linux-kernel - [PATCH v3 15/25] drm/sun4i: sun6i_mipi_dsi: Set proper vblk timing calculation

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Date:   Fri, 26 Oct 2018 20:13:34 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, Icenowy Zheng <icenowy@...c.io>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Cc:     Jagan Teki <jagan@...rulasolutions.com>
Subject: [PATCH v3 15/25] drm/sun4i: sun6i_mipi_dsi: Set proper vblk timing calculation

Unlike hblk, the vblk timings should follow an equation to compute
the desired value for lane 4 devices and rest of devices it would be 0.

BSP code from BPI-M64-bsp is computing vblk as for 4-lane devices
(in drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
tmp = (ht*dsi_pixel_bits[format]/8)*vt-(4+dsi_hblk+2);
dsi_vblk = (lane-tmp%lane);

So, update the vblk timing calculation accordingly.

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

Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
Tested-by: Jagan Teki <jagan@...rulasolutions.com>
---
Changes for v3:
- new patch
Changes for v2:
- none

 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 20e330186b7f..42bd7506abaf 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -511,8 +511,19 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 	 * Allwinner BSP is using a rather convoluted calculation
 	 * there only for 4 lanes. However, using 0 (the !4 lanes
 	 * case) even with a 4 lanes screen seems to work...
+	 *
+	 * The vertical blank is set using a blanking packet (4 bytes +
+	 * payload + 2 bytes). Its minimal size is therefore 6 bytes
 	 */
-	vblk = 0;
+#define VBLK_PACKET_OVERHEAD	6
+	if (device->lanes == 4) {
+		int tmp;
+
+		tmp = (mode->htotal * Bpp) * mode->vtotal - (hblk + VBLK_PACKET_OVERHEAD);
+		vblk =(device->lanes - tmp % device->lanes);
+	} else {
+		vblk = 0;
+	}
 
 	/* How many bytes do we need to send all payloads? */
 	bytes = max_t(size_t, max(max(hfp, hblk), max(hsa, hbp)), vblk);
-- 
2.18.0.321.gffc6fa0e3