Re: [PATCH] watchdog: imx2_wdt: fix min() calculation in imx2_wdt_set_timeout

From: Guenter Roeck
Date: Mon Aug 12 2019 - 09:28:11 EST


On 8/12/19 6:13 AM, Rasmus Villemoes wrote:
Converting from ms to s requires dividing by 1000, not multiplying. So
this is currently taking the smaller of new_timeout and 1.28e8,
i.e. effectively new_timeout.

The driver knows what it set max_hw_heartbeat_ms to, so use that
value instead of doing a division at run-time.

FWIW, this can easily be tested by booting into a busybox shell and
doing "watchdog -t 5 -T 130 /dev/watchdog" - without this patch, the
watchdog fires after 130&127 == 2 seconds.

Fixes: b07e228eee69 "watchdog: imx2_wdt: Fix set_timeout for big timeout values"
Cc: stable@xxxxxxxxxxxxxxx # 5.2 plus anything the above got backported to
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

---
This should really be handled in the watchdog core for any driver that
reports max_hw_heartbeat_ms.

Good point. I'll see if I can write a patch.

Guenter

The same pattern appears in aspeed_wdt.c. I don't have the hardware, but
s#wdd->max_hw_heartbeat_ms * 1000#WDT_MAX_TIMEOUT_MS/1000U# should fix that one.


drivers/watchdog/imx2_wdt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 32af3974e6bb..8d019a961ccc 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -55,7 +55,7 @@
#define IMX2_WDT_WMCR 0x08 /* Misc Register */
-#define IMX2_WDT_MAX_TIME 128
+#define IMX2_WDT_MAX_TIME 128U
#define IMX2_WDT_DEFAULT_TIME 60 /* in seconds */
#define WDOG_SEC_TO_COUNT(s) ((s * 2 - 1) << 8)
@@ -180,7 +180,7 @@ static int imx2_wdt_set_timeout(struct watchdog_device *wdog,
{
unsigned int actual;
- actual = min(new_timeout, wdog->max_hw_heartbeat_ms * 1000);
+ actual = min(new_timeout, IMX2_WDT_MAX_TIME);
__imx2_wdt_set_timeout(wdog, actual);
wdog->timeout = new_timeout;
return 0;