Re: ACPI C4 support

Pavel Machek
2004-03-01T19:27:38Z

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...

Pavel
--
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]