linux-kernel - [PATCH V8 1/7] drm: bridge: samsung-dsim: fix blanking packet size calculation

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Message-Id: <20230526030559.326566-2-aford173@gmail.com>
Date:   Thu, 25 May 2023 22:05:53 -0500
From:   Adam Ford <aford173@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     aford@...conembedded.com, Lucas Stach <l.stach@...gutronix.de>,
        Adam Ford <aford173@...il.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Inki Dae <inki.dae@...sung.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH V8 1/7] drm: bridge: samsung-dsim: fix blanking packet size calculation

From: Lucas Stach <l.stach@...gutronix.de>

Scale the blanking packet sizes to match the ratio between HS clock
and DPI interface clock. The controller seems to do internal scaling
to the number of active lanes, so we don't take those into account.

Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
Signed-off-by: Adam Ford <aford173@...il.com>
Tested-by: Chen-Yu Tsai <wenst@...omium.org>
Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de>
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Jagan Teki <jagan@...rulasolutions.com>
Tested-by: Jagan Teki <jagan@...rulasolutions.com> # imx8mm-icore
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 0f3f6846beea..a2d1eaf0ed1c 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -881,17 +881,29 @@ static void samsung_dsim_set_display_mode(struct samsung_dsim *dsi)
 	u32 reg;
 
 	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
+		int byte_clk_khz = dsi->burst_clk_rate / 1000 / 8;
+		int hfp = (m->hsync_start - m->hdisplay) * byte_clk_khz / m->clock;
+		int hbp = (m->htotal - m->hsync_end) * byte_clk_khz / m->clock;
+		int hsa = (m->hsync_end - m->hsync_start) * byte_clk_khz / m->clock;
+
+		/* remove packet overhead when possible */
+		hfp = max(hfp - 6, 0);
+		hbp = max(hbp - 6, 0);
+		hsa = max(hsa - 6, 0);
+
+		dev_dbg(dsi->dev, "calculated hfp: %u, hbp: %u, hsa: %u",
+			hfp, hbp, hsa);
+
 		reg = DSIM_CMD_ALLOW(0xf)
 			| DSIM_STABLE_VFP(m->vsync_start - m->vdisplay)
 			| DSIM_MAIN_VBP(m->vtotal - m->vsync_end);
 		samsung_dsim_write(dsi, DSIM_MVPORCH_REG, reg);
 
-		reg = DSIM_MAIN_HFP(m->hsync_start - m->hdisplay)
-			| DSIM_MAIN_HBP(m->htotal - m->hsync_end);
+		reg = DSIM_MAIN_HFP(hfp) | DSIM_MAIN_HBP(hbp);
 		samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
 
 		reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
-			| DSIM_MAIN_HSA(m->hsync_end - m->hsync_start);
+			| DSIM_MAIN_HSA(hsa);
 		samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
 	}
 	reg =  DSIM_MAIN_HRESOL(m->hdisplay, num_bits_resol) |
-- 
2.39.2