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

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Message-ID: <CA+h21ho29TRG8JYfSaaSsoxM-mg0-yOKBNCq9wbHDHCf2pkdUg@mail.gmail.com>
Date:   Mon, 17 Feb 2020 17:33:33 +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

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?

> > +                                             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