That patch just adds the correct register defines, to replace the current reverse-engineered info. It doesn't change functionality on its own but it provides programming info which should help with the remaining work.
Alex emailed two more patches to dri-devel; one which fixes interrupts and another which needs more work so was pushed to agd5f's repo rather than upstream kernel.
interrupts : http://lists.freedesktop.org/archive...ch/020855.html
the rest : http://lists.freedesktop.org/archive...ch/020857.html