https://bugs.freedesktop.org/show_bug.cgi?id=59089
--- Comment #11 from Alexandre Demers alexandre.f.demers@gmail.com --- (In reply to comment #9)
Mesa is at latest git, however, my kernel wasn't at Linus' git, so that may be the issue, using HD 6950. I will try the newest kernel and if it doesn't work I'll create a new bug report.
Also, you could see if updating libdrm and/or ddx driver could help, there were some commits for both of them in the last couple of weeks.