[PATCH 5/5] watchdog: rzn1: Add support for direct hardware reset

[Herve Codina (Schneider Electric)]

The watchdog timeout is signaled using an interrupt and, on this
interrupt, a software initiated reset is performed.

The watchdog is able to control directly the hardware reset without
any operation done by the interrupt handler. This feature allows the
watchdog to not depend on the software to reset the system when the
watchdog timeout occurs.

The 'renesas,reset-line' device-tree property has been recently
introduced in order to describe the hardware reset line used by the
watchdog on its timeout.

Handle this property in the driver and add support for the related
direct hardware reset.

Signed-off-by: Herve Codina (Schneider Electric) <herve.codina@xxxxxxxxxxx>
---
 drivers/watchdog/rzn1_wdt.c | 41 +++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/watchdog/rzn1_wdt.c b/drivers/watchdog/rzn1_wdt.c
index 98978b5cc5b4..bf623ea31be1 100644
--- a/drivers/watchdog/rzn1_wdt.c
+++ b/drivers/watchdog/rzn1_wdt.c
@@ -17,7 +17,9 @@
 #include <linux/of_irq.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
+#include <linux/soc/renesas/r9a06g032-sysctrl.h>
 #include <linux/watchdog.h>
+#include <dt-bindings/watchdog/renesas,rzn1-wdt.h>
 
 #define DEFAULT_TIMEOUT		60
 
@@ -98,6 +100,41 @@ static const struct watchdog_ops rzn1_wdt_ops = {
 	.ping = rzn1_wdt_ping,
 };
 
+static int rzn1_wdt_setup_rst_line(struct device *dev)
+{
+	enum r9a06g032_sysctrl_rst_src rst_src;
+	u32 reset_line;
+	int ret;
+
+	ret = of_property_read_u32(dev->of_node, "renesas,reset-line", &reset_line);
+	if (ret) {
+		if (ret == -EINVAL)
+			return 0; /* Property not present -> Ok, nothing to do */
+
+		return dev_err_probe(dev, ret, "Read 'renesas,reset-line' failed\n");
+	}
+
+	switch (reset_line) {
+	case RZN1_WDT_A7_0:
+		rst_src = R9A06G032_RST_WATCHDOG_CA7_0;
+		break;
+	case RZN1_WDT_A7_1:
+		rst_src = R9A06G032_RST_WATCHDOG_CA7_1;
+		break;
+
+	default:
+		return dev_err_probe(dev, -EINVAL,
+				     "Invalid 'renesas,reset-line' (%u)\n",
+				     reset_line);
+	}
+
+	ret = r9a06g032_sysctrl_enable_rst(rst_src);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable reset\n");
+
+	return 0;
+}
+
 static int rzn1_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -116,6 +153,10 @@ static int rzn1_wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(wdt->base))
 		return PTR_ERR(wdt->base);
 
+	ret = rzn1_wdt_setup_rst_line(dev);
+	if (ret)
+		return ret;
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;
-- 
2.53.0