AW: hang check triggered at low temperatures

[Lucas Stach]

Am Dienstag, den 05.06.2018, 13:04 +0000 schrieb Sven Schmitt:
> Hi Lucas,
> 
> > Hi Sven,
> > 
> > Am Montag, den 04.06.2018, 06:31 +0000 schrieb Sven Schmitt:
> > > Hello,
> > > 
> > > we have discovered a sneaky, temperature based problem in the
> > > imx6
> > > etnaviv driver.
> > > 
> > > If the chip temperature falls bellow 10 degrees celsius and
> > > display
> > > update rate raises above 200ms the etnaviv gpu hang check is
> > > triggered reproducible [1].
> > > We have the suspicion that the runtime pm autosuspend mechanism
> > > (configured to 200ms [2]) is the root of the problem.
> > > Disabling CONFIG_PM heals the bug.
> > 
> > My guess would be that this isn't directly related to the GPU or
> > it's
> > driver, but a bug in the power gating. To confirm/dismiss my
> > suspicion
> > you may change imx6_pm_domain_power_off() in drivers/soc/imx/gpc.c
> > to
> > always return -EBUSY early to prevent the domain from being power
> > gated.
> 
> You're right. I've set "err009619_present = true" in "struct
> imx_gpc_dt_data imx6q_dt_data" which has the same effect.
> Is this a appropriate solution for the problem?

This is a workaround at best.
My guess is that the power up sequencing takes a bit longer in your
case. Can you check if manually adjusting the delay in
imx6_pm_domain_power_on() to wait a bit longer before the clocks are
switched off make any difference?

Regards,
Lucas