Broken watchdog in u-boot master branch

[Tom Rini]

On Mon, Oct 10, 2022 at 07:22:56PM +0200, Pali Rohár wrote:
> On Monday 10 October 2022 12:28:18 Tom Rini wrote:
> > On Sun, Oct 09, 2022 at 09:12:25PM +0200, Pali Rohár wrote:
> > > Hello! Watchdog code seems to be broken in u-boot master branch.
> > > On Nokia N900 I'm getting following message in qemu:
> > > 
> > > cyclic function rx51_watchdog took too long: 10000us vs 1000us max, disabling
> > > 
> > > Seems that watchdog core code is not prepared for "slower" watchdogs
> > > which communicate over slower i2c bus, like it is the case for N900.
> > > 
> > > Disabling slower watchdog is a bad idea as it would result in reboot
> > > loop instead of slower - but working code.
> > 
> > So, looking at this in more detail, we have
> > CONFIG_CYCLIC_MAX_CPU_TIME_US as a configuration option (which is where
> > the too long comes from). And picking a random CI run:
> > https://source.denx.de/u-boot/u-boot/-/jobs/511177
> > I do see we hit this in CI once, but not every time, QEMU runs here. Is
> > that the max time is configurable enough to satisfy your concerns here?
> 
> It is needed to investigate, how to _properly_ fix this issue, not just
> workarounded it. Probably other boards may be affected.

So it's the cyclic watchdog code, which we merged as early as possible
that's the reason here. And it was merged as early as we could to see if
there's problems. Are there problems? We're seeing "system too slow,
disabling" on QEMU, sometimes, and the value of too slow is
configurable. I know you reported other problems with n900 HW, so we
can't see if it's failing there, and I don't have any omap3 HW setup in
my lab atm, just newer generation boards and don't see the problem
there. Which is why I'm asking, is being able to configure the "too
slow" value enough? Or is there something else that needs to be done?

-- 
Tom
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