[PATCH v9 2/5] drm/sun4i: sun6i_mipi_dsi: Fix TCON DRQ set bits

[Jagan Teki <jagan@amarulasolutions.com>]

TCON DRQ for non-burst DSI mode can computed based on horizontal
front porch value, but the current driver trying to include sync
timings along with front porch resulting wrong drq.

This patch is trying to update the drq by subtracting hsync_start
with hdisplay, which is horizontal front porch.

Current code:
------------
mode->hsync_end - mode->hdisplay => horizontal front porch + sync

With this patch:
----------------
mode->hsync_start - mode->hdisplay => horizontal front porch

BSP code form BPI-M64-bsp is computing TCON DRQ set bits
for non-burts as (from linux-sunxi/
drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)

=> panel->lcd_ht -    panel->lcd_x - panel->lcd_hbp
=> (timmings->hor_front_porch + panel->lcd_hbp + panel->lcd_x)
   - panel->lcd_x - panel->hbp
=> timmings->hor_front_porch
=> mode->hsync_start - mode->hdisplay

So, update the DRQ set bits accordingly.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Merlijn Wajer <merlijn@wizzup.org>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 465e7fc57899..140e55f5ed2e 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -436,9 +436,9 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
 			     SUN6I_DSI_BURST_LINE_SYNC_POINT(SUN6I_DSI_SYNC_POINT));
 
 		val = SUN6I_DSI_TCON_DRQ_ENABLE_MODE;
-	} else if ((mode->hsync_end - mode->hdisplay) > 20) {
+	} else if ((mode->hsync_start - mode->hdisplay) > 20) {
 		/* Maaaaaagic */
-		u16 drq = (mode->hsync_end - mode->hdisplay) - 20;
+		u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
 
 		drq *= mipi_dsi_pixel_format_to_bpp(device->format);
 		drq /= 32;
-- 
2.18.0.321.gffc6fa0e3