linux-kernel - Re: [linux-pm] suspend blockers & Android integration

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Message-ID: <Pine.LNX.4.44L0.1006111638040.19894-100000@netrider.rowland.org>
Date:	Fri, 11 Jun 2010 16:48:15 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	James Bottomley <James.Bottomley@...e.de>
cc:	David Brownell <david-b@...bell.net>, <tytso@....edu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Neil Brown <neilb@...e.de>,
	Brian Swetland <swetland@...gle.com>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [linux-pm] suspend blockers & Android integration

On Fri, 11 Jun 2010, Mark Brown wrote:

> On Fri, Jun 11, 2010 at 10:46:27AM -0400, Alan Stern wrote:
> > On Fri, 11 Jun 2010, James Bottomley wrote:
> 
> > > The one thing that does look difficult is that these power constraints
> > > are device (and sometimes SoC) specific.  Expressing them in a generic
> > > way for the cpu govenors to make sense of might be hard.
> 
> > Doesn't the clock framework already handle this sort of thing?
> 
> The clock framework is implemented independantly for each CPU.

That's not an impediment, since drivers' requirements regarding which 
clocks remain running in which power states are necessarily 
platform-dependent also.


On Fri, 11 Jun 2010, James Bottomley wrote:

> Well, there are two elements to "this sort of thing":
> 
>      1. Allow a driver to request that a given clock not be turned off.
>      2. Make the cpuidle governors aware of a pending "don't turn off X
>         clock source" so they can keep the system in a state where the
>         clock doesn't get powered down.
> 
> As far as I can tell from the code, neither currently exists at the
> moment.

Well then, can (or should) the clock framework interact with the
pm-qos subsystem so that drivers don't have to worry about it?

Alan Stern

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