linux-kernel - Re: [PATCH v6 08/30] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc: Add support for QMC HDLC

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Message-ID: <20230925101703.1bf083f1@bootlin.com>
Date:   Mon, 25 Sep 2023 10:17:03 +0200
From:   Herve Codina <herve.codina@...tlin.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, Lee Jones <lee@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Qiang Zhao <qiang.zhao@....com>, Li Yang <leoyang.li@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Shengjiu Wang <shengjiu.wang@...il.com>,
        Xiubo Li <Xiubo.Lee@...il.com>,
        Fabio Estevam <festevam@...il.com>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Randy Dunlap <rdunlap@...radead.org>, netdev@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, alsa-devel@...a-project.org,
        Simon Horman <horms@...nel.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v6 08/30] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc:
 Add support for QMC HDLC

Hi Krzysztof,

On Sat, 23 Sep 2023 19:39:49 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 22/09/2023 09:58, Herve Codina wrote:
> > The QMC (QUICC mutichannel controller) is a controller present in some
> > PowerQUICC SoC such as MPC885.
> > The QMC HDLC uses the QMC controller to transfer HDLC data.
> > 
> > Additionally, a framer can be connected to the QMC HDLC.
> > If present, this framer is the interface between the TDM bus used by the
> > QMC HDLC and the E1/T1 line.
> > The QMC HDLC can use this framer to get information about the E1/T1 line
> > and configure the E1/T1 line.
> > 
> > Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> > ---
> >  .../soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml      | 24 +++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml b/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
> > index 82d9beb48e00..61dfd5ef7407 100644
> > --- a/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
> > +++ b/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
> > @@ -101,6 +101,27 @@ patternProperties:
> >            Channel assigned Rx time-slots within the Rx time-slots routed by the
> >            TSA to this cell.
> >  
> > +      compatible:
> > +        const: fsl,qmc-hdlc  
> 
> Why this is not a device/SoC specific compatible?

This compatible is present in a QMC channel.
The parent node (the QMC itself) contains a compatible with device/SoC:
--- 8< ---
  compatible:
    items:
      - enum:
          - fsl,mpc885-scc-qmc
          - fsl,mpc866-scc-qmc
      - const: fsl,cpm1-scc-qmc
--- 8< ---

At the child level (ie QMC channel), I am not sure that adding device/SoC
makes sense. This compatible indicates that the QMC channel is handled by
the QMC HDLC driver.
At this level, whatever the device/SoC, we have to be QMC compliant.

With these details, do you still think I need to change the child (channel)
compatible ?

> 
> > +
> > +      fsl,framer:
> > +        $ref: /schemas/types.yaml#/definitions/phandle
> > +        description:
> > +          phandle to the framer node. The framer is in charge of an E1/T1 line
> > +          interface connected to the TDM bus. It can be used to get the E1/T1 line
> > +          status such as link up/down.
> > +
> > +    allOf:
> > +      - if:
> > +          properties:
> > +            compatible:
> > +              not:
> > +                contains:
> > +                  const: fsl,qmc-hdlc
> > +        then:
> > +          properties:
> > +            fsl,framer: false
> > +
> >      required:
> >        - reg
> >        - fsl,tx-ts-mask
> > @@ -159,5 +180,8 @@ examples:
> >              fsl,operational-mode = "hdlc";
> >              fsl,tx-ts-mask = <0x00000000 0x0000ff00>;
> >              fsl,rx-ts-mask = <0x00000000 0x0000ff00>;
> > +
> > +            compatible = "fsl,qmc-hdlc";  
> 
> compatible is always the first property.

Will be moved to the first property in the next iteration.

Best regards,
Hervé

> 
> > +            fsl,framer = <&framer>;
> >          };
> >      };  
> 
> Best regards,
> Krzysztof
>