[PATCH] drm/mediatek: Add no pending_planes flag checking for mtk_crtc_finish_page_flip()

[Jason-JH.Lin]

mtk_crtc_finish_page_flip() is used to notify the page flip that has
been completed to the userspace, so userspace can free the frame buffer
of the last frame and commit the next frame.

However, mtk_crtc_finish_page_flip() cannot guarantee the GCE has
configured all the display hardware settings of the last frame.
This may cause the display hardware to still access the last frame
buffer released by the userspace.

So add the checking condition of no pending_plens flags to make sure
GCE has executed all the pending planes configuration.

Fixes: 7f82d9c43879 ("drm/mediatek: Clear pending flag when cmdq packet is done")
Signed-off-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_crtc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
index eb0e1233ad04..b03b9102ff90 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
@@ -113,7 +113,8 @@ static void mtk_drm_finish_page_flip(struct mtk_crtc *mtk_crtc)
 	drm_crtc_handle_vblank(&mtk_crtc->base);
 
 	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
-	if (!mtk_crtc->config_updating && mtk_crtc->pending_needs_vblank) {
+	if (!mtk_crtc->config_updating && mtk_crtc->pending_needs_vblank &&
+	    !mtk_crtc->pending_planes) {
 		mtk_crtc_finish_page_flip(mtk_crtc);
 		mtk_crtc->pending_needs_vblank = false;
 	}
-- 
2.43.0