drm: Add drm_atomic_helper_wait_for_flip_done()

Add an helper to wait for all page flips of an atomic state to be done.

v2:
- Pimp kerneldoc as discussed with Boris on irc
- Add missing doc for @dev.
- Use old_state for consitency with wait_for_vblanks

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v1)
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1496392332-8722-2-git-send-email-boris.brezillon@free-electrons.com

drivers/gpu/drm/drm_atomic_helper.c

@@ -1185,9 +1185,13 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_fences);
  *
  * Helper to, after atomic commit, wait for vblanks on all effected
  * crtcs (ie. before cleaning up old framebuffers using
- * drm_atomic_helper_cleanup_planes()). It will only wait on crtcs where the
+ * drm_atomic_helper_cleanup_planes()). It will only wait on CRTCs where the
  * framebuffers have actually changed to optimize for the legacy cursor and
  * plane update use-case.
+ *
+ * Drivers using the nonblocking commit tracking support initialized by calling
+ * drm_atomic_helper_setup_commit() should look at
+ * drm_atomic_helper_wait_for_flip_done() as an alternative.
  */
 void
 drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
@@ -1234,6 +1238,43 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);
 
+/**
+ * drm_atomic_helper_wait_for_flip_done - wait for all page flips to be done
+ * @dev: DRM device
+ * @old_state: atomic state object with old state structures
+ *
+ * Helper to, after atomic commit, wait for page flips on all effected
+ * crtcs (ie. before cleaning up old framebuffers using
+ * drm_atomic_helper_cleanup_planes()). Compared to
+ * drm_atomic_helper_wait_for_vblanks() this waits for the completion of on all
+ * CRTCs, assuming that cursors-only updates are signalling their completion
+ * immediately (or using a different path).
+ *
+ * This requires that drivers use the nonblocking commit tracking support
+ * initialized using drm_atomic_helper_setup_commit().
+ */
+void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
+					  struct drm_atomic_state *old_state)
+{
+	struct drm_crtc_state *crtc_state;
+	struct drm_crtc *crtc;
+	int i;
+
+	for_each_crtc_in_state(old_state, crtc, crtc_state, i) {
+		struct drm_crtc_commit *commit = old_state->crtcs[i].commit;
+		int ret;
+
+		if (!commit)
+			continue;
+
+		ret = wait_for_completion_timeout(&commit->flip_done, 10 * HZ);
+		if (ret == 0)
+			DRM_ERROR("[CRTC:%d:%s] flip_done timed out\n",
+				  crtc->base.id, crtc->name);
+	}
+}
+EXPORT_SYMBOL(drm_atomic_helper_wait_for_flip_done);
+
 /**
  * drm_atomic_helper_commit_tail - commit atomic update to hardware
  * @old_state: atomic state object with old state structures

include/drm/drm_atomic_helper.h

@@ -52,6 +52,9 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 void drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
 					struct drm_atomic_state *old_state);
 
+void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
+					  struct drm_atomic_state *old_state);
+
 void
 drm_atomic_helper_update_legacy_modeset_state(struct drm_device *dev,
 					      struct drm_atomic_state *old_state);

include/drm/drm_modeset_helper_vtables.h

@@ -1169,7 +1169,8 @@ struct drm_mode_config_helper_funcs {
 	 * After the atomic update is committed to the hardware this hook needs
 	 * to call drm_atomic_helper_commit_hw_done(). Then wait for the upate
 	 * to be executed by the hardware, for example using
-	 * drm_atomic_helper_wait_for_vblanks(), and then clean up the old
+	 * drm_atomic_helper_wait_for_vblanks() or
+	 * drm_atomic_helper_wait_for_flip_done(), and then clean up the old
 	 * framebuffers using drm_atomic_helper_cleanup_planes().
 	 *
 	 * When disabling a CRTC this hook _must_ stall for the commit to