Comment 372 for bug 370173

I neglected to mention that to use the new power management feature on R700 and newer hardware (other than APUs) requires installation of the latest AMD graphics microcode (ucode) files to /lib/firmware/radeon
These are available at http://people.freedesktop.org/~agd5f/radeon_ucode/
Get the version ending in "smc".

R700 basically means Radeon HD 4000 series and newer. However note that according to Wikipedia and http://xorg.freedesktop.org/wiki/RadeonFeature/#index5h2 the Mobility Radeon HD 4225/4250 is a RV620 chip, so anyone with one of those shouldn't need the updated firmware files.