Re: [PATCH v7 5/8] CPPC: Add a CPUFreq driver for use with CPPC

[Sudeep Holla <sudeep.holla@arm.com>]

On 20/07/15 23:07, Rafael J. Wysocki wrote:
> On Monday, July 20, 2015 03:22:09 PM Sudeep Holla wrote:
>>
>> On 09/07/15 19:04, Ashwin Chaugule wrote:
>>> This driver utilizes the methods introduced in the previous
>>> patch - "ACPI: Introduce CPU performance controls using CPPC"
>>> and enables usage with existing CPUFreq governors.
>>>
>>> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
>>> Reviewed-by: Al Stone <al.stone@linaro.org>
>>> ---
>>>    drivers/cpufreq/Kconfig.arm    |  16 ++++
>>>    drivers/cpufreq/Makefile       |   2 +
>>>    drivers/cpufreq/cppc_cpufreq.c | 197 +++++++++++++++++++++++++++++++++++++++++
>>>    3 files changed, 215 insertions(+)
>>>    create mode 100644 drivers/cpufreq/cppc_cpufreq.c
>>>
>>> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
>>> index 4f3dbc8..578384d 100644
>>> --- a/drivers/cpufreq/Kconfig.arm
>>> +++ b/drivers/cpufreq/Kconfig.arm
>>> @@ -272,3 +272,19 @@ config ARM_PXA2xx_CPUFREQ
>>>    	  This add the CPUFreq driver support for Intel PXA2xx SOCs.
>>>
>>>    	  If in doubt, say N.
>>> +
>>> +config ACPI_CPPC_CPUFREQ
>>> +	tristate "CPUFreq driver based on the ACPI CPPC spec"
>>> +	depends on ACPI_CPPC_LIB
>>> +	default n
>>> +	help
>>> +	  This adds a CPUFreq driver which uses CPPC methods
>>> +	  as described in the ACPIv5.1 spec. CPPC stands for
>>> +	  Collaborative Processor Performance Controls. It
>>> +	  is based on an abstract continuous scale of CPU
>>> +	  performance values which allows the remote power
>>> +	  processor to flexibly optimize for power and
>>> +	  performance. CPPC relies on power management firmware
>>> +	  for its operation.
>>
>> Why is this ARM specific ? It might be used only on ARM but doesn't mean
>> it should be visible only on ARM ACPI systems.
>
> Why bother people with considering Kconfig options that are useless to them?
>

I agree to some extent, but main worry is that we are then making these
features architecture specific while ACPI is supposed to be architecture
agnostic. I was just trying to avoid doing so.

Regards,
Sudeep