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

From: Conor Dooley <[email-masked]>
Date: Wed, 13 Sep 2023 15:56:16 +0100

On Wed, Sep 13, 2023 at 04:52:50PM +0200, Herve Codina wrote:
> On Wed, 13 Sep 2023 15:42:45 +0100
> Conor Dooley <[email-masked]> 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 <[email-masked]> 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 <[email-masked]>
> > > > > ---
> > > > >  .../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).

Ah apologies, I had it backwards! Your suggestion seems fair in that
case.

Thanks,
Conor.