can: sja1000: Add support for RZ/N1 SJA1000 CAN Controller

The SJA1000 CAN controller on RZ/N1 SoC has no clock divider register
(CDR) support compared to others.

This patch adds support for RZ/N1 SJA1000 CAN Controller, by adding
SoC specific compatible to handle this difference as well as using
clk framework to retrieve the CAN clock frequency.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/all/20220710115248.190280-7-biju.das.jz@bp.renesas.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/sja1000/sja1000_platform.c

@@ -14,6 +14,7 @@
 #include <linux/irq.h>
 #include <linux/can/dev.h>
 #include <linux/can/platform/sja1000.h>
+#include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
@@ -103,6 +104,11 @@ static void sp_technologic_init(struct sja1000_priv *priv, struct device_node *o
 	spin_lock_init(&tp->io_lock);
 }
 
+static void sp_rzn1_init(struct sja1000_priv *priv, struct device_node *of)
+{
+	priv->flags = SJA1000_QUIRK_NO_CDR_REG;
+}
+
 static void sp_populate(struct sja1000_priv *priv,
 			struct sja1000_platform_data *pdata,
 			unsigned long resource_mem_flags)
@@ -153,11 +159,13 @@ static void sp_populate_of(struct sja1000_priv *priv, struct device_node *of)
 		priv->write_reg = sp_write_reg8;
 	}
 
-	err = of_property_read_u32(of, "nxp,external-clock-frequency", &prop);
-	if (!err)
-		priv->can.clock.freq = prop / 2;
-	else
-		priv->can.clock.freq = SP_CAN_CLOCK; /* default */
+	if (!priv->can.clock.freq) {
+		err = of_property_read_u32(of, "nxp,external-clock-frequency", &prop);
+		if (!err)
+			priv->can.clock.freq = prop / 2;
+		else
+			priv->can.clock.freq = SP_CAN_CLOCK; /* default */
+	}
 
 	err = of_property_read_u32(of, "nxp,tx-output-mode", &prop);
 	if (!err)
@@ -192,8 +200,13 @@ static struct sja1000_of_data technologic_data = {
 	.init = sp_technologic_init,
 };
 
+static struct sja1000_of_data renesas_data = {
+	.init = sp_rzn1_init,
+};
+
 static const struct of_device_id sp_of_table[] = {
 	{ .compatible = "nxp,sja1000", .data = NULL, },
+	{ .compatible = "renesas,rzn1-sja1000", .data = &renesas_data, },
 	{ .compatible = "technologic,sja1000", .data = &technologic_data, },
 	{ /* sentinel */ },
 };
@@ -210,6 +223,7 @@ static int sp_probe(struct platform_device *pdev)
 	struct device_node *of = pdev->dev.of_node;
 	const struct sja1000_of_data *of_data = NULL;
 	size_t priv_sz = 0;
+	struct clk *clk;
 
 	pdata = dev_get_platdata(&pdev->dev);
 	if (!pdata && !of) {
@@ -234,6 +248,11 @@ static int sp_probe(struct platform_device *pdev)
 		irq = platform_get_irq(pdev, 0);
 		if (irq < 0)
 			return irq;
+
+		clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
+		if (IS_ERR(clk))
+			return dev_err_probe(&pdev->dev, PTR_ERR(clk),
+					     "CAN clk operation failed");
 	} else {
 		res_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 		if (!res_irq)
@@ -262,6 +281,15 @@ static int sp_probe(struct platform_device *pdev)
 	priv->reg_base = addr;
 
 	if (of) {
+		if (clk) {
+			priv->can.clock.freq  = clk_get_rate(clk) / 2;
+			if (!priv->can.clock.freq) {
+				err = -EINVAL;
+				dev_err(&pdev->dev, "Zero CAN clk rate");
+				goto exit_free;
+			}
+		}
+
 		sp_populate_of(priv, of);
 
 		if (of_data && of_data->init)