linux-kernel - [PATCH] drm: bridge: dw-hdmi: Fix RGB to YUV color space conversion

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Date:   Sat,  6 Nov 2021 14:00:44 +0100
From:   Alex Bee <knaerzche@...il.com>
To:     Neil Armstrong <narmstrong@...libre.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Cc:     Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Alex Bee <knaerzche@...il.com>
Subject: [PATCH] drm: bridge: dw-hdmi: Fix RGB to YUV color space conversion

As per CEA-861 quantization range is always limited in case of YUV
output - indepentently which CEA mode it is or if it is an DMT mode.

This is already correctly setup in HDMI AVI inforame, but we always do
a RGB to YUV conversion which doesn't consider that RGB input can be
full range as well.
That leads to incorrect colors for all CEA modes except mode 1 for HDMI
and always for DVI.

To fix this, provide additional csc coefficents for converting from RGB
full range to EITU601/EITU709 limited range and rename the existing
arrays to clarify their meaning.

Signed-off-by: Alex Bee <knaerzche@...il.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 24 +++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 62ae63565d3a..1cba08b70091 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -80,13 +80,25 @@ static const u16 csc_coeff_rgb_out_eitu709[3][4] = {
 	{ 0x2000, 0x0000, 0x3b61, 0x7e25 }
 };
 
-static const u16 csc_coeff_rgb_in_eitu601[3][4] = {
+static const u16 csc_coeff_rgb_full_in_eitu601[3][4] = {
+	{ 0x2044, 0x106f, 0x0644, 0x0040 },
+	{ 0xe677, 0x1c1c, 0xfd46, 0x0200 },
+	{ 0xed60, 0xf685, 0x1c1c, 0x0200 }
+};
+
+static const u16 csc_coeff_rgb_limited_in_eitu601[3][4] = {
 	{ 0x2591, 0x1322, 0x074b, 0x0000 },
 	{ 0x6535, 0x2000, 0x7acc, 0x0200 },
 	{ 0x6acd, 0x7534, 0x2000, 0x0200 }
 };
 
-static const u16 csc_coeff_rgb_in_eitu709[3][4] = {
+static const u16 csc_coeff_rgb_full_in_eitu709[3][4] = {
+	{ 0x2750, 0x0baf, 0x03f8, 0x0040 },
+	{ 0xe677, 0x1c1c, 0xfd6d, 0x0200 },
+	{ 0xea55, 0xf98f, 0x1c1c, 0x0200 }
+};
+
+static const u16 csc_coeff_rgb_limted_in_eitu709[3][4] = {
 	{ 0x2dc5, 0x0d9b, 0x049e, 0x0000 },
 	{ 0x62f0, 0x2000, 0x7d11, 0x0200 },
 	{ 0x6756, 0x78ab, 0x2000, 0x0200 }
@@ -1023,9 +1035,13 @@ static void dw_hdmi_update_csc_coeffs(struct dw_hdmi *hdmi)
 			csc_coeff = &csc_coeff_rgb_out_eitu709;
 	} else if (is_input_rgb && !is_output_rgb) {
 		if (hdmi->hdmi_data.enc_out_encoding == V4L2_YCBCR_ENC_601)
-			csc_coeff = &csc_coeff_rgb_in_eitu601;
+			csc_coeff = hdmi->hdmi_data.rgb_limited_range
+				? &csc_coeff_rgb_limited_in_eitu601
+				: &csc_coeff_rgb_full_in_eitu601;
 		else
-			csc_coeff = &csc_coeff_rgb_in_eitu709;
+			csc_coeff = hdmi->hdmi_data.rgb_limited_range
+				? &csc_coeff_rgb_limted_in_eitu709
+				: &csc_coeff_rgb_full_in_eitu709;
 		csc_scale = 0;
 	} else if (is_input_rgb && is_output_rgb &&
 		   hdmi->hdmi_data.rgb_limited_range) {

base-commit: 89636a06fa2ee7826a19c39c19a9bc99ab9340a9
-- 
2.30.2