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

From: Pavel Machek
Date: Sun Sep 24 2006 - 17:06:03 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?
> 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...
(cesky, pictures)
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