The generic atomic helper likes to skip a prepare_plane_fb() if it
decides that the plane->fb is unchanged. This is wrong for us for a
couple of reasons:

 - if the pipe is reconfigured (i.e. a size change) but the framebuffer
   is untouched, we still have to flush any rendering prior to the
   reconfiguration to prevent wait-for-scanline GPU hangs

 - if the framebuffer is rotated, it remains the same but has a
   different view and a different address.

Finally, even if the framebuffer is unchanged the flip/modeset should be
ordered with respect to rendering to the frontbuffer.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_atomic_plane.c |  2 -
 drivers/gpu/drm/i915/intel_display.c      | 61 ++++++++++++++++++++++++-------
 drivers/gpu/drm/i915/intel_drv.h          |  4 --
 3 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_atomic_plane.c 
b/drivers/gpu/drm/i915/intel_atomic_plane.c
index cb5594411bb6..4ed5b2e49691 100644
--- a/drivers/gpu/drm/i915/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/intel_atomic_plane.c
@@ -192,8 +192,6 @@ static void intel_plane_atomic_update(struct drm_plane 
*plane,
 }
 
 const struct drm_plane_helper_funcs intel_plane_helper_funcs = {
-       .prepare_fb = intel_prepare_plane_fb,
-       .cleanup_fb = intel_cleanup_plane_fb,
        .atomic_check = intel_plane_atomic_check,
        .atomic_update = intel_plane_atomic_update,
 };
diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 6c817215f61a..69720a126c67 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14146,7 +14146,7 @@ static int intel_atomic_check(struct drm_device *dev,
  *
  * Returns 0 on success, negative error code on failure.
  */
-int
+static int
 intel_prepare_plane_fb(struct drm_plane *plane,
                       struct drm_plane_state *new_state)
 {
@@ -14241,7 +14241,7 @@ intel_prepare_plane_fb(struct drm_plane *plane,
  *
  * Must be called with struct_mutex held.
  */
-void
+static void
 intel_cleanup_plane_fb(struct drm_plane *plane,
                       struct drm_plane_state *old_state)
 {
@@ -14260,6 +14260,50 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
                intel_unpin_fb_obj(old_state->fb, old_state->rotation);
 }
 
+static int intel_atomic_commit_prepare_planes(struct drm_atomic_state *state)
+{
+       struct drm_plane *plane;
+       struct drm_plane_state *plane_state;
+       int i, j, ret;
+
+       ret = mutex_lock_interruptible(&state->dev->struct_mutex);
+       if (ret)
+               return ret;
+
+       for_each_plane_in_state(state, plane, plane_state, i) {
+               ret = intel_prepare_plane_fb(plane, plane_state);
+               if (ret)
+                       break;
+       }
+
+       if (ret) {
+               for_each_plane_in_state(state, plane, plane_state, j) {
+                       if (j >= i)
+                               break;
+
+                       intel_cleanup_plane_fb(plane, plane_state);
+               }
+       }
+
+       mutex_unlock(&state->dev->struct_mutex);
+
+       return ret;
+}
+
+static void intel_atomic_commit_cleanup_planes(struct drm_atomic_state *state)
+{
+       struct drm_plane *plane;
+       struct drm_plane_state *plane_state;
+       int i;
+
+       mutex_lock(&state->dev->struct_mutex);
+
+       for_each_plane_in_state(state, plane, plane_state, i)
+               intel_cleanup_plane_fb(plane, plane_state);
+
+       mutex_unlock(&state->dev->struct_mutex);
+}
+
 static int intel_atomic_prepare_commit(struct drm_device *dev,
                                       struct drm_atomic_state *state)
 {
@@ -14280,14 +14324,7 @@ static int intel_atomic_prepare_commit(struct 
drm_device *dev,
                        flush_workqueue(dev_priv->wq);
        }
 
-       ret = mutex_lock_interruptible(&dev->struct_mutex);
-       if (ret)
-               return ret;
-
-       ret = drm_atomic_helper_prepare_planes(dev, state);
-       mutex_unlock(&dev->struct_mutex);
-
-       return ret;
+       return intel_atomic_commit_prepare_planes(state);
 }
 
 u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc)
@@ -14614,9 +14651,7 @@ static void intel_atomic_commit_tail(struct 
drm_atomic_state *state)
        if (intel_state->modeset)
                intel_display_power_put(dev_priv, POWER_DOMAIN_MODESET);
 
-       mutex_lock(&dev->struct_mutex);
-       drm_atomic_helper_cleanup_planes(dev, state);
-       mutex_unlock(&dev->struct_mutex);
+       intel_atomic_commit_cleanup_planes(state);
 
        drm_atomic_helper_commit_cleanup_done(state);
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index f5975fe4553d..610f2f969a9a 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1292,10 +1292,6 @@ __intel_framebuffer_create(struct drm_device *dev,
 void intel_finish_page_flip_cs(struct drm_i915_private *dev_priv, int pipe);
 void intel_finish_page_flip_mmio(struct drm_i915_private *dev_priv, int pipe);
 void intel_check_page_flip(struct drm_i915_private *dev_priv, int pipe);
-int intel_prepare_plane_fb(struct drm_plane *plane,
-                          struct drm_plane_state *new_state);
-void intel_cleanup_plane_fb(struct drm_plane *plane,
-                           struct drm_plane_state *old_state);
 int intel_plane_atomic_get_property(struct drm_plane *plane,
                                    const struct drm_plane_state *state,
                                    struct drm_property *property,
-- 
2.10.1

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