linux-kernel - Re: [PATCH RFC 2/5] ACPI / processor: always compile perflib if CONFIG_ACPI

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Date:	Fri, 08 May 2015 11:06:26 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>
CC:	Sudeep Holla <sudeep.holla@....com>,
	linux acpi <linux-acpi@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"ahs3@...hat.com" <ahs3@...hat.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Subject: Re: [PATCH RFC 2/5] ACPI / processor: always compile perflib if CONFIG_ACPI_PROCESSOR



On 08/05/15 09:52, Hanjun Guo wrote:
> On 2015年05月07日 02:36, Ashwin Chaugule wrote:
>> Hello,
>>
>> On 6 May 2015 at 10:31, Sudeep Holla <sudeep.holla@....com> wrote:
>>> Similar to the  idle, thermal and throttling libraries, always compile
>>> the perflib if CONFIG_ACPI_PROCESSOR is enabled. This not only makes
>>> perflib alligned with other libraries but also helps in some sanity
>>> testing of these ACPI methods even when a particular feature is not
>>> enabled in the kernel configuration.
>>>
>>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>>> ---
>>>    drivers/acpi/Makefile    |  2 +-
>>>    include/acpi/processor.h | 29 -----------------------------
>>>    include/linux/cpufreq.h  |  4 ++++
>>>    3 files changed, 5 insertions(+), 30 deletions(-)
>>>
>>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>>> index 8a063e276530..33aef9d8b260 100644
>>> --- a/drivers/acpi/Makefile
>>> +++ b/drivers/acpi/Makefile
>>> @@ -84,7 +84,7 @@ obj-$(CONFIG_ACPI_BGRT)               += bgrt.o
>>>    # processor has its own "processor." module_param namespace
>>>    processor-y                    := processor_driver.o processor_throttling.o
>>>    processor-y                    += processor_idle.o processor_thermal.o
>>> -processor-$(CONFIG_CPU_FREQ)   += processor_perflib.o
>>> +processor-y                    += processor_perflib.o
>>
>> I'd prefer that we create a separate kconfig option for this. (perhaps
>> even default it to 'y'). This library is quite specific to a certain
>> type of CPU performance management methods (includes _PSS and friends)
>> which are superseded by CPPC. The OS is not expected to support both
>> at runtime, so by keeping this a config option, we can then disable it
>> at compile time when CPPC is enabled. We could couple
>
> I agree. CPPC and _PSS are different way of controlling CPU freq,
> and I think _PSS may not be used on ARM.
>

While I agree having a separate config option is good, but I won't
assume _PSS might not be used on ARM as I have seen patches posted on
the list in past to use _PSS on ARM platform[1].

Regards,
Sudeep

[1] http://marc.info/?l=linaro-acpi&m=139745485418399&w=2
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