How to make use of Graphics Chips Power Management features

From ThinkWiki
Revision as of 22:08, 27 October 2005 by Wyrfel (Talk | contribs) (→‎X.org on Debian)
Jump to: navigation, search

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

DynamicClocks in the Radeon Xorg driver

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.

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.

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 or here.

You can also add the following line to your repository list: 

deb http://people.debian.org/~nobse/xorg-x11/ sarge main

External Sources

Retrieved from "https://www.thinkwiki.org/w/index.php?title=How_to_make_use_of_Graphics_Chips_Power_Management_features&oldid=12208"