linux-kernel - [PATCH v2] mediatek: dsi: Correct calculation formula of PHY Timing

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Date: Fri, 12 Apr 2024 11:11:39 +0800
From: Shuijing Li <shuijing.li@...iatek.com>
To: <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>, <airlied@...il.com>,
	<daniel@...ll.ch>, <matthias.bgg@...il.com>,
	<angelogioacchino.delregno@...labora.com>, <jitao.shi@...iatek.com>
CC: <dri-devel@...ts.freedesktop.org>, <linux-mediatek@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<Project_Global_Chrome_Upstream_Group@...iatek.com>, Shuijing Li
	<shuijing.li@...iatek.com>
Subject: [PATCH v2] mediatek: dsi: Correct calculation formula of PHY Timing

This patch correct calculation formula of PHY timing.
The spec define HS-PREPARE should be from 40ns+4*UI(44ns) to
85ns+6*UI(91ns). But current duration is 88ns and is near the boundary.
So this patch make the duration to 64ns so it is near the safe range.

Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
---
Changes in v2:
Add a commit to describe the improvements to this patch in detail,
per suggestion frome previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240315072945.19502-1-shuijing.li@mediatek.com/
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 33 +++++++++++++++---------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index a2fdfc8ddb15..d1bd7d671880 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -235,22 +235,23 @@ static void mtk_dsi_phy_timconfig(struct mtk_dsi *dsi)
 	u32 data_rate_mhz = DIV_ROUND_UP(dsi->data_rate, 1000000);
 	struct mtk_phy_timing *timing = &dsi->phy_timing;
 
-	timing->lpx = (60 * data_rate_mhz / (8 * 1000)) + 1;
-	timing->da_hs_prepare = (80 * data_rate_mhz + 4 * 1000) / 8000;
-	timing->da_hs_zero = (170 * data_rate_mhz + 10 * 1000) / 8000 + 1 -
-			     timing->da_hs_prepare;
-	timing->da_hs_trail = timing->da_hs_prepare + 1;
-
-	timing->ta_go = 4 * timing->lpx - 2;
-	timing->ta_sure = timing->lpx + 2;
-	timing->ta_get = 4 * timing->lpx;
-	timing->da_hs_exit = 2 * timing->lpx + 1;
-
-	timing->clk_hs_prepare = 70 * data_rate_mhz / (8 * 1000);
-	timing->clk_hs_post = timing->clk_hs_prepare + 8;
-	timing->clk_hs_trail = timing->clk_hs_prepare;
-	timing->clk_hs_zero = timing->clk_hs_trail * 4;
-	timing->clk_hs_exit = 2 * timing->clk_hs_trail;
+	timing->lpx = (80 * data_rate_mhz / (8 * 1000)) + 1;
+	timing->da_hs_prepare = (59 * data_rate_mhz + 4 * 1000) / 8000 + 1;
+	timing->da_hs_zero = (163 * data_rate_mhz + 11 * 1000) / 8000 + 1 -
+		timing->da_hs_prepare;
+	timing->da_hs_trail = (78 * data_rate_mhz + 7 * 1000) / 8000 + 1;
+
+	timing->ta_go = 4 * timing->lpx;
+	timing->ta_sure = 3 * timing->lpx / 2;
+	timing->ta_get = 5 * timing->lpx;
+	timing->da_hs_exit = (118 * data_rate_mhz / (8 * 1000)) + 1;
+
+	timing->clk_hs_prepare = (57 * data_rate_mhz / (8 * 1000)) + 1;
+	timing->clk_hs_post = (65 * data_rate_mhz + 53 * 1000) / 8000 + 1;
+	timing->clk_hs_trail = (78 * data_rate_mhz + 7 * 1000) / 8000 + 1;
+	timing->clk_hs_zero = (330 * data_rate_mhz / (8 * 1000)) + 1 -
+		timing->clk_hs_prepare;
+	timing->clk_hs_exit = (118 * data_rate_mhz / (8 * 1000)) + 1;
 
 	timcon0 = timing->lpx | timing->da_hs_prepare << 8 |
 		  timing->da_hs_zero << 16 | timing->da_hs_trail << 24;
-- 
2.43.0