watchdog: orion: Handle the interrupt so it's properly acked

DT-enabled plaforms, where the irqchip driver for the brigde interrupt
controller is available, can handle the watchdog IRQ properly. Therefore,
request the interrupt and add a dummy handler that merely calls panic().

This is done in order to have an initial 'ack' of the interruption,
which clears the watchdog state.

Furthermore, since some platforms don't have such IRQ, this commit
makes the interrupt specification optional.
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Tested-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

Documentation/devicetree/bindings/watchdog/marvel.txt

@@ -7,6 +7,7 @@ Required Properties:
 
 Optional properties:
 
+- interrupts	: Contains the IRQ for watchdog expiration
 - timeout-sec	: Contains the watchdog timeout in seconds
 
 Example:
@@ -14,6 +15,7 @@ Example:
 	wdt@20300 {
 		compatible = "marvell,orion-wdt";
 		reg = <0x20300 0x28>;
+		interrupts = <3>;
 		timeout-sec = <10>;
 		status = "okay";
 	};

drivers/watchdog/orion_wdt.c

@@ -19,6 +19,7 @@
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>
 #include <linux/init.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/clk.h>
 #include <linux/err.h>
@@ -119,10 +120,16 @@ static struct watchdog_device orion_wdt = {
 	.min_timeout = 1,
 };
 
+static irqreturn_t orion_wdt_irq(int irq, void *devid)
+{
+	panic("Watchdog Timeout");
+	return IRQ_HANDLED;
+}
+
 static int orion_wdt_probe(struct platform_device *pdev)
 {
 	struct resource *res;
-	int ret;
+	int ret, irq;
 
 	clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(clk)) {
@@ -161,6 +168,21 @@ static int orion_wdt_probe(struct platform_device *pdev)
 	if (!orion_wdt_enabled())
 		orion_wdt_stop(&orion_wdt);
 
+	/* Request the IRQ only after the watchdog is disabled */
+	irq = platform_get_irq(pdev, 0);
+	if (irq > 0) {
+		/*
+		 * Not all supported platforms specify an interrupt for the
+		 * watchdog, so let's make it optional.
+		 */
+		ret = devm_request_irq(&pdev->dev, irq, orion_wdt_irq, 0,
+				       pdev->name, &orion_wdt);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "failed to request IRQ\n");
+			goto disable_clk;
+		}
+	}
+
 	watchdog_set_nowayout(&orion_wdt, nowayout);
 	ret = watchdog_register_device(&orion_wdt);
 	if (ret)