linux-kernel - Re: [PATCH] powercap / RAPL : remove dependency on iosf

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Date:	Tue, 22 Sep 2015 11:11:36 +0800
From:	Pengyu Ma <pengyu.ma@...driver.com>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<rafael.j.wysocki@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powercap / RAPL : remove dependency on iosf_mbi



On 09/22/2015 05:36 AM, Jacob Pan wrote:
> On Mon, 21 Sep 2015 11:48:14 +0800
> Pengyu Ma <pengyu.ma@...driver.com> wrote:
>
>>
>> On 09/18/2015 11:43 PM, Jacob Pan wrote:
>>> On Fri, 18 Sep 2015 02:09:55 +0200
>>> "Rafael J. Wysocki" <rjw@...ysocki.net> wrote:
>>>
>>>> On Thursday, September 17, 2015 03:31:41 PM Pengyu Ma wrote:
>>>>> iosf_mbi is supported on Quark, Braswell, Baytrail and some Atom
>>>>> SoC, but RAPL is not limited to these SoC, it supports almost
>>>>> Intel CPUs. Remove this dependece to make RAPL support more Intel
>>>>> CPUs.
>>>>>
>>>>> Please select IOSF_MBI on Atom SoCs.
>>>>>
>>> Unlike Quark, I don't think we want to or do differentiate Atom from
>>> other x86 at compile time. IOSF driver can be compiled as a module
>>> also, therefore RAPL driver needs this explicit dependency at
>>> compile time.
>> As commit had exported iosf_mbi to let user use it.
>>
>> commit aa8e4f22ab7773352ba3895597189b8097f2c307
>> Author: David E. Box <david.e.box@...ux.intel.com>
>> Date:   Wed Aug 27 14:40:39 2014 -0700
>>
>>       x86/iosf: Add Kconfig prompt for IOSF_MBI selection
>>
>>
>> While selecting IOSF_MBI is preferred, it does mean carrying extra
>> code on non-SoC architectures.
>>
>> We can NOT force user to build in iosf_mbi if they want use RAPL on
>> haswell/broadwell/skylake.
>> And RAPL can be compiled and worked well on haswell/broadwell/skylake
>> without IOSF_MBI.
>> RAPL is really NOT depended on IOSF_MBI.
>>
> True for haswell/broadwell/skylake platforms. But if we want binary
> compatibility for Atom and Core, I can' see how simply removing the
> dependency would work, unless we have runtime detection of IOSF.
If you want use iosf_mbi on atom, please select it on generic x86 config.
But not force it depend on another feature that not related on it with 
other boards.
I don't care how iosf_mbi is added to kernel config, but why should I be 
forced to add it if I want use RAPL?
It doesn't make any sense.

Pengyu

>
>> Pengyu
>>>>> Signed-off-by: Pengyu Ma <pengyu.ma@...driver.com>
>>>> Jacob?
>>>>
>>>>> ---
>>>>>    drivers/powercap/Kconfig | 2 +-
>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig
>>>>> index 85727ef..a7c81b5 100644
>>>>> --- a/drivers/powercap/Kconfig
>>>>> +++ b/drivers/powercap/Kconfig
>>>>> @@ -17,7 +17,7 @@ if POWERCAP
>>>>>    # Client driver configurations go here.
>>>>>    config INTEL_RAPL
>>>>>    	tristate "Intel RAPL Support"
>>>>> -	depends on X86 && IOSF_MBI
>>>>> +	depends on X86
>>>>>    	default n
>>>>>    	---help---
>>>>>    	  This enables support for the Intel Running Average
>>>>> Power Limit (RAPL)
>>>>>
>>> [Jacob Pan]
> [Jacob Pan]

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