Re: [linux-usb-devel] usb still sucks battery in -rc7-mm1

From: Pavel Machek
Date: Sun Sep 24 2006 - 16:21:11 EST


> >I made some quick experiments, and usb still eats 4W of battery
> >power. (With whole machine eating 9W, that's kind of a big deal)...
> >
> >This particular machine has usb bluetooth, but it can be disabled by
> >firmware, and appears unplugged. (I did that). It also has fingerprint
> >scanner, that can't be disabled, but that does not have driver (only
> >driven by useland, and was unused in this experiment).
> >
> >Any ideas?
> (I have not followed the thread, so bear with me if I say anything
> irrelavant)
> I have encountered at least 3 hubs (2 usb2 & 1 usb1) that will consume a
> lot of power (about 2-2.5W if the laptop power consumption readings are to
> be trusted) and heat up a lot (to the point of being too hot to touch for
> more than a few seconds) even when no devices are connected, at least on
> Linux. I have not tested them on a Windows machine to see if this is the
> case there. The USB2 ones used Cypress chips. I do not know what your h/w
> config is, but perhaps this is a similar case ?

> PS: Note that the 2-2.5W consumption is the maximum that the laptop USB
> port can provide, and I have noticed that with the hub's external power
> supply connected it heats up even more.

I'm not using any external hubs. I believe it is old "uhci keeps cpu
from reaching deep c states" problem. I just want to ping greg/list,
because greg told me problem is solved in -mm.
(cesky, pictures)
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