netdev - Re: [PATCH 2/2] dt-bindings: net: dwmac: document 'mac-mode' property

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Message-ID: <dd3877616b2dee81cf35cfc9f53bbbb47335a357.camel@analog.com>
Date:   Tue, 17 Sep 2019 07:21:54 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "andrew@...n.ch" <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>
Subject: Re: [PATCH 2/2] dt-bindings: net: dwmac: document 'mac-mode' property

On Mon, 2019-09-16 at 12:49 +0300, Alexandru Ardelean wrote:
> On Fri, 2019-09-13 at 15:36 +0100, Rob Herring wrote:
> > [External]
> > 
> > On Fri, Sep 06, 2019 at 04:02:56PM +0300, Alexandru Ardelean wrote:
> > > This change documents the 'mac-mode' property that was introduced in
> > > the
> > > 'stmmac' driver to support passive mode converters that can sit in-
> > > between
> > > the MAC & PHY.
> > > 
> > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> > > ---
> > >  Documentation/devicetree/bindings/net/snps,dwmac.yaml | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > index c78be15704b9..ebe4537a7cce 100644
> > > --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > @@ -112,6 +112,14 @@ properties:
> > >    reset-names:
> > >      const: stmmaceth
> > >  
> > > +  mac-mode:
> > > +    maxItems: 1
> > 
> > Is this an array because {min,max}Items is for arrays? It should be 
> > defined as a string with possible values.
> > 
> > As this property is the same as another, you can do this:
> > 
> > $ref: ethernet-controller.yaml#/properties/phy-connection-type
> > 
> > Unless only a small subset of those values are valid here, then you
> > may 
> > want to list them here.
> > 
> 
> Ack.
> Thank you.
> 
> Will investigate and re-spin.

Looking at '$ref: ethernet-controller.yaml#/properties/phy-connection-type'
it looks like 'mac-mode' could cover almost all 'phy-connection-type'
except for a few (1 or 2). The 'dwmac' driver is pretty complex/big.

There was a note that Andrew made on a previous change, that we could have
a 'mac-mode' (similar to 'phy-mode') and that could become generic (either
in phylib or maybe somewhere else in netdev).

In any case, the conclusion [from my side] would be that
'$ref: ethernet-controller.yaml#/properties/phy-connection-type'
could work, and be sufficiently future-proof.

Thanks
Alex

> 
> 
> > > +    description:
> > > +      The property is identical to 'phy-mode', and assumes that
> > > there is mode
> > > +      converter in-between the MAC & PHY (e.g. GMII-to-RGMII). This
> > > converter
> > > +      can be passive (no SW requirement), and requires that the MAC
> > > operate
> > > +      in a different mode than the PHY in order to function.
> > > +
> > >    snps,axi-config:
> > >      $ref: /schemas/types.yaml#definitions/phandle
> > >      description:
> > > -- 
> > > 2.20.1
> > >