linux-kernel - [PATCH AUTOSEL 6.0 11/73] drm/edid: add a quirk for two LG monitors to get them to work on 10bpc

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Date:   Sun, 18 Dec 2022 11:06:39 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hamza Mahfooz <hamza.mahfooz@....com>, Roman Li <roman.li@....com>,
        Harry Wentland <harry.wentland@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.0 11/73] drm/edid: add a quirk for two LG monitors to get them to work on 10bpc

From: Hamza Mahfooz <hamza.mahfooz@....com>

[ Upstream commit aa193f7eff8ff753577351140b8af13b76cdc7c2 ]

The LG 27GP950 and LG 27GN950 have visible display corruption when
trying to use 10bpc modes. So, to fix this, cap their maximum DSC
target bitrate to 15bpp.

Suggested-by: Roman Li <roman.li@....com>
Reviewed-by: Harry Wentland <harry.wentland@....com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/drm_edid.c  | 12 ++++++++++++
 include/drm/drm_connector.h |  6 ++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index eaa819381281..fefcfac999d9 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -87,6 +87,8 @@ static int oui(u8 first, u8 second, u8 third)
 #define EDID_QUIRK_FORCE_10BPC			(1 << 11)
 /* Non desktop display (i.e. HMD) */
 #define EDID_QUIRK_NON_DESKTOP			(1 << 12)
+/* Cap the DSC target bitrate to 15bpp */
+#define EDID_QUIRK_CAP_DSC_15BPP		(1 << 13)
 
 #define MICROSOFT_IEEE_OUI	0xca125c
 
@@ -147,6 +149,12 @@ static const struct edid_quirk {
 	EDID_QUIRK('F', 'C', 'M', 13600, EDID_QUIRK_PREFER_LARGE_75 |
 				       EDID_QUIRK_DETAILED_IN_CM),
 
+	/* LG 27GP950 */
+	EDID_QUIRK('G', 'S', 'M', 0x5bbf, EDID_QUIRK_CAP_DSC_15BPP),
+
+	/* LG 27GN950 */
+	EDID_QUIRK('G', 'S', 'M', 0x5b9a, EDID_QUIRK_CAP_DSC_15BPP),
+
 	/* LGD panel of HP zBook 17 G2, eDP 10 bpc, but reports unknown bpc */
 	EDID_QUIRK('L', 'G', 'D', 764, EDID_QUIRK_FORCE_10BPC),
 
@@ -6116,6 +6124,7 @@ static void drm_reset_display_info(struct drm_connector *connector)
 
 	info->mso_stream_count = 0;
 	info->mso_pixel_overlap = 0;
+	info->max_dsc_bpp = 0;
 }
 
 static u32 update_display_info(struct drm_connector *connector,
@@ -6202,6 +6211,9 @@ static u32 update_display_info(struct drm_connector *connector,
 		info->non_desktop = true;
 	}
 
+	if (quirks & EDID_QUIRK_CAP_DSC_15BPP)
+		info->max_dsc_bpp = 15;
+
 	return quirks;
 }
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 7df7876b2ad5..d9879fc9ceb1 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -635,6 +635,12 @@ struct drm_display_info {
 	 * @mso_pixel_overlap: eDP MSO segment pixel overlap, 0-8 pixels.
 	 */
 	u8 mso_pixel_overlap;
+
+	/**
+	 * @max_dsc_bpp: Maximum DSC target bitrate, if it is set to 0 the
+	 * monitor's default value is used instead.
+	 */
+	u32 max_dsc_bpp;
 };
 
 int drm_display_info_set_bus_formats(struct drm_display_info *info,
-- 
2.35.1