linux-kernel - [PATCH] watchdog: imx2_wdt: fix min() calculation in imx2_wdt_set

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Date:   Mon, 12 Aug 2019 15:13:56 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     Georg Hofmann <georg@...mannsweb.com>,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        stable@...r.kernel.org
Subject: [PATCH] watchdog: imx2_wdt: fix min() calculation in imx2_wdt_set_timeout

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@...r.kernel.org # 5.2 plus anything the above got backported to
Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
This should really be handled in the watchdog core for any driver that
reports max_hw_heartbeat_ms.

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;
-- 
2.20.1