From: Timur Kristóf <timur.kristof@gmail.com>
Date: Tue, 28 Apr 2026 11:40:44 +0000 (+0200)
Subject: drm/amd/display: Read EDID from VBIOS embedded panel info
X-Git-Tag: v7.1-rc2~7^2~1^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9ea16f64189bf7b6ba50fc7f0325b3c1f836d105;p=thirdparty%2Fkernel%2Flinux.git

drm/amd/display: Read EDID from VBIOS embedded panel info

Some board manufacturers hardcode the EDID for the embedded
panel in the VBIOS. This EDID should be used when the panel
doesn't have a DDC.

For reference, see the legacy non-DC display code:
amdgpu_atombios_encoder_get_lcd_info()

This is necessary to support embedded connectors without DDC.

Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5192
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit eb105e63b474c11ef6a84a1c6b18100d851ff364)
---

diff --git a/drivers/gpu/drm/amd/display/dc/bios/bios_parser.c b/drivers/gpu/drm/amd/display/dc/bios/bios_parser.c
index e270b1d2457c..c307f42fe0b9 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/bios_parser.c
+++ b/drivers/gpu/drm/amd/display/dc/bios/bios_parser.c
@@ -1313,6 +1313,60 @@ 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)
@@ -1429,6 +1483,10 @@ 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;
 }
 
@@ -1554,6 +1612,10 @@ 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/drivers/gpu/drm/amd/display/include/grph_object_ctrl_defs.h b/drivers/gpu/drm/amd/display/include/grph_object_ctrl_defs.h
index 38a77fa9b4af..a0f03fb67605 100644
--- a/drivers/gpu/drm/amd/display/include/grph_object_ctrl_defs.h
+++ b/drivers/gpu/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 {