How to make use of Graphics Chips Power Management features

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ATI Radeon Mobility chips

Power saving with a framebuffer console

In order to use the dynamic GPU clock-scaling similar to what X.org has, you need to use the radeonfb kernel module. You'll need to enable the CONFIG_FB_RADEON in your kernel configuration. If setup correctly you should see something like the following in your kernel log: 

radeonfb: Dynamic Clock Power Management enabled

Using the X.org Radeon driver

Activation

The xorg X server has support for a power saving feature from ATI called PowerPlay. Xorg calls this feature DynamicClocks. It can be enabled in the server by adding Option "DynamicClocks" "on" in the Device section in /etc/X11/xorg.conf 

Section "Device"
       Identifier  "Videocard0"
       Driver      "radeon"
       VendorName  "IBM ThinkPad"
       BoardName   "ATI Radeon Mobility M9"
       Option      "DynamicClocks" "on"
EndSection

With this option enabled, the X11 server should print (/var/log/Xorg.0.log): 

(**) RADEON(0): Option "DynamicClocks" "on"
(II) RADEON(0): Dynamic Clock Scaling Enabled

You do not need to do anything else, it dynamically manages the power consumption itself.

NOTE!
Enabling DynamicClocks crashes some models. If the CPU is entering one of the lower power states (C3 or lower) during Xorg startup the display may stay black. As a workaround disable DynamicClocks in Xorg and use Rovclock instead. But it does not scale the clocks to match the workload. Update 5/2/2006: Seems fixed in Xorg6.9

Problem with vbetool

When vbetool is used to restore the display state (as done by some suspend/resume scripts), the setting of DynamicClocks is forgotten and the GPU will consume more power until the next X server startup. You can manually enable DynamicTools again by starting a blank second X server (e.g., by running # X :1) and then exiting it via CtrlAltBackspace.

Problem with suspend-to-disk

Upon resume from suspend-to-disk, the setting of DynamicClocks is forgotten and the GPU will consume more power until the next X server startup. You can manually enable DynamicClocks again by starting a blank second X server (e.g., by running # X :1) and then exiting it via CtrlAltBackspace.

If you're using the hibernate script that's part of Software Suspend 2, setting UseDummyXServer to yes in hibernate.conf automatically starts a second X server, hence enabling DynamicClocks again. (Remember to disable UseDummyXServer if you switch to the fglrx driver, otherwise your computer will hang upon resume.)

NOTE!
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Debian Notes

If your Debian doesn't have Xorg, yet, see Installing a non-intrusive X.org server on Debian.

Sarge backports are available from here.

For those running Squeeze or later the radeon driver now uses kernal-mode-settings (KMS) by default. At this time, squeeze/sid do not have power management support for radeon in KMS. To enable UMS (user mode settings) which uses the xorg.conf edits above (and therefore gives you power management) you must change modeset=1 to modest=0 in /etc/modprobe.d/radeon-kms. Additionally, on a t60 running squeeze "DynamicPM" "on" worked, whereas "DynamicClocks" "on" failed.

Using the ATI proprietary driver

Versions 8.19.10 and higher of the ATI fglrx driver support "PowerPlay", which "allows for the user to switch between power consumption modes".

To list available modes do:

# aticonfig --list-powerstates
   core/mem     [flags]
---------------
1: 105/122 MHz  [low voltage]
2: 209/182 MHz  [low voltage]
3: 297/230 MHz  [default state]

(Strangely, the same ThinkPad T43 with ATI Mobility Radeon X300 running fglrx 8.19.10 sometimes gives other, non-sensical results, perhaps due to interaction with rovclock.)

To changing the power mode on the fly:

# aticonfig --set-powerstate=2 --effective=now
NOTE!
The powerstate command is exclusive in newer versions of fglrx. All other commands will be ignored.

With newer driver versions (8.26 and later), atieventsd should dynamically change the power state and clock, depending on thermal conditions and AC plug.

Limitations (as of fglrx 8.19.10):

  • You can't set the power state in /etc/X11/xorg.conf .
  • You can't activate power saving when using dual-head mode (e.g., LCD+CRT).
NOTE!
fglrx power saving is not compatible with the Rovclock utility. Setting power saving mode using both fglrx and Rovclock results in an unusably slow desktop.

External sources

Other graphics chips

No instructions are presently known for other chips.

But see Problem with display remaining black after resume.

Recent kernel and X with kernel modesetting (KMS)

On recent systems (e.g. Ubuntu Maverick) with kernel modesetting 

echo profile > /sys/class/drm/card0/device/power_method
echo low > /sys/class/drm/card0/device/power_profile

switches to low power mode. (On a T43 this is too slow to play fullscreen video.) See also Power saving with the Radeon driver.

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