Problem with high power drain in ACPI sleep

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Information about the problem of too high power drain in ACPI sleep mode.

Problem description

Several people realised that their ThinkPads eat up too much power while suspended to ram via ACPI. Compared to APM suspend to ram the power drain is experienced to be about 10 times as high, 2-5 Watts. This empties the battery within one or two days.

Affected Models

  • Different symptoms have been reported for different models. In some models the origin of the power drain is obvious (backlight on during suspend), in other models there is no obvious reason.
  • On some models/configurations the higher power drain couldn't even be realized or was at least significantly lower.
  • The T4x thinkpad series (T40, T40p, T41, T41p, T42, T42p) suspends to ram just fine, and there are no components that are obviously left powered up. The ultrabay and network light is on, but that is the same under windows (but under APM sleep to RAM those lights are OFF).

The following table gives an overview of the models suffering from the mysterious power drain. To find out about your model, you may use the following script. It creates a file /var/log/battery.log which will tell you if you are affected or not.

affected models unaffected models

Affected Operating Systems

  • Linux, all flavours.
  • Windows, for some models as well (only when using non-IBM drivers).

Status

The cause of the problem is not really clear, yet.

A faulty DSDT might be responsible for the phenomena. The thinkpad T4x DSDT has a few small bugs, none of which should cause the extra power drain. (Interesting to note: The DSDT from BIOS 3.13 (Nov 04) for the T42p compiles without bugs.)

There is a interesting discussion taking place in the OSDL Bugzilla.

Solutions

A proposed solution is to remove the CONFIG_PPC_PMAC condition in drivers/video/aty/radeon_pm.c as discussed in kernel bug 3022. There you can also find a proposed patch doing this.

ATTENTION!
This solution enables doing suspend-to-D2 on non-PPC-machines, which is not tested at all and supposed to be the wrong thing to do! Be careful and have a look at the bugs discussion before applying the patch.

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