[PATCH 4.9 190/212] watchdog: f71808e_wdt: clear watchdog timeout occurred flag

[Greg Kroah-Hartman]

From: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>

commit 4f39d575844148fbf3081571a1f3b4ae04150958 upstream.

The flag indicating a watchdog timeout having occurred normally persists
till Power-On Reset of the Fintek Super I/O chip. The user can clear it
by writing a `1' to the bit.

The driver doesn't offer a restart method, so regular system reboot
might not reset the Super I/O and if the watchdog isn't enabled, we
won't touch the register containing the bit on the next boot.
In this case all subsequent regular reboots will be wrongly flagged
by the driver as being caused by the watchdog.

Fix this by having the flag cleared after read. This is also done by
other drivers like those for the i6300esb and mpc8xxx_wdt.

Fixes: b97cb21a4634 ("watchdog: f71808e_wdt: Fix WDTMOUT_STS register read")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200611191750.28096-5-a.fatoum@xxxxxxxxxxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/watchdog/f71808e_wdt.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/watchdog/f71808e_wdt.c
+++ b/drivers/watchdog/f71808e_wdt.c
@@ -704,6 +704,13 @@ static int __init watchdog_init(int sioa
 	wdt_conf = superio_inb(sioaddr, F71808FG_REG_WDT_CONF);
 	watchdog.caused_reboot = wdt_conf & BIT(F71808FG_FLAG_WDTMOUT_STS);
 
+	/*
+	 * We don't want WDTMOUT_STS to stick around till regular reboot.
+	 * Write 1 to the bit to clear it to zero.
+	 */
+	superio_outb(sioaddr, F71808FG_REG_WDT_CONF,
+		     wdt_conf | BIT(F71808FG_FLAG_WDTMOUT_STS));
+
 	superio_exit(sioaddr);
 
 	err = watchdog_set_timeout(timeout);