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: <20230913165250.02bab2ad@bootlin.com>
Date:   Wed, 13 Sep 2023 16:52:50 +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

On Wed, 13 Sep 2023 15:42:45 +0100
Conor Dooley <conor@...nel.org> wrote:

> On Wed, Sep 13, 2023 at 09:26:40AM +0200, Herve Codina wrote:
> > 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< ---  
> 
> The regular sort of
> if:
> 	compatible:
> 		contains:
> 			const: foo
> then:
> 	required:
> 		- fsl,framer
> would fit the bill, no?

Not sure.
"fsl,framer" is an optional property (depending on the hardware we can have
a framer or not).

Hervé