Re: [PATCH v2 4/5] ACPI / processor_idle : introduce ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE

[Sudeep Holla]

On 24/09/15 11:31, Ashwin Chaugule wrote:
> Hi Sudeep,
>
> On 16 September 2015 at 09:59, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> > ACPI 6.0 adds a new method to specify the CPU idle states(C-states)
> > called Low Power Idle(LPI) states. Since new architectures like ARM64
> > use only LPIs, introduce ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE to
> > encapsulate all the code supporting the old style C-states(_CST)
> >
> > This patch will help to extend the processor_idle module to support
> > LPI.
> >
> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> > Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>

[...]

> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index 7aef2d52daa0..173075c48df8 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -34,6 +34,7 @@ config X86
> >          select ARCH_MIGHT_HAVE_ACPI_PDC         if ACPI
> >          select ARCH_MIGHT_HAVE_PC_PARPORT
> >          select ARCH_MIGHT_HAVE_PC_SERIO
> > +       select ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE if ACPI
> >          select ARCH_SUPPORTS_ATOMIC_RMW
> >          select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
> >          select ARCH_SUPPORTS_INT128             if X86_64
> > diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> > index 5d1015c26ff4..1eb0b8a84a65 100644
> > --- a/drivers/acpi/Kconfig
> > +++ b/drivers/acpi/Kconfig
> > @@ -48,6 +48,9 @@ config ACPI_LEGACY_TABLES_LOOKUP
> >   config ARCH_MIGHT_HAVE_ACPI_PDC
> >          bool
> >
> > +config ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE
> > +       bool
> > +
> >   config ACPI_GENERIC_GSI
> >          bool
>
> Can't this be auto selected under ACPI_PROCESSOR_IDLE if X86 || IA64
> instead?

It can be done. The idea was to have ACPI_PROCESSOR_IDLE selected on
both x86 and ARM64.

processor_idle driver will support both _CST and _LPI
1. to avoid some code duplication
2. for easy enabling of _LPI on x86 if needed in future

Regards,
Sudeep
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