Re: [PATCH v2 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping

[AngeloGioacchino Del Regno]

Il 15/09/22 06:00, Johnson Wang ha scritto:
> Hi Angelo,
>
> Thanks for your review.
>
> On Wed, 2022-09-14 at 15:46 +0200, AngeloGioacchino Del Regno wrote:
> > Il 14/09/22 14:45, Johnson Wang ha scritto:
> > > Add the new binding documentation for MediaTek frequency hopping
> > > and spread spectrum clocking control.
> > >
> > > Co-developed-by: Edward-JW Yang <edward-jw.yang@xxxxxxxxxxxx>
> > > Signed-off-by: Edward-JW Yang <edward-jw.yang@xxxxxxxxxxxx>
> > > Signed-off-by: Johnson Wang <johnson.wang@xxxxxxxxxxxx>
> > > ---
> > >    .../bindings/arm/mediatek/mediatek,fhctl.yaml | 47
> > > +++++++++++++++++++
> > >    1 file changed, 47 insertions(+)
> > >    create mode 100644
> > > Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
> > >
> > > diff --git
> > > a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > > l
> > > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > > l
> > > new file mode 100644
> > > index 000000000000..7b0fd0889bb6
> > > --- /dev/null
> > > +++
> > > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > > l
> > > @@ -0,0 +1,47 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id:
> > > https://urldefense.com/v3/__http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml*__;Iw!!CTRNKA9wMg0ARbw!3sumdhtrK5Ah5_rfIilgm4UUmnwkkqMpc3r_ZfkLfsXsLn-_AKm9ZokhJGD1Fl-gJpckAKHZh-jNVW64KRU8Duv1kg$
> > >   
> > > +$schema:
> > > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!3sumdhtrK5Ah5_rfIilgm4UUmnwkkqMpc3r_ZfkLfsXsLn-_AKm9ZokhJGD1Fl-gJpckAKHZh-jNVW64KRWMb8jIsw$
> > >   
> > > +
> > > +title: MediaTek frequency hopping and spread spectrum clocking
> > > control
> > > +
> > > +maintainers:
> > > +  - Edward-JW Yang <edward-jw.yang@xxxxxxxxxxxx>
> > > +
> > > +description: |
> > > +  Frequency hopping control (FHCTL) is a piece of hardware that
> > > control
> > > +  some PLLs to adopt "hopping" mechanism to adjust their
> > > frequency.
> > > +  Spread spectrum clocking (SSC) is another function provided by
> > > this hardware.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: mediatek,mt8186-fhctl
> > > +
> > > +  reg:
> > > +    maxItems: 1
> >
> > There are still a few issues in this binding that I can immediately
> > see...
> >
> > > +
> > > +  clocks:
> >
> > MT8195 has 23 PLLs, MT8186 has 14, but perhaps in the future we may
> > see
> > something more than that on some newer SoC, so...
> >
> >     clocks:
> >       maxItems: 30
>
> May I add "minItems: 1" to clocks property?

Of course you can! Sorry for the incomplete advice here :-)

> Without this, dt_binding_check will fail because we don't have enough
> clocks in the example. (Both MT8195 and MT8186 don't have 30 PLLs)
>
> > > +    description: Phandles of the PLL with FHCTL hardware
> > > capability.
> > > +
> > > +  mediatek,hopping-ssc-percents:
> > > +    description: The percentage of spread spectrum clocking for
> > > one PLL.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> >
> > This is an array, so...
> > $ref: /schemas/types.yaml#/definitions/uint32-array
> >
> > ...also, maxItems?
>
> As you know, mediatek,hopping-ssc-percents property is used to specify
> ssc rate for matching clocks.
>
> If we have to add maxItems, I think we should specify the same value
> as clocks property. Is my understanding wrong?

Your understanding is right. The number of min/max items on the ssc
percents will be the same as clocks.

Regards,
Angelo

> Thanks!
>
> BRs,
> Johnson Wang
> > and you should also specify:
> >
> > default: 0   <- because, by default, SSC is disabled
> > minimum: 0   <- because this is the minimum accepted value
> >
> >
> > Regards,
> > Angelo
> >
> > > +    maximum: 8
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - clocks
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/clock/mt8186-clk.h>
> > > +    fhctl: fhctl@1000ce00 {
> > > +        compatible = "mediatek,mt8186-fhctl";
> > > +        reg = <0x1000c000 0xe00>;
> > > +        clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
> > > +        mediatek,hopping-ssc-percents = <3>;
> > > +    };

--
AngeloGioacchino Del Regno
Software Engineer

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