AMD's Alex Deucher just pushed out new power table define statements for the xf86-video-ati and xf86-video-radeonhd drivers. Nothing is yet depending upon these new C define statements within the open-source ATI drivers, but it will allow a variety of new PowerPlay information to revealed.
Among the newly exposed information is for the minimum and maximum fan RPM speeds, thermal controller information, PowerPlay state information, classifications (limited power, 3D performance, UVD engine playback, boot, etc), PCI Express link speed, load balancing controls, voltages, and HT link frequencies. These details are for the R500/600/700 (and R800 Evergreen we would expect to be compatible too) graphics cards through AtomBIOS with PowerPlay, though some of the defines are only relevant to R600+ and other specific ASICs. The PowerPlay table definitions for pre-R500 (Radeon X1000 series) hardware has already been available.
Look for more good information to come soon for power management and the open-source ATI driver. See this commit for the new code.