hang check triggered at low temperatures

[Lucas Stach]

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.

Please let me know your results.

Regards,
Lucas