[Intel-gfx] [RFC 09/10] drm/i915: Trivial virtual engine implementation

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-01-25 14:26:53)
> 
> On 25/01/2018 13:57, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-01-25 13:33:32)
> >> -       if (engine && ((caps & engine->caps) != caps))
> >> -               return -EINVAL;
> >> +               do {
> >> +                       engine = i915->engine[_VCS(instance)];
> >> +                       instance ^= 1;
> >> +                       vcs_instances--;
> >> +               } while ((caps & engine->caps) != caps && vcs_instances > 0);
> >> +
> >> +               if ((caps & engine->caps) != caps)
> >> +                       return -EINVAL;
> >> +
> >> +               timeline = i915_gem_context_lookup_timeline_class(eb->ctx,
> >> +                                                                 VIDEO_DECODE_CLASS);
> >> +               spin_lock_irq(&timeline->lock);
> >> +               prev_req = list_first_entry_or_null(&timeline->requests,
> >> +                                                   struct drm_i915_gem_request,
> >> +                                                   ctx_link);
> >> +               spin_unlock_irq(&timeline->lock);
> > 
> > This isn't doing anything yet as we aren't using the timeline. The idea
> > is sound though, we need to rejig timelines to make them more flexible
> > so that we can combine them to use one per-queue. Ok.
> 
> I think it works - as far as I looked at the trace.pl HTML output it 
> seems to.

You are syncing against the oldest, not the previous (which would be
timeline->last_request).
-Chris