linux-kernel - [PATCH 1/2] drm/mediatek: dsi: Reduce the time of dsi from LP11 to sending cmd

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Date:   Fri, 6 Jan 2023 11:05:20 +0800
From:   <xinlei.lee@...iatek.com>
To:     <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>,
        <airlied@...ux.ie>, <daniel@...ll.ch>, <matthias.bgg@...il.com>,
        <angelogioacchino.delregno@...labora.com>,
        <jitao.shi@...iatek.com>, <thierry.reding@...il.com>,
        <sam@...nborg.org>
CC:     <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Xinlei Lee <xinlei.lee@...iatek.com>
Subject: [PATCH 1/2] drm/mediatek: dsi: Reduce the time of dsi from LP11 to sending cmd

From: Xinlei Lee <xinlei.lee@...iatek.com>

According to Figure 16 Turnaround Procedure on page 36 in [1], you
can see the status of LP-00 -> LP10 -> LP11. This state can correspond
to the state of DSI from LP00 -> LP11 in mtk_dsi_lane_ready function
in mtk_dsi.c.

LP-00 -> LP10 -> LP11 takes about 2*TLPX time (refer to [1] page 51
to see that TLPX is 50ns).

The delay at the end of the mtk_dsi_lane_ready function should be
greater than the 2*TLPX specified by the DSI spec, and less than
the time specified by the DSI_RX (generally 6ms to 40ms), to avoid
problems caused by the RX specification.

[1]:mipi_D-PHY_specification_v1-1

Fixes: 39e8d062b03c ("drm/mediatek: Keep dsi as LP00 before dcs cmds transfer")
Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 3b7d13028fb6..9e1363c9fcdb 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -721,7 +721,7 @@ static void mtk_dsi_lane_ready(struct mtk_dsi *dsi)
 		mtk_dsi_clk_ulp_mode_leave(dsi);
 		mtk_dsi_lane0_ulp_mode_leave(dsi);
 		mtk_dsi_clk_hs_mode(dsi, 0);
-		msleep(20);
+		usleep_range(1000, 3000);
 		/* The reaction time after pulling up the mipi signal for dsi_rx */
 	}
 }
-- 
2.18.0