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

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Date:	Thu, 20 Nov 2014 17:30:53 -0800
From:	Kevin Hilman <khilman@...nel.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Grygorii Strashko <grygorii.strashko@...com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, ssantosh@...nel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm\@vger.kernel.org" <linux-pm@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains

Geert Uytterhoeven <geert@...ux-m68k.org> writes:

> On Thu, Nov 20, 2014 at 10:48 PM, Kevin Hilman <khilman@...nel.org> wrote:
>>>> So what exactly are we talking about with "PM" clocks, and why are they
>>>> "special" when it comes to PM domains?  IOW, why are the clocks to be
>>>> managed during PM domain transitions for a given device any different
>>>> than the clocks that need to be managed for a runtime suspend/resume (or
>>>> system suspend/resume) sequence for the same device?
>>>
>>> (Speaking for my case, shmobile)
>>>
>>> They're not. The clocks to be managed during PM domain transitions are the
>>> same as the clocks that need to be managed for a runtime suspend/resume
>>> (or system suspend/resume) sequence.
>>>
>>> The special thing is that this is more a platform than a driver thing: the same
>>> module may have a "PM/functional" clock (that is documented to enable/disable
>>> the module) on one Soc, but noet on another.
>>
>> So why isn't the presence or absence of the clock described in the .dtsi
>> for the SoC instead of being handled by special PM domain logic?
>
> It is. Cfr. the presence/absence of clocks for renesas,rcar-gpio nodes.

Hmm, OK, Good.  

So now I'm confused about why the PM domain has to do anything special
if the presence/absence of the clocks is already handled by the DT.

Kevin



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