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

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Date:	Thu, 27 May 2010 07:22:07 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Kevin Hilman <khilman@...prootsystems.com>
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

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; it's much more convenient for cpuidle developers
if they're all in one place.
Think of it this way: you're not putting the NIC driver for your SOC in
a architecture directory either...


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
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