Date: Mon, 19 Jan 2004 18:44:23 +0100
To: Dave Jones <davej@redhat.com>, Robert Love <rml@ximian.com>,
       Matthew Garrett <mgarrett@chiark.greenend.org.uk>,
       linux-kernel@vger.kernel.org
Subject: Re: Laptops & CPU frequency
Message-ID: <20040119174423.GA29844@poupinou.org>
References: <20040111025623.GA19890@ncsu.edu> <20040111025623.GA19890@ncsu.edu> <1073791061.1663.77.camel@localhost> <E1Afj2b-0004QN-00@chiark.greenend.org.uk> <E1Afj2b-0004QN-00@chiark.greenend.org.uk> <1073841200.1153.0.camel@localhost> <E1AfjdT-0008OH-00@chiark.greenend.org.uk> <1073843690.1153.12.camel@localhost> <20040114045945.GB23845@redhat.com>
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From: Ducrot Bruno <poup@poupinou.org>
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On Wed, Jan 14, 2004 at 04:59:45AM +0000, Dave Jones wrote:
> On Sun, Jan 11, 2004 at 12:54:51PM -0500, Robert Love wrote:
>  > On Sun, 2004-01-11 at 12:44, Matthew Garrett wrote:
>  > 
>  > > Is there any realistic way of noticing this sort of change?
>  > 
>  > Sure.  That is how Speedstep works, right?  We have an interface for
>  > Speedstep, so the kernel knows about it.  We do not have an interface
>  > for the proprietary BIOS stuff, I assume, so the kernel is oblivious.
> 
> Speedstep support is one way right now. We tell the CPU "switch to this mode"
> and it does. What we don't know how to do in cpufreq is detect when someone pulls
> the power out, or plugs back in. BIOS SMM magick happens, and it all
> gets taken care of transparently without us having a clue that anything
> happened.
> 
> We *could* hook into the APM 'power source changed' notifiers, (and I
> guess ACPI has something similar somewhere). That should take care of things.
> 
>  > But if you had the docs, I suppose you could code a solution and tie it
>  > into the cpufreq code, just as we have proper support for Speedstep,
>  > Longrun, etc.
> 
> Of all the implementations I've played with (longhaul/powernow/speedstep-smi)
> speedstep is the only one that does funky shit with SMM. The others are quite
> dumb (and friendly) in comparison. (Ie, nothing happens on power source change)

I'm wondering if there is a need to get bios ownership like in
the speedstep-smi if not in acpi mode, in speedstep-ich? 

Anyway speedstep-ich should be fine if you explicitely configure BIOS
in order to boot always in high performance mode.

-- 
Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.
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