linux-kernel - Re: [linux-pm] [PATCH V3] cpuidle: Add a sysfs entry to disable specific C state for debug purpose.

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Date:	Wed, 14 Mar 2012 08:55:00 +0800
From:	Yanmin Zhang <yanmin_zhang@...ux.intel.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"Brown, Len" <len.brown@...el.com>,
	ShuoX Liu <shuox.liu@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	"H. Peter Anvin" <hpa@...or.com>, andi.kleen@...el.com,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH V3] cpuidle: Add a sysfs entry to disable
 specific C state for debug purpose.

On Tue, 2012-03-13 at 12:29 -0700, Greg KH wrote:
> On Tue, Mar 13, 2012 at 09:36:34AM +0800, Yanmin Zhang wrote:
> > On Mon, 2012-03-12 at 12:29 -0700, Greg KH wrote:
> > > On Mon, Mar 12, 2012 at 06:11:51PM +0000, Mark Brown wrote:
> > > > On Tue, Mar 06, 2012 at 06:39:35AM -0800, Greg KH wrote:
> > > > 
> > > > > Do you know of any tools using these files?  I have never heard of them,
> > > > > and I was told we should move these files years ago.  So I don't think
> > > > > there should be any api issues.
> > > > 
> > > > powertop uses them.
> > > 
> > > Ok, then we can't move them all.
> > > 
> > > We should then just move the ones that have multiple lines, as I'm
> > > pretty sure powertop doesn't use them, right?
> > All sys files under cpu/cpuXXX/cpuidle have single line. If we move
> > some files to debugfs and keep others under sysfs, users might be confused.
> > 
> > Should we go back to the 1st version which just adds the new entry to
> > sysfs?
> 
> Wait, I thought this whole thing started when we wanted to move the
> files that had multiple lines out of sysfs?
No. Liu Shuo's patch adds a new entry under cpu/cpuXXX/cpuidle and users
can disable specific C state.
A gentleman raised that if we should move it to debugfs, then you suggested
to move all files under cpu/cpuXXX/cpuidle to debugfs.

> 
> If none of these do, and they all are being used by tools already, then
> fine, they should stay.
Agree.

> 
> But for some reason, I thought there was a problem here.  Perhaps that
> was in the cpufreq code?
I checked cpufreq quickly. Every file has single-line, but some have
multiple-fields.

We would send a new patch based on sysfs as the new entry has
single line.


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