drm/amd/display: Guard Freesync HDMI parsing with dc_lock

[Why]
All calls into DC must be guarded by dc_lock because DC code
is not safe against multi-thread or re-entry.

[How]
Hold dc_lock when calling DC interfaces to parse Freesync HDMI.
Reviewed-by: Roman Li <Roman.Li@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -10213,11 +10213,15 @@ static bool parse_edid_cea(struct amdgpu_dm_connector *aconnector,
 		struct amdgpu_hdmi_vsdb_info *vsdb_info)
 {
 	struct amdgpu_device *adev = drm_to_adev(aconnector->base.dev);
+	bool ret;
 
+	mutex_lock(&adev->dm.dc_lock);
 	if (adev->dm.dmub_srv)
-		return parse_edid_cea_dmub(&adev->dm, edid_ext, len, vsdb_info);
+		ret = parse_edid_cea_dmub(&adev->dm, edid_ext, len, vsdb_info);
 	else
-		return parse_edid_cea_dmcu(&adev->dm, edid_ext, len, vsdb_info);
+		ret = parse_edid_cea_dmcu(&adev->dm, edid_ext, len, vsdb_info);
+	mutex_unlock(&adev->dm.dc_lock);
+	return ret;
 }
 
 static int parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,