linux-kernel - Re: [PATCH 5/6] intel_idle: Add ->enter

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Date:	Thu, 05 Mar 2015 08:09:10 +0800
From:	"Li, Aubrey" <aubrey.li@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	John Stultz <john.stultz@...aro.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 5/6] intel_idle: Add ->enter_freeze callbacks

On 2015/3/5 8:18, Rafael J. Wysocki wrote:
> On Thursday, March 05, 2015 07:50:26 AM Li, Aubrey wrote:
>> On 2015/2/13 0:24, Rafael J. Wysocki wrote:
>>> On Thursday, February 12, 2015 02:26:43 PM Peter Zijlstra wrote:
>>>>
>>>> Why bother with enter_freeze() for any but the deepest state (C6 in this
>>>> case)?
>>>
>>> User space may disable the deepest one (and any of them in general) via sysfs
>>> and there's no good reason to ignore its choice in this particular case while
>>> we're honoring it otherwise.
>>>
>>> So the logic is basically "find the deepest one which isn't disabled" and
>>> setting the pointers costs us nothing really.
>>>
>>
>> If the user has chance to disable C6 via /sys, that means c6 works?
>> Shouldn't we ignore user space setting during freeze? Otherwise, we will
>> lost S0ix?
> 
> We can't ignore it, because we don't know the reason why the state was
> disabled.
> 

> It may just not work reliably enough on the given platform.
>
okay, make sense to me. Thanks, -Aubrey

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