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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Wed, 14 Jun 2017 11:42:35 +0200
Message-ID: <CAMuHMdU6ZsqbRhG7=dYE=B_7To=ioWrwWwdoRYGdEQJwB4wW6A@mail.gmail.com>
Subject: Re: [PATCH v2] Documentation: clock: address more for clock-cells property
To: Chunyan Zhang <zhang.chunyan@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-clk <linux-clk@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        zhang.lyra@gmail.com
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Hi Chunyan,

On Wed, Jun 14, 2017 at 11:21 AM, Chunyan Zhang
<zhang.chunyan@linaro.org> wrote:
> The value of property 'clock-cells' is not determined only by the number
> of clock outputs in one clock node, it is determined by whether the clock
> output in this node can be referenced directly without index. If the
> output clock has to be referenced by a index, the clock-cell of this
> clock node can't be defined 0.
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
> ---
>  Documentation/devicetree/bindings/clock/clock-bindings.txt | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> index 2ec489e..e2b76b4 100644
> --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> @@ -18,6 +18,9 @@ Required properties:
>                    with a single clock output and 1 for nodes with multiple
>                    clock outputs.
>
> +                  There's one exception, please see the description for
> +                  clock-indices below.
> +
>  Optional properties:
>  clock-output-names: Recommended to be a list of strings of clock output signal
>                     names indexed by the first cell in the clock specifier.
> @@ -48,6 +51,13 @@ clock-indices:          If the identifying number for the clocks in the node
>                    is not linear from zero, then this allows the mapping of
>                    identifiers into the clock-output-names array.
>
> +                  This property not only servers for clocks with multiple

serves

> +                  clock outputs, but also for clocks with a single clock
> +                  output whose identifying number is not zero.

Why would you want a single clock and a non-zero identifying number?

> +                  So long as clock-indices is set, clock-cells cannot be
> +                  set zero.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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