watchdog: sp805: set WDOG_HW_RUNNING when appropriate

If the watchdog hardware is already enabled during the boot process,
when the Linux watchdog driver loads, it should reset the watchdog and
tell the watchdog framework. As a result, ping can be generated from
the watchdog framework, until the userspace watchdog daemon takes over
control

Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/sp805_wdt.c

@@ -42,6 +42,7 @@
 	/* control register masks */
 	#define	INT_ENABLE	(1 << 0)
 	#define	RESET_ENABLE	(1 << 1)
+	#define	ENABLE_MASK	(INT_ENABLE | RESET_ENABLE)
 #define WDTINTCLR		0x00C
 #define WDTRIS			0x010
 #define WDTMIS			0x014
@@ -74,6 +75,15 @@ module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout,
 		"Set to 1 to keep watchdog running after device release");
 
+/* returns true if wdt is running; otherwise returns false */
+static bool wdt_is_running(struct watchdog_device *wdd)
+{
+	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL);
+
+	return (wdtcontrol & ENABLE_MASK) == ENABLE_MASK;
+}
+
 /* This routine finds load value that will reset system in required timout */
 static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
 {
@@ -253,6 +263,15 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
 	watchdog_init_timeout(&wdt->wdd, 0, &adev->dev);
 	wdt_setload(&wdt->wdd, wdt->wdd.timeout);
 
+	/*
+	 * If HW is already running, enable/reset the wdt and set the running
+	 * bit to tell the wdt subsystem
+	 */
+	if (wdt_is_running(&wdt->wdd)) {
+		wdt_enable(&wdt->wdd);
+		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
+	}
+
 	ret = watchdog_register_device(&wdt->wdd);
 	if (ret) {
 		dev_err(&adev->dev, "watchdog_register_device() failed: %d\n",