From 3d237fe2dec49bbfd7276923167d4c46de37a872 Mon Sep 17 00:00:00 2001
From: jsg <jsg@openbsd.org>
Date: Mon, 25 May 2026 09:49:17 +0000
Subject: [PATCH] drm/amd/display: Read EDID from VBIOS embedded panel info

From Timur Kristof
8b85ffe5205262682b4dc9e2e35beaeb7365aceb in linux-6.18.y/6.18.33
9ea16f64189bf7b6ba50fc7f0325b3c1f836d105 in mainline linux
---
 .../pci/drm/amd/display/dc/bios/bios_parser.c | 62 +++++++++++++++++++
 .../display/include/grph_object_ctrl_defs.h   |  4 ++
 2 files changed, 66 insertions(+)

diff --git a/sys/dev/pci/drm/amd/display/dc/bios/bios_parser.c b/sys/dev/pci/drm/amd/display/dc/bios/bios_parser.c
index 154fd2c18e8..c800c603bf7 100644
--- a/sys/dev/pci/drm/amd/display/dc/bios/bios_parser.c
+++ b/sys/dev/pci/drm/amd/display/dc/bios/bios_parser.c
@@ -1215,6 +1215,60 @@ static enum bp_result bios_parser_get_embedded_panel_info(
 	return BP_RESULT_FAILURE;
 }
 
+static enum bp_result get_embedded_panel_extra_info(
+	struct bios_parser *bp,
+	struct embedded_panel_info *info,
+	const uint32_t table_offset)
+{
+	uint8_t *record = bios_get_image(&bp->base, table_offset, 1);
+	ATOM_PANEL_RESOLUTION_PATCH_RECORD *panel_res_record;
+	ATOM_FAKE_EDID_PATCH_RECORD *fake_edid_record;
+
+	while (*record != ATOM_RECORD_END_TYPE) {
+		switch (*record) {
+		case LCD_MODE_PATCH_RECORD_MODE_TYPE:
+			record += sizeof(ATOM_PATCH_RECORD_MODE);
+			break;
+		case LCD_RTS_RECORD_TYPE:
+			record += sizeof(ATOM_LCD_RTS_RECORD);
+			break;
+		case LCD_CAP_RECORD_TYPE:
+			record += sizeof(ATOM_LCD_MODE_CONTROL_CAP);
+			break;
+		case LCD_FAKE_EDID_PATCH_RECORD_TYPE:
+			fake_edid_record = (ATOM_FAKE_EDID_PATCH_RECORD *)record;
+			if (fake_edid_record->ucFakeEDIDLength) {
+				if (fake_edid_record->ucFakeEDIDLength == 128)
+					info->fake_edid_size =
+						fake_edid_record->ucFakeEDIDLength;
+				else
+					info->fake_edid_size =
+						fake_edid_record->ucFakeEDIDLength * 128;
+
+				info->fake_edid = fake_edid_record->ucFakeEDIDString;
+
+				record += struct_size(fake_edid_record,
+						      ucFakeEDIDString,
+						      info->fake_edid_size);
+			} else {
+				/* empty fake edid record must be 3 bytes long */
+				record += sizeof(ATOM_FAKE_EDID_PATCH_RECORD) + 1;
+			}
+			break;
+		case LCD_PANEL_RESOLUTION_RECORD_TYPE:
+			panel_res_record = (ATOM_PANEL_RESOLUTION_PATCH_RECORD *)record;
+			info->panel_width_mm = panel_res_record->usHSize;
+			info->panel_height_mm = panel_res_record->usVSize;
+			record += sizeof(ATOM_PANEL_RESOLUTION_PATCH_RECORD);
+			break;
+		default:
+			return BP_RESULT_BADBIOSTABLE;
+		}
+	}
+
+	return BP_RESULT_OK;
+}
+
 static enum bp_result get_embedded_panel_info_v1_2(
 	struct bios_parser *bp,
 	struct embedded_panel_info *info)
@@ -1331,6 +1385,10 @@ static enum bp_result get_embedded_panel_info_v1_2(
 	if (ATOM_PANEL_MISC_API_ENABLED & lvds->ucLVDS_Misc)
 		info->lcd_timing.misc_info.API_ENABLED = true;
 
+	if (lvds->usExtInfoTableOffset)
+		return get_embedded_panel_extra_info(bp, info,
+			le16_to_cpu(lvds->usExtInfoTableOffset) + DATA_TABLES(LCD_Info));
+
 	return BP_RESULT_OK;
 }
 
@@ -1456,6 +1514,10 @@ static enum bp_result get_embedded_panel_info_v1_3(
 			(uint32_t) (ATOM_PANEL_MISC_V13_GREY_LEVEL &
 				lvds->ucLCD_Misc) >> ATOM_PANEL_MISC_V13_GREY_LEVEL_SHIFT;
 
+	if (lvds->usExtInfoTableOffset)
+		return get_embedded_panel_extra_info(bp, info,
+			le16_to_cpu(lvds->usExtInfoTableOffset) + DATA_TABLES(LCD_Info));
+
 	return BP_RESULT_OK;
 }
 
diff --git a/sys/dev/pci/drm/amd/display/include/grph_object_ctrl_defs.h b/sys/dev/pci/drm/amd/display/include/grph_object_ctrl_defs.h
index cc467031651..05eda9b28b3 100644
--- a/sys/dev/pci/drm/amd/display/include/grph_object_ctrl_defs.h
+++ b/sys/dev/pci/drm/amd/display/include/grph_object_ctrl_defs.h
@@ -153,6 +153,10 @@ struct embedded_panel_info {
 	uint32_t drr_enabled;
 	uint32_t min_drr_refresh_rate;
 	bool realtek_eDPToLVDS;
+	uint16_t panel_width_mm;
+	uint16_t panel_height_mm;
+	uint16_t fake_edid_size;
+	const uint8_t *fake_edid;
 };
 
 struct dc_firmware_info {