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. I realize that 1-5 seconds is challenging for userspace, but having a soft timer in the kernel side sounds like making the system heavier instead of lighter. Not sure I'm making sense here, but I would think twice before adding bloat. Maybe Ariel can submit his v2 (with basic watchdog support, which BTW also provides a reset handler) now and we can pospone this discussion. -- Ezequiel García, VanguardiaSur www.vanguardiasur.com.ar -- 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
