netdev - Re: [net-next 2/2] ravb: Add support for an optional MDIO mode

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Date: Mon, 11 Mar 2024 10:32:35 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: Sergey Shtylyov <s.shtylyov@....ru>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, 
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, Biju Das <biju.das.jz@...renesas.com>, 
	netdev@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next 2/2] ravb: Add support for an optional MDIO mode

Hi Niklas,

On Sat, Mar 9, 2024 at 4:55 PM Niklas Söderlund
<niklas.soderlund+renesas@...natech.se> wrote:
> The driver used the OF node of the device itself when registering the
> MDIO bus. While this works it creates a problem, it forces any MDIO bus
> properties to also be set on the devices OF node. This mixes the
> properties of two distinctly different things and is confusing.
>
> This change adds support for an optional mdio node to be defined as a
> child to the device OF node. The child node can then be used to describe
> MDIO bus properties that the MDIO core can act on when registering the
> bus.
>
> If no mdio child node is found the driver fallback to the old behavior
> and register the MDIO bus using the device OF node. This change is
> backward compatible with old bindings in use.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>

Thanks for your patch!

> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -2582,8 +2583,20 @@ static int ravb_mdio_init(struct ravb_private *priv)
>         snprintf(priv->mii_bus->id, MII_BUS_ID_SIZE, "%s-%x",
>                  pdev->name, pdev->id);
>
> -       /* Register MDIO bus */
> -       error = of_mdiobus_register(priv->mii_bus, dev->of_node);
> +       /* Register MDIO bus
> +        *
> +        * Look for a mdio child node, if it exist use it when registering the
> +        * MDIO bus. If no node is found fallback to old behavior and use the
> +        * device OF node. This is used to be able to describe MDIO bus
> +        * properties that are consumed when registering the MDIO bus.
> +        */
> +       mdio_node = of_get_child_by_name(dev->of_node, "mdio");
> +       if (mdio_node) {
> +               error = of_mdiobus_register(priv->mii_bus, mdio_node);
> +               of_node_put(mdio_node);
> +       } else {
> +               error = of_mdiobus_register(priv->mii_bus, dev->of_node);
> +       }
>         if (error)
>                 goto out_free_bus;
>

Perhaps the code should be streamlined for the modern case?

        mdio_node = of_get_child_by_name(dev->of_node, "mdio");
        if (!mdio_node) {
                /* backwards compatibility for DT lacking mdio subnode */
                mdio_node = of_node_get(dev->of_node);
        }

        error = of_mdiobus_register(priv->mii_bus, mdio_node);
        of_node_put(mdio_node);

When deemed necessary, you can easily replace the backwards
compatibility handling by error handling later.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds