Difference between revisions of "Problem with high power drain in ACPI sleep"

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Revision as of 20:27, 8 July 2005

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

Problem description

Several people realized 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, T43, T43p) 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).
  • This is a driver problem and can be fixed in software. For the T4x series, there is a fix available but it has not yet made its way into the official kernel (as of linux 2.6.12).

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
  • R40
    • 2722-5MG
    • 2722-B3G
    • 2897-GWU
  • R50
    • 1829-7RG
    • 1829-6DM
    • 1836-3SU
  • R51
    • 1829-9MG
    • 1829-EHG
    • 1830-DG4
    • 1836-Q6U
  • T23
    • 2647-???
  • T30
    • 2366-81A
    • 2366-97U
  • T40
    • 2373-MU3
    • 2373-82U
    • 2373-92U
    • 2373-22G
    • 2373-19G
    • 2373-A1U
  • T40p
    • 2373-G1U
    • 2373-G3U
    • 2373-G3G
    • 2373-G1G
    • 2373-G5G
  • T41
    • 2379-DJU
    • 2373-9HU
    • 2373-4FG
    • 2373-4PG
    • 2373-1FG
    • 2373-2FG
    • 2373-6U4
    • 2373-7JU
    • 2373-CY0
    • 2373-TG5
  • T41p
    • 2373-9FU
  • T42
  • X21

Affected Operating Systems

  • Linux, all flavours.
  • Windows, for some models as well (only when using non-IBM drivers).
  • FreeBSD (on the A22M)


  • The cause of the mysterious power drain is the radeon GPU, which requires extra steps to suspend properly. Unfortunately, this fix might break non-Thinkpad machines and therefore is not yet in the official kernel sources.
  • The official bugzilla entry for the radeon suspend issue is in the OSDL Bugzilla. There you can find a patch which will solve the power drain issue.
This solution enables doing suspend-to-D2 on non-PPC-machines, which is not properly documented! Be careful and have a look at the discussion for kernel bug 3022 (see above) before applying the patch. By default, the patch enables the suspend-to-D2 only on machines where it is know to work. This behaviour can be overridden with a module option.
  • Most certainly, the DSDT is not at fault. (Interesting to note: The DSDT from BIOS 3.13 (Nov 04) for the T42p compiles without bugs.)
  • Some additional power savings can be achieved by turning off the wake-on-lan (ethtool -s eth0 wol d). The power drain of the wol feature is far smaller than the radeon bug, but can be noticeable.


For Thinkpads with Radeon graphic driver

You must use a patched version of the radeon frame buffer, even if you are only interested in using the X window system. This modified radeon frame buffer then suspends the radeon chip correctly during ACPI sleep. This patch is not yet in the official (kernel.org) kernels.

The patch contains a list of Thinkpads where it is known to work, and by default only activates on these machines. If you think that your computer would profit from the patch as well, you can force it by including the module parameter radeon_force_sleep=1.

Fedora Core 4 official kernel

Fedora ships a patched radeon frame buffer (radeonfb.ko), but you must enable it yourself. Fedora Core 4 compiles it as a module rather than including it in the kernel, therefore you cannot activate it at boot time. You must arrange for the module to be loaded before X starts (for example, using an init script).

If you want to try the radeon frame buffer, you can enable it as follows (assuming you are at the gdm login screen). First, switch to a console (Ctrl-Alt-F1) and log in as root. Stop X:

init 3

Now you can load the module:

modprobe radeonfb radeon_force_sleep=1

Finally, resume X:

init 5

Fedora Core 3/4 custom kernel

For Fedora Core there are precompiled patched kernels available:

These kernels contain additional thinkpad-related patches, including software suspend2 and trackpoint support. Suspend to disk and suspend to ram should work with them. If your Thinkpad model is not yet whitelisted in the patch, you might have to enable the radeon fix by including the parameter video=radeonfb:radeon_force_sleep=1 on the kernel command line.

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.

Technical Discussion

The 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 divide into 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 other models without radeon graphics

Nothing yet.