ACPI: Introduce CPU performance controls using CPPC

CPPC stands for Collaborative Processor Performance Controls
and is defined in the ACPI v5.0+ spec. It describes CPU
performance controls on an abstract and continuous scale
allowing the platform (e.g. remote power processor) to flexibly
optimize CPU performance with its knowledge of power budgets
and other architecture specific knowledge.

This patch adds a shim which exports commonly used functions
to get and set CPPC specific controls for each CPU. This enables
CPUFreq drivers to gather per CPU performance data and use
with exisiting governors or even allows for customized governors
which are implemented inside CPUFreq drivers.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/Kconfig

@@ -197,6 +197,20 @@ config ACPI_PROCESSOR_IDLE
 	bool
 	select CPU_IDLE
 
+config ACPI_CPPC_LIB
+	bool
+	depends on ACPI_PROCESSOR
+	depends on !ACPI_CPU_FREQ_PSS
+	select MAILBOX
+	select PCC
+	help
+	  If this option is enabled, this file implements common functionality
+	  to parse CPPC tables as described in the ACPI 5.1+ spec. The
+	  routines implemented are meant to be used by other
+	  drivers to control CPU performance using CPPC semantics.
+	  If your platform does not support CPPC in firmware,
+	  leave this option disabled.
+
 config ACPI_PROCESSOR
 	tristate "Processor"
 	depends on X86 || IA64