watchdog: sp5100-tco: Abort if watchdog is disabled by hardware

If the watchdog control register indicates that the watchdog hardware
is disabled even after we tried to enable it, there is no point to
instantiate the driver.

Cc: Zoltán Böszörményi <zboszor@pr.hu>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/sp5100_tco.c

@@ -273,14 +273,20 @@ static int sp5100_tco_setupdevice(struct device *dev,
 	/* Setup the watchdog timer */
 	tco_timer_enable();
 
-	/* Check that the watchdog action is set to reset the system */
 	val = readl(SP5100_WDT_CONTROL(tco->tcobase));
+	if (val & SP5100_WDT_DISABLED) {
+		dev_err(dev, "Watchdog hardware is disabled\n");
+		ret = -ENODEV;
+		goto unreg_region;
+	}
+
 	/*
 	 * Save WatchDogFired status, because WatchDogFired flag is
 	 * cleared here.
 	 */
 	if (val & SP5100_WDT_FIRED)
 		wdd->bootstatus = WDIOF_CARDRESET;
+	/* Set watchdog action to reset the system */
 	val &= ~SP5100_WDT_ACTION_RESET;
 	writel(val, SP5100_WDT_CONTROL(tco->tcobase));
 

drivers/watchdog/sp5100_tco.h

@@ -19,6 +19,7 @@
 #define SP5100_WDT_START_STOP_BIT	BIT(0)
 #define SP5100_WDT_FIRED		BIT(1)
 #define SP5100_WDT_ACTION_RESET		BIT(2)
+#define SP5100_WDT_DISABLED		BIT(3)
 #define SP5100_WDT_TRIGGER_BIT		BIT(7)
 
 #define SP5100_PM_IOPORTS_SIZE		0x02