Re: [PATCH v7 2/8] ACPI: Split out ACPI PSS from ACPI Processor driver

[Sudeep Holla <sudeep.holla@arm.com>]

On 09/07/15 19:04, Ashwin Chaugule wrote:
> The ACPI processor driver is currently tied too closely
> to the ACPI P-states (PSS) and other related constructs
> for controlling CPU performance.
>
> The newer ACPI specification (v5.1 onwards) introduces
> alternative methods to PSS. These new mechanisms are
> described within each ACPI Processor object and so they
> need to be scanned whenever a new Processor object is detected.
> This patch introduces a new Kconfig symbol to allow for
> finer configurability among the two options for controlling
> performance states. There is no change in functionality and
> the option is auto-selected by the architecture Kconfig files.
>
> The following patchwork introduces CPPC: A newer method of
> controlling CPU performance. The OS is not expected to support
> CPPC and PSS at runtime. So the kconfig option lets us make
> these two mutually exclusive at compile time.
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
> ---
>   arch/x86/Kconfig                |  1 +
>   drivers/acpi/Kconfig            | 19 ++++++---
>   drivers/acpi/Makefile           |  6 +--
>   drivers/acpi/processor_driver.c | 86 +++++++++++++++++++++++++------------
>   drivers/cpufreq/Kconfig         |  2 +-
>   drivers/cpufreq/Kconfig.x86     |  2 +
>   include/acpi/processor.h        | 94 +++++++++++++++++++++++++++--------------
>   7 files changed, 142 insertions(+), 68 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 226d569..93d150d 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -143,6 +143,7 @@ config X86
>          select ACPI_LEGACY_TABLES_LOOKUP if ACPI
>          select X86_FEATURE_NAMES if PROC_FS
>          select SRCU
> +       select ACPI_CPU_FREQ_PSS if ACPI
>
>   config INSTRUCTION_DECODER
>          def_bool y
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ab2cbb5..00748dc 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -166,17 +166,26 @@ config ACPI_DOCK
>            This driver supports ACPI-controlled docking stations and removable
>            drive bays such as the IBM Ultrabay and the Dell Module Bay.
>
> +config ACPI_CPU_FREQ_PSS
> +       bool
> +       depends on ACPI_PROCESSOR && CPU_FREQ
> +       select THERMAL
> +       help
> +         This driver implements ACPI methods for controlling CPU performance
> +         using PSS methods as described in the ACPI spec. It also enables support
> +         for ACPI based performance throttling (TSS) and ACPI based thermal
> +         monitoring. It is required by several flavors of cpufreq
> +         performance-state drivers.
> +

Though I agree CPUFreq and the thermal control are related, having _PSS
in config name shouldn't match well IMO. You can have more generic name.

You are selecting one config while depending on the other, any
particular reason ?

I don't like adding these, but I leave it to Rafael.

Regards,
Sudeep