drm/mediatek: Detect CMDQ execution timeout

CMDQ is used to update display register in vblank period, so
it should be execute in next vblank. If it fail to execute
in next 2 vblank, tiemout happen.

Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
index f99c9d2..71f770e 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
@@ -52,6 +52,7 @@
 	struct mbox_client		cmdq_cl;
 	struct mbox_chan		*cmdq_chan;
 	u32				cmdq_event;
+	u32				cmdq_vblank_cnt;
 #endif
 
 	struct device			*mmsys_dev;
@@ -244,6 +245,7 @@
 	struct mtk_drm_crtc *mtk_crtc = container_of(cl, struct mtk_drm_crtc, cmdq_cl);
 	struct cmdq_cb_data *data = mssg;
 
+	mtk_crtc->cmdq_vblank_cnt = 0;
 	cmdq_pkt_destroy(mtk_crtc->cmdq_chan, data->pkt);
 }
 #endif
@@ -494,6 +496,11 @@
 					   cmdq_handle->pa_base,
 					   cmdq_handle->cmd_buf_size,
 					   DMA_TO_DEVICE);
+		/*
+		 * CMDQ command should execute in next vblank,
+		 * If it fail to execute in next 2 vblank, timeout happen.
+		 */
+		mtk_crtc->cmdq_vblank_cnt = 2;
 		cmdq_pkt_flush_async(mtk_crtc->cmdq_chan, cmdq_handle);
 	}
 #endif
@@ -674,10 +681,14 @@
 
 #if IS_REACHABLE(CONFIG_MTK_CMDQ)
 	if (!priv->data->shadow_register && !mtk_crtc->cmdq_chan)
+		mtk_crtc_ddp_config(crtc, NULL);
+	else if (mtk_crtc->cmdq_vblank_cnt && --mtk_crtc->cmdq_vblank_cnt == 0)
+		DRM_ERROR("mtk_crtc %d CMDQ execute command timeout!\n",
+			  drm_crtc_index(&mtk_crtc->base));
 #else
 	if (!priv->data->shadow_register)
-#endif
 		mtk_crtc_ddp_config(crtc, NULL);
+#endif
 
 	mtk_drm_finish_page_flip(mtk_crtc);
 }