linux-kernel - Re: [PATCH 5/6] power: pcf50633: properly reenable charging when the supply conditions change

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Date:	Thu, 5 Nov 2009 00:16:35 +0100
From:	Pavel Machek <pavel@....cz>
To:	Paul Fertser <fercerpav@...il.com>
Cc:	Anton Vorontsov <cbou@...l.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] power: pcf50633: properly reenable charging when
 the supply conditions change

On Thu 2009-11-05 01:24:31, Paul Fertser wrote:
> Hi,
> 
> On Wed, Nov 04, 2009 at 10:46:22PM +0100, Pavel Machek wrote:
> > On Thu 2009-11-05 00:24:58, Paul Fertser wrote:
> > > If chgmod == BATFULL, setting chgena has no effect. Datasheet says we
> > > need to set resume instead but when autoresume is used resume doesn't
> > > work. Clear and set chgena instead.
> > > 
> > > This enables a user to force charging by re-plugging USB even when the
> > > charger entered Battery Full mode, might be handy before a long
> > > trip.
> > 
> > And is against manufacturer recommendation and will unneccessary
> > shorted life of battery with frequent plugs/unplugs. Is it good idea?
> 
> Well, to me it seems that frequent plugs/unplugs is not exactly common
> usecase so i consider that to be acceptable.

Well, they are quite common here with my HTC Dream at least (I'm not
sure what your device is). Often, I unplug it from 1A charger to
connect it to PC for file transfer, and back.

> Especially comparing to millions of laptops and netbooks that always
> top their battery while being externally powered and heat it at the
> same time, probably the worst conditions lifetime-wise one can
> imagine.

Well, at least thinkpads will not start charging the battery when over
95%. (And the limit is configurable).

> > If you want to "top-up" the battery, perhaps that should be on
> > explicit request, like something in /sys?
> 
> Well, probably but to me it seems like an unnecessary complexity. 

And leaving behaviour before patch, that is "do not charge if battery
is over 80%" -- AFAICT from the changelog.

>Also
> since Li* batteries are dominating the market nowadays this
> functionality would need to be introduced in the power_supply core to
> provide userspace with a consistent interface. Anton, can you please
> comment on this?

I agree that it is not important part of functionality, but at least
Dream, Spitz and Collie could use that support....
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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