[PATCH v3 10/25] drm/sun4i: sun6i_mipi_dsi: Fix DSI hbp timing value

[Jagan Teki]

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@xxxxxxxxxxxxxxxxxxxx>
Tested-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
---
Changes for v3:
- Fixed proper commit message
- add tested credit
Changes for v2:
- none

 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 6bece492b1f7..78bad71045ca 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