linux-kernel - Re: [PATCH 7/10 v6] PM / Domains: Don't stop wakeup devices during system sleep transitions

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Date:	Fri, 1 Jul 2011 01:25:25 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Kevin Hilman <khilman@...com>
Cc:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Magnus Damm <magnus.damm@...il.com>,
	Paul Walmsley <paul@...an.com>,
	Alan Stern <stern@...land.harvard.edu>,
	LKML <linux-kernel@...r.kernel.org>, linux-sh@...r.kernel.org,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH 7/10 v6] PM / Domains: Don't stop wakeup devices during system sleep transitions

On Friday, July 01, 2011, Rafael J. Wysocki wrote:
> On Friday, July 01, 2011, Kevin Hilman wrote:
> > "Rafael J. Wysocki" <rjw@...k.pl> writes:
...
> > The decision of whether or not to clock gate and/or power gate based on
> > wakeup capabilies has to be made somewhere (and in fact is already made
> > by existing code.)  But IMO, that decision should only be made where
> > wakeup capabilies are known, so that sensible decisions (for power
> > management) can be made.
> > 
> > Until there is a way in the generic code to distinguish between the
> > various ways a device can wakeup, this decision should be left up to the
> > code that knows how.
> 
> OK, so I suppose your suggestion is to drop the patch and let the
> .stop_device() and .power_off() PM domain callbacks to hand

That should have been "handle".

> that, is this correct?

Anyway, neither .stop_device(), nor .power_off() can make such decisions,
because they are used for both runtime PM and system suspend, so they shouldn't
do system suspend-specific checks.

So the only way forward I can see is to add a special PM domain callback,
say .active_wakeup(), that will return "true" if the device is to be left
active if wakeup-enabled.  So the check you don't like will become
something like:

if (device_may_wakeup(dev) && genpd->active_wakeup
    && genpd->active_wakeup(dev))
        return 0;

Would that be better?

Rafael
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