Works with no 3d acceleration on Dragora and Trisquel but not in parabola
By default: does not work, says there is no free firmware, and soon shows garbage (not a hang).
With radeon.modeset=0 or nomodeset in boot options, text console works. Haven't tried starting X.
On Debian GNU/Linux wheezy/sid, it is the same before X is started. If Xorg has been started, showing the text (fb) console requires KMS and the binary-only microcode, sending no signal to the monitor when those are not available. So I say it is not usable.
lspci -nnk: 00:01.0 VGA compatible controller : Advanced Micro Devices [AMD] nee ATI Wrestler [Radeon HD 6310] [1002:9802] Subsystem: ASRock Incorporation Device [1849:9802] Kernel driver in use: radeon