Thread (30 messages) 30 messages, 2 authors, 2019-02-14
STALE2685d REVIEWED: 1 (0M)
Revisions (4)
  1. v3 [diff vs current]
  2. v4 [diff vs current]
  3. v6 [diff vs current]
  4. v7 current

[PATCH v7 22/23] drm/sun4i: sun6i_mipi_dsi: Fix DSI hfp timing value

From: Jagan Teki <hidden>
Date: 2019-02-01 15:43:36
Also in: dri-devel, linux-arm-kernel, linux-clk, lkml
Subsystem: drm drivers, drm drivers and misc gpu patches, drm drivers for allwinner a10, the rest · Maintainers: David Airlie, Simona Vetter, Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Chen-Yu Tsai, Linus Torvalds

Current driver is calculating hfp maximum value by subtracting
htotal with hsync_end which is front back value, but the
hpp refers to front porch.

Front porch value is calculating by subtracting hsync_start with
hdisplay as per drm_mode timings, and BSP code from BPI-M64-bsp
is eventually following the same.

BPI-M64-bsp is computing hfp as (from linux-sunxi/
drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)

dsi_hbp = (hbp-hspw)*dsi_pixel_bits[format]/8 - (4+2);
dsi_hact = x * dsi_pixel_bits[format]/8;
dsi_hblk = (ht-hspw)*dsi_pixel_bits[format]/8-(4+4+2);
dsi_hfp = dsi_hblk - (4+dsi_hact+2) - (4+dsi_hbp+2);

Example,
u32 fmt = dsi_pixel_bits[format]/8;
=> ((ht-hspw)*fmt - 10) - (6 + x * fmt) - (6 + (hbp-hspw)*fmt - 6)
=> (ht - hspw - x - (hbp - hspw)) * fmt - 16
=> (ht - x - hbp) * fmt - 16
=> (ht - x - (timmings->hor_total_time - timmings->hor_front_porch - x)
* fmt - 16
=> (timmings->hor_total_time - x - timmings->hor_total_time +
timmings->hor_front_porch + x) * fmt - 16
=> timmings->hor_front_porch * fmt - 16

So, update the DSI hfp timing accordingly.

Tested on 2-lane, 4-lane MIPI-DSI LCD panels.

Signed-off-by: Jagan Teki <jagan-dyjBcgdgk7Pe9wHmmfpqLFaTQe2KTcn/@public.gmane.org>
Tested-by: Merlijn Wajer <redacted>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 780b1906c661..3fbe2132eb6a 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -587,7 +587,8 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 	 */
 #define HFP_PACKET_OVERHEAD	6
 	hfp = max((unsigned int)HFP_PACKET_OVERHEAD,
-		  (mode->htotal - mode->hsync_end) * Bpp - HFP_PACKET_OVERHEAD);
+		  (mode->hsync_start - mode->hdisplay) * Bpp -
+		  HFP_PACKET_OVERHEAD);
 
 	/*
 	 * hblk seems to be the line + porches length.
-- 
2.18.0.321.gffc6fa0e3
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help