watchdog: omap_wdt: implement get_timeleft

The omap watchdog hardware is able to read the watchdog timer counter
register. This implements this functionality in the omap_wdt driver, so
one is can read the time until the watchdog will trigger the reset in
seconds using WDIOC_GETTIMELEFT.
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/omap_wdt.c

@@ -198,6 +198,16 @@ static int omap_wdt_set_timeout(struct watchdog_device *wdog,
 	return 0;
 }
 
+static unsigned int omap_wdt_get_timeleft(struct watchdog_device *wdog)
+{
+	struct omap_wdt_dev *wdev = watchdog_get_drvdata(wdog);
+	void __iomem *base = wdev->base;
+	u32 value;
+
+	value = readl_relaxed(base + OMAP_WATCHDOG_CRR);
+	return GET_WCCR_SECS(value);
+}
+
 static const struct watchdog_info omap_wdt_info = {
 	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
 	.identity = "OMAP Watchdog",
@@ -209,6 +219,7 @@ static const struct watchdog_ops omap_wdt_ops = {
 	.stop		= omap_wdt_stop,
 	.ping		= omap_wdt_ping,
 	.set_timeout	= omap_wdt_set_timeout,
+	.get_timeleft	= omap_wdt_get_timeleft,
 };
 
 static int omap_wdt_probe(struct platform_device *pdev)

drivers/watchdog/omap_wdt.h

@@ -50,5 +50,6 @@
 
 #define PTV			0	/* prescale */
 #define GET_WLDR_VAL(secs)	(0xffffffff - ((secs) * (32768/(1<<PTV))) + 1)
+#define GET_WCCR_SECS(val)	((0xffffffff - (val) + 1) / (32768/(1<<PTV)))
 
 #endif				/* _OMAP_WATCHDOG_H */