[Intel-gfx] [PATCH 2/2] drm/i915: Force GPU idle on suspend

[Chris Wilson]

Quoting Chris Wilson (2019-03-07 10:45:30)
> To facilitate the next patch to allow preemptible kernels not to incur
> the wrath of hangcheck, we need to ensure that we can still suspend and
> shutdown. That is we will not be able to rely on hangcheck to terminate
> a blocking kernel and instead must manually do so ourselves. The
> advantage is that we can apply more pressure!
> 
> As we now perform a GPU reset to clean up any residual kernels, we leave
> the GPU in an unknown state and in particular can not talk to the GuC
> before we reinitialise it following resume. For example, we no longer
> need to tell the GuC to suspend itself, as it is already reset.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Also note that part of the future plan, is that we first try to
preempt-to-idle before forcing idling. Which should be a minor change at
the high level, but will require a few tweaks to the submission. Hmm,
probably best to export an engine->stop_submission() or something.

Anyway, part of the raison d'etre of this patch to judge if anyone
actually notices being terminated across suspend :)
-Chris