linux-kernel - [PATCH v8 4/8] drm/sun4i: sun6i_mipi_dsi: Fix DSI hblk timing calculation

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Message-Id: <20190214192544.7314-5-jagan@amarulasolutions.com>
Date:   Fri, 15 Feb 2019 00:55:40 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Chen-Yu Tsai <wens@...e.org>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-amarula@...rulasolutions.com,
        Michael Trimarchi <michael@...rulasolutions.com>,
        Jagan Teki <jagan@...rulasolutions.com>
Subject: [PATCH v8 4/8] drm/sun4i: sun6i_mipi_dsi: Fix DSI hblk timing calculation

horizontal blank is computed by adding all porch timing values,
or htotal total timing value without sync time.

Based on "DRM kernel-internal display mode structure" from
include/drm/drm_modes.h

hblk = htotal - (hsync value);
hblk = htotal - (hsync_end - hsync_start);

Current driver is subtracting htotal with hsa, but the hsa is
bounded with packet overhead. So subtract htotal with hsync
value(hsync_end - hsync_start) proper hblk computation.

BPI-M64-bsp is computing hbp as (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);
=> (timmings->hor_total_time - timmings->hor_sync_time)
=> (mode->htotal - (mode->hsync_end - mode->hsync_start))

So, update the hblk value accordingly in sun6i_dsi_setup_timings.

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

Signed-off-by: Jagan Teki <jagan@...rulasolutions.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 21f39f11a8de..6b26dba883e8 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -486,7 +486,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 	/*
 	 * hblk seems to be the line + porches length.
 	 */
-	hblk = mode->htotal * Bpp - hsa;
+	hblk = (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp;
 
 	/*
 	 * And I'm not entirely sure what vblk is about. The driver in
-- 
2.18.0.321.gffc6fa0e3