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

From: Grygorii Strashko
Date: Thu Nov 20 2014 - 07:03:59 EST

On 11/20/2014 01:34 PM, Ulf Hansson wrote:
> On 19 November 2014 14:47, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> On Wednesday 19 November 2014 13:32:45 Grygorii Strashko wrote:
>>> On 11/18/2014 09:32 PM, Arnd Bergmann wrote:
>>>> On Tuesday 18 November 2014 20:54:36 Grygorii Strashko wrote:
>>>> Have one pmdomain driver in the generic code that knows about clocks,
>>>> possibly also regulators and pins and just turns them on when needed.
>>>> You can have a "simple-pmdomain" or "generic-pmdomain" compatible
>>>> string.
>>>> I'm a bit surprised that your pmdomain code looks up the clocks from the
>>>> respective device, rather than know about the clocks itself. There is
>>>> probably a good reason for this, but I don't see it yet.
>>> The keystone 2 uses simple PM schema based on clocks only:
>>> - clocks enabled -> dev is active
>>> - clocks disabled -> dev is suspended
>>> To achieve explained above the Generic clock manipulation PM callbacks framework (pm_clk) is used.
>>> - list of managed clocks is filled for each device (for non-DT case the con_id list
>>> is specified by platform code like:
>>> .con_ids = { "fck", "master", "slave", NULL },
>>> - or -
>>> .con_ids = { }, <-- in this case only first clock will be added to pm_clk
>>> )
> According to earlier comments in this thread, device's clocks are
> split into "functional" and "PM" clocks.
> If I understand correctly, a typical platform driver will enable it's
> "functional" clocks during ->probe() and you want the PM domain to
> take care of the "PM" clocks, when the device changes runtime PM
> status.
> How will you describe these different set of device clocks in DT?

True :( You can dig deeper in the history of this series if you wish.
- first Geert Uytterhoeven proposed to use CLK_RUNTIME_PM there
- second I proposed to introduce smth. like "clkops-clocks", "pm-clocks" there
or "fck-clocks"/"opt-clocks" later.


So, this implementation picks up all clocks for each device, which is ok for
Keystone 2 and, because it's platform specific.

>> Yes, it would definitely solve the problem that I see with the infrastructure
>> code that the current version adds into the platform directory.
>> The exact binding of course should be reviewed by the pmdomain and
>> DT maintainers, to ensure that it is done the best possible way, because
>> I assume we will end up using it a lot, and it would be a shame to get
>> it slightly wrong.
>> One possible variation I can think of would be to just use "simple-pmdomain"
>> as the compatible string, and use properties in the node itself to decide
>> what the domain should control, e.g.
>> clk_pmdomain: pmdomain {
>> compatible = "simple-pmdomain";
>> pmdomain-enable-clocks;
>> #power-domain-cells = <0>;
>> };
>> clk_regulator_pmdomain: pmdomain {
>> compatible = "simple-pmdomain";
>> pmdomain-enable-clocks;
>> pmdomain-enable-regulators;
>> #power-domain-cells = <0>;
>> };
>> and then have each device link to one of the nodes as the pmdomain.
> That's seems like a good approach to me.

Yes, but your previous comment is still actual :(

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