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

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Date:	Sun, 24 Sep 2006 23:05:27 +0200
From:	Pavel Machek <pavel@....cz>
To:	Alan Stern <stern@...land.harvard.edu>
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?
> 
> The USB autosuspend patches are still not entirely in -mm.  They contain a
> couple of bugs that have to get fixed first.  When they do get merged you
> should see considerable improvement.  Note that although they will reduce
> the amount of power being used by the USB controllers and will stop the
> DMA activity (thus allowing your CPU to enter C2), they won't put the
> controllers into D3.  For that you'll have to get PCI autosuspend...
> :-)

I have not measured that, but I _hope_ drain by controller itself will
not be big enough.

> In the meantime, if all you care about is power consumption there are 
> some things you can do.  The easiest is simply to rmmod ehci-hcd, 
> ohci-hcd, and uhci-hcd.  After all, if you're not using USB there's no 
> reason to let the drivers eat up memory, CPU time, and power.

Are autosuspend patches available somewhere? (Relative to -mm, or
relative to 2.6.18?) I'd like to play with them...
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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