linux-kernel - Re: [PATCH net-next v3 10/11] net: mdio: add C45-over-C22 fallback to fwnode_mdiobus_register

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Message-ID: <3fd646ef7c4f92187a2d44af6d1c9a03@kernel.org>
Date:   Wed, 19 Jul 2023 09:32:19 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Marek Behún <kabel@...nel.org>,
        Xu Liang <lxu@...linear.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v3 10/11] net: mdio: add C45-over-C22 fallback to
 fwnode_mdiobus_register_phy()

Am 2023-07-19 02:03, schrieb Andrew Lunn:
>> Please note, that both with the old and the new code compatible =
>> "ethernet-phy-idNNNN.NNNN" only works for the C22 case. I'm wondering 
>> if
>> compatible = "ethernet-phy-idNNNN.NNNN", "ethernet-phy-ieee802.3-c45
>> even makes sense because there might be multiple C45 ids. At least it 
>> is
>> an allowed pattern according to the device tree bindings. But with the
>> current code, the ethernet-phy-idNNNN.NNNN is ignored in the c45 case.
> 
> I think these two should be orthogonal.
> 
> ethernet-phy-idNNNN.NNNN should be used to load the driver. The driver
> has a list of IDs it can drive, and we want the module loading
> machinery to load a module which can driver this ID.

See [1]. It is used to overwrite the PHY ID. Which I think works
in the c22 case.

> "ethernet-phy-ieee802.3-c45" should be about how to read the ID
> registers, if ethernet-phy-idNNNN.NNNN is not present.

And if it's present? See [2].

-michael

[1] 
https://elixir.bootlin.com/linux/v6.4.3/source/Documentation/devicetree/bindings/net/ethernet-phy.yaml#L38
[2] 
https://elixir.bootlin.com/linux/v6.4.3/source/Documentation/devicetree/bindings/net/ethernet-phy.yaml#L50