[PATCH 1/2] drm/i915: Restore GT coarse power gating workaround

[Chris Wilson]

Quoting Imre Deak (2019-11-14 16:42:24)
> The workaround to disable coarse power gating is still needed on SKL
> GT3/GT4 machines and since the RC6 context corruption was discovered by
> the hardware team also on all GEN9 machines. Restore applying the
> workaround.

What exactly is the link between powergating and the rc6 power context
corruption? Disabling powergating entirely is quite a significant
regression -- and we can't partially enable powergating for idle engines
as the HW refuses to cooperate.

So is it safe to enable powergating if only vcs is busy [rcs is idle]?
-Chris