Subject: Re: [PATCH net-next] net: dsa: mt7530: support OF-based registration of switch MDIO bus

From: Simon Horman <[email-masked]>
Date: Sun, 7 Jan 2024 19:52:41 +0000

On Sat, Jan 06, 2024 at 03:21:42PM +0300, Arınç ÜNAL wrote:
> From: David Bauer <[email-masked]>
> 
> Currently the MDIO bus of the switches the MT7530 DSA subdriver controls
> can only be registered as non-OF-based. Bring support for registering the
> bus OF-based.
> 
> The subdrivers that control switches [with MDIO bus] probed on OF must
> follow this logic to support all cases properly:
> 
> No switch MDIO bus defined: Populate ds->user_mii_bus, register the MDIO
> bus, set the interrupts for PHYs if "interrupt-controller" is defined at
> the switch node. This case should only be covered for the switches which
> their dt-bindings documentation didn't document the MDIO bus from the
> start. This is to keep supporting the device trees that do not describe the
> MDIO bus on the device tree but the MDIO bus is being used nonetheless.
> 
> Switch MDIO bus defined: Don't populate ds->user_mii_bus, register the MDIO
> bus, set the interrupts for PHYs if ["interrupt-controller" is defined at
> the switch node and "interrupts" is defined at the PHY nodes under the
> switch MDIO bus node].
> 
> Switch MDIO bus defined but explicitly disabled: If the device tree says
> status = "disabled" for the MDIO bus, we shouldn't need an MDIO bus at all.
> Instead, just exit as early as possible and do not call any MDIO API.
> 
> The use of ds->user_mii_bus is inappropriate when the MDIO bus of the
> switch is described on the device tree [1], which is why we don't populate
> ds->user_mii_bus in that case.
> 
> Link: https://lore.kernel.org/netdev/20231213120656.x46fyad6ls7sqyzv@skbuf/ [1]
> Suggested-by: David Bauer <[email-masked]>
> Signed-off-by: Arınç ÜNAL <[email-masked]>
> ---
>  drivers/net/dsa/mt7530.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 391c4dbdff42..39d7e7ad7154 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -2153,17 +2153,25 @@ mt7530_free_irq(struct mt7530_priv *priv)
>  static int
>  mt7530_setup_mdio(struct mt7530_priv *priv)
>  {
> +	struct device_node *mnp, *np = priv->dev->of_node;
>  	struct dsa_switch *ds = priv->ds;
>  	struct device *dev = priv->dev;
>  	struct mii_bus *bus;
>  	static int idx;
> -	int ret;
> +	int ret = 0;
> +
> +	mnp = of_get_child_by_name(np, "mdio");
> +
> +	if (mnp && !of_device_is_available(mnp))
> +		goto out;

nit: I think it would easier on the eyes to simply

		return 0;

>  
>  	bus = devm_mdiobus_alloc(dev);
>  	if (!bus)
>  		return -ENOMEM;
>  
> -	ds->user_mii_bus = bus;
> +	if (!mnp)
> +		ds->user_mii_bus = bus;
> +
>  	bus->priv = priv;
>  	bus->name = KBUILD_MODNAME "-mii";
>  	snprintf(bus->id, MII_BUS_ID_SIZE, KBUILD_MODNAME "-%d", idx++);
> @@ -2174,16 +2182,18 @@ mt7530_setup_mdio(struct mt7530_priv *priv)
>  	bus->parent = dev;
>  	bus->phy_mask = ~ds->phys_mii_mask;
>  
> -	if (priv->irq)
> +	if (priv->irq && !mnp)
>  		mt7530_setup_mdio_irq(priv);
>  
> -	ret = devm_mdiobus_register(dev, bus);
> +	ret = devm_of_mdiobus_register(dev, bus, mnp);
> +	of_node_put(mnp);
>  	if (ret) {
>  		dev_err(dev, "failed to register MDIO bus: %d\n", ret);
>  		if (priv->irq)
>  			mt7530_free_mdio_irq(priv);
>  	}
>  
> +out:
>  	return ret;
>  }
>  
> -- 
> 2.40.1
>