While Linux 4.5 brings support for PowerPlay in the AMDGPU DRM driver to allow the modern discrete Radeon graphics cards to run much faster thanks to re-clocking, this major feature isn’t being enabled by default for Linux 4.5. 

AMDGPU PowerPlay for graphics cards like Tonga and Fiji isn’t enabled by default with the code in DRM-Next for Linux 4.5. There are basically two steps needed to ensure there is working AMDGPU PowerPlay support on 4.5.