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

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 27df17a0e620..89c3dd62ba21 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.