can: xilinx_can: Add support for controller reset

Add support for an optional reset for the CAN controller using the reset
driver. If the CAN node contains the "resets" property, then this logic
will perform CAN controller reset.
Signed-off-by: Srinivas Neeli <srinivas.neeli@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/all/ab7e6503aa3343e39ead03c1797e765be6c50de2.1689164442.git.michal.simek@amd.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/xilinx_can.c

@@ -30,6 +30,7 @@
 #include <linux/can/error.h>
 #include <linux/phy/phy.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 
 #define DRIVER_NAME	"xilinx_can"
 
@@ -200,6 +201,7 @@ struct xcan_devtype_data {
  * @can_clk:			Pointer to struct clk
  * @devtype:			Device type specific constants
  * @transceiver:		Optional pointer to associated CAN transceiver
+ * @rstc:			Pointer to reset control
  */
 struct xcan_priv {
 	struct can_priv can;
@@ -218,6 +220,7 @@ struct xcan_priv {
 	struct clk *can_clk;
 	struct xcan_devtype_data devtype;
 	struct phy *transceiver;
+	struct reset_control *rstc;
 };
 
 /* CAN Bittiming constants as per Xilinx CAN specs */
@@ -1799,6 +1802,16 @@ static int xcan_probe(struct platform_device *pdev)
 	priv->can.do_get_berr_counter = xcan_get_berr_counter;
 	priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
 					CAN_CTRLMODE_BERR_REPORTING;
+	priv->rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(priv->rstc)) {
+		dev_err(&pdev->dev, "Cannot get CAN reset.\n");
+		ret = PTR_ERR(priv->rstc);
+		goto err_free;
+	}
+
+	ret = reset_control_reset(priv->rstc);
+	if (ret)
+		goto err_free;
 
 	if (devtype->cantype == XAXI_CANFD) {
 		priv->can.data_bittiming_const =
@@ -1827,7 +1840,7 @@ static int xcan_probe(struct platform_device *pdev)
 	/* Get IRQ for the device */
 	ret = platform_get_irq(pdev, 0);
 	if (ret < 0)
-		goto err_free;
+		goto err_reset;
 
 	ndev->irq = ret;
 
@@ -1843,21 +1856,21 @@ static int xcan_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->can_clk)) {
 		ret = dev_err_probe(&pdev->dev, PTR_ERR(priv->can_clk),
 				    "device clock not found\n");
-		goto err_free;
+		goto err_reset;
 	}
 
 	priv->bus_clk = devm_clk_get(&pdev->dev, devtype->bus_clk_name);
 	if (IS_ERR(priv->bus_clk)) {
 		ret = dev_err_probe(&pdev->dev, PTR_ERR(priv->bus_clk),
 				    "bus clock not found\n");
-		goto err_free;
+		goto err_reset;
 	}
 
 	transceiver = devm_phy_optional_get(&pdev->dev, NULL);
 	if (IS_ERR(transceiver)) {
 		ret = PTR_ERR(transceiver);
 		dev_err_probe(&pdev->dev, ret, "failed to get phy\n");
-		goto err_free;
+		goto err_reset;
 	}
 	priv->transceiver = transceiver;
 
@@ -1904,6 +1917,8 @@ static int xcan_probe(struct platform_device *pdev)
 err_disableclks:
 	pm_runtime_put(priv->dev);
 	pm_runtime_disable(&pdev->dev);
+err_reset:
+	reset_control_assert(priv->rstc);
 err_free:
 	free_candev(ndev);
 err:
@@ -1920,9 +1935,11 @@ static int xcan_probe(struct platform_device *pdev)
 static void xcan_remove(struct platform_device *pdev)
 {
 	struct net_device *ndev = platform_get_drvdata(pdev);
+	struct xcan_priv *priv = netdev_priv(ndev);
 
 	unregister_candev(ndev);
 	pm_runtime_disable(&pdev->dev);
+	reset_control_assert(priv->rstc);
 	free_candev(ndev);
 }