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

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Message-ID: <20150212162525.GW5029@twins.programming.kicks-ass.net>
Date:	Thu, 12 Feb 2015 17:25:25 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...ux.intel.com>,
	"Li, Aubrey" <aubrey.li@...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 Thu, Feb 12, 2015 at 05:24:51PM +0100, 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.
> 
> > Also, should we ignore things like intel_idle.max_cstate for this
> > selection?
> 
> No, we shouldn't.  The deeper ones may just not work then.

OK, fair enough.
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