linux-kernel - Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains

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Date:	Tue, 25 Nov 2014 11:33:57 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Grygorii Strashko <grygorii.strashko@...com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Kevin Hilman <khilman@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <robh+dt@...nel.org>, ssantosh@...nel.org
Subject: Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains

On Monday 24 November 2014 22:44:06 Mike Turquette wrote:
> Quoting Arnd Bergmann (2014-11-24 02:50:28)
> > 
> > Could the driver maybe identify the clocks that it wants to manage itself
> > to the pm-domain code? If it's safe for a device to have the clock turned
> > on at the default rate before loading the driver, any device that is connected
> > to the simple clk-pm-domain code could have all its clocks start out as
> > owned by the pm-domain, but then claim the clocks it needs to reprogram for
> > itself and take them out of the pmdomain.
> 
> I was thinking along similar lines. The functional versus optional stuff
> is really a property of the consuming device, not the clock signal
> itself.
> 
> Instead of adding a new property to the clock binding (e.g. fck-clocks
> or optional-clocks), could we simply wrap those lists of clocks in
> another node? E.g:
> 
> mandatory-clocks {
>        clocks = <&papllclk>, <&clkcpgmac>;
>        clock-names = "clk_pa", "clk_cpgmac";
> }
> 
> clocks = <&papllclk>, <&clkcpgmac>, <&chipclk12>;
>        clocks = <&clkcpgmac>;
>        clock-names = "cpsw_cpts_rft_clk";
> }
> 
> I'm showing my DT ignorance on this one. I haven't really thought
> through how these sub-nodes would work with of_clk_* handlers in
> drivers/clk/clkdev.c.

I'm not sure I even understand what you intended the example to look
like, it does't parse ;-)

My point above was completely different, the suggestion I made was
to not classify the clocks in DT at all, but to leave it all in
the client driver.

	Arnd
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