[Intel-gfx] [PATCH 1/2] drm/i915: Wait upon the last request seqno, rather than a future seqno

[Daniel Vetter]

On Tue, Nov 27, 2012 at 10:40:51AM +0200, Mika Kuoppala wrote:
> On Thu, 22 Nov 2012 13:07:20 +0000, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > In commit 69c2fc891343cb5217c866d10709343cff190bdc
> > Author: Chris Wilson <chris at chris-wilson.co.uk>
> > Date:   Fri Jul 20 12:41:03 2012 +0100
> > 
> >     drm/i915: Remove the per-ring write list
> > 
> > the explicit flush was removed from i915_ring_idle(). However, we
> > continued to wait upon the next seqno which now did not correspond to
> > any request (except for the unusual condition of a failure to queue a
> > request after execbuffer) and so would wait indefinitely.
> > 
> > This has an important side-effect that i915_gpu_idle() does not cause
> > the seqno to be incremented. This is vital if we are to be able to idle
> > the GPU to handle seqno wraparound, as in subsequent patches.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c |   23 +++++++++++++++++++++--
> >  1 file changed, 21 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index b0016bb..9be450e 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -2462,10 +2462,29 @@ i915_gem_object_unbind(struct drm_i915_gem_object *obj)
> >  
> >  static int i915_ring_idle(struct intel_ring_buffer *ring)
> >  {
> > -	if (list_empty(&ring->active_list))
> > +	u32 seqno;
> > +	int ret;
> > +
> > +	/* We need to add any requests required to flush the objects */
> > +	if (!list_empty(&ring->active_list)) {
> > +		seqno = list_entry(ring->active_list.prev,
> > +				   struct drm_i915_gem_object,
> > +				   ring_list)->last_read_seqno;
> > +
> > +		ret = i915_gem_check_olr(ring, seqno);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	/* Wait upon the last request to be completed */
> > +	if (list_empty(&ring->request_list))
> >  		return 0;
> >  
> > -	return i915_wait_seqno(ring, i915_gem_next_request_seqno(ring));
> > +	seqno = list_entry(ring->request_list.prev,
> > +			   struct drm_i915_gem_request,
> > +			   list)->seqno;
> > +
> > +	return i915_wait_seqno(ring, seqno);
> >  }
> >  
> >  int i915_gpu_idle(struct drm_device *dev)
> > -- 
> > 1.7.10.4
> 
> Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>
Queued for -next, thanks for the patch. I'll wait for v2 on patch 2 ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch