[PATCH v2 8/8] board: ns3: start sp805 watchdog service

[Stefan Roese]

Hi Rayagonda,

On 10.06.20 18:35, Rayagonda Kokatanur wrote:
> Hi Stefan,
> 
> On Wed, Jun 10, 2020 at 4:33 PM Stefan Roese <sr at denx.de> wrote:
>>
>> On 10.06.20 12:52, Rayagonda Kokatanur wrote:
>>> Start sp805 watchdog service.
>>>
>>> Parse wdt timeout from env and dts, give precedence to env
>>> timeout if defined. Set default timeout to 60s if both env
>>> and dts doesn't specifiy timeout.
>>>
>>> Stop the WDT in board late init and start the
>>> WDT service before giving control to Linux.
>>
>> I don't really understand, why you need such a board specific
>> watchdog handling. You disable and enable it at some points? Why
>> exactly? Usually the common WDT IF is used and it enables and
>> services the WDT (if configured this way) until the OS is started.
>> Then the OS needs to service the WDT. If the OS fails here (doesn't
>> start correctly etc), then the board will reset via the WDT.
>>
>> So what is missing in the commin WDT IF for your setup?
> 
> Our boot sequence is , first we check for valid Linux images in
> Linux_part_1, Linux_part_2 and Linux_part_3 of eMMC partition tables.
> If the Linux image is not available, then we check for a valid Linux
> image on a USB device. If it is not available in USB devices, then we
> attempt for PXE boot. We observe the WDT trigger for the PXE boot
> case.

So the WDT triggers a reset while you are booting via PXE boot? While
a image is loaded via PXE boot (pxe command)? If this is the case,
I would prefer to fix this issue (WDT reset while running a U-Boot
command).

> U-boot is used for updating the binaries (like fip.bin {ATF, optee,
> and uboot}, Linux and file system). For updating, we use tftp
> protocol, which will take more time and depends up on the network
> speed.
> 
> Hence we stop and start wdt service.

Sure it takes time to update images. But all this should be possible
with an actively serviced watchdog while still running in U-Boot.
This is why we have all these WATCHDOG_RESET() calls sprinkled all over
the system. If some code paths are missing such WDT triggering, then we
should find and fix them.

Thanks,
Stefan