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From:   Rob Herring <robh+dt@kernel.org>
Date:   Wed, 13 Apr 2022 16:44:02 -0500
Message-ID: <CAL_JsqLsE9kGzpHr6bkLmU9xmdxXiq-dWBFFO-W+4Z33iqK8_g@mail.gmail.com>
Subject: Re: [PATCH v1] dt-bindings: clock: convert rockchip,rk3188-cru.txt to YAML
To:     Stephen Boyd <sboyd@kernel.org>
Cc:     Johan Jonker <jbx6244@gmail.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        "heiko@sntech.de" <heiko@sntech.de>,
        Krzysztof Kozlowski <krzk+dt@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        linux-clk <linux-clk@vger.kernel.org>,
        devicetree@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thu, Mar 31, 2022 at 5:38 PM Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Krzysztof Kozlowski (2022-03-25 00:31:25)
> > On 25/03/2022 01:51, Stephen Boyd wrote:
> > > Quoting Johan Jonker (2022-03-24 12:51:36)
> > >> Hi Heiko, Krzysztof,
> > >>
> > >> Question for the Rockchip clock maintainer:
> > >> What clock should be used here and other SoCs with several clock parents
> > >> in the tree?
> > >>
> > >> The clock.yaml produces a lot off notifications like:
> > >>
> > >> /arch/arm/boot/dts/rk3036-evb.dtb: clock-controller@20000000: 'clocks'
> > >> is a dependency of 'assigned-clocks'
> > >
> > > 'clocks' is not a dependency of 'assigned-clocks'. The dt-schema should
> > > be fixed to remove that requirement.
> >
> > If the driver does not have any clock inputs ("clocks" property), why
> > does it care about some clock frequencies and parents?
>
> Because it's a clock provider itself. In this case I suspect because
> this is a clock-controller node it was skipping describing some crystal
> input though. Maybe it wants to configure the various PLLs in the
> clock-controller for a particular board. I can imagine some node with
> #clock-cells may want to configure the frequency of the clock outputs or
> configure the clk parents for a certain board/SoC. In that case there
> may not be any clocks property, but we still want to configure things.
>
> >
> > The clocks is the logical dependency of assigned-clocks, because
> > otherwise hardware description is not complete.
>
> Sure, but also #clock-cells indicating that this is a clock-controller
> itself means something. The existing bindings are what they are so
> forcing bindings to be updated to comply with having a 'clocks' property
> doesn't seem very nice.
>
> >
> > What should be here for Rockhip? We had similar cases like this for many
> > drivers, I was fixing some of Exynos as well. In my case usually the
> > root/external clock was missing, so I supplied is as input clock to the
> > clock controller.
> >
>
> Can the schema consider either #clock-cells or clocks? I think that will
> work for most cases. It would also be good to have a comment in the
> schema or more detail around the definition of assigned-clocks in
> bindings/clock/clock-bindings.txt that clocks or #clock-cells are
> required. It would be super cool if assigned-clocks only applied if
> #clock-cells was present, otherwise clocks property applies, but I doubt
> we can do that anymore given how long the binding has been around.

I've just made a schema change to allow this. This will still require
'assigned-clocks' to be explicitly listed in the clock controller
schemas if 'clocks' is not present.

Please don't add to clock-bindings.txt, but improve the schema
instead. I need Samsung's permission to relicense all the
assigned-clocks text though.

Rob