https://bugs.freedesktop.org/show_bug.cgi?id=43829
--- Comment #16 from Helge Bahmann hcb@chaoticmind.net --- (In reply to comment #15)
A patch referencing this bug report has been merged in Linux v3.7-rc1:
commit bced76f27165ca7733437715185c3a1aa526f7a1 Author: Alex Deucher alexander.deucher@amd.com Date: Fri Sep 14 09:45:50 2012 -0400
drm/radeon: restore backlight level on resume
appears to be the same patch as mentioned in comment #10, and (at least for me) still does not fix the issue