On 17 July 2015 at 20:01, Rafael J. Wysocki [off-list ref] wrote:

On Thursday, July 09, 2015 02:04:18 PM Ashwin Chaugule wrote:

quoted

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.

So are you not agreeing with what I've said for a few times already or are you
just not listening?

This option should *not* be user-selectable.  So please drop the help part
and make it look like ACPI_SLEEP, for example.

Fine. I followed some other examples in the kernel. As long as there
is no text after the 'bool', it doesn't show up as a user configurable
option in the menuconfig. Having some help text even in such cases
seemed helpful to me.

Thanks,
Ashwin.