For UVD on older Radeons, this post has the latest information from AMD. In short: it is implemented, but legal review is holding the release up, possibly indefinitely.
Originally Posted by jakubo
i wonder if glamor on SI can outperform evergreens dedicated 2D hardware support (without much CPU overhead) - efficiency-wise
There is no dedicated 2D hardware on Evergreen (well if you don't count the hardware overlay for the mouse cursor...)