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

From: Rafael J. Wysocki
Date: Thu Feb 14 2013 - 12:29:48 EST

On Thursday, February 14, 2013 07:34:56 AM Dirk Brandewie wrote:
> 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@xxxxxxxxx> 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
> >
> 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.

Right, I forgot about that and recalled it just a minute after sending that

> 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.

But then we need to allow the user to choose acpi_cpufreq anyway if it's
preferred whatever the reason.


I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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