u-boot leaves watchdog enabled by default

[Stefan Roese]

Hi Michael,
Hi Chris,

On 15.09.20 12:44, Chris Packham wrote:
> 
> 
> On Tue, 15 Sep 2020, 7:54 PM Michael Walle, <michael at walle.cc> wrote:
> 
>     Am 2020-09-15 09:44, schrieb Rayagonda Kokatanur:
>      > On Tue, Sep 15, 2020 at 12:56 PM Michael Walle <michael at walle.cc>
>      > wrote:
>      >>
>      >> Hi Stefan,
>      >>
>      >> it appears that since commit 06985289d45 ("watchdog: Implement
>     generic
>      >> watchdog_reset() version") - by default - the first watchdog is
>      >> started
>      >> unconditionally if CONFIG_WDT is set but never stopped before
>     booting
>      >> the operating system.
>      >>
>      >> Shouldn't it also be stopped uncondionally? What's worse is that on
>      >> one
>      >> board/arch the watchdog is stopped in arch_preboot_os() which is
>     never
>      >> called in the bootefi case. So even if I'd do a workaround and
>     stop it
>      >> manually in my board code, I couldn't do that consistently for
>      >> bootm/bootefi.
>      >>
>      >> Or am I missing something here?
>      >
>      > Define CONFIG_WATCHDOG.
>      > This takes care of resetting wdt.
> 
>     Yes as along as you're inside the bootloader, but when u-boot hands
>     control over the OS the watchdog is not serviced anymore; which wouldn't
>     be a problem per se, but it is enabled unconditionally by u-boot.
> 
> 
> Just to add some data. At $dayjob we use this behaviour as a failsafe to 
> make sure our userspace gets to a point where it is servicing the 
> watchdog.

Yes, this is exactly how this is supposed to work AFAIK.

Michael, are you sure that the watchdog was disabled in U-Boot when
booting into the OS before this patch?

> That said having a leave-wdt-running environment variable 
> would work for our use case.

I would rather use it the other way around. Something like "wdt-stop-
pre-os" to optionally stop the WDT before booting into the OS.

Remark:
IMHO, if you don't use the WDT in the OS, it does not make much sense
to enable the WDT in U-Boot.

Thanks,
Stefan