linux-kernel - Re: [PATCH devicetree 3/4] arm64: dts: fsl: ls1028a: add node for Felix switch

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Date:   Mon, 17 Feb 2020 19:24:25 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Shawn Guo <shawnguo@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: Re: [PATCH devicetree 3/4] arm64: dts: fsl: ls1028a: add node for
 Felix switch

On Mon, 17 Feb 2020 at 17:33, Vladimir Oltean <olteanv@...il.com> wrote:
>
> Hi Andrew,
>
> On Mon, 17 Feb 2020 at 17:29, Andrew Lunn <andrew@...n.ch> wrote:
> >
> > Hi Vladimir
> >
> > > +                                     /* Internal port with DSA tagging */
> > > +                                     mscc_felix_port4: port@4 {
> > > +                                             reg = <4>;
> > > +                                             phy-mode = "gmii";
> >
> > Is it really using gmii? Often in SoC connections use something else,
> > and phy-mode = "internal" is more appropriate.
> >
>
> What would be that "something else"? Given that the host port and the
> switch are completely different hardware IP blocks, I would assume
> that a parallel GMII is what's connecting them, no optimizations done.
> Certainly no serializer. But I don't know for sure.
> Does it matter, in the end?
>

To clarify, the reason I'm asking whether it matters is because I'd
have to modify PHY_INTERFACE_MODE_GMII in
drivers/net/dsa/ocelot/felix_vsc9959.c too, for the internal ports.
Then I'm not sure anymore what tree this device tree patch should go
in through.

> > > +                                             ethernet = <&enetc_port2>;
> > > +
> > > +                                             fixed-link {
> > > +                                                     speed = <2500>;
> > > +                                                     full-duplex;
> > > +                                             };
> >
> > gmii and 2500 also don't really go together.
>
> Not even if you raise the clock frequency?
>
> >
> >      Andrew
>
> Thanks,
> -Vladimir