linux-kernel - Re: [PATCH/RFC 3/4] of/clk: Register clocks suitable for Runtime PM with the PM core

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Date:	Wed, 30 Apr 2014 23:23:11 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>,
	Simon Horman <horms@...ge.net.au>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Felipe Balbi <balbi@...com>,
	Mike Turquette <mturquette@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-sh@...r.kernel.org,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Tomasz Figa <tomasz.figa@...il.com>
Subject: Re: [PATCH/RFC 3/4] of/clk: Register clocks suitable for Runtime PM with the PM core

Hi Ulf and Geert,

On Thursday 24 April 2014 15:11:24 Ulf Hansson wrote:
> On 24 April 2014 12:13, Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> > When adding a device from DT, check if its clocks are suitable for Runtime
> > PM, and register them with the PM core.
> > If Runtime PM is disabled, just enable the clock.
> > 
> > This allows the PM core to automatically manage gate clocks of devices for
> > Runtime PM.
> 
> Normally I don't think it's a good idea to "automatically" manage
> clocks from PM core or any other place but from the driver (and
> possibly the subsystem).
> 
> The reason is simply that we hide things that normally is supposed to
> be handled by the driver. Typically a cross SOC driver should work
> fine both with and without a pm_domain. It should also not rely on
> CONFIG_PM_RUNTIME.

That's a very good point. Geert, what do you think should happen if 
CONFIG_PM_RUNTIME is not set ? I don't have a strong opinion (yet) on whether 
we could require CONFIG_PM_RUNTIME, but it would indeed be nice to support 
both cases. One option would be to keep the clocks enabled unconditionally in 
that case, as not setting CONFIG_PM_RUNTIME means that the user doesn't care 
(or cares less) about power consumption.

> > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

-- 
Regards,

Laurent Pinchart

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