Hi Rafael,
On 8 July 2015 at 09:34, Rafael J. Wysocki rafael@kernel.org wrote:
Hi Ashwin,
On Wed, Jul 8, 2015 at 3:27 AM, Ashwin Chaugule ashwin.chaugule@linaro.org wrote:
On 7 July 2015 at 21:07, Rafael J. Wysocki rjw@rjwysocki.net wrote:
On Monday, June 15, 2015 04:09:06 PM Ashwin Chaugule wrote:
The ACPI processor driver is currently tied too closely to the ACPI C-states (CST), P-states (PSS) and other related constructs for controlling CPU idle and CPU performance.
The newer ACPI specification (v5.1 onwards) introduces alternative methods to CST and 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 two new Kconfig symbols to allow for finer configurability among the various options for controlling CPU idle and performance states. There is no change in functionality and these options are defaulted to enabled to maintain previous behaviour.
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 Reviewed-by: Al Stone al.stone@linaro.org
drivers/acpi/Kconfig | 31 +++++++++-- drivers/acpi/Makefile | 7 ++- drivers/acpi/processor_driver.c | 86 ++++++++++++++++++---------- drivers/cpufreq/Kconfig | 2 +- drivers/cpufreq/Kconfig.x86 | 2 + include/acpi/processor.h | 120 ++++++++++++++++++++++++++++------------ 6 files changed, 176 insertions(+), 72 deletions(-)
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig index ab2cbb5..5942754 100644 --- a/drivers/acpi/Kconfig +++ b/drivers/acpi/Kconfig @@ -166,18 +166,39 @@ 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_PROCESSOR
tristate "Processor"select THERMALselect CPU_IDLE+config ACPI_CST
bool "ACPI C states (CST) driver"depends on ACPI_PROCESSOR depends on X86 || IA64select CPU_IDLE default y help This driver installs ACPI as the idle handler for Linux and uses ACPI C2 and C3 processor states to save power on systems that
support it. It is required by several flavors of cpufreq
support it.+config ACPI_PSS
bool "ACPI P States (PSS) driver"depends on ACPI_PROCESSORdepends on X86 || IA64select THERMALdefault yhelpThis driver implements ACPI methods for controlling CPU performanceusing PSS methods as described in the ACPI spec. It also enables supportfor ACPI based performance throttling (TSS) and ACPI based thermalmonitoring. It is required by several flavors of cpufreq performance-state drivers.For starters, I don't like these new Kconfig options.
Isn't there a way to implement what you need without adding them?
We need to use the ACPI Processor driver for CPPC without including all its current dependencies. (i.e. PSS, TSS, CSS etc.). The upcoming LPI work from Sudeep will also face the same issue. I considered the alternative of adding a probe routine which matches ACPI_PROCESSOR_OBJECT/DEVICE_HID to each driver, but this seemed like a better option. Do you have any other ideas?
First of all, I don't see what _CST has to do with CPPC.
Second, it looks like the problem is that x86 probably won't use CPPC, while arm64 probably won't use _PSS.
That can be addressed by adding Kconfig options, but those options should not be user-selectable (because quite honestly users don't have to know what those things are and they don't care *and* things break if they make a wrong choice). Instead, I'd make architecture Kconfigs select those options automatically.
I've made changes locally. Basically s/ACPI_PSS/HAVE_ACPI_PSS/ and in arch/x86/Kconfig; select HAVE_ACPI_PSS if ACPI. Similarly for CST. Just wanted to check if there were any other comments before sending out v7.
Thanks, Ashwin.