There's been Radeon DPM power management since the Linux 3.11 kernel for improving the thermal performance and power consumption of AMD Radeon graphics processors. The results have been great and the Radeon DPM support was extended in the Linux 3.12 kernel.
The latest work on the Radeon power management front has been for adding run-time power management to support Radeon PowerXpress laptops -- mobile systems bearing a combination of Intel and Radeon GPUs. Landed in the Linux 3.12 kernel was GPU run-time power management support but the initial implementation for Optimus laptops.
David Airlie started working on this PowerXpress power management support while it's now been extended by Alex Deucher with this patch series. Alex is reporting the PowerXpress power management support is now working well on the hardware he's had access to testing.