Re: [PATCH v1] watchdog: sama5d4_wdt: Reset delay on start

[Guenter Roeck]

On 03/04/2016 01:06 AM, Romain Izard wrote:
> Hi Wenyou, Guenter,
>
> 2016-03-04 6:23 GMT+01:00 Guenter Roeck <linux@xxxxxxxxxxxx>:
> > On 03/03/2016 05:35 PM, Yang, Wenyou wrote:
> > > On 2016/3/3 18:29, 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
> > >
> > > I didn't reproduce your issue on my side,
> > >
> > > run the your commands as follows, it works fine,  the system reset
> > > doesn't happen.
>
> I've just verified with the factory image provided on the SAMA5D2
> Xplained board. It does not display this behaviour.
>
> But the difference is that in the case without the issue, I'm using the
> AT91bootstrap SPL, U-Boot, and the kernel from the QSPI chip. When I
> have the issue, I have a U-Boot based SPL, U-Boot itself and the kernel
> that come from the FAT partition of an SD-Card.
>
> Userspace does not seem to be involved in the issue, as I can reproduce
> it both with my buildroot environment, and the Yocto environment from
> the factory image.
>
> > Different chip revision ? Different chip type ? Different chip
> > initialization by ROMMON ?
> >
> > Can we get exact chip revisions and types for both cases (working and
> > not working), and (if it might be relevant) a dump of all associated
> > chip registers ?
>
>
> > > I also check the WDT_MR register before and after enabling watchdog,
> > > the WDV and WDD fields are correct.
> > >
> > > Can you check it again? thank you.
>
> Working case:
> MR on kernel startup:   0x3fffafff
> MR after watchdog init: 0x0fffafff
> MR after start:         0x0fff2fff
>
> Problem case:
> MR on kernel startup:   0x00008000
> MR after watchdog init: 0x0fffafff
> MR after start:         0x0fff2fff
>
> So this means that the counter reload does not seem to work very well if
> WDD/WDV have been set to 0 in the past. The other question is why does
> U-Boot (from the Atmel branch based on 2015.1) put this stange value in
> this register.

Can you check the value of AT91_WDT_SR ? Maybe it tells us something.

Also, in the error case, can you check if the watchdog times out at all
after you applied your patch ?

Thanks,
Guenter

> Best regards,