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From a887adadb7b9ef9eb4ee48e4ad575aefcfd1db14 Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@amd.com>
Date: Fri, 21 Aug 2015 18:07:38 -0400
Subject: [PATCH 0475/1050] drm/amdgpu: Don't link train DisplayPort on HPD
 until we get the dpcd

This is a port of:
DRM - radeon: Don't link train DisplayPort on HPD until we get the dpcd
to amdgpu.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 27df17a..89c3dd6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -75,6 +75,11 @@ void amdgpu_connector_hotplug(struct drm_connector *connector)
 			if (!amdgpu_display_hpd_sense(adev, amdgpu_connector->hpd.hpd)) {
 				drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
 			} else if (amdgpu_atombios_dp_needs_link_train(amdgpu_connector)) {
+				/* Don't try to start link training before we
+				 * have the dpcd */
+				if (!amdgpu_atombios_dp_get_dpcd(amdgpu_connector))
+					return;
+
 				/* set it to OFF so that drm_helper_connector_dpms()
 				 * won't return immediately since the current state
 				 * is ON at this point.
-- 
1.9.1