watchdog: imx2_wdt: avoid to ping before resume back

Since watchdog_ping_work is not freezable so that it maybe scheduled before
imx2_wdt_resume where watchdog clock enabled, hence, kernel will hang in
imx2_wdt_ping without clock, and then watchdog reset happen. Add clk_is_on
to prevent the above case by ignoring ping until watchdog driver resume
back indeed.
Signed-off-by: Robin Gong <yibin.gong@nxp.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/1621012875-22667-1-git-send-email-yibin.gong@nxp.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/imx2_wdt.c

@@ -65,6 +65,7 @@ struct imx2_wdt_device {
 	struct regmap *regmap;
 	struct watchdog_device wdog;
 	bool ext_reset;
+	bool clk_is_on;
 };
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -160,6 +161,9 @@ static int imx2_wdt_ping(struct watchdog_device *wdog)
 {
 	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
 
+	if (!wdev->clk_is_on)
+		return 0;
+
 	regmap_write(wdev->regmap, IMX2_WDT_WSR, IMX2_WDT_SEQ1);
 	regmap_write(wdev->regmap, IMX2_WDT_WSR, IMX2_WDT_SEQ2);
 	return 0;
@@ -301,6 +305,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	wdev->clk_is_on = true;
+
 	regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
 	wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;
 
@@ -361,6 +367,8 @@ static int __maybe_unused imx2_wdt_suspend(struct device *dev)
 
 	clk_disable_unprepare(wdev->clk);
 
+	wdev->clk_is_on = false;
+
 	return 0;
 }
 
@@ -375,6 +383,8 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev)
 	if (ret)
 		return ret;
 
+	wdev->clk_is_on = true;
+
 	if (watchdog_active(wdog) && !imx2_wdt_is_running(wdev)) {
 		/*
 		 * If the watchdog is still active and resumes