On Sunday I wrote that the community beat AMD to Evergreen HDMI audio support. This milestone was largely achieved by Rafał Miłecki, a long-standing open-source contributor. Since his initial patches that were published over the weekend, the community has provided him with more Radeon register dumps to evolve this audio output support.
Rafał has announced via his blog and an email to Phoronix that the Evergreen support should be pretty much complete for stereo support. In his new patches the driver is no longer using a single hard-coded HDMI block, which was done due to not knowing how the HDMI block mapping was handled by the hardware. However, thanks to the dumps from the community -- in part organized on the Phoronix Forums -- a solution was devised. The HDMI block mapping is done based on the DIG encoder, so it should work across the spectrum of Evergreen (Radeon HD 5000 series) graphics cards.
The patch series for the Evergreen support begins with this mailing list message. These patches don't cover the Radeon HD 6000 series (Northern Islands / Cayman) series support, but hopefully AMD will publish their HDMI support patches in the near future to fill in the missing bits. (Right now their patches are still held up in legal review.)
The Evergreen HDMI audio support should at least land in the Linux 3.3 kernel. If you're using the proprietary Catalyst Linux driver, HDMI audio should already work across the spectrum of support graphics cards.
Nice work Rafał Miłecki!