Open-Source AMD Polaris Audio Support Isn't Coming Until DAL Lands

Just as a quick word of warning, the open-source AMD Linux driver stack won't be supporting HDMI/DP audio with the new Radeon RX 460/470/480 "Polaris" graphics cards until its massive DAL code-base is merged.

Alex Deucher of AMD has confirmed via a bug report that Polaris audio support is only supported by the DAL display abstraction code that isn't yet mainlined.

DAL is a massive chunk of code that received some early criticism and is still being cleaned up for mainline acceptance. DAL's code is originally derived in a large part from the proprietary AMD driver stack. DAL will allow more features to the AMDGPU driver, such as FreeSync support to be implemented over DAL and proper HDMI 2.0 support. Polaris audio is another feature depending upon DAL.

The DAL code didn't get mainlined for Linux 4.8 (nor was it proposed for merging during this cycle) so now this functionality won't be present until at least the Linux 4.9 kernel. Unfortunately, Linux 4.9 makes it out of reach for the stock kernel of Ubuntu 16.10 and Fedora 25. Linux 4.9 will be released late in the year.

For the time being there are the options of this branched code that has the DAL support present in a 4.6-based kernel or using the AMDGPU-PRO driver with its out-of-tree module.