[PATCH]: watchdog: Allow watchdog to remain enabled after probe

[Regis Dargent <regis.dargent@gmail.com>]

---
The sunxi_wdt watchdog unconditionally stops the watchdog during probe (on my Allwinner H616).
This avoids automatic reboot in case a problem occurs during boot (and for example handling in the bootloader).

The driver should detect if the HW watchdog is already running during probe and set its appropriate status bit to allow the kernel to handle the watchdog pings itself.
The call to sunxi_wdt_start/stop allows for proper driver and device configuration.
By default, the kernel will then ping the HW watchdog at apropriate frequency, but the user can have it stop after a time with open_timeout parameter.

 drivers/watchdog/sunxi_wdt.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/sunxi_wdt.c b/drivers/watchdog/sunxi_wdt.c
index b85354a99582..20fe7da445ea 100644
--- a/drivers/watchdog/sunxi_wdt.c
+++ b/drivers/watchdog/sunxi_wdt.c
@@ -192,6 +192,16 @@ static int sunxi_wdt_start(struct watchdog_device *wdt_dev)
 	return 0;
 }
 
+static int sunxi_wdt_enabled(struct sunxi_wdt_dev *wdt)
+{
+	u32 reg;
+	void __iomem *wdt_base = wdt->wdt_base;
+	const struct sunxi_wdt_reg *regs = wdt->wdt_regs;
+
+	reg = readl(wdt_base + regs->wdt_mode);
+	return (reg & WDT_MODE_EN);
+}
+
 static const struct watchdog_info sunxi_wdt_info = {
 	.identity	= DRV_NAME,
 	.options	= WDIOF_SETTIMEOUT |
@@ -268,6 +278,11 @@ static int sunxi_wdt_probe(struct platform_device *pdev)
 	sunxi_wdt->wdt_dev.max_timeout = WDT_MAX_TIMEOUT;
 	sunxi_wdt->wdt_dev.min_timeout = WDT_MIN_TIMEOUT;
 	sunxi_wdt->wdt_dev.parent = dev;
+	if (sunxi_wdt_enabled(sunxi_wdt)) {
+		set_bit(WDOG_HW_RUNNING, &sunxi_wdt->wdt_dev.status);
+	} else {
+		clear_bit(WDOG_HW_RUNNING, &sunxi_wdt->wdt_dev.status);
+	}
 
 	watchdog_init_timeout(&sunxi_wdt->wdt_dev, timeout, dev);
 	watchdog_set_nowayout(&sunxi_wdt->wdt_dev, nowayout);
@@ -275,7 +290,10 @@ static int sunxi_wdt_probe(struct platform_device *pdev)
 
 	watchdog_set_drvdata(&sunxi_wdt->wdt_dev, sunxi_wdt);
 
-	sunxi_wdt_stop(&sunxi_wdt->wdt_dev);
+	if (watchdog_hw_running(&sunxi_wdt->wdt_dev))
+		sunxi_wdt_start(&sunxi_wdt->wdt_dev);
+	else
+		sunxi_wdt_stop(&sunxi_wdt->wdt_dev);
 
 	watchdog_stop_on_reboot(&sunxi_wdt->wdt_dev);
 	err = devm_watchdog_register_device(dev, &sunxi_wdt->wdt_dev);
-- 
2.25.1