drm/amd/display: Report non-DP display as disconnected without EDID

[Why]
Some boards seem to have a problem where HPD is high on HDMI even though
no display is connected. We don't want to report these as connected. DP
spec still requires us to report DP displays as connected when HPD is
high but we can't read the EDID in order to go to fail-safe mode.

[How]
If connector_signal is not DP abort detection if we can't retrieve the
EDID.

v2: Add Bugzilla and stable

Bugzilla: https://bugs.freedesktop.org/107390
Bugzilla: https://bugs.freedesktop.org/106846
Cc: stable@vger.kernel.org
Signed-off-by: NHarry Wentland <harry.wentland@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NNicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -744,6 +744,17 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
 			break;
 		case EDID_NO_RESPONSE:
 			DC_LOG_ERROR("No EDID read.\n");
+
+			/*
+			 * Abort detection for non-DP connectors if we have
+			 * no EDID
+			 *
+			 * DP needs to report as connected if HDP is high
+			 * even if we have no EDID in order to go to
+			 * fail-safe mode
+			 */
+			if (!dc_is_dp_signal(link->connector_signal))
+				return false;
 		default:
 			break;
 		}