From: Harry Wentland <harry.wentland@amd.com>
Date: Thu, 2 Aug 2018 15:32:01 -0400
Subject: drm/amd/display: Only require EDID read for HDMI and DVI
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Git-commit: 16196776185cb19bb8c2318ebd1dbbefb5350d6a
Patch-mainline: v4.19-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

[Why]
VGA sometimes has trouble retrieving the EDID on very long cables, KVM
switches, or old displays.

[How]
Only require EDID read for HDMI and DVI and exempt other types (DP,
VGA). We currently don't support VGA but if anyone adds support in the
future this might get overlooked.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Suggested-by: Michel Dänzer <michel@daenzer.net>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -753,7 +753,8 @@ bool dc_link_detect(struct dc_link *link
 			 * even if we have no EDID in order to go to
 			 * fail-safe mode
 			 */
-			if (!dc_is_dp_signal(link->connector_signal))
+			if (dc_is_hdmi_signal(link->connector_signal) ||
+			    dc_is_dvi_signal(link->connector_signal))
 				return false;
 		default:
 			break;