This xf86-video-ati DDX driver update has the recently merged support for acceleration on Cayman GPU, Fusion tiling fixes, and other miscellaneous fixes. Within the DDX driver, the Radeon HD 6900 "Cayman" series finally has EXA and X-Video acceleration support that was just very recently merged although the hardware itself is several months old. The X.Org driver has already had this same level of acceleration support for the rest of the Radeon HD 6000 "Northern Islands" hardware, albeit there's still problems elsewhere in the stack.
This point release also has in new PCI IDs, Fusion tiling fixes, hardware DFS support for Fusion, DRI2, KMS, and EXA fixes, etc.
The release announcement with source download link can be found on the X.Org mailing list.
Speaking of AMD Cayman, shortly after the DDX acceleration push, the necessary 3D acceleration bits for the Radeon HD 6900 series had also landed in the AMD Gallium3D "R600g" driver. Namely, this code commit with over 1,500 lines of changes to support this latest generation of Radeon hardware. This will be part of Mesa 7.11.