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

Dominik Brodowski
2009-12-13T08:43:19Z

On Sat, Dec 12, 2009 at 06:55:49PM -0500, Youquan,Song wrote:
> On Sat, Dec 12, 2009 at 03:27:27PM +0100, Dominik Brodowski wrote:
> > On Sat, Dec 12, 2009 at 01:14:42PM -0500, Youquan,Song wrote:
> > > On Nehalem-EX, CPU C3 is mapped to ACPI C3, but C-states information in /proc
> > > and /sys are conflicting with ACPI C2 mapping and confused user.
> >
> > Well, isn't the "type" only losely related to the C-state number anyway, if
> > you have more than 3 states?
>
> 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...

Best,
Dominik