[PATCH 1/1] PCI: armada8k: add device reset to link-down handle

[Jenishkumar Maheshbhai Patel <jpatel2@xxxxxxxxxxx>]

Added pcie reset via gpio support as described in the
designware-pcie.txt DT binding document.
In cases link down cause still exist in device.
The device need to be reset to reestablish the link.
If reset-gpio pin provided in the device tree, then the linkdown
handle resets the device before reestablishing link.

Signed-off-by: Jenishkumar Maheshbhai Patel <jpatel2@xxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-armada8k.c | 24 ++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-armada8k.c b/drivers/pci/controller/dwc/pcie-armada8k.c
index b1b48c2016f7..9a48ef60be51 100644
--- a/drivers/pci/controller/dwc/pcie-armada8k.c
+++ b/drivers/pci/controller/dwc/pcie-armada8k.c
@@ -23,6 +23,7 @@
 #include <linux/of_pci.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
+#include <linux/of_gpio.h>
 
 #include "pcie-designware.h"
 
@@ -37,6 +38,8 @@ struct armada8k_pcie {
 	struct regmap *sysctrl_base;
 	u32 mac_rest_bitmask;
 	struct work_struct recover_link_work;
+	enum of_gpio_flags flags;
+	struct gpio_desc *reset_gpio;
 };
 
 #define PCIE_VENDOR_REGS_OFFSET		0x8000
@@ -238,9 +241,18 @@ static void armada8k_pcie_recover_link(struct work_struct *ws)
 	}
 	pci_lock_rescan_remove();
 	pci_stop_and_remove_bus_device(root_port);
+	/* Reset device if reset gpio is set */
+	if (pcie->reset_gpio) {
+		/* assert and then deassert the reset signal */
+		gpiod_set_value_cansleep(pcie->reset_gpio, 0);
+		msleep(100);
+		gpiod_set_value_cansleep(pcie->reset_gpio,
+					 (pcie->flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1);
+	}
 	/*
-	 * Sleep needed to make sure all pcie transactions and access
-	 * are flushed before resetting the mac
+	 * Sleep used for two reasons.
+	 * First make sure all pcie transactions and access are flushed before resetting the mac
+	 * and second to make sure pci device is ready in case we reset the device
 	 */
 	msleep(100);
 
@@ -376,6 +388,7 @@ static int armada8k_pcie_probe(struct platform_device *pdev)
 	struct armada8k_pcie *pcie;
 	struct device *dev = &pdev->dev;
 	struct resource *base;
+	int reset_gpio;
 	int ret;
 
 	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
@@ -420,6 +433,13 @@ static int armada8k_pcie_probe(struct platform_device *pdev)
 		goto fail_clkreg;
 	}
 
+	/* Config reset gpio for pcie if the reset connected to gpio */
+	reset_gpio = of_get_named_gpio_flags(pdev->dev.of_node,
+					     "reset-gpios", 0,
+					     &pcie->flags);
+	if (gpio_is_valid(reset_gpio))
+		pcie->reset_gpio = gpio_to_desc(reset_gpio);
+
 	pcie->sysctrl_base = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
 						       "marvell,system-controller");
 	if (IS_ERR(pcie->sysctrl_base)) {
-- 
2.25.1