Hi Ariel, > On 07/01/2015 05:02 AM, Ariel D'Alessandro wrote: > >(Sorry, I sent the last mail with an incorrect mail account) > > > >El 01/07/15 a las 08:30, adalessandro escibió: > >> > >>El 29/06/15 a las 01:47, Guenter Roeck escibió: > >>>On 06/28/2015 11:13 AM, Ariel D'Alessandro wrote: > >>>>>>+/* Timeout values in seconds */ > >>>>>>+#define LPC_WDT_DEF_TIMEOUT 1 > >>>>>>+ > >>>>> > >>>>>One second ? This is highly unusual. 30 or 60 seconds is more common, > >>>>>and one second would be very challenging for user space. > >>>>> > >>>>>Any special reason for using such a tight default ? > >>>> > >>>>Considering that LPC18xx Watchdog has a fixed divide-by-4 clock > >>>>pre-scaler and a 24-bit counter and that Watchdog clock runs at a fixed > >>>>frequency of 12MHz, timeout range goes from 1 to 5 seconds. > >>>> > >>>>I think you're right, 1 sec is very challenging, so it's 5 secs then. > >>>> > >>>Ultimately you might want to consider a soft timer as backup to the > >>>system > >>>timeout. But that can be done later if/when needed. > >> > >>I understand your point, but just to be sure, what do mean by soft timer? > >> > > A kernel function which pings the watchdog periodically even if the > watchdog is open. > > Example: Timeout is set to 30 seconds. Since the HW watchdog times out > earlier than that, it needs to be pinged regularly (eg every 2.5 seconds). > The kernel does that with a timer unless user space does not ping the > watchdog within the configured interval of 30 seconds.
See at91sam9_wdt.c as an example. I'll add some sample code to linux-watchdog-next also in the very near future. Kind regards, Wim. -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
