From: Jerry Zuo <Jerry.Zuo@amd.com>
Date: Fri, 8 Sep 2017 16:40:34 -0400
Subject: drm/amd/display: Fix NULL pointer on MST chained mode
Git-commit: fc17235fe65b0179969e0793a086cba93afcc078
Patch-mainline: v4.15-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Prevent NULL pointer on new_stream being added to ctx
when added MST connectors cannot be found in existing crtc_state
in the chained mode

Signed-off-by: Jerry Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4462,6 +4462,13 @@ static int dm_update_crtcs_state(struct
 			*lock_and_validation_needed = true;
 
 		} else {/* Add stream for any updated/enabled CRTC */
+			/*
+			 * Quick fix to prevent NULL pointer on new_stream when
+			 * added MST connectors not found in existing crtc_state in the chained mode
+			 * TODO: need to dig out the root cause of that
+			 */
+			if (!aconnector || (!aconnector->dc_sink && aconnector->mst_port))
+				continue;
 
 			if (modereset_required(new_crtc_state))
 				goto next_crtc;