[PATCH] drm: vc4: Don't wait for vblank when updating the cursor

[Michael Zoran]

Commonly used desktop environments such as xfce4 and gnome
on debian sid can flood the graphics drivers with cursor
updates.  Because the current implementation is waiting
for a vblank between cursor updates, this will cause the
display to hang for a long time since a typical refresh
rate is only 60Hz.

This is unnecessary and unexpected by user mode software,
so simply swap out the cursor frame buffer without waiting.

Signed-off-by: Michael Zoran <mzoran at crowfest.net>
---
 drivers/gpu/drm/vc4/vc4_plane.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index f7a229df572d..110224c3a3ac 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -20,6 +20,7 @@
 
 #include "vc4_drv.h"
 #include "vc4_regs.h"
+#include "drm_atomic.h"
 #include "drm_atomic_helper.h"
 #include "drm_fb_cma_helper.h"
 #include "drm_plane_helper.h"
@@ -769,12 +770,6 @@ vc4_update_plane(struct drm_plane *plane,
 	if (!plane_state)
 		goto out;
 
-	/* If we're changing the cursor contents, do that in the
-	 * normal vblank-synced atomic path.
-	 */
-	if (fb != plane_state->fb)
-		goto out;
-
 	/* No configuring new scaling in the fast path. */
 	if (crtc_w != plane_state->crtc_w ||
 	    crtc_h != plane_state->crtc_h ||
@@ -783,6 +778,11 @@ vc4_update_plane(struct drm_plane *plane,
 		goto out;
 	}
 
+	if (fb != plane_state->fb) {
+		drm_atomic_set_fb_for_plane(plane->state, fb);
+		vc4_plane_async_set_fb(plane, fb);
+	}
+
 	/* Set the cursor's position on the screen.  This is the
 	 * expected change from the drm_mode_cursor_universal()
 	 * helper.
-- 
2.11.0