Re: [PATCH] Enable bit 11 in _PDC to advertise hw coord

[Jens Axboe <jens.axboe@oracle.com>]

On Mon, Feb 02 2009, Pallipadi, Venkatesh wrote:
> 
> Bit 11 in intel PDC definitions is meant for OS capability to handle
> hardware coordination of P-states. In Linux we have always supported
> hwardware coordination of P-states. Just let the BIOSes know that we
> support it, by setting this bit.
> 
> Some BIOSes use this bit to choose between hardware or software coordination
> and without this change below, BIOSes switch to software coordination, which
> is not very optimal in terms of power consumption and extra wakeups from idle.

I can confirm that this fixes the excessive reschedule ipi count on an
x60 with the ondemand governor. Can we please get this into 2.6.29?

> 
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> 
> ---
>  include/acpi/pdc_intel.h |    2 ++
>  1 file changed, 2 insertions(+)
> 
> Index: linux-2.6/include/acpi/pdc_intel.h
> ===================================================================
> --- linux-2.6.orig/include/acpi/pdc_intel.h	2009-01-20 16:11:20.000000000 -0800
> +++ linux-2.6/include/acpi/pdc_intel.h	2009-02-02 10:32:06.000000000 -0800
> @@ -14,6 +14,7 @@
>  #define ACPI_PDC_SMP_T_SWCOORD		(0x0080)
>  #define ACPI_PDC_C_C1_FFH		(0x0100)
>  #define ACPI_PDC_C_C2C3_FFH		(0x0200)
> +#define ACPI_PDC_SMP_P_HWCOORD		(0x0800)
>  
>  #define ACPI_PDC_EST_CAPABILITY_SMP	(ACPI_PDC_SMP_C1PT | \
>  					 ACPI_PDC_C_C1_HALT | \
> @@ -22,6 +23,7 @@
>  #define ACPI_PDC_EST_CAPABILITY_SWSMP	(ACPI_PDC_SMP_C1PT | \
>  					 ACPI_PDC_C_C1_HALT | \
>  					 ACPI_PDC_SMP_P_SWCOORD | \
> +					 ACPI_PDC_SMP_P_HWCOORD | \
>  					 ACPI_PDC_P_FFH)
>  
>  #define ACPI_PDC_C_CAPABILITY_SMP	(ACPI_PDC_SMP_C2C3  | \

-- 
Jens Axboe