watchdog: mtk_wdt: Remove mtk_wdt_stop() in probe() to prevent the system...

watchdog: mtk_wdt: Remove mtk_wdt_stop() in probe() to prevent the system freeze and it doesn't reboot by watchdog problem

Before user space daemon start to access the watchdog device,
there is a time interval that watchdog is disabled in the
original flow. If the system freezing at this interval, it
cannot be rebooted by watchdog hardware automatically.

In order to solve this problem, the watchdog hardware should be
kept working, and start hrtimer in framework to ping it by
setting max_hw_heartbeat_ms and HW_RUNNING used in
watchdog_need_worker to determine whether the worker should be
started or not. Besides the redundant setting of max_timeout is
also removed.
Signed-off-by: freddy.hsin <freddy.hsin@mediatek.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/1609316157-3748-1-git-send-email-freddy.hsin@mediatek.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/mtk_wdt.c

@@ -195,6 +195,19 @@ static int mtk_wdt_set_timeout(struct watchdog_device *wdt_dev,
 	return 0;
 }
 
+static void mtk_wdt_init(struct watchdog_device *wdt_dev)
+{
+	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
+	void __iomem *wdt_base;
+
+	wdt_base = mtk_wdt->wdt_base;
+
+	if (readl(wdt_base + WDT_MODE) & WDT_MODE_EN) {
+		set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
+		mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
+	}
+}
+
 static int mtk_wdt_stop(struct watchdog_device *wdt_dev)
 {
 	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
@@ -264,7 +277,7 @@ static int mtk_wdt_probe(struct platform_device *pdev)
 	mtk_wdt->wdt_dev.info = &mtk_wdt_info;
 	mtk_wdt->wdt_dev.ops = &mtk_wdt_ops;
 	mtk_wdt->wdt_dev.timeout = WDT_MAX_TIMEOUT;
-	mtk_wdt->wdt_dev.max_timeout = WDT_MAX_TIMEOUT;
+	mtk_wdt->wdt_dev.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT * 1000;
 	mtk_wdt->wdt_dev.min_timeout = WDT_MIN_TIMEOUT;
 	mtk_wdt->wdt_dev.parent = dev;
 
@@ -274,7 +287,7 @@ static int mtk_wdt_probe(struct platform_device *pdev)
 
 	watchdog_set_drvdata(&mtk_wdt->wdt_dev, mtk_wdt);
 
-	mtk_wdt_stop(&mtk_wdt->wdt_dev);
+	mtk_wdt_init(&mtk_wdt->wdt_dev);
 
 	watchdog_stop_on_reboot(&mtk_wdt->wdt_dev);
 	err = devm_watchdog_register_device(dev, &mtk_wdt->wdt_dev);