drm-radeon-testing is the cutting edge KMS radeon branch, it is going to be rebased and things will be added/removed as they are worked on by developers. So you can base patches on it but you should talk to the developer who owns the area first.
I've just pushed a rebased tree now with the following:
latest i2c algo + hw i2c engine code + all fixes squashed: This adds support for hw i2c engines found on radeons and
exposes them + sw i2c buses to userspace so i2c tools can use them. (agd5f).
pll algorithm reworking + quirks: cleans up the code to allow for the selection of the old pll algorithm on some hardware. (agd5f)
pm support so far: Adds all the current PM patches - just does engine reclocking so far using the power tables from the BIOS. (Zajec/agd5f)
Evergreen (Radeon HD 5xxx) support: basic KMS support for the evergreen range of devices - no irqs or accel yet. (agd5f)
radeon unlocked ioctl support (airlied)
bad CS recording (glisse)
misc cleanups/fixes - Dell/Sun server support ported from userspace hopefully.
The tree did contain Jerome's r600 CS checker but I've dropped it for now at his request as he has newer patches