linux-kernel - Re: [PATCH 0/5] Add P state driver for Intel Core Processors

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Date:	Thu, 14 Feb 2013 07:23:44 -0800
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Viresh Kumar <viresh.kumar@...aro.org>,
	Dirk Brandewie <dirk.brandewie@...il.com>,
	Dave Jones <davej@...hat.com>, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org
Subject: Re: [PATCH 0/5] Add P state driver for Intel Core Processors

On 02/14/2013 04:21 AM, Rafael J. Wysocki wrote:
> On Thursday, February 14, 2013 09:38:21 AM Viresh Kumar wrote:
>> On Wed, Feb 13, 2013 at 10:08 PM, Dirk Brandewie
>> <dirk.brandewie@...il.com> wrote:
>>> For the case where both are built-in the load order works my driver uses
>>> device_initcall() and acpi_cpufreq uses late_initcall().
>>>
>>> For the case where both are a module (which I was sure I tested) you are
>>> right
>>> I will have to do something.
>>>
>>> For now I propose to make my driver built-in only while I sort out the right
>>> solution for the module build.  Does this seem reasonable to everyone?
>>
>> Of-course i am missing something here. Why would anybody want to insert
>> acpi-cpufreq module when the system supports the pstate driver.
>>
>> In case they are mutually exclusive, then we can have something like
>> depends on !ACPI-DRIVER in the kconfig option of pstate driver.
>
> Yes.  Or the other way around (i.e. make acpi_cpufreq depend on
> !X86_INTEL_PSTATE).
>

The issue is that acpi-cpufreq still needs to be available for Intel processors 
before SandyBridge and for other x86 compatible processors we can't make
intel_pstate and acpi-cpufreq mutually exclusive.

Having intel_pstate built-in solves the issue without the need to patch
acpi-cpufreq.  I believe that most distros build the scaling drivers in
so the distro/user will make the explicit decision to use intel_pstate.


> Thanks,
> Rafael
>
>

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