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

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Date:	Sun, 24 Sep 2006 22:20:25 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Theodoros V. Kalamatianos" <thkala@...tlab.ece.ntua.gr>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>,
	Linux usb mailing list 
	<linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [linux-usb-devel] usb still sucks battery in -rc7-mm1

Hi!

> >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.
								Pavel 
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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