Tip: power management settings for Radeon

From kernel 2.6.35 and up Radeon driver supports power management (PM). The default behavior is performance oriented, thus if you want to save some power you will need to tune the defaults. You can select from two PM methods: dynpm and profile. The dynpm method dynamically change the GPU clocks according to GPU load. With this method you have enough performance when needed and power savings when in idle. But this method can cause flickering during reclocking and doesn't support multi heads. To activate this method use:

# echo dynpm > /sys/class/drm/card0/device/power_method

With profile method you can select from several profiles: default, auto, low, mid and high. Default settings is the default profile. It uses default clocks and doesn't change power states. The low, mid, high profiles change the GPU clocks accordingly. The auto profile switches automatically between high and mid depending whether the system is running on AC or battery. It also switches to low when the monitors are in dpms off. Not all cards supports all profiles. For example to activate the auto profile, use:

# echo profile > /sys/class/drm/card0/device/power_method
# echo auto > /sys/class/drm/card0/device/power_profile

More details can be found on http://www.x.org/wiki/RadeonFeature.

We also added experimental support for this to tuned. We activate the power savings in desktop and laptop profiles. The code is currently in tuned git.