linux-kernel - Re: [PATCH v2 3/5] arm64: dts: meson: g12a: add mdio multiplexer

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Message-ID: <20190520190533.GF22024@lunn.ch>
Date:   Mon, 20 May 2019 21:05:33 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        devicetree@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org, f.fainelli@...il.com,
        hkallweit1@...il.com
Subject: Re: [PATCH v2 3/5] arm64: dts: meson: g12a: add mdio multiplexer

> > +                               int_mdio: mdio@1 {
> > +                                       reg = <1>;
> > +                                       #address-cells = <1>;
> > +                                       #size-cells = <0>;
> > +
> > +                                       internal_ephy: ethernet_phy@8 {
> > +                                               compatible = "ethernet-phy-id0180.3301",
> > +                                                            "ethernet-phy-ieee802.3-c22";
> Based on your comment on v1 of this patch [0] the Ethernet PHY ID is
> defined by this "mdio-multiplexer" (write arbitrary value to a
> register then that's the PHY ID which will show up on the bus)
> I'm fine with explicitly listing the ID which the PHY driver binds to
> because I don't know a better way.

Does reading the ID registers give the correct ID, once you have poked
registers in the mdio-multiplexer? If so, you don't need this
compatible string.

If the read is giving the wrong ID, then yes, you do want this. But
then please add a comment in the DT blob. This is very unusual, so
should have some explanation why it is needed.

Thanks
	Andrew