[PATCH 19/26] drm: support more than one write fence in drm_gem_plane_helper_prepare_fb

[Daniel Vetter]

On Fri, Nov 26, 2021 at 11:30:19AM +0100, Christian König wrote:
> Am 25.11.21 um 16:47 schrieb Daniel Vetter:
> > On Tue, Nov 23, 2021 at 03:21:04PM +0100, Christian König wrote:
> > > Use dma_resv_get_singleton() here to eventually get more than one write
> > > fence as single fence.
> > Yeah this is nice, atomic commit helpers not supporting multiple write
> > fences was really my main worry in this entire endeavour. Otherwise looks
> > all rather reasonable.
> > 
> > I'll try to find some review bandwidth, but would be really if you can
> > volunteer others too (especially making sure ttm drivers set the KERNEL
> > fences correctly in all cases).
> 
> Maybe I should split that up into switching over to adding the enum and then
> switching to kernel/bookkeep(previously other) for some use cases.
> 
> It would be good if I could get an rb on the trivial driver cleanups first.
> I can send those out individually if that helps.

Yeah some of the conversion patches might make sense to be split a bit
more. Especially when there's functional changes hiding, but I tought
you've split them out? But didn't read them in detail.

Either way for stuff like this I think it's always best to split the
mechanical stuff from the concept intro/docs and functional changes,
except when it's really very obvious what's going on and just as small
patch.
-Daniel

> 
> Thanks,
> Christian.
> 
> > -Daniel
> > 
> > 
> > > Signed-off-by: Christian König <christian.koenig at amd.com>
> > > ---
> > >   drivers/gpu/drm/drm_gem_atomic_helper.c | 18 +++++++-----------
> > >   1 file changed, 7 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
> > > index c3189afe10cb..9338ddb7edff 100644
> > > --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
> > > +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
> > > @@ -143,25 +143,21 @@
> > >    */
> > >   int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane, struct drm_plane_state *state)
> > >   {
> > > -	struct dma_resv_iter cursor;
> > >   	struct drm_gem_object *obj;
> > >   	struct dma_fence *fence;
> > > +	int ret;
> > >   	if (!state->fb)
> > >   		return 0;
> > >   	obj = drm_gem_fb_get_obj(state->fb, 0);
> > > -	dma_resv_iter_begin(&cursor, obj->resv, false);
> > > -	dma_resv_for_each_fence_unlocked(&cursor, fence) {
> > > -		/* TODO: Currently there should be only one write fence, so this
> > > -		 * here works fine. But drm_atomic_set_fence_for_plane() should
> > > -		 * be changed to be able to handle more fences in general for
> > > -		 * multiple BOs per fb anyway. */
> > > -		dma_fence_get(fence);
> > > -		break;
> > > -	}
> > > -	dma_resv_iter_end(&cursor);
> > > +	ret = dma_resv_get_singleton(obj->resv, false, &fence);
> > > +	if (ret)
> > > +		return ret;
> > > +	/* TODO: drm_atomic_set_fence_for_plane() should be changed to be able
> > > +	 * to handle more fences in general for multiple BOs per fb.
> > > +	 */
> > >   	drm_atomic_set_fence_for_plane(state, fence);
> > >   	return 0;
> > >   }
> > > -- 
> > > 2.25.1
> > > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch