[Intel-gfx] [PATCH 1/1] drm/i915: Suspend GuC during GEM Suspend prior to GPU Reset

[Kamble, Sagar A]

On 4/5/2017 2:30 PM, Chris Wilson wrote:
> On Wed, Apr 05, 2017 at 11:04:34AM +0530, Sagar Arun Kamble wrote:
>> During S3/S4 suspend, i915 sends HOST2GUC with ENTER_S_STATE action
>> for suspending GuC. GuC stops scheduling at this point. i915 is
>> currently doing explicit GPU reset during suspend ensuring GEM is idle.
>> Suspend GuC prior to triggering GPU Reset to ensure GuC stays idle too.
> Why would a gpu reset cause the guc to think it was not idle, and
> futhermore ignore the suspend request afterwards? Should we not be
> completely disabling the guc along the system suspend path? Especially
> if it is so easily confused?
> -Chris
Post GPU reset, GuC firmware is unloaded and GuC is not ready till we 
reinitialize the firmware so
all Host to GuC actions are bound to fail. ENTER_S_STATE is disabling 
GuC scheduling completely.
GuC is saving the needed state and ensuring wake events are disabled. So 
we need to trigger this
action prior to resetting GPU in suspend path.
>