While the Ubuntu Kernel Mainline PPA continues producing daily Linux kernel Git builds, sadly they do not yet enable the CONFIG_AMD_DRM_POWERPLAY Kconfig option needed for compiling the PowerPlay support in the AMDGPU driver. Thus even with the latest Ubuntu daily kernel, you won't get any decent performance out of this driver. Hopefully they'll end up enabling this option in the Ubuntu kernel builds by the time Linux 4.5 is stable. Upstream, this option is disabled by default.
Therefore I went ahead and spun up a Linux 4.5-rc1 kernel for Ubuntu x86_64 systems with this kernel enabled. However, even with this option enabled, you still need to pass the amdgpu.powerplay=1 kernel module parameter for enabling the support at runtime, as previously detailed in How To Use AMDGPU PowerPlay On The Linux 4.5 Kernel. But at least now you don't need to rebuild this kernel yourself.
Additionally, this kernel build I uploaded today also enables CONFIG_DRM_AMDGPU_CIK. This option enables the AMDGPU DRM driver to work for Sea Islands GPUs. This was the unofficial option for pre-Tonga hardware where AMD had initially developed this driver but then disabled the support since the CIK GPUs are already supported by Radeon DRM. However, given the new Catalyst driver and forthcoming Vulkan driver being tied to the AMDGPU driver, enabling AMDGPU support for older GCN GPUs is one of the options being looked at by AMD. So if you want to test it, go ahead and try this kernel.
You can download this AMDGPU PowerPlay-enabled Linux 4.5-rc1 kernel build via Phoronix.net.