linux-kernel - Re: [PATCH v4 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping

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Date:   Mon, 17 Oct 2022 12:55:09 +0000
From:   Johnson Wang (王聖鑫) 
        <Johnson.Wang@...iatek.com>
To:     "sboyd@...nel.org" <sboyd@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Kuan-Hsin Lee (李冠新) 
        <Kuan-Hsin.Lee@...iatek.com>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Yu-Chang Wang (王煜樟) 
        <Yu-Chang.Wang@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        Edward-JW Yang (楊哲維) 
        <Edward-JW.Yang@...iatek.com>
Subject: Re: [PATCH v4 2/4] dt-bindings: arm: mediatek: Add new bindings of
 MediaTek frequency hopping

On Fri, 2022-10-14 at 13:42 -0700, Stephen Boyd wrote:
> Quoting Johnson Wang (2022-10-13 04:23:34)
> > Add the new binding documentation for MediaTek frequency hopping
> > and spread spectrum clocking control.
> > 
> > Co-developed-by: Edward-JW Yang <edward-jw.yang@...iatek.com>
> > Signed-off-by: Edward-JW Yang <edward-jw.yang@...iatek.com>
> > Signed-off-by: Johnson Wang <johnson.wang@...iatek.com>
> > Reviewed-by: AngeloGioacchino Del Regno <
> > angelogioacchino.delregno@...labora.com>
> > Reviewed-by: Rob Herring <robh@...nel.org>
> > ---
> >  .../arm/mediatek/mediatek,mt8186-fhctl.yaml   | 53
> > +++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
> > fhctl.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
> > fhctl.yaml
> > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
> > fhctl.yaml
> > new file mode 100644
> > index 000000000000..59111946966c
> > --- /dev/null
> > +++
> > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
> > fhctl.yaml
> > @@ -0,0 +1,53 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: 
> > https://urldefense.com/v3/__http://devicetree.org/schemas/arm/mediatek/mediatek,mt8186-fhctl.yaml*__;Iw!!CTRNKA9wMg0ARbw!yfDH4W14Pek7w3YBrdcBAGj3OSSWGlWk8av4DmHT69Ej4ax75zKqpy89ZvX1Z_aKDPzu$
> >  
> > +$schema: 
> > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!yfDH4W14Pek7w3YBrdcBAGj3OSSWGlWk8av4DmHT69Ej4ax75zKqpy89ZvX1Z9gRczPi$
> >  
> > +
> > +title: MediaTek frequency hopping and spread spectrum clocking
> > control
> 
> The driver patch is in drivers/clk so why not put the binding in
> bindings/clock as well?
> 
Hi Stephen,

Sure, I will move this binding in the next version.

> > +
> > +maintainers:
> > +  - Edward-JW Yang <edward-jw.yang@...iatek.com>
> > +
> 
> [...]
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/mt8186-clk.h>
> > +    fhctl: fhctl@...0ce00 {
> 
> Is it a clock-controller? 'fhctl' isn't a generic node name.
> 

This node is used for determining if PLLs adopt "hopping" method to
adjust their frequency.
It doesn't provide any clock but actually change the behavior of some
PLLs with new .set_rate callback.
Do you think this node acts like one kind of clock-controller?


BRs,
Johnson Wang
> > +        compatible = "mediatek,mt8186-fhctl";
> > +        reg = <0x1000ce00 0x200>;
> > +        clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
> > +        mediatek,hopping-ssc-percent = <3>;