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 <redacted>
---
 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.