drm/vc4: Workaround for crtc scanout device problem

Currently, the crtc device does not start a scanout, the time of
vblank is always calculated as future value. As a workaround, always
change vpos to a positive number.

Change-Id: I02527a0cfbd03d7713fa992d8ee039ffc8e0c5de
Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index f73d734..7b53dcd 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -172,7 +172,13 @@ static bool vc4_crtc_get_scanout_position(struct drm_crtc *crtc,
                 * contention on event_lock or vblank_time lock in
                 * the core.
                 */
-               *vpos = -vblank_lines;
+               /*
+                * The scanout does not occur due to device problem.
+                * Fixed vpos to a positive value with workaround.
+                * TODO. This issue should be corrected.
+                * We should check the scanout action of the crtc device.
+                */
+               *vpos = vblank_lines;
 
                if (stime)
                        *stime = vc4_crtc->t_vblank;