On Wed, Jul 01, 2015 at 12:22:12PM -0300, Ezequiel Garcia wrote: > Hi Guenter, > > First of all, thanks a lot for your feedback. > > On 1 July 2015 at 10:54, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > 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. > > > > Do we really need this? It sounds like bloat to me. Considering this watchdog > controller is included in cortex-M MCUs, you wouldn't expect the > scheduler to be under so much pressure. > No, this would be your call. There are also plans to add this into the watchdog core, which is really where it should be. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
