drm/atomic: add drm_atomic_set_fence_for_plane()

This new function should be used by drivers when setting a implicit
fence for the plane. It abstracts the fact that the user might have
chosen explicit fencing instead.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1478513013-3221-1-git-send-email-gustavo@padovan.org

3 files changed, 33 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index c32fb3c1d6f0..5e7395455108 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1147,6 +1147,36 @@ drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
 EXPORT_SYMBOL(drm_atomic_set_fb_for_plane);
 
 /**
+ * drm_atomic_set_fence_for_plane - set fence for plane
+ * @plane_state: atomic state object for the plane
+ * @fence: dma_fence to use for the plane
+ *
+ * Helper to setup the plane_state fence in case it is not set yet.
+ * By using this drivers doesn't need to worry if the user choose
+ * implicit or explicit fencing.
+ *
+ * This function will not set the fence to the state if it was set
+ * via explicit fencing interfaces on the atomic ioctl. It will
+ * all drope the reference to the fence as we not storing it
+ * anywhere.
+ *
+ * Otherwise, if plane_state->fence is not set this function we
+ * just set it with the received implict fence.
+ */
+void
+drm_atomic_set_fence_for_plane(struct drm_plane_state *plane_state,
+                               struct dma_fence *fence)
+{
+        if (plane_state->fence) {
+                dma_fence_put(fence);
+                return;
+        }
+
+        plane_state->fence = fence;
+}
+EXPORT_SYMBOL(drm_atomic_set_fence_for_plane);
+
+/**
  * drm_atomic_set_crtc_for_connector - set crtc for connector
  * @conn_state: atomic state object for the connector
  * @crtc: crtc to use for the connector
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index fc8af53b18aa..2d1e9c944b54 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -345,6 +345,8 @@ drm_atomic_set_crtc_for_plane(struct drm_plane_state *plane_state,
                               struct drm_crtc *crtc);
 void drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
                                  struct drm_framebuffer *fb);
+void drm_atomic_set_fence_for_plane(struct drm_plane_state *plane_state,
+                                    struct dma_fence *fence);
 int __must_check
 drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
                                   struct drm_crtc *crtc);
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index c5e8a0df1623..68f6d221a3da 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -59,7 +59,7 @@ struct drm_plane_state {
 
         struct drm_crtc *crtc;   /* do not write directly, use drm_atomic_set_crtc_for_plane() */
         struct drm_framebuffer *fb;  /* do not write directly, use drm_atomic_set_fb_for_plane() */
-        struct dma_fence *fence;
+        struct dma_fence *fence; /* do not write directly, use drm_atomic_set_fence_for_plane() */
 
         /* Signed dest location allows it to be partially off screen */
         int32_t crtc_x, crtc_y;