linux-kernel - [PATCH v8 2/8] drm/sun4i: sun6i_mipi

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Message-Id: <20190214192544.7314-3-jagan@amarulasolutions.com>
Date:   Fri, 15 Feb 2019 00:55:38 +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 2/8] drm/sun4i: sun6i_mipi_dsi: Fix DSI hbp timing value

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 hbp value accordingly in sun6i_dsi_setup_timings.

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

Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
Tested-by: Merlijn Wajer <merlijn@...zup.org>
---
 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 d70a8c43a4b8..982ae6b17654 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -472,7 +472,7 @@ 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