Re: [PATCH net-next v3 07/11] dt-bindings: phy: add DT binding for Microsemi Ocelot SerDes muxing

[Quentin Schulz <quentin.schulz@bootlin.com>]

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Hi Rob,

I'm not sure I've understood the way you wanted me to so let me know if
I'm not on the right path.

On Wed, Sep 26, 2018 at 04:35:09PM -0500, Rob Herring wrote:
> On Fri, Sep 14, 2018 at 10:16:05AM +0200, Quentin Schulz wrote:
> > Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
> > ---
> >  Documentation/devicetree/bindings/phy/phy-ocelot-serdes.txt | 40 +++++++-
> >  1 file changed, 40 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/phy/phy-ocelot-serdes.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/phy/phy-ocelot-serdes.txt b/Documentation/devicetree/bindings/phy/phy-ocelot-serdes.txt
> > new file mode 100644
> > index 0000000..2a88cc3
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/phy-ocelot-serdes.txt
> > @@ -0,0 +1,40 @@
> > +Microsemi Ocelot SerDes muxing driver
> > +-------------------------------------
> > +
> > +On Microsemi Ocelot, there is a handful of registers in HSIO address
> > +space for setting up the SerDes to switch port muxing.
> > +
> > +A SerDes X can be "muxed" to work with switch port Y or Z for example.
> > +One specific SerDes can also be used as a PCIe interface.
> > +
> > +Hence, a SerDes represents an interface, be it an Ethernet or a PCIe one.
> > +
> > +There are two kinds of SerDes: SERDES1G supports 10/100Mbps in
> > +half/full-duplex and 1000Mbps in full-duplex mode while SERDES6G supports
> > +10/100Mbps in half/full-duplex and 1000/2500Mbps in full-duplex mode.
> > +
> > +Also, SERDES6G number (aka "macro") 0 is the only interface supporting
> > +QSGMII.
> > +
> > +Required properties:
> > +
> > +- compatible: should be "mscc,vsc7514-serdes"
> > +- #phy-cells : from the generic phy bindings, must be 2.
> > +	       The first number defines the input port to use for a given
> > +	       SerDes macro. The second defines the macro to use. They are
> > +	       defined in dt-bindings/phy/phy-ocelot-serdes.h
> 
> You need to define what this is a child of.
> 

This is a child of the HSIO syscon on the Microsemi Ocelot. I don't
expect all Microsemi SoCs that could use this driver to have the SerDes
node in the HSIO syscon.

Among the latest additions in Documentation/devicetree/bindings/phy I
couldn't find anything close to my understanding of "define what this is
a child of", could you elaborate on what you want exactly?

> > +
> > +Example:
> > +
> > +	serdes: serdes {
> > +		compatible = "mscc,vsc7514-serdes";
> > +		#phy-cells = <2>;
> 
> However, if there are no other resources associated with this, then you 
> don't even need this child node. The parent can be a phy provider and 
> provider of other functions too.
> 

The parent is a syscon with multiple features (SerDes, PLL
configuration, temp sensor, SyncE, ...) so I'm not sure it's possible to
do what you're asking me to. For now, there is only a SerDes node but
ultimately there'll be more than one I guess.

Thanks,
Quentin

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