linux-kernel - Re: [ibm-acpi-devel] [RFC] Controlling the ThinkPad battery charger

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Date:	Mon, 9 May 2011 11:47:40 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	ibm-acpi-devel@...ts.sourceforge.net,
	Anton Vorontsov <cbou@...l.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org
Subject: Re: [ibm-acpi-devel] [RFC] Controlling the ThinkPad battery charger

On Mon, May 9, 2011 at 11:29 AM, Henrique de Moraes Holschuh
<hmh@....eng.br> wrote:
> On Mon, 09 May 2011, Andrew Lutomirski wrote:
>> > The SBS interface exposes more data about the battery, including
>> > per-cell-group voltage and pack microcontroller aging counters, alarms, and
>> > the "needs to get through the fuel-gaugue reset procedure" semasphore.
>>
>> If I'm feeling really motivated, I'll look at that.  I'm currently
>> more interested in the charging thresholds, though, which I think is
>> independent of the choice of SBS vs ACPI to access the battery state.
>> (From a quick glance at the SBS spec, you can inhibit charging
>> entirely but you can't ask for thresholds.  I assume that the EC takes
>> care of that.  If I'm wrong, please tell me, but SMAPI seems like a
>> fine way to access the thresholds.)
>
> Yeah, SMAPI is the safest way to deal with all this.  It is an interface
> layer that Lenovo is not fond of breaking (or touches very rarely.  Amounts
> to the same in the end).
>
> SBS does not take care of thresholds, indeed.  The EC does (and I know how
> to program the threshold in a few models, if you do want to test it in your
> X220, I can send you the information.  It is safe to test if you use it
> together with SMAPI to cross-check).

That would be great.  I think it's EC register 0x24 for the BAT0 stop
threshold and EC register 0x25 for the BAT1 stop threshold.  If you
have any hints about the start threshold I can test them, but I
suspect that, in the X220, the EC figures out the start threshold on
its own.

>
> The SBS ACPI interface would be useful to provide a single driver that can
> replace the ACPI battery one to deliver full functionality in one place.
>

I'll save that for later :)

--Andy

> --
>  "One disk to rule them all, One disk to find them. One disk to bring
>  them all and in the darkness grind them. In the Land of Redmond
>  where the shadows lie." -- The Silicon Valley Tarot
>  Henrique Holschuh
>
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