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Subject[PATCH 5.9 098/152] drm/mediatek: dsi: Modify horizontal front/back porch byte formula
Date
From: CK Hu <ck.hu@mediatek.com>

[ Upstream commit 487778f8d22fcdebb6436f0a5f96484ffa237b0b ]

In the patch to be fixed, horizontal_backporch_byte become too large
for some panel, so roll back that patch. For small hfp or hbp panel,
using vm->hfront_porch + vm->hback_porch to calculate
horizontal_backporch_byte would make it negtive, so
use horizontal_backporch_byte itself to make it positive.

Fixes: 35bf948f1edb ("drm/mediatek: dsi: Fix scrolling of panel with small hfp or hbp")

Signed-off-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Tested-by: Bilal Wasim <bilal.wasim@imgtec.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/mediatek/mtk_dsi.c | 61 +++++++++++-------------------
1 file changed, 22 insertions(+), 39 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 80b7a082e8740..d6e0a29ea6b28 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -444,7 +444,10 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
u32 horizontal_sync_active_byte;
u32 horizontal_backporch_byte;
u32 horizontal_frontporch_byte;
+ u32 horizontal_front_back_byte;
+ u32 data_phy_cycles_byte;
u32 dsi_tmp_buf_bpp, data_phy_cycles;
+ u32 delta;
struct mtk_phy_timing *timing = &dsi->phy_timing;

struct videomode *vm = &dsi->vm;
@@ -466,50 +469,30 @@ 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;
+ horizontal_backporch_byte = vm->hback_porch * dsi_tmp_buf_bpp - 10;
else
horizontal_backporch_byte = (vm->hback_porch + vm->hsync_len) *
- dsi_tmp_buf_bpp;
+ dsi_tmp_buf_bpp - 10;

data_phy_cycles = timing->lpx + timing->da_hs_prepare +
- 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 >
- 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;
- }
+ timing->da_hs_zero + timing->da_hs_exit + 3;
+
+ delta = dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST ? 18 : 12;
+
+ horizontal_frontporch_byte = vm->hfront_porch * dsi_tmp_buf_bpp;
+ horizontal_front_back_byte = horizontal_frontporch_byte + horizontal_backporch_byte;
+ data_phy_cycles_byte = data_phy_cycles * dsi->lanes + delta;
+
+ if (horizontal_front_back_byte > data_phy_cycles_byte) {
+ horizontal_frontporch_byte -= data_phy_cycles_byte *
+ horizontal_frontporch_byte /
+ horizontal_front_back_byte;
+
+ horizontal_backporch_byte -= data_phy_cycles_byte *
+ horizontal_backporch_byte /
+ horizontal_front_back_byte;
} 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");
}

writel(horizontal_sync_active_byte, dsi->regs + DSI_HSA_WC);
--
2.27.0


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