linux-kernel - Re: Smart Battery System Design (was: Re: Question about userspace-consumer)

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Message-ID: <20090822092845.GE11448@elf.ucw.cz>
Date:	Sat, 22 Aug 2009 11:28:45 +0200
From:	Pavel Machek <pavel@....cz>
To:	Mark Brown <broonie@...ena.org.uk>
Cc:	Felipe Balbi <me@...ipebalbi.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>,
	Mike Rapoport <mike@...pulab.co.il>,
	linux-kernel@...r.kernel.org
Subject: Re: Smart Battery System Design (was: Re: Question about
	userspace-consumer)

Hi!

> > Ok, well... anyway many machines _want_ fastcharge while suspended,
> > and putting charging into userland would break them (or make that
> > fairly difficult).
> 
> Are you sure that's a real need?  Disabling user interaction I can see
> but forcing the system into sleep doesn't seem to be any particular
> benefit - devices like this tend to be designed to appear to be always
> on and clearly when fast charging there's no need to save power
> > which is

At least zaurus sl-3000c is designed like a notebook -- inactive in
s2ram. It is quite old design.

Charging while suspended is preffered, because it allows faster
charge. The machine eats non-trivial power while active, charger is
only 1A, and there's not enough current left for a charge with machine
active.

> the main motiviation for going into suspend.  Also bear in mind that a
> soft SBS system requires constant activity from the CPU for basic
> management of the charge cycle so suspend isn't going to be a real
> option anyway, you'd be suspending for seconds at a time.

Well, if the code is to be useful for something else than SBS... (And
suspending for seconds at a time is okay on zaurus type machines).

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