linux-kernel - Re: [RFC PATCH V4 3/5] cpuidle: default idle driver for x86

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Message-ID: <20110324163220.GB16408@dirshya.in.ibm.com>
Date:	Thu, 24 Mar 2011 22:02:20 +0530
From:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
To:	Trinabh Gupta <trinabh@...ux.vnet.ibm.com>
Cc:	Len Brown <lenb@...nel.org>, arjan@...ux.intel.com,
	peterz@...radead.org, suresh.b.siddha@...el.com,
	benh@...nel.crashing.org, venki@...gle.com, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, sfr@...b.auug.org.au,
	xen-devel@...ts.xensource.com
Subject: Re: [RFC PATCH V4 3/5] cpuidle: default idle driver for x86

* Trinabh Gupta <trinabh@...ux.vnet.ibm.com> [2011-03-23 15:01:14]:

> 
> On 03/23/2011 08:43 AM, Len Brown wrote:
> >Why is this patch a step forward?
> 
> Hi Len,
> 
> I have basically moved the code for arch default and mwait
> idle from arch/x86/kernel/process.c to a driver. This was
> suggested by Venki (https://lkml.org/lkml/2010/10/19/460)
> as part of pm_idle cleanup and direct call of
> cpuidle_idle_call(). There is not much new code here.
> 
> >
> >>+obj-$(CONFIG_X86)                              += default_driver.o
> >
> >BTW, that's a pretty generic name for an x86 specific idle driver...
> >
> >I think that on builds that support intel_idle and acpi_idle,
> >everything in this file will be unused, unless somebody uses some
> >debugging cmdline params that should have been deleted ages ago.
> 
> Yes, I agree that the name has to be x86 specific. I think the
> routines would be used for pre-nehalem architectures that use
> arch default or mwait.

Mainly selection between default_idle (safe_halt), mwait_idle and
c1e_idle needs to be placed in a default driver.  This is the code
that was 'outside' of cpuidle framework and directly used pm_idle().
This is mostly unused and overridden by intel_idle or acpi_idle, but
still cannot be discarded.

Maybe keep this as a module and probe/load only if both intel_idle and
acpi_idle failed to load or excluded by command line or otherwise.

--Vaidy

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