linux-kernel - Re: [PATCH v5 08/31] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc: Add support for QMC HDLC

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Message-ID: <20230913092640.76934b31@bootlin.com>
Date:   Wed, 13 Sep 2023 09:26:40 +0200
From:   Herve Codina <herve.codina@...tlin.com>
To:     Conor Dooley <conor@...nel.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 v5 08/31] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc:
 Add support for QMC HDLC

Hi Conor,

On Tue, 12 Sep 2023 18:21:58 +0100
Conor Dooley <conor@...nel.org> wrote:

> On Tue, Sep 12, 2023 at 12:10:18PM +0200, 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>
> > ---
> >  .../bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml   | 13 +++++++++++++
> >  1 file changed, 13 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..b5073531f3f1 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 +101,16 @@ patternProperties:
> >            Channel assigned Rx time-slots within the Rx time-slots routed by the
> >            TSA to this cell.
> >  
> > +      compatible:
> > +        const: fsl,qmc-hdlc
> > +
> > +      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.  
> 
> Sounds like this fsl,framer property should depend on the compatible
> being present, no?

Well from the implementation point of view, only the QMC HDLC driver uses this
property.

From the hardware description point of view, this property means that the time slots
handled by this channel are connected to the framer. So I think it makes sense for
any channel no matter the compatible (even if compatible is not present).

Should I change and constraint the fsl,framer property to the compatible presence ?
If so, is the following correct for this contraint ?
   --- 8< ---
   dependencies:
     - fsl,framer: [ compatible ];
   --- 8< ---

Regards,
Hervé

> 
> Thanks,
> Conor.
> 
> > +
> >      required:
> >        - reg
> >        - fsl,tx-ts-mask
> > @@ -159,5 +169,8 @@ examples:
> >              fsl,operational-mode = "hdlc";
> >              fsl,tx-ts-mask = <0x00000000 0x0000ff00>;
> >              fsl,rx-ts-mask = <0x00000000 0x0000ff00>;
> > +
> > +            compatible = "fsl,qmc-hdlc";
> > +            fsl,framer = <&framer>;
> >          };
> >      };
> > -- 
> > 2.41.0
> >