AMD has made known the changes they have lined up for the Linux 3.13 kernel
merge window. Among the work includes finally enabling Radeon Dynamic Power Management (DPM) for some graphics processors and also restoring HDMI audio support to be enabled by default.
The initial pull request changes to be merged for the Linux 3.13 kernel that affect the Radeon DRM graphics driver include enabling Dynamic Power Management for some ASICs by default, HDMI audio by default, dynamically powering down discrete GPUs on PowerXpress systems, and shipping a lot of bug-fixes.
appeared in the Linux 3.11 kernel to save power and boost performance for some GPUs but was disabled by default. Dynamic Power Management was further improved in the 3.11 and 3.12 kernel cycles. Now with 3.13, it will be enabled by default. DPM is to be enabled by default for Radeon HD 4000 through Radeon HD 7000 series graphics processors but with some specific ASICs being excluded. See this article
for details on the many Radeon DPM improvements.
The other nice power change for Radeon owners with the Linux 3.13 kernel is support for dynamically powering on/off discrete GPUs as part of ATI/AMD PowerXpress systems.
The Radeon HDMI audio support by default comes after the support has long been available but has been turned off since for a small number of users it caused adverse problems. The Radeon HDMI audio problems now appear to be worked out so with Linux 3.13 they will attempt to turn it on for all users.
More details on the Radeon changes queued up for Linux 3.13 can be found on the dri-devel mailing list