linux-kernel - [PATCH] drm: rockchip: dw-mipi-dsi: Fix hsclk calculation for non-burst video modes

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Message-ID: <20240217184720.1753730-1-megi@xff.cz>
Date: Sat, 17 Feb 2024 19:47:15 +0100
From: Ondřej Jirman <megi@....cz>
To: linux-kernel@...r.kernel.org
Cc: Ondrej Jirman <megi@....cz>,
	Sandy Huang <hjc@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	Andy Yan <andy.yan@...k-chips.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	dri-devel@...ts.freedesktop.org (open list:DRM DRIVERS FOR ROCKCHIP),
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Rockchip SoC support),
	linux-rockchip@...ts.infradead.org (open list:ARM/Rockchip SoC support)
Subject: [PATCH] drm: rockchip: dw-mipi-dsi: Fix hsclk calculation for non-burst video modes

From: Ondrej Jirman <megi@....cz>

For panels that don't use video burst mode, hsclock should match the
pixel clock * bpp / lane exactly. This fixes display image corruption
on Pinephone Pro, which doesn't use video burst mode to drive the panel.

To simplify the addition of exact fout calculation for non-burst modes,
the code is re-organized in order to not redo the same calculation
multiple times, and to use identical algorithm for per-lane bitrate
for internal and external dphy use cases.

Signed-off-by: Ondrej Jirman <megi@....cz>
---
 .../gpu/drm/rockchip/dw-mipi-dsi-rockchip.c   | 28 ++++++++-----------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
index 4cc8ed8f4fbd..7468324872ec 100644
--- a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
@@ -548,8 +548,6 @@ dw_mipi_dsi_get_lane_mbps(void *priv_data, const struct drm_display_mode *mode,
 {
 	struct dw_mipi_dsi_rockchip *dsi = priv_data;
 	int bpp;
-	unsigned long mpclk, tmp;
-	unsigned int target_mbps = 1000;
 	unsigned int max_mbps = dppa_map[ARRAY_SIZE(dppa_map) - 1].max_mbps;
 	unsigned long best_freq = 0;
 	unsigned long fvco_min, fvco_max, fin, fout;
@@ -567,30 +565,28 @@ dw_mipi_dsi_get_lane_mbps(void *priv_data, const struct drm_display_mode *mode,
 		return bpp;
 	}
 
-	mpclk = DIV_ROUND_UP(mode->clock, MSEC_PER_SEC);
-	if (mpclk) {
-		/* take 1 / 0.8, since mbps must big than bandwidth of RGB */
-		tmp = mpclk * (bpp / lanes) * 10 / 8;
-		if (tmp < max_mbps)
-			target_mbps = tmp;
-		else
-			DRM_DEV_ERROR(dsi->dev,
-				      "DPHY clock frequency is out of range\n");
+	fout = mode->clock * bpp / lanes;
+	if (mode_flags & MIPI_DSI_MODE_VIDEO_BURST)
+		fout = fout * 10 / 8;
+	fout *= MSEC_PER_SEC;
+
+	if (fout > max_mbps * USEC_PER_SEC) {
+		DRM_DEV_ERROR(dsi->dev,
+			      "DPHY clock frequency is out of range\n");
+		return -EINVAL;
 	}
 
-	/* for external phy only a the mipi_dphy_config is necessary */
+	/* for external phy only the mipi_dphy_config is necessary */
 	if (dsi->phy) {
-		phy_mipi_dphy_get_default_config(mode->clock * 1000 * 10 / 8,
-						 bpp, lanes,
+		phy_mipi_dphy_get_default_config_for_hsclk(fout, lanes,
 						 &dsi->phy_opts.mipi_dphy);
-		dsi->lane_mbps = target_mbps;
+		dsi->lane_mbps = DIV_ROUND_UP(fout, USEC_PER_SEC);
 		*lane_mbps = dsi->lane_mbps;
 
 		return 0;
 	}
 
 	fin = clk_get_rate(dsi->pllref_clk);
-	fout = target_mbps * USEC_PER_SEC;
 
 	/* constraint: 5Mhz <= Fref / N <= 40MHz */
 	min_prediv = DIV_ROUND_UP(fin, 40 * USEC_PER_SEC);
-- 
2.43.0