[PATCH v4 13/26] drm/sun4i: sun6i_mipi_dsi: Add DSI hblk packet overhead

[Jagan Teki]

Add 10 bytes packet overhead for hblk where blank is set using
a blanking packet like (4 bytes + 4 bytes + payload + 2 bytes)

This is according to BSP code from BPI-M64-bsp (from linux-sunxi/
drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)

dsi_hblk = (ht-hspw)*dsi_pixel_bits[format]/8-(4+4+2);

So, add 10 bytes packet overhead for DSI hblk.

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

Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index cd657ac4bdae..1a3cdd5b72a0 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -494,8 +494,13 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 
 	/*
 	 * hblk seems to be the line + porches length.
+	 * The blank is set using a blanking packet (4 bytes + 4 bytes +
+	 * payload + 2 bytes). So minimal size is 10 bytes
 	 */
-	hblk = (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp;
+#define HBLK_PACKET_OVERHEAD	10
+	hblk = max((unsigned int)HBLK_PACKET_OVERHEAD,
+		   (mode->htotal - (mode->hsync_end - mode->hsync_start)) *
+		   Bpp - HBLK_PACKET_OVERHEAD);
 
 	/*
 	 * And I'm not entirely sure what vblk is about. The driver in
-- 
2.18.0.321.gffc6fa0e3