[PATCH v1] drm/mediatek: fix up 1440x900 dp display black screen issue

[yongqiang.niu]

From: Yongqiang Niu <yongqiang.niu@xxxxxxxxxxxx>

This patch fix up 1440x900 dp display black screen issue
the computed result will overflow rdma1 fifo max size
when external display pixel clock bigger than 74MHZ

Signed-off-by: Yongqiang Niu <yongqiang.niu@xxxxxxxxxxxx>
---
 drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
index c1abde3..41143f5 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
@@ -152,6 +152,10 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
 	 * account for blanking, and with a pixel depth of 4 bytes:
 	 */
 	threshold = width * height * vrefresh * 4 * 7 / 1000000;
+
+	if (threshold > rdma_fifo_size)
+		threshold = rdma_fifo_size;
+
 	reg = RDMA_FIFO_UNDERFLOW_EN |
 	      RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
 	      RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);
-- 
1.8.1.1.dirty