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: b07e228e "watchdog: imx2_wdt: Fix set_timeout for big timeout values"
Cc: stable@vger.kernel.org # 5.2 plus anything the above got backported to
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190812131356.23039-1-linux@rasmusvillemoes.dkSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

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;