Re: [PATCH]acpi c-states: Fix ACPI C3 is wrongly mapped to C2

Dominik Brodowski
2009-12-14T08:16:28Z

Hey,

On Mon, Dec 14, 2009 at 05:02:00AM -0500, Youquan,Song wrote:
> > > That's true, if CPU has more 3 states such as C3, C6, C7, there are
> > > all mapped to ACPI C3. But the current situation is that if platform
> > > does NOT support ACPI C2, the user interface /sys show us ACPI C2 is
> > > supported which actual is ACPI C3.
> > >
> > > As you know, ACPI C3 and ACPI C2 have much different, such as: BUS SNOOP
> > > or not, ACPI C3 has better power saving etc. we should not mix them.
> >
> > Yes, but what happens if there are two states of type C2? The whole concept
> > of "type C<number>" and "state C<number>" was broken from the beginning...
>
> Sorry. In my mind, there is no two states of ACPI C2. If processor C3
> above are mapped to ACPI C3, so processor C1 is mapped to ACPI C1,
> processor C2 is mapped to ACPI C2.

Well, there may be none now, but the ACPI spec 4.0 provides for it in section
8.1.5... The whole mapping of ACPI C-state Types to C-state numbers _is_
confusing.

Best,
Dominik