Re: [PATCH v2 net-next 02/15] net: mdio: add driver for NXP SJA1110 100BASE-T1 embedded PHYs

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Jan 22, 2026 at 12:56:41PM +0200, Vladimir Oltean wrote:
> This driver is the standalone variant of drivers/net/dsa/sja1105/sja1105_mdio.c.
> In terms of differences:
> 
> - this one uses regmaps provided by the parent as a method to abstract
>   away the sja1105_xfer_u32() calls for register access
> - the driver prefix has been changed from sja1105 to sja1110 (this MDIO
>   controller is not present on the older SJA1105 family)
> - in the sja1105 driver, each memory word has 32 bits, so addresses as
>   seen by regmap need to be multiplied by 4. This affects what
>   sja1110_base_t1_encode_addr() returns, and is different compared to
>   sja1105_base_t1_encode_addr().

...

> +static int sja1110_base_t1_mdio_read_c22(struct mii_bus *bus, int phy, int reg)
> +{
> +	struct sja1110_base_t1_private *priv = bus->priv;
> +	struct regmap *regmap = priv->regmap;
> +	unsigned int addr, val;
> +	int err;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C22, reg & 0x1f);

GENMASK() ? Or do you have already a defined mask for this?

> +	err = regmap_read(regmap, priv->base + addr, &val);
> +	if (err)
> +		return err;
> +
> +	return val & 0xffff;

lower_16_bits() from wordpart.h?

> +}

...

> +static int sja1110_base_t1_mdio_read_c45(struct mii_bus *bus, int phy,
> +					 int mmd, int reg)
> +{
> +	struct sja1110_base_t1_private *priv = bus->priv;
> +	struct regmap *regmap = priv->regmap;
> +	unsigned int addr, val;
> +	int err;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C45_ADDR, mmd);
> +	err = regmap_write(regmap, priv->base + addr, reg);
> +	if (err)
> +		return err;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C45_DATA, mmd);
> +	err = regmap_read(regmap, priv->base + addr, &val);
> +	if (err)
> +		return err;
> +
> +	return val & 0xffff;

Ditto.

> +}

...

> +static int sja1110_base_t1_mdio_write_c22(struct mii_bus *bus, int phy, int reg,
> +					  u16 val)
> +{
> +	struct sja1110_base_t1_private *priv = bus->priv;
> +	struct regmap *regmap = priv->regmap;
> +	unsigned int addr;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C22, reg & 0x1f);
> +	return regmap_write(regmap, priv->base + addr, val & 0xffff);

val is already u16.

> +}

...

> +static int sja1110_base_t1_mdio_write_c45(struct mii_bus *bus, int phy,
> +					  int mmd, int reg, u16 val)
> +{
> +	struct sja1110_base_t1_private *priv = bus->priv;
> +	struct regmap *regmap = priv->regmap;
> +	unsigned int addr;
> +	int err;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C45_ADDR, mmd);
> +	err = regmap_write(regmap, priv->base + addr, reg);
> +	if (err)
> +		return err;
> +
> +	addr = sja1110_base_t1_encode_addr(phy, SJA1110_C45_DATA, mmd);
> +	return regmap_write(regmap, priv->base + addr, val & 0xffff);

Ditto.

> +}

...

> +static int sja1110_base_t1_mdio_probe(struct platform_device *pdev)
> +{
> +	struct sja1110_base_t1_private *priv;
> +	struct device *dev = &pdev->dev;
> +	struct regmap *regmap;
> +	struct resource *res;
> +	struct mii_bus *bus;
> +	int err;

> +	if (!dev->of_node || !dev->parent)

Can we avoid dereferencing? And perhaps dev_fwnode(dev)?

> +		return -ENODEV;
> +
> +	regmap = dev_get_regmap(dev->parent, NULL);
> +	if (!regmap)
> +		return -ENODEV;
> +
> +	bus = mdiobus_alloc_size(sizeof(*priv));
> +	if (!bus)
> +		return -ENOMEM;
> +
> +	bus->name = "SJA1110 100base-T1 MDIO bus";
> +	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
> +	bus->read = sja1110_base_t1_mdio_read_c22;
> +	bus->write = sja1110_base_t1_mdio_write_c22;
> +	bus->read_c45 = sja1110_base_t1_mdio_read_c45;
> +	bus->write_c45 = sja1110_base_t1_mdio_write_c45;
> +	bus->parent = dev;
> +	priv = bus->priv;
> +	priv->regmap = regmap;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_REG, 0);
> +	if (res)
> +		priv->base = res->start;
> +
> +	err = of_mdiobus_register(bus, dev->of_node);
> +	if (err)
> +		goto err_free_bus;
> +
> +	priv->bus = bus;
> +	platform_set_drvdata(pdev, priv);
> +
> +	return 0;
> +
> +err_free_bus:
> +	mdiobus_free(bus);
> +
> +	return err;
> +}

...

> +static const struct of_device_id sja1110_base_t1_mdio_match[] = {
> +	{ .compatible = "nxp,sja1110-base-t1-mdio", },

Inner comma is redundant.

> +	{},

Terminator is terminator, trailing comma is confusing here.

> +};

...

> +static struct platform_driver sja1110_base_t1_mdio_driver = {
> +	.probe = sja1110_base_t1_mdio_probe,
> +	.remove = sja1110_base_t1_mdio_remove,
> +	.driver = {
> +		.name = "sja1110-base-t1-mdio",
> +		.of_match_table = sja1110_base_t1_mdio_match,
> +	},
> +};

> +

Redundant blank line.

> +module_platform_driver(sja1110_base_t1_mdio_driver);

-- 
With Best Regards,
Andy Shevchenko