Problem with high power drain in ACPI sleep
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.
Update: it seems that the most significant difference can be made by properly turning off the video chip.
Solutions
A proposed solution is to remove the CONFIG_PPC_PMAC condition for enabling D2 sleep in drivers/video/aty/radeon_pm.c as discussed in kernel bug 3022. There you can also find patches doing this. The patches devide in unconditional ones like this one for 2.6.11-rc2 and conditional ones. The conditional ones only do D2 on models where it has been reported to work, the unconditional ones force D2 sleep on every model and you might experience hangs on resume with those.
For Fedora Core there's are precompiled patched kernels (2.6.11-rc2 based) available:
If you try, please send the result (hang yes/no, battery drain yes/no) with the precise model number (for example, I have a IBM thinkpad T41 2379-DJU) to vbraun at physics dot upenn dot edu, it would be nice if your subject line would include "RADEONFB:" to make sure that I do not miss any emails.
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.
