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

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Message-ID: <554C7960.4040107@linaro.org>
Date:	Fri, 08 May 2015 16:52:48 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>
CC:	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>, Al Stone <ahs3@...hat.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH RFC 2/5] ACPI / processor: always compile perflib if CONFIG_ACPI_PROCESSOR

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 which are superseded by CPPC.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.

Thanks
Hanjun
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