Comment 6 for bug 19711

Disabling the loading of the dri module in xorg.conf gives a ratio of approx.
3/2 for the states C3/C2 as reported by /proc/acpi/processor/CPU0/power.

Enabling the dri modules changes the ratio to approx. 0.00001/1. That is, the
CPU nearly never enters C3 power saving mode.

Example output:
cat /proc/acpi/processor/CPU/power
active state: C2
max_cstate: C8
bus master activity: 08888844
states:
    C1: type[C1] promotion[C2] demotion[--] latency[000]
usage[00000010]
   *C2: type[C2] promotion[C3] demotion[C1] latency[001]
usage[02173881]
    C3: type[C3] promotion[--] demotion[C2] latency[085]
usage[00000047]

Typical time on battery decreases from appr. 2h45m to 2h15m. (This is with KDE
started but no special program activity such as glxgears or whatever.)

System is a Thinkpad X31, Debian unstable, Radeon driver 6.5.8.0-1,
libgl1-mesa-dri 6.5.0beta (driver from 060327).

I don´t know if this is an expected behaviour. It affects battery time quite a
lot though.

If you need any more infos, I´ll be glad to deliver them.

Michael