Seems like AMD is working like crazy with their FOSS contributions lately, and doing a lot of pre-release work for Polaris on Linux. From another article:
The work sitting around since last week is for providing next-gen Polaris GPU support for AMDGPU, clean-ups for the VCE and UVD video encode/decode support, GPUVM improvements, scheduler improvements, clock gating and PowerPlay power management improvements, asynchronous page-flipping support, and many other changes. Polaris is the most dominating part of the Radeon/AMDGPU updates set for Linux 4.7, but aside from that soon-to-launch GPU support there are also many other improvements.
This current Polaris support for Linux 4.7 includes power management, graphics, compute, SDMA, UVD, and VCE support so it's nice and well rounded ahead of the launch.
They also open-sourced their compression tool. I'm really impressed. I hope it pays off for them. I need a video card upgrade soon and things are sounding really good for Radeon on Linux.