can: sun4i_can: add support for R40 CAN controller

Allwinner R40 (also known as A40i, T3, V40) has a CAN controller. The
controller is the same as in earlier A10 and A20 SoCs, but needs reset
line to be deasserted before use.

This patch adds a new compatible for R40 CAN controller. Depending
on the compatible, reset line can be requested from DT.

Link: https://lore.kernel.org/all/20211122104616.537156-3-boger@wirenboard.com
Signed-off-by: Evgeny Boger <boger@wirenboard.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/sun4i_can.c

@@ -61,6 +61,7 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
+#include <linux/reset.h>
 
 #define DRV_NAME "sun4i_can"
 
@@ -200,10 +201,20 @@
 #define SUN4I_CAN_MAX_IRQ	20
 #define SUN4I_MODE_MAX_RETRIES	100
 
+/**
+ * struct sun4ican_quirks - Differences between SoC variants.
+ *
+ * @has_reset: SoC needs reset deasserted.
+ */
+struct sun4ican_quirks {
+	bool has_reset;
+};
+
 struct sun4ican_priv {
 	struct can_priv can;
 	void __iomem *base;
 	struct clk *clk;
+	struct reset_control *reset;
 	spinlock_t cmdreg_lock;	/* lock for concurrent cmd register writes */
 };
 
@@ -702,6 +713,13 @@ static int sun4ican_open(struct net_device *dev)
 		goto exit_irq;
 	}
 
+	/* software reset deassert */
+	err = reset_control_deassert(priv->reset);
+	if (err) {
+		netdev_err(dev, "could not deassert CAN reset\n");
+		goto exit_soft_reset;
+	}
+
 	/* turn on clocking for CAN peripheral block */
 	err = clk_prepare_enable(priv->clk);
 	if (err) {
@@ -723,6 +741,8 @@ static int sun4ican_open(struct net_device *dev)
 exit_can_start:
 	clk_disable_unprepare(priv->clk);
 exit_clock:
+	reset_control_assert(priv->reset);
+exit_soft_reset:
 	free_irq(dev->irq, dev);
 exit_irq:
 	close_candev(dev);
@@ -736,6 +756,7 @@ static int sun4ican_close(struct net_device *dev)
 	netif_stop_queue(dev);
 	sun4i_can_stop(dev);
 	clk_disable_unprepare(priv->clk);
+	reset_control_assert(priv->reset);
 
 	free_irq(dev->irq, dev);
 	close_candev(dev);
@@ -750,9 +771,27 @@ static const struct net_device_ops sun4ican_netdev_ops = {
 	.ndo_start_xmit = sun4ican_start_xmit,
 };
 
+static const struct sun4ican_quirks sun4ican_quirks_a10 = {
+	.has_reset = false,
+};
+
+static const struct sun4ican_quirks sun4ican_quirks_r40 = {
+	.has_reset = true,
+};
+
 static const struct of_device_id sun4ican_of_match[] = {
-	{.compatible = "allwinner,sun4i-a10-can"},
-	{},
+	{
+		.compatible = "allwinner,sun4i-a10-can",
+		.data = &sun4ican_quirks_a10
+	}, {
+		.compatible = "allwinner,sun7i-a20-can",
+		.data = &sun4ican_quirks_a10
+	}, {
+		.compatible = "allwinner,sun8i-r40-can",
+		.data = &sun4ican_quirks_r40
+	}, {
+		/* sentinel */
+	},
 };
 
 MODULE_DEVICE_TABLE(of, sun4ican_of_match);
@@ -771,10 +810,28 @@ static int sun4ican_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct clk *clk;
+	struct reset_control *reset = NULL;
 	void __iomem *addr;
 	int err, irq;
 	struct net_device *dev;
 	struct sun4ican_priv *priv;
+	const struct sun4ican_quirks *quirks;
+
+	quirks = of_device_get_match_data(&pdev->dev);
+	if (!quirks) {
+		dev_err(&pdev->dev, "failed to determine the quirks to use\n");
+		err = -ENODEV;
+		goto exit;
+	}
+
+	if (quirks->has_reset) {
+		reset = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+		if (IS_ERR(reset)) {
+			dev_err(&pdev->dev, "unable to request reset\n");
+			err = PTR_ERR(reset);
+			goto exit;
+		}
+	}
 
 	clk = of_clk_get(np, 0);
 	if (IS_ERR(clk)) {
@@ -818,6 +875,7 @@ static int sun4ican_probe(struct platform_device *pdev)
 				       CAN_CTRLMODE_3_SAMPLES;
 	priv->base = addr;
 	priv->clk = clk;
+	priv->reset = reset;
 	spin_lock_init(&priv->cmdreg_lock);
 
 	platform_set_drvdata(pdev, dev);