A patch referencing this bug report has been merged in Linux v3.9-rc4:

commit fa8d387dc3f62062a6b4afbbb2a3438094fd8584
Author: Alex Deucher <alexander.deucher@amd.com>
Date:   Tue Mar 12 12:53:13 2013 -0400

    drm/radeon/benchmark: make sure bo blit copy exists before using it