Re: ACPI C4 support

[Bruno Ducrot <ducrot-kk6yZipjEM5g9hUCZPvPmw@public.gmane.org>]

On Mon, Mar 01, 2004 at 08:27:38PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > [mailto:acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org] On Behalf Of 
> > > Stefan Behlert
> > > > No.  pblk_length is 0 or 6.  Not 5 nor 7 ;)
> > > 
> > > Sorry, I don't understand: We've a Laptop with a DSDT with
> > >   Processor (\_PR.CPU0, 0x01, 0x00001010, 0x07)
> > > in it.
> > > Comment from the responsible BIOS-team:
> > > "Our processor block object is 7 bytes in length because we 
> > > also support
> > >  C4 (P_LVL4) which is at <P_BLK>+6.  Therefore, the 
> > > size/length must be
> > >  reported as 7 and not 6."
> > > 
> > > Is the '7' the BIOS-developer mentioned the same '7' as 
> > > mentioned by you?
> > 
> > This is wrong.
> > 
> > There is confusion here because what older systems do on C3 is different
> > from what more recent systems do on C3, at the electrical level. I know
> > at least internally the improved C3-like state was called "C4" but to
> > the OS it just looks just like C3, and the value for C4 should go in
> > P_LVL3. P_BLK length should remain 6.
> > 
> > The only way to get more than C1, C2, and C3 is via the _CST object.
> > 
> > Please tell the BIOS developer this. I have an old BIOS developers guide
> > version that agrees with them but I just asked the experts internally
> > and they said no.
> 
> If there is old BIOS guide telling them to use length of 7, could we
> make Linux accept that? Its likely a lot of developers have read
> that...
> 
> Allowing length of 7 is one line change; if we do it, such notebooks
> will be able to use C1..C3, but not C4. That does not seem too bad...
> 

The problem is that, from strict acpi point of view, it will be too easy
to allow '7', and _CST support is much better.  Don't ask me why, I'm not
an expert.  So perhaps it may be possible to add the (bahh, beurk)
length of 7 if there exist a bad written bios developper guide released
apparently by Intel, at least as a non pedantic acpi option?

-- 
Bruno Ducrot

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


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