drm/amd/display: Prevent dpcd reads with passive dongles

[why]
During hotplug, a DP port may be connected to the sink through
passive adapter which does not support DPCD reads. Issuing reads
without checking for this condition will result in errors

[how]
Ensure the link is in aux_mode before initiating operation that result
in a DPCD read.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 94c29b7..9c83c13 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2008,17 +2008,22 @@ void amdgpu_dm_update_connector_after_detect(
                dc_sink_retain(aconnector->dc_sink);
                if (sink->dc_edid.length == 0) {
                        aconnector->edid = NULL;
-                       drm_dp_cec_unset_edid(&aconnector->dm_dp_aux.aux);
+                       if (aconnector->dc_link->aux_mode) {
+                               drm_dp_cec_unset_edid(
+                                       &aconnector->dm_dp_aux.aux);
+                       }
                } else {
                        aconnector->edid =
-                               (struct edid *) sink->dc_edid.raw_edid;
-
+                               (struct edid *)sink->dc_edid.raw_edid;
 
                        drm_connector_update_edid_property(connector,
-                                       aconnector->edid);
-                       drm_dp_cec_set_edid(&aconnector->dm_dp_aux.aux,
-                                           aconnector->edid);
+                                                          aconnector->edid);
+
+                       if (aconnector->dc_link->aux_mode)
+                               drm_dp_cec_set_edid(&aconnector->dm_dp_aux.aux,
+                                                   aconnector->edid);
                }
+
                amdgpu_dm_update_freesync_caps(connector, aconnector->edid);
                update_connector_ext_caps(aconnector);
        } else {