[PATCH v2] watchdog: fix watchdog_set_timeout breakage for drivers like imxwd

[Ahmad Fatoum]

Commit 0b944fce55f4 ("watchdog: permit `wd 0` for non-stoppable, but
inactive, watchdogs") silently broke use of watchdogs, that report
being inactive at driver probe time, altogether.
Because those always had watchdog_hw_running evaluating to false,
it early exited without a chance to ever actually set the timeout
(and for watchdog_hw_running to evaluate to != false).

This results in following watchdog drivers being broken in v2020.08.0:

 - imxwd
 - f71808e_wdt
 - at91sam9_wdt

Fixes: 0b944fce55f4 ("watchdog: permit `wd 0` for non-stoppable, but inactive, watchdogs")
Reported-by: Bastian Krause <bst at pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
v1 -> v2:
 - made commit message about scope of breakage more accurate
 - moved check back to top, but in fixed form, as suggested by Sascha
---
 drivers/watchdog/wd_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/watchdog/wd_core.c b/drivers/watchdog/wd_core.c
index ab1dcaa40a3a..665338af6197 100644
--- a/drivers/watchdog/wd_core.c
+++ b/drivers/watchdog/wd_core.c
@@ -45,7 +45,7 @@ int watchdog_set_timeout(struct watchdog *wd, unsigned timeout)
 	if (timeout > wd->timeout_max)
 		return -EINVAL;
 
-	if (watchdog_hw_running(wd) == false)
+	if (!timeout && !watchdog_hw_running(wd))
 		return 0;
 
 	pr_debug("setting timeout on %s to %ds\n", watchdog_name(wd), timeout);
-- 
2.28.0