The key features of this xf86-video-ati driver point release is the DDX support for the AMD Fusion "Trinity" APUs (also requires the updated Mesa / DRM / libdrm), 2D tiling support for R600+ ASICs, KMS tiling support for R100 and R200 ASICs, and lots of bug-fixes. Benchmarks of the new R600+ 2D color tiling support can be found in Radeon Gallium3D Still Long Shot From Catalyst.
The R100/R200 hardware finally handles KMS tiling, although the old hardware support should just die. Newer Radeon hardware has already supported KMS tiling.
Bug fixes for this Radeon X.Org driver update are listed in the mailing list release announcement.
On a related note, when it comes to HDMI/DisplayPort audio, there is some unfortunate news. Yesterday I reported that a new Radeon DRM patch with a lot of new audio registers was published by AMD.
Lastly, Alex Deucher of AMD published some new register definitions today for HDMI/DisplayPort audio for the Radeon DRM driver. See this mailing list post. DCE2 was introduced on the R600 series (Radeon HD 2000), DCE3 was on the RV620/RV635/RS780/RS880 (Radeon HD 3000 series), DCE3.1 for the RV770, DCE3.2 for the RV710/730/740, DCE4 for the Radeon HD 5000 series, and DCE5 is the Radeon HD 6000 series. (The new Radeon HD 7000 series is on DCE6.)
This patch simply drops in all of these new defines for the Radeon HD 2000/3000/4000/5000/6000 series audio, but no actual code implementation. Since last year open-source Radeon users were waiting for Evergreen-era HDMI audio support, but the code was tied up in legal/technical review at AMD. In the meantime, the HDMI audio support was reverse-engineered with basic support in place and the code was already merged to mainline. It looks like AMD's more extensive audio code is finally clearing the review process and making it out several months later.
Unfortunately, of AMD's legal/technical review of the DisplayPort/HDMI audio code for modern generations of their Radeon GPUs, it was only these register definitions that they were able to release. Last night within the Phoronix Forums, AMD's John Bridgman wrote, "We weren't able to release the full HDMI audio implementation developed internally -- the data structures relied on some other standards where it wasn't clear we could get rights to use it in open source code -- but we did get the final bit of approval today to release register info for the blocks that control HDMI audio on newer chips." Hopefully Rafał Miłecki, the one that reverse-engineered the Evergreen audio support a few months back, will now be able to fill in the blanks.