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

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Message-ID: <CAMuHMdV7zASj8_NtLRir1VubXEKTkq0vBGMXeYXDACu8UC2tZA@mail.gmail.com>
Date:	Thu, 20 Nov 2014 21:26:55 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Kevin Hilman <khilman@...nel.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@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.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

Hi Kevin,

On Thu, Nov 20, 2014 at 9:22 PM, Kevin Hilman <khilman@...nel.org> wrote:
> Grygorii Strashko <grygorii.strashko@...com> writes:
>> On 11/20/2014 03:32 PM, Geert Uytterhoeven wrote:
>>> On Thu, Nov 20, 2014 at 2:12 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> [...]
>
>>>> So I really think we need to decide on how to address the split of the
>>>> device clocks. Before that's done, I don't think it make sense to add
>>>> a "simple-pmdomain" compatible, since it will likely not be that many
>>>> SoC that can use it.
>>>>
>>>> So, does anyone have a suggestion on how to deal with the split of the
>>>> device clocks into "functional" clocks and into "PM" clocks?
>>
>> Would it be better to say "functional" and "optional"? In my opinion
>> "PM" == "functional". Also, such clock's separation is used in TRM/DM/UMs on HW.
>
> Yes!  I really don't like the name "PM" clock, since it's not at all
> obvious what that means.  To me, "PM" == "functional" as well.
>
> 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 not on another.

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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