Re: [v2 1/2] Docs/devicetree: add serdes-output-amplitude-mv to marvell.txt

[Andrew Lunn <andrew@lunn.ch>]

> > diff --git a/Documentation/devicetree/bindings/net/dsa/marvell.txt b/Documentation/devicetree/bindings/net/dsa/marvell.txt
> > index 2363b412410c..9292b6f960df 100644
> > --- a/Documentation/devicetree/bindings/net/dsa/marvell.txt
> > +++ b/Documentation/devicetree/bindings/net/dsa/marvell.txt
> > @@ -46,6 +46,11 @@ Optional properties:
> >  - mdio?		: Container of PHYs and devices on the external MDIO
> >  			  bus. The node must contains a compatible string of
> >  			  "marvell,mv88e6xxx-mdio-external"
> > +- serdes-output-amplitude-mv: Configure the output amplitude of the serdes
> > +			      interface in millivolts. This option can be
> > +                              set in the ports node as it is a property of
> > +                              the port.
> > +    serdes-output-amplitude-mv = <210>;
> 
> The suffix should be millivolt, as can be seen in other bindings.

My bad. I recommended that. It does seem like both are used, but
millivolt is more popular.

> Also I think maybe use "tx" instead of "output"? It is more common to
> refere to serdes pairs as rx/tx instead of input/output:
> 
>   serdes-tx-amplitude-millivolt
> 
> I will probably want to add this property also either to mvneta, or to
> A3720 common PHY binding. Andrew, do you think it should be put
> somewhere more generic?

Not sure what the common location would be. I assume for mvneta and
A3720 it is part of the generic phy comphy driver? Does generic phy
have any properties like this already?

Here we are using it in DSA. And it could also be used in a Marvell
phy driver node.

So maybe something like serdes.yaml?
bindings/phy/microchip,sparx5-serdes.yaml actually mentions

  * Tx output amplitude control

but does not define a property for it, but that looks like another use
case for it.

     Andrew