[Intel-gfx] [PATCH] drm/i915: Stop discarding GTT cache-domain on unbind vma

[Chris Wilson]

On Tue, Oct 06, 2015 at 02:40:26PM +0200, Daniel Vetter wrote:
> On Tue, Oct 06, 2015 at 01:02:22PM +0100, Chris Wilson wrote:
> > Since
> > 
> > commit 43566dedde54f9729113f5f9fde77d53e75e61e9
> > Author: Chris Wilson <chris at chris-wilson.co.uk>
> > Date:   Fri Jan 2 16:29:29 2015 +0530
> > 
> >     drm/i915: Broaden application of set-domain(GTT)
> > 
> > we allowed objects to be in the GTT domain, but unbound. Therefore
> > removing the GTT cache domain when removing the GGTT vma is no longer
> > semantically correct.
> > 
> > An unfortunate side-effect is we lose the wondrously named
> > i915_gem_object_finish_gtt(), not to be confused with
> > i915_gem_gtt_finish_object()!
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Akash Goel <akash.goel at intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c | 20 +++-----------------
> >  1 file changed, 3 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 8f498d4d874d..682af2ae3681 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3183,20 +3183,6 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
> >  	return 0;
> >  }
> >  
> > -static void i915_gem_object_finish_gtt(struct drm_i915_gem_object *obj)
> > -{
> > -	/* Force a pagefault for domain tracking on next user access */
> > -	i915_gem_release_mmap(obj);
> > -
> > -	if ((obj->base.read_domains & I915_GEM_DOMAIN_GTT) == 0)
> > -		return;
> > -
> > -	obj->base.read_domains &= ~I915_GEM_DOMAIN_GTT;
> > -	obj->base.write_domain &= ~I915_GEM_DOMAIN_GTT;
> > -
> > -	trace_i915_gem_object_change_domain(obj);
> > -}
> > -
> >  int i915_vma_unbind(struct i915_vma *vma)
> >  {
> >  	struct drm_i915_gem_object *obj = vma->obj;
> > @@ -3228,12 +3214,12 @@ int i915_vma_unbind(struct i915_vma *vma)
> >  	 */
> >  
> >  	if (vma->is_ggtt && vma->ggtt_view.type == I915_GGTT_VIEW_NORMAL) {
> > -		i915_gem_object_finish_gtt(obj);
> > -
> > -		/* release the fence reg _after_ flushing */
> >  		ret = i915_gem_object_put_fence(obj);
> >  		if (ret)
> >  			return ret;
> > +
> > +		/* Force a pagefault for domain tracking on next user access */
> > +		i915_gem_release_mmap(obj);
> 
> Can't put_fence before release_mmap ... I guess we should have a testcase
> for this somewhere? Hard to provoke probably ...

Why not? i915_gem_object_put_fence() has to release the mmaps itself if
it has a fence register assigned for the object.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre