[PATCH v5 08/17] drm/sun4i: sun6i_mipi_dsi: Fix DSI hbp timing value

Jagan Teki
2018-12-10T16:18:02Z

Current driver is calculating hbp maximum value by subtracting
hsync_start with hdisplay which is front porch value, but the
hbp refers to back porch.

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

BPI-M64-bsp is computing hbp as
(in drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
dsi_hbp = (hbp-hspw)*dsi_pixel_bits[format]/8 - (4+2);
=> (panel->lcd_hbp - timmings->hor_sync_time)
=> (timmings->hor_back_porch + timmings->hor_sync_time -
timmings->hor_sync_time)
=> timmings->hor_back_porch
=> mode->htotal - mode->hsync_end

So, update the MIPI-DSI hbp value accordingly.

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

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index cb41fea4f3ee..81151d7633f9 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -482,7 +482,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
*/
#define HBP_PACKET_OVERHEAD 6
hbp = max((unsigned int)HBP_PACKET_OVERHEAD,
- (mode->hsync_start - mode->hdisplay) * Bpp - HBP_PACKET_OVERHEAD);
+ (mode->htotal - mode->hsync_end) * Bpp - HBP_PACKET_OVERHEAD);

/*
* The frontporch is set using a blanking packet (4 bytes +
--
2.18.0.321.gffc6fa0e3