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

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Date:	Thu, 1 May 2014 00:06:07 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	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 list <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 Laurent,

On Wed, Apr 30, 2014 at 11:23 PM, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> 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.

This is already handled by my patch. If CONFIG_PM_RUNTIME is disabled,
the clocks are enabled by calling clk_prepare_enabled().

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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