Hi Sudeep, On 8 July 2015 at 09:43, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > > > On 08/07/15 02:27, Ashwin Chaugule wrote: >> >> On 7 July 2015 at 21:07, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> 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@xxxxxxxxxx> >>>> Reviewed-by: Al Stone <al.stone@xxxxxxxxxx> >>>> --- >>>> 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 THERMAL >>>> - select CPU_IDLE >>>> +config ACPI_CST >>>> + bool "ACPI C states (CST) driver" >>>> + depends on ACPI_PROCESSOR >>>> depends on X86 || IA64 >>>> + select 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_PROCESSOR >>>> + depends on X86 || IA64 >>>> + select THERMAL >>>> + default y >>>> + 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. >>> >>> >>> 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. > > > Ashwin, I am trying to keep Kconfig options minimum, iff necessary and > selected by ARCH code(i.e. not user selectable). Also I am not entirely > sure if we need to make PSS and CPPC mutually exclusive. Agree. Moving this to ARCH does seem like a better option. I need to explore that some more. Per the ACPI spec, the OS is not expected to support PSS and CPPC at runtime. I want to avoid getting into whitelist/blacklist issues which would be inevitable if we keep both available at runtime. Some of the X86 drivers run into this already. > > I had seen patches to support PSS on ARM and if we have to support > single Image to handle both they can't be exclusive. Theres been one attempt about 1.5 years ago and AFAIK those folks have completely backed out of the ARM64 Server space . ;) We can revisit when someone proposes a more recent solution for PSS on ARM64. It shouldn't be too hard to change the Kconfig dependencies accordingly. Regards, Ashwin. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
