[PATCH v4 2/2] drm/mediatek: dsi: fix scrolling of panel with small hfp or hbp

[Jitao Shi]

Replace horizontal_backporch_byte with vm->hback_porch * bpp to aovid
flowing judgement negative number.

if ((vm->hfront_porch * dsi_tmp_buf_bpp + horizontal_backporch_byte) >
	data_phy_cycles * dsi->lanes + delta)

Signed-off-by: Jitao Shi <jitao.shi at mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 54 ++++++++++++++------------------------
 1 file changed, 19 insertions(+), 35 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 16fd99dcdacf..ddddf69ebeaf 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -445,6 +445,7 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
 	u32 horizontal_backporch_byte;
 	u32 horizontal_frontporch_byte;
 	u32 dsi_tmp_buf_bpp, data_phy_cycles;
+	u32 delta;
 	struct mtk_phy_timing *timing = &dsi->phy_timing;
 
 	struct videomode *vm = &dsi->vm;
@@ -475,42 +476,25 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
 	data_phy_cycles = timing->lpx + timing->da_hs_prepare +
 			  timing->da_hs_zero + timing->da_hs_exit + 3;
 
-	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) {
-		if ((vm->hfront_porch + vm->hback_porch) * dsi_tmp_buf_bpp >
-		    data_phy_cycles * dsi->lanes + 18) {
-			horizontal_frontporch_byte =
-				vm->hfront_porch * dsi_tmp_buf_bpp -
-				(data_phy_cycles * dsi->lanes + 18) *
-				vm->hfront_porch /
-				(vm->hfront_porch + vm->hback_porch);
-
-			horizontal_backporch_byte =
-				horizontal_backporch_byte -
-				(data_phy_cycles * dsi->lanes + 18) *
-				vm->hback_porch /
-				(vm->hfront_porch + vm->hback_porch);
-		} else {
-			DRM_WARN("HFP less than d-phy, FPS will under 60Hz\n");
-			horizontal_frontporch_byte = vm->hfront_porch *
-						     dsi_tmp_buf_bpp;
-		}
+	delta = (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) ? 18 : 12;
+
+	if ((vm->hfront_porch * dsi_tmp_buf_bpp + horizontal_backporch_byte) >
+	    data_phy_cycles * dsi->lanes + delta) {
+		horizontal_frontporch_byte =
+			vm->hfront_porch * dsi_tmp_buf_bpp -
+			(data_phy_cycles * dsi->lanes + delta) *
+			vm->hfront_porch /
+			(vm->hfront_porch + vm->hback_porch);
+
+		horizontal_backporch_byte =
+			horizontal_backporch_byte -
+			(data_phy_cycles * dsi->lanes + delta) *
+			vm->hback_porch /
+			(vm->hfront_porch + vm->hback_porch);
 	} else {
-		if ((vm->hfront_porch + vm->hback_porch) * dsi_tmp_buf_bpp >
-		    data_phy_cycles * dsi->lanes + 12) {
-			horizontal_frontporch_byte =
-				vm->hfront_porch * dsi_tmp_buf_bpp -
-				(data_phy_cycles * dsi->lanes + 12) *
-				vm->hfront_porch /
-				(vm->hfront_porch + vm->hback_porch);
-			horizontal_backporch_byte = horizontal_backporch_byte -
-				(data_phy_cycles * dsi->lanes + 12) *
-				vm->hback_porch /
-				(vm->hfront_porch + vm->hback_porch);
-		} else {
-			DRM_WARN("HFP less than d-phy, FPS will under 60Hz\n");
-			horizontal_frontporch_byte = vm->hfront_porch *
-						     dsi_tmp_buf_bpp;
-		}
+		DRM_WARN("HFP + HBP less than d-phy, FPS will under 60Hz\n");
+		horizontal_frontporch_byte = vm->hfront_porch *
+					     dsi_tmp_buf_bpp;
 	}
 
 	writel(horizontal_sync_active_byte, dsi->regs + DSI_HSA_WC);
-- 
2.12.5