Comment # 9 on bug 56561 from dmotd

(In reply to comment #7)
> Make sure you have the radeon firmware installed and available in your
> initrd if you are using one.


The firmware should be loading (I am using stock arch linux kernels), when
3.4.7 or 3.6.3-nomodeset boots I see '[drm] Loading R500 Microcode' in the
logs. (Sorry I wrote r300 in the bug title which should be r500).