Re: [Intel-gfx] [PATCH 24/28] drm: use new iterator in drm_gem_plane_helper_prepare_fb

[Tvrtko Ursulin]

On 01/10/2021 11:06, Christian König wrote:
Makes the handling a bit more complex, but avoids the use of
dma_resv_get_excl_unlocked().

Signed-off-by: Christian König <christian.koe...@amd.com>
---
  drivers/gpu/drm/drm_gem_atomic_helper.c | 13 +++++++++++--
  1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c 
b/drivers/gpu/drm/drm_gem_atomic_helper.c
index e570398abd78..21ed930042b8 100644
--- a/drivers/gpu/drm/drm_gem_atomic_helper.c
+++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
@@ -143,6 +143,7 @@
   */
  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;
  
@@ -150,9 +151,17 @@ int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane, struct drm_plane_st
                return 0;
  
  	obj = drm_gem_fb_get_obj(state->fb, 0);
-       fence = dma_resv_get_excl_unlocked(obj->resv);
-       drm_atomic_set_fence_for_plane(state, fence);
+       dma_resv_iter_begin(&cursor, obj->resv, false);
+       dma_resv_for_each_fence_unlocked(&cursor, fence) {
+               dma_fence_get(fence);
+               dma_resv_iter_end(&cursor);
+               /* TODO: We only use the first write fence here */

What is the TODO? NB instead?

+               drm_atomic_set_fence_for_plane(state, fence);
+               return 0;
+       }
+       dma_resv_iter_end(&cursor);
  
+	drm_atomic_set_fence_for_plane(state, NULL);

        dma_resv_iter_begin(&cursor, obj->resv, false);
        dma_resv_for_each_fence_unlocked(&cursor, fence) {
                dma_fence_get(fence);
                break;
        }
        dma_resv_iter_end(&cursor);

        drm_atomic_set_fence_for_plane(state, fence);

Does this work?

But overall I am not sure this is nicer. Is the goal to remove 
dma_resv_get_excl_unlocked as API it just does not happen in this series?

Regards,

Tvrtko

        return 0;
  }
  EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);