[PATCH] watchdog: use time_after_eq() in watchdog_reset()

Rasmus Villemoes rasmus.villemoes at prevas.dk
Tue Apr 13 16:43:20 CEST 2021

Some boards don't work with the rate-limiting done in the generic
watchdog_reset() provided by wdt-uclass.

For example, on powerpc, get_timer() ceases working during bootm since
interrupts are disabled before the kernel image gets decompressed, and
when the decompression takes longer than the watchdog device
allows (or enough of the budget that the kernel doesn't get far enough
to assume responsibility for petting the watchdog), the result is a
non-booting board.

As a somewhat hacky workaround (because DT is supposed to describe
hardware), allow specifying hw_margin_ms=0 in device tree to
effectively disable the ratelimiting and actually ping the watchdog
every time watchdog_reset() is called. For that to work, the "has
enough time passed" check just needs to be tweaked a little to allow
the now==next_reset case as well.

Suggested-by: Christophe Leroy <christophe.leroy at csgroup.eu>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>

It's the option I dislike the most (because of the DT abuse), but I
also do accept that it's the one with the minimal code impact, and
apparently the path of least resistance. So here it is.

 drivers/watchdog/wdt-uclass.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/watchdog/wdt-uclass.c b/drivers/watchdog/wdt-uclass.c
index 0603ffbd36..2687135296 100644
--- a/drivers/watchdog/wdt-uclass.c
+++ b/drivers/watchdog/wdt-uclass.c
@@ -148,7 +148,7 @@ void watchdog_reset(void)
 	/* Do not reset the watchdog too often */
 	now = get_timer(0);
-	if (time_after(now, next_reset)) {
+	if (time_after_eq(now, next_reset)) {
 		next_reset = now + reset_period;

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