[Intel-gfx] [PATCH 1/2] drm/i915: Make sure engines are idle during GPU idling in LR mode

[Imre Deak]

On Fri, 2016-11-04 at 21:01 +0000, Chris Wilson wrote:
> On Fri, Nov 04, 2016 at 10:33:24PM +0200, Imre Deak wrote:
> > On Thu, 2016-11-03 at 21:14 +0000, Chris Wilson wrote:
> > > Where is that guaranteed? I thought we only serialised with the
> > > pm
> > > interrupts. Remember this happens before rpm suspend, since
> > > gem_idle_work_handler is responsible for dropping the GPU
> > > wakelock.
> > 
> > I meant that the 100msec after the last request signals completion
> > and
> > this handler is scheduled is normally enough for the context
> > complete
> > interrupt to get delivered. But yea, it's not a guarantee.
> 
> If only it was that deterministic! The idle_worker was scheduled
> 100ms
> after some retire_worker, just not necessarily the most recent. So it
> could be running exactly as active_requests -> 0 and so before the
> context-interrupt.

Right, but we don't poll in that case, so there is no overhead.

> Anyway, it was a good find!
> -Chris
>