drm: use new iterator in drm_gem_plane_helper_prepare_fb v3

Makes the handling a bit more complex, but avoids the use of
dma_resv_get_excl_unlocked().

v2: improve coding and documentation
v3: adjust the TODO comment as suggested by Daniel

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-25-christian.koenig@amd.com

diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
index e570398..c3189af 100644 (file)
--- 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 +151,18 @@ 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) {
+               /* 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);
 
+       drm_atomic_set_fence_for_plane(state, fence);
        return 0;
 }
 EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);