[linux-pm] Re: [RFC][PATCH] swsusp: warn about USB devices in documentation

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On Po 20-02-06 11:41:49, Alan Stern wrote:
> On Mon, 20 Feb 2006, Pavel Machek wrote:
> 
> > Hi!
> > > > > Can you update the patch to fix this paragraph?
> > > > 
> > > > Well, this is talking about suspend-to-disk... That is expected to
> > > > power down machine, without providing USB bus power. If box
> > > > suspends-to-disk and leaves USB up, something is wrong with the
> > > > machine.
> > > 
> > > Oh, sorry, I didn't realize that.
> > > 
> > > Isn't there an ACPI mode that powers down most things (including RAM) but
> > > is able to respond to wakeup events?  I can't remember the mode's name,
> > > except that it's almost certainly "S" followed by some meaningless number
> > > followed by some unhelpful word. :-)  Since USB plug/unplug is potentially
> > > a wakeup event, such a mode must provide suspend power to the USB
> > > controller.
> > 
> > Maybe S4 does that, but I'm not sure...
> > 
> > > Does swsusp still support these not-completely-powered-off modes?
> > 
> > Yes. echo platform > /sys/power/disk.
> 
> So if you did that, you could suspend-to-disk while leaving USB up, right?  
> Without anything being wrong with the machine.

Not sure... never seen such machine. My impression is that USB needs
more power than RAMs in self-refresh mode...

You are right that maybe some machines where USB has power in S4
exist.. I never seen one.
								Pavel
-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...

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