drm/amd/display: Fix wrong resolution with DP/VGA adapter

[Why]
Hotplugging the VGA side of some DP/VGA adapters caused the display to
light up with the wrong (non-native) resolution.

This is caused by the adapter misbehaving by reporting the wrong number
of downstream ports when the VGA side is unplugged (reports 1 instead of
0), but only if the SINK_COUNT DPCD register is read more than once.

[How]
To work around the adapter behavior, remove the sink if link is
detected, but EDID cannot be read.
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Signed-off-by: Ilya <Ilya.Bakoulin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -1197,6 +1197,22 @@ static bool detect_link_and_local_sink(struct dc_link *link,
 
 				return false;
 			}
+
+			if (link->type == dc_connection_sst_branch &&
+					link->dpcd_caps.dongle_type ==
+						DISPLAY_DONGLE_DP_VGA_CONVERTER &&
+					reason == DETECT_REASON_HPDRX) {
+				/* Abort detection for DP-VGA adapters when EDID
+				 * can't be read and detection reason is VGA-side
+				 * hotplug
+				 */
+				if (prev_sink)
+					dc_sink_release(prev_sink);
+				link_disconnect_sink(link);
+
+				return true;
+			}
+
 			break;
 		default:
 			break;

drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c

@@ -298,6 +298,9 @@ static uint32_t defer_delay_converter_wa(
 
 	if (link->dpcd_caps.dongle_type == DISPLAY_DONGLE_DP_VGA_CONVERTER &&
 		link->dpcd_caps.branch_dev_id == DP_BRANCH_DEVICE_ID_0080E1 &&
+		(link->dpcd_caps.branch_fw_revision[0] < 0x01 ||
+				(link->dpcd_caps.branch_fw_revision[0] == 0x01 &&
+				link->dpcd_caps.branch_fw_revision[1] < 0x40)) &&
 		!memcmp(link->dpcd_caps.branch_dev_name,
 		    DP_VGA_DONGLE_BRANCH_DEV_NAME,
 			sizeof(link->dpcd_caps.branch_dev_name)))