERST via reset GPIO for 1ms\n");
+	gpiod_set_value_cansleep(pcie->reset_gpio, 1);
+	usleep_range(1000, 2000);
+	gpiod_set_value_cansleep(pcie->reset_gpio, 0);
+}
+
 static void advk_pcie_setup_hw(struct advk_pcie *pcie)
 {
 	u32 reg;
 
+	advk_pcie_issue_perst(pcie);
+
 	/* Set to Direct mode */
 	reg = advk_readl(pcie, CTRL_CONFIG_REG);
 	reg &= ~(CTRL_MODE_MASK << CTRL_MODE_SHIFT);
@@ -1045,6 +1061,22 @@ static int advk_pcie_probe(struct platform_device *pdev)
 	}
 	pcie->root_bus_nr = bus->start;
 
+	pcie->reset_gpio = devm_gpiod_get_from_of_node(dev, dev->of_node,
+						       "reset-gpios", 0,
+						       GPIOD_OUT_LOW,
+						       "pcie1-reset");
+	ret = PTR_ERR_OR_ZERO(pcie->reset_gpio);
+	if (ret) {
+		if (ret == -ENOENT) {
+			pcie->reset_gpio = NULL;
+		} else {
+			if (ret != -EPROBE_DEFER)
+				dev_err(dev, "Failed to get reset-gpio: %i\n",
+					ret);
+			return ret;
+		}
+	}
+
 	pcie->link_gen = of_pci_get_max_link_speed(dev->of_node);
 	if (pcie->link_gen < 1 || pcie->link_gen > 2)
 		pcie->link_gen = 2;
-- 
2.24.1