linux-kernel - Re: [PATCH 5/5] power_supply: add a charge_type status to the api, and use it for olpc driver

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Message-ID: <20090630155713.GG13961@sirena.org.uk>
Date:	Tue, 30 Jun 2009 16:57:14 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Anton Vorontsov <avorontsov@...mvista.com>
Cc:	Andres Salomon <dilinger@...labora.co.uk>, cbou@...l.ru,
	dwmw2@...radead.org, linux-kernel@...r.kernel.org,
	richard@...top.org, Andrew Morton <akpm@...ux-foundation.org>,
	Paul Fox <pgf@...top.org>, dsaxena@...top.org
Subject: Re: [PATCH 5/5] power_supply: add a charge_type status to the api,
	and use it for olpc driver

On Tue, Jun 30, 2009 at 07:37:19PM +0400, Anton Vorontsov wrote:
> On Tue, Jun 30, 2009 at 11:04:30AM -0400, Andres Salomon wrote:

> > As far as the slow type, I don't see the need either, but I assumed
> > Anton was aware of devices that differentiated between slow and
> > trickle charging.

> Yep, there are two charging modes in Openmoko Neo FreeRunners:

> - 100 mA. It's "slow" mode -- used when the Neo couldn't negotiate
>   with USB host, so it is permitted to only draw 100 mA from VBUS.

I strongly suspect you will find that the "slow" mode there is actually
a trickle charge.  It's a lot more practical to trickle charge in mobile
phone sized systems since the batteries are so much smaller than laptop
batteries.  

> - 500/1000 mA. It's so-called "fast" mode, can be enabled after
>   successful negotiation with the USB host.

Even if the 500mA is available you'll not always be able to do a fast
charge from a USB supply - some systems draw enough current to require
that the USB supply be suppliemented from battery when they're being
heavily used.

> Well, this kind slow charging isn't official terminology, and
> I'm not sure if we should use it. But I'm fine with it since we
> can always remove "Slow" mode (i.e. report it as "Fast"), and
> userspace won't break.

I guess my main question was if it was distinguishable from trickle
charging.
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