watchdog: bcm2835_wdt: set WDOG_HW_RUNNING bit when appropriate

A bootloader may start the watchdog device before handing control to
the kernel - in that case, we should tell the kernel about it so the
watchdog framework can keep it alive until userspace opens
/dev/watchdog0.
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/watchdog/bcm2835_wdt.c

@@ -55,6 +55,15 @@ struct bcm2835_wdt {
 static unsigned int heartbeat;
 static bool nowayout = WATCHDOG_NOWAYOUT;
 
+static bool bcm2835_wdt_is_running(struct bcm2835_wdt *wdt)
+{
+	uint32_t cur;
+
+	cur = readl(wdt->base + PM_RSTC);
+
+	return !!(cur & PM_RSTC_WRCFG_FULL_RESET);
+}
+
 static int bcm2835_wdt_start(struct watchdog_device *wdog)
 {
 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
@@ -181,6 +190,17 @@ static int bcm2835_wdt_probe(struct platform_device *pdev)
 	watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
 	watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
 	bcm2835_wdt_wdd.parent = &pdev->dev;
+	if (bcm2835_wdt_is_running(wdt)) {
+		/*
+		 * The currently active timeout value (set by the
+		 * bootloader) may be different from the module
+		 * heartbeat parameter or the value in device
+		 * tree. But we just need to set WDOG_HW_RUNNING,
+		 * because then the framework will "immediately" ping
+		 * the device, updating the timeout.
+		 */
+		set_bit(WDOG_HW_RUNNING, &bcm2835_wdt_wdd.status);
+	}
 	err = watchdog_register_device(&bcm2835_wdt_wdd);
 	if (err) {
 		dev_err(dev, "Failed to register watchdog device");