[PATCH 4.19 001/195] Revert "drm/sun4i: dsi: Change the start delay calculation"

[Greg Kroah-Hartman]

From: Icenowy Zheng <icenowy@xxxxxxx>

[ Upstream commit a00d17e0a71ae2e4fdaac46e1c12785d3346c3f2 ]

This reverts commit da676c6aa6413d59ab0a80c97bbc273025e640b2.

The original commit adds a start parameter to the calculation of the
start delay according to some old BSP versions from Allwinner. However,
there're two ways to add this delay -- add it in DSI controller or add
it in the TCON. Add it in both controllers won't work.

The code before this commit is picked from new versions of BSP kernel,
which has a comment for the 1 that says "put start_delay to tcon". By
checking the sun4i_tcon0_mode_set_cpu() in sun4i_tcon driver, it has
already added this delay, so we shouldn't repeat to add the delay in DSI
controller, otherwise the timing won't match.

Signed-off-by: Icenowy Zheng <icenowy@xxxxxxx>
Reviewed-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20191001080253.6135-2-icenowy@xxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 97a0573cc5145..79eb11cd185d1 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -357,8 +357,7 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
 static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
 					   struct drm_display_mode *mode)
 {
-	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
-	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
+	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
 
 	if (delay > mode->vtotal)
 		delay = delay % mode->vtotal;
-- 
2.20.1