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From: Jung-uk Kim <jkim@FreeBSD.org>
To: Andriy Gapon <avg@freebsd.org>
Date: Tue, 28 Jun 2011 17:39:45 -0400
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Cc: freebsd-acpi@freebsd.org, Vitaly Magerya <vmagerya@gmail.com>
Subject: Re: (Missing) power states of an Atom N455-based netbook
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On Tuesday 28 June 2011 05:18 pm, Andriy Gapon wrote:
> on 29/06/2011 00:13 Jung-uk Kim said the following:
> > On Tuesday 28 June 2011 03:37 pm, Vitaly Magerya wrote:
> >>> I think that part (but not all) of the differences between
> >>> FreeBSD and Linux can be explained by the fact that FreeBSD
> >>> currently doesn't advertise itself as featuring
> >>> ACPI_CAP_SMP_C1_NATIVE and ACPI_CAP_SMP_C3_NATIVE.  I am not
> >>> sure what it would take to actually support these features.  I
> >>> think that Linux does support (or at least advertise support)
> >>> for these features.
> >>
> >> Is there some simple way of sending fake advertisement? Or will
> >> that lead to disaster?
> >
> > Actually, ACPI_CAP_SMP_C1_NATIVE is kinda supported but without
> > hints from ACPI _CST FFH.  It sits in machdep.c as
> > cpu_idle_mwait().  So, I think you can advertise them.  The
> > easist way is this (not tested):
>
> But don't we currently ignore FFH-type C state definitions?

Correct.

> I am not sure that mwait that we use (its parameters) would be the
> same as the system would expect us to use unless we actually parse
> FFH data.  Even for C1 sate.

It is unfortunate but you're correct.  We don't have correct support 
code yet.

> Also I am not sure if that would give much gain/difference.

Just for the sake of testing your theory, nothing more, nothing less.

Jung-uk Kim