https://bugs.freedesktop.org/show_bug.cgi?id=72785
--- Comment #22 from Alex Deucher agd5f@yahoo.com --- If you are using 3.14, you may have to force your performance level to high or revert this patch for SI parts: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ff...