Re: [Intel-gfx] [PATCH 2/9] drm/i915: Pull waiting on an external dma-fence into its routine

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Mika Kuoppala <mika.kuoppala@linux.intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 2/9] drm/i915: Pull waiting on an external dma-fence into its routine
Date: Fri, 08 May 2020 11:26:56 +0100	[thread overview]
Message-ID: <158893361621.11903.8192692245953803179@build.alporthouse.com> (raw)
In-Reply-To: <87imh6ybiq.fsf@gaia.fi.intel.com>

Quoting Mika Kuoppala (2020-05-08 11:19:25)
> Chris Wilson <chris@chris-wilson.co.uk> writes:
> 
> > As a means for a small code consolidation, but primarily to start
> > thinking more carefully about internal-vs-external linkage, pull the
> > pair of i915_sw_fence_await_dma_fence() calls into a common routine.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_request.c | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> > index be2ce9065a29..94189c7d43cd 100644
> > --- a/drivers/gpu/drm/i915/i915_request.c
> > +++ b/drivers/gpu/drm/i915/i915_request.c
> > @@ -1067,6 +1067,14 @@ i915_request_await_request(struct i915_request *to, struct i915_request *from)
> >       return 0;
> >  }
> >  
> > +static int
> > +i915_request_await_external(struct i915_request *rq, struct dma_fence *fence)
> > +{
> > +     return i915_sw_fence_await_dma_fence(&rq->submit, fence,
> > +                                          fence->context ? I915_FENCE_TIMEOUT : 0,
> > +                                          I915_FENCE_GFP);
> > +}
> > +
> >  int
> >  i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
> >  {
> > @@ -1114,9 +1122,7 @@ i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
> >               if (dma_fence_is_i915(fence))
> >                       ret = i915_request_await_request(rq, to_request(fence));
> >               else
> > -                     ret = i915_sw_fence_await_dma_fence(&rq->submit, fence,
> > -                                                         fence->context ? I915_FENCE_TIMEOUT : 0,
> > -                                                         I915_FENCE_GFP);
> > +                     ret = i915_request_await_external(rq, fence);
> 
> For us (rq, rq), for external (rq, fence).
> 
> It looks neat for a reader. But then, how can external fence have
> a context?

The 'context' here is the dma_fence timeline context. All dma_fences
have a context:seqno tuple which denotes their timeline and position
along the timeline.
-Chris
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