[PATCH] drm/edid: Add HDR Static Metadata Type 1 quirk for LG UltraGear

[Xela <git@xela.zone>]

The LG UltraGear monitor (PNP ID GSM 0x7766) advertises HDR support in
its CTA-861 Extension block with SMPTE ST 2084 (PQ) EOTF support
(byte 0x9e = 0x05) and valid desired content luminance descriptors
(351 cd/m^2 max CLL/FALL at bytes 0xa0-0xa2).

However, due to a factory firmware bug, the HDR Static Metadata Data
Block descriptor byte (byte 0x9f) is reported as 0x00 instead of 0x01,
omitting the Static Metadata Type 1 capability bit (bit 0).

Because of this omitted bit, drm_parse_hdr_metadata_block() sets
metadata_type to 0. Consequently, drm_calculate_luminance_range()
rejects the block, and userspace attempts to perform atomic KMS commits
configuring HDR output metadata fail with -EINVAL (Error 22), preventing
compositors (Plasma, Gamescope, MPV) from engaging HDR on this display.

Introduce EDID_QUIRK_FORCE_HDR_STATIC_METADATA_TYPE1 to force the Static
Metadata Type 1 descriptor bit for displays with this defective EDID block,
and register the LG UltraGear (GSM 0x7766) in the EDID quirk table.

Signed-off-by: Xela <git@xela.zone>
---
 drivers/gpu/drm/drm_edid.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 07970e5b5..dd279fad1 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -96,6 +96,8 @@ enum drm_edid_internal_quirk {
 	EDID_QUIRK_NON_DESKTOP,
 	/* Cap the DSC target bitrate to 15bpp */
 	EDID_QUIRK_CAP_DSC_15BPP,
+	/* Force Static Metadata Type 1 for HDR Static Metadata Data Block */
+	EDID_QUIRK_FORCE_HDR_STATIC_METADATA_TYPE1,
 };
 
 #define MICROSOFT_IEEE_OUI	0xca125c
@@ -195,6 +197,9 @@ static const struct edid_quirk {
 	/* LG 27GN950 */
 	EDID_QUIRK('G', 'S', 'M', 0x5b9a, BIT(EDID_QUIRK_CAP_DSC_15BPP)),
 
+	/* LG UltraGear (GSM 0x7766) */
+	EDID_QUIRK('G', 'S', 'M', 0x7766, BIT(EDID_QUIRK_FORCE_HDR_STATIC_METADATA_TYPE1)),
+
 	/* LGD panel of HP zBook 17 G2, eDP 10 bpc, but reports unknown bpc */
 	EDID_QUIRK('L', 'G', 'D', 764, BIT(EDID_QUIRK_FORCE_10BPC)),
 
@@ -5498,6 +5503,10 @@ drm_parse_hdr_metadata_block(struct drm_connector *connector, const u8 *db)
 	hdr_metadata->eotf = eotf_supported(db);
 	hdr_metadata->metadata_type = hdr_metadata_type(db);
 
+	if (drm_edid_has_internal_quirk(connector,
+				       EDID_QUIRK_FORCE_HDR_STATIC_METADATA_TYPE1))
+		hdr_metadata->metadata_type |= BIT(HDMI_STATIC_METADATA_TYPE1);
+
 	if (len >= 4)
 		hdr_metadata->max_cll = db[4];
 	if (len >= 5)
-- 
2.54.0