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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jitao Shi <jitao.shi@mediatek.com>,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 045/118] drm/mediatek: dsi: Fix scrolling of panel with small hfp or hbp
Date:   Mon, 21 Sep 2020 18:27:37 +0200
Message-Id: <20200921162038.407019155@linuxfoundation.org>
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From: Jitao Shi <jitao.shi@mediatek.com>

[ Upstream commit 35bf948f1edbf507f6e57e0879fa6ea36d2d2930 ]

horizontal_backporch_byte should be hbp * bpp - hbp extra bytes.
So remove the wrong subtraction 10.

Fixes: 7a5bc4e22ecf ("drm/mediatek: change the dsi phytiming calculate method")
Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 02ac55c13a80b..ee011a0633841 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -470,14 +470,13 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
 	horizontal_sync_active_byte = (vm->hsync_len * dsi_tmp_buf_bpp - 10);
 
 	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
-		horizontal_backporch_byte =
-			(vm->hback_porch * dsi_tmp_buf_bpp - 10);
+		horizontal_backporch_byte = vm->hback_porch * dsi_tmp_buf_bpp;
 	else
-		horizontal_backporch_byte = ((vm->hback_porch + vm->hsync_len) *
-			dsi_tmp_buf_bpp - 10);
+		horizontal_backporch_byte = (vm->hback_porch + vm->hsync_len) *
+					    dsi_tmp_buf_bpp;
 
 	data_phy_cycles = timing->lpx + timing->da_hs_prepare +
-			  timing->da_hs_zero + timing->da_hs_exit + 3;
+			  timing->da_hs_zero + timing->da_hs_exit;
 
 	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) {
 		if ((vm->hfront_porch + vm->hback_porch) * dsi_tmp_buf_bpp >
-- 
2.25.1