watchdog: mtk_wdt: add wdt shutdown callback to disable wdt if enabled

Without .shutdown(), watchdog might reset the system during power off.
For example, if watchdog's timeout is set to 30s, then it is reset to
zero by mtk_wdt_ping(). During power off, no app will ping watchdog,
but watchdog is still running and may trigger reset.
Signed-off-by: Greta Zhang <greta.zhang@mediatek.com>
Signed-off-by: Eddie Huang <eddie.huang@mediatek.com>
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/mtk_wdt.c

@@ -210,6 +210,14 @@ static int mtk_wdt_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static void mtk_wdt_shutdown(struct platform_device *pdev)
+{
+	struct mtk_wdt_dev *mtk_wdt = platform_get_drvdata(pdev);
+
+	if (watchdog_active(&mtk_wdt->wdt_dev))
+		mtk_wdt_stop(&mtk_wdt->wdt_dev);
+}
+
 static int mtk_wdt_remove(struct platform_device *pdev)
 {
 	struct mtk_wdt_dev *mtk_wdt = platform_get_drvdata(pdev);
@@ -259,6 +267,7 @@ static const struct dev_pm_ops mtk_wdt_pm_ops = {
 static struct platform_driver mtk_wdt_driver = {
 	.probe		= mtk_wdt_probe,
 	.remove		= mtk_wdt_remove,
+	.shutdown	= mtk_wdt_shutdown,
 	.driver		= {
 		.name		= DRV_NAME,
 		.pm		= &mtk_wdt_pm_ops,