https://bugs.freedesktop.org/show_bug.cgi?id=54675
--- Comment #4 from Chris Rankin rankincj@googlemail.com 2012-09-09 11:21:38 UTC --- Apparently, the KMS IRQ can fail even when radeon.audio=0. So it looks like the audio IRQ always fails and sometimes takes the KMS IRQ with it - seemingly at random.