netdev - Re: Re: [PATCH v4 1/4] dt-bindings: net: phy: Add support for NXP TJA11xx

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Date:   Mon, 23 Mar 2020 16:14:23 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Christian Herber <christian.herber@....com>
Cc:     Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Marek Vasut <marex@...x.de>, netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: Re: [PATCH v4 1/4] dt-bindings: net: phy: Add support for NXP
 TJA11xx

> Yes, it is one device with two address. This is if you call the entire IC a device. If you look at it from a PHY perspective, it is two devices with 1 address.
> If you just look at it as a single device, it gets difficult to add PHY specific properties in the future, e.g. master/slave selection.

> In my opinion its important to have some kind of container for the
> entire IC, but likewise for the individual PHYs.

Yes, we need some sort of representation of two devices.

Logically, the two PHYs are on the same MDIO bus, so you could have
two nodes on the main bus.

Or you consider the secondary PHY as being on an internal MDIO bus
which is transparently bridged to the main bus. This is what was
proposed in the last patchset.

Because this bridge is transparent, the rest of the PHY/MDIO framework
has no idea about it. So i prefer that we keep with two PHY nodes on
the main bus. But i still think we need the master PHY to register the
secondary PHY, due to the missing PHY ID, and the other constrains
like resets which the master PHY has to handle.

     Andrew