drm/atomic-helpers: Recover full cursor plane behaviour

Cursor plane updates have historically been fully async and mutliple
updates batched together for the next vsync. And userspace relies upon
that. Since implementing a full queue of async atomic updates is a bit
of work lets just recover the cursor specific behaviour with a hint
flag and some hacks to drop the vblank wait.

v2: Fix kerneldoc, reported by Wu Fengguang.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 6112ec261c3b..d0c3611402da 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -909,6 +909,11 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
                 if (!crtc->state->enable)
                         continue;
 
+                /* Legacy cursor ioctls are completely unsynced, and userspace
+                 * relies on that (by doing tons of cursor updates). */
+                if (old_state->legacy_cursor_update)
+                        continue;
+
                 if (!framebuffer_changed(dev, old_state, crtc))
                         continue;
 
@@ -1335,6 +1340,9 @@ retry:
         if (ret != 0)
                 goto fail;
 
+        if (plane == crtc->cursor)
+                state->legacy_cursor_update = true;
+
         /* Driver takes ownership of state on successful commit. */
         return 0;
 fail:
@@ -1410,6 +1418,9 @@ retry:
         plane_state->src_h = 0;
         plane_state->src_w = 0;
 
+        if (plane == plane->crtc->cursor)
+                state->legacy_cursor_update = true;
+
         ret = drm_atomic_commit(state);
         if (ret != 0)
                 goto fail;