[ltp] High power consumption on Z61m

[Johannes Bittner]

Hello,

I own a Thinkpad Z61m, nearly everything runs fine with linux (the
distribution is debian, kernel 2.6.25.4), alas the power consumption is
very high compared to MS Windows. I searched for the reason of the
problem, and noticed that when I unload some USB kernel modules (namely:
ehci_hcd, uhci_hcd), the power consumption is reduced by 5W (!). Here
are the outputs of powertop before respectively after the removal of the
USB kernel modules:

With USB: http://img128.imageshack.us/my.php?image=powertopusbjn5.png
Without: http://img149.imageshack.us/my.php?image=powertopnousbap6.png

In both cases, WLAN/Bluetooth was turned off, display backlight set to
minimum, no USB devices connected except for the internal ones, and no
mouse/keyboard activity.

I really don't know how USB could use that much energy. I have a
internal webcam in my thinkpad (I don't know if there are any current
thinkpad models which have one, as the Z thinkpad series production has
stopped AFAIR) for which I don't have a driver, could this be the reason
for the high power consumption?

I'm using a custom kernel, but the problem remains with a standard
debian kernel, as well as with ubuntu.

Thanks for any help in advance :)

Greets,
Johannes