[RFC PATCH 4/8] xilinx: tsn: Add Ethernet MAC (EMAC) and MDIO support to the TSN driver

[Andrew Lunn]

> +static int tsn_mdio_read(struct mii_bus *bus, int phy_id, int reg)
> +{
> +	u32 rc;
> +	int ret;
> +	struct tsn_emac *emac = bus->priv;
> +	struct tsn_priv *common = emac->common;
> +
> +	scoped_guard(mutex, &common->mdio_lock) {

What is this mutex protecting?

> +		tsn_mdio_mdc_enable(emac);

It is unusual to stop MDC. I suspect some PHYs will not like this.
What is your reason for doing this.

> +/**
> + * tsn_mdio_setup - Setup MDIO bus for TSN EMAC
> + * @emac: Pointer to TSN EMAC structure
> + * @mac_np: Device tree node for MAC
> + *
> + * This function initializes the MDIO bus for the TSN EMAC interface.
> + * It allocates an MII bus structure, configures MDIO timing, finds
> + * the MDIO device tree node, and registers the MDIO bus with the kernel.
> + *
> + * Return: 0 on success, negative error code on failure
> + */
> +int tsn_mdio_setup(struct tsn_emac *emac, struct device_node *mac_np)
> +{
> +	struct tsn_priv *common = emac->common;
> +	struct device_node *mdio_node;
> +	struct mii_bus *bus;
> +	int ret;
> +
> +	bus = mdiobus_alloc();
> +	if (!bus)
> +		return -ENOMEM;
> +
> +	snprintf(bus->id, MII_BUS_ID_SIZE, "tsn-mac-%.8llx",
> +		 (unsigned long long)emac->regs_start);
> +
> +	bus->priv = emac;
> +	bus->name = "Xilinx TSN Ethernet MDIO";
> +	bus->read = tsn_mdio_read;
> +	bus->write = tsn_mdio_write;
> +	bus->parent = common->dev;
> +	emac->mii_bus = bus;
> +
> +	mdio_node = of_get_child_by_name(mac_np, "mdio");
> +	if (!mdio_node) {
> +		dev_err(common->dev, "MAC%d: missing 'mdio' child node\n",
> +			emac->emac_num);
> +		ret = -ENODEV;
> +		goto unregister;
> +	}

I forget, does the binding have a required: for the MDIO node?

> +	ret = tsn_mdio_enable(emac);
> +	if (ret < 0)
> +		goto unregister;
> +	ret = of_mdiobus_register(bus, mdio_node);

Having a node in DT is generally optional. You can pass NULL to
of_mdiobus_register() and it will do the right thing.

	Andrew