linux-kernel - Re: [RFD] PM: Device tree representation of power domains

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Message-Id: <201207052217.48086.rjw@sisk.pl>
Date:	Thu, 5 Jul 2012 22:17:47 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [RFD] PM: Device tree representation of power domains

On Wednesday, July 04, 2012, Mark Brown wrote:
> On Tue, Jul 03, 2012 at 11:02:17PM +0200, Rafael J. Wysocki wrote:
> 
> > I actually don't have any ideas how to do that at the moment, but I wonder
> > if anyone has already thought about it?
> 
> > For one, I don't think that representing a power domain as a platform device
> > would be a good approach and I'm not sure how to represent the relationships
> > between devices and the domains they belong to.
> 
> I guess the OMAP hwmod stuff is the closest thing we've got at the
> minute (I don't recall seeing any other implementations in mainline) but
> the hwmods themselves don't appear in the DTS right now.  They have a
> ti,hwmods property on each device naming the hwmod it's in, something
> like that seems like a reasonable approach, possibly a reference to
> another DT node rather than or as well as a string?  That seems fairly
> easy.

Well, it looks like (and please tell me if I'm wrong) the hwmons are just
string attributes that are parsed by the platform-specific code through
a platform bus type notifier.

We could do that for power domains too, but then each platform wanting to
use them would need to implement such a notifier and add its own routine
for parsing those strings.  Would that be acceptable to everyone concerned?

Rafael
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