linux-kernel - Re: [PATCH 8/8] intel_idle: create a native cpuidle driver for select intel processors

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Message-ID: <87ocg1jts7.fsf@deeprootsystems.com>
Date:	Thu, 27 May 2010 07:36:40 -0700
From:	Kevin Hilman <khilman@...prootsystems.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Len Brown <lenb@...nel.org>, x86@...nel.org,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 8/8] intel_idle: create a native cpuidle driver for select intel processors

Arjan van de Ven <arjan@...radead.org> writes:

> On Thu, 27 May 2010 07:14:46 -0700
> Kevin Hilman <khilman@...prootsystems.com> wrote:
>
>> Len Brown <lenb@...nel.org> writes:
>> 
>> > From: Len Brown <len.brown@...el.com>
>> >
>> > This EXPERIMENTAL driver supersedes acpi_idle
>> > on modern Intel processors. (Nehalem and Atom Processors).
>> >
>> > For CONFIG_INTEL_IDLE=y, intel_idle probes before acpi_idle,
>> > no matter if CONFIG_ACPI_PROCESSOR=y or =m.
>> >
>> > Boot with "intel_idle.max_cstate=0" to disable the driver
>> > and to fall back on ACPI.
>> >
>> > CONFIG_INTEL_IDLE=m is not recommended unless the system
>> > has a method to guarantee intel_idle loads before ACPI's
>> > processor_idle.
>> >
>> > This driver does not yet know about cpu online/offline
>> > and thus will not yet play well with cpu-hotplug.
>> >
>> > Signed-off-by: Len Brown <len.brown@...el.com>
>> > ---
>> >  MAINTAINERS                     |    7 +
>> >  drivers/Makefile                |    2 +-
>> >  drivers/acpi/processor_driver.c |    6 +-
>> >  drivers/idle/Kconfig            |   11 +
>> >  drivers/idle/Makefile           |    1 +
>> >  drivers/idle/intel_idle.c       |  446
>> > +++++++++++++++++++++++++++++++++++++++
>> 
>> Any reason this arch-specific driver needs to be in drivers/idle
>> instead of under a platform specific dir like arch/x86?
>> 
>> On embedded SoCs that have never had ACPI, we have our
>> platform-specific CPUidle drivers in with the rest of our platform
>> specific code.
>> 
>
> it's really inconvenient to have such drivers hidden in the
> architecture code;

I'm not sure how puting architecture-specific code into an
architecture-specific directory is hiding it, but maybe I'm missing
something.

> it's much more convenient for cpuidle developers if they're all in
> one place.

So should we move all the embedded SoC specific CPUidle drivers into
drivers/idle too?

To me that would be much less convenient as I expect to maintain my
platform-specific CPUidle driver along with the rest of my
platform-specific code.

Kevin
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