2016-03-04 14:09 GMT+01:00 Guenter Roeck <linux@xxxxxxxxxxxx>: > On 03/04/2016 01:06 AM, Romain Izard wrote: >> 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. > I didn't report it because it contained 0 at all times. So no information. > Also, in the error case, can you check if the watchdog times out at all > after you applied your patch ? It times out after 16s as expected, and reboot occurs correctly. -- Romain Izard -- 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
