| From 8c86027ad3db60a274d0e826f6fc58253735b647 Mon Sep 17 00:00:00 2001 |
| From: Maxime Ripard <maxime.ripard@bootlin.com> |
| Date: Mon, 11 Feb 2019 15:41:23 +0100 |
| Subject: drm/sun4i: dsi: Change the start delay calculation |
| |
| [ Upstream commit da676c6aa6413d59ab0a80c97bbc273025e640b2 ] |
| |
| The current calculation for the video start delay in the current DSI driver |
| is that it is the total vertical size, minus the front porch and sync length, |
| plus 1. This equals to the active vertical size plus the back porch plus 1. |
| |
| That 1 is coming in the Allwinner BSP from an variable that is set to 1. |
| However, if we look at the Allwinner BSP more closely, and especially in |
| the "legacy" code for the display (in drivers/video/sunxi/legacy/), we can |
| see that this variable is actually computed from the porches and the sync |
| minus 10, clamped between 8 and 100. |
| |
| This fixes the start delay symptom we've seen on some panels (vblank |
| timeouts with vertical white stripes at the bottom of the panel). |
| |
| Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com> |
| Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com> |
| Link: https://patchwork.freedesktop.org/patch/msgid/6e5f72e68f47ca0223877464bf12f0c3f3978de8.1549896081.git-series.maxime.ripard@bootlin.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c |
| index 318994cd1b851..25d8cb9f92661 100644 |
| --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c |
| +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c |
| @@ -358,7 +358,9 @@ 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; |
| + u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100); |
| + |
| + return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start; |
| } |
| |
| static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi, |
| -- |
| 2.20.1 |
| |