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Subject[PATCH v3 09/25] drm/sun4i: sun6i_mipi_dsi: Refactor vertical video start delay
Date
Video start delay can be computed by subtracting total vertical
timing with front porch timing and with adding 1 delay line for TCON.

BSP code form BPI-M64-bsp is computing video start delay as
(in linux-sunxi/drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)

u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
=> (panel->lcd_vt) - panel->lcd_y - (panel->lcd_vbp)
=> (timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y)
- panel->lcd_y - (panel->lcd_vbp)
=> timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y
- panel->lcd_y - panel->lcd_vbp
=> timmings->ver_front_porch

So, update the start delay computation accordingly.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>
---
Changes for v3:
- Fixed proper commit message
- add tested credit
Changes for v2:
- none

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 8d154cf2e6d6..6bece492b1f7 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -358,7 +358,17 @@ 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)
{
- return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
+ u32 vfp = mode->vsync_start - mode->vdisplay;
+ u32 start_delay;
+
+ start_delay = mode->vtotal - vfp + 1;
+ if (start_delay > mode->vtotal)
+ start_delay -= mode->vtotal;
+
+ if (!start_delay)
+ start_delay = 1;
+
+ return start_delay;
}

static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
--
2.18.0.321.gffc6fa0e3
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