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    SubjectRe: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains
    On 11/20/2014 01:34 PM, Ulf Hansson wrote:
    > On 19 November 2014 14:47, Arnd Bergmann <arnd@arndb.de> 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
    https://lkml.org/lkml/2014/11/6/319
    - second I proposed to introduce smth. like "clkops-clocks", "pm-clocks" there
    https://lkml.org/lkml/2014/6/12/436
    or "fck-clocks"/"opt-clocks" later.

    ^failed.

    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 :(

    Regards,
    -grygorii


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