On 03/03/2016 02:29 AM, Romain Izard wrote:
If the internal counter is not refreshed when the watchdog is started for the first time, the watchdog will trigger very rapidly. For example, opening /dev/watchdog without writing in it will immediately trigger a reboot, instead of waiting for the delay to expire. To avoid this problem, reload the timer on opening the watchdog device. Command: "while sleep 5; do echo 1; done > /dev/watchdog" Before: system reset After: the watchdog runs correctly Signed-off-by: Romain Izard <romain.izard.pro@xxxxxxxxx>
Subject might better read "ping watchdog on start" or similar. Does the watchdog have to be pinged before it is enabled ? I am a bit concerned that there may still be a 125 uS window during which the system could restart. Thanks, Guenter
--- drivers/watchdog/sama5d4_wdt.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c index a49634cdc1cc..e162fe140ae1 100644 --- a/drivers/watchdog/sama5d4_wdt.c +++ b/drivers/watchdog/sama5d4_wdt.c @@ -15,6 +15,7 @@ #include <linux/platform_device.h> #include <linux/reboot.h> #include <linux/watchdog.h> +#include <linux/delay.h> #include "at91sam9_wdt.h" @@ -58,6 +59,8 @@ static int sama5d4_wdt_start(struct watchdog_device *wdd) reg = wdt_read(wdt, AT91_WDT_MR); reg &= ~AT91_WDT_WDDIS; wdt_write(wdt, AT91_WDT_MR, reg); + udelay(125); /* > 4 cycles at 32,768 Hz */ + wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT); return 0; }
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