linux-kernel - Re: [PATCH v4 net-next 05/10] net: dsa: microchip: add DSA support for microchip lan937x

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Date:   Thu, 7 Oct 2021 23:00:05 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
Cc:     andrew@...n.ch, netdev@...r.kernel.org, robh+dt@...nel.org,
        UNGLinuxDriver@...rochip.com, Woojung.Huh@...rochip.com,
        hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v4 net-next 05/10] net: dsa: microchip: add DSA support
 for microchip lan937x

On Thu, Oct 07, 2021 at 08:41:55PM +0530, Prasanna Vengateshan wrote:
> +static int lan937x_mdio_register(struct dsa_switch *ds)
> +{
> +	struct device_node *mdio_np;
> +	int ret;
> +
> +	mdio_np = of_get_child_by_name(ds->dev->of_node, "mdio");
> +	if (!mdio_np) {
> +		dev_err(ds->dev, "no MDIO bus node\n");
> +		return -ENODEV;
> +	}
> +
> +	ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
> +	if (!ds->slave_mii_bus)
> +		return -ENOMEM;
> +
> +	ds->slave_mii_bus->priv = ds->priv;
> +	ds->slave_mii_bus->read = lan937x_sw_mdio_read;
> +	ds->slave_mii_bus->write = lan937x_sw_mdio_write;
> +	ds->slave_mii_bus->name = "lan937x slave smi";
> +	snprintf(ds->slave_mii_bus->id, MII_BUS_ID_SIZE, "SMI-%d", ds->index);
> +	ds->slave_mii_bus->parent = ds->dev;
> +	ds->slave_mii_bus->phy_mask = ~ds->phys_mii_mask;
> +
> +	ret = of_mdiobus_register(ds->slave_mii_bus, mdio_np);

Please use devm_of_mdiobus_register if you're going to use
devm_mdiobus_alloc, or no devres at all.
https://patchwork.kernel.org/project/netdevbpf/patch/20210920214209.1733768-3-vladimir.oltean@nxp.com/

> +	if (ret) {
> +		dev_err(ds->dev, "unable to register MDIO bus %s\n",
> +			ds->slave_mii_bus->id);
> +	}
> +
> +	of_node_put(mdio_np);
> +
> +	return ret;
> +}
> +
> +static phy_interface_t lan937x_get_interface(struct ksz_device *dev, int port)
> +{
> +	phy_interface_t interface;
> +	u8 data8;
> +	int ret;
> +
> +	if (lan937x_is_internal_phy_port(dev, port))
> +		return PHY_INTERFACE_MODE_NA;

Typically we use PHY_INTERFACE_MODE_INTERNAL.

> +
> +	/* read interface from REG_PORT_XMII_CTRL_1 register */
> +	ret = lan937x_pread8(dev, port, REG_PORT_XMII_CTRL_1, &data8);
> +	if (ret < 0)
> +		return PHY_INTERFACE_MODE_NA;
> +
> +	switch (data8 & PORT_MII_SEL_M) {
> +	case PORT_RMII_SEL:
> +		interface = PHY_INTERFACE_MODE_RMII;
> +		break;
> +	case PORT_RGMII_SEL:
> +		interface = PHY_INTERFACE_MODE_RGMII;
> +		if (data8 & PORT_RGMII_ID_EG_ENABLE)
> +			interface = PHY_INTERFACE_MODE_RGMII_TXID;
> +		if (data8 & PORT_RGMII_ID_IG_ENABLE) {
> +			interface = PHY_INTERFACE_MODE_RGMII_RXID;
> +			if (data8 & PORT_RGMII_ID_EG_ENABLE)
> +				interface = PHY_INTERFACE_MODE_RGMII_ID;
> +		}
> +		break;
> +	case PORT_MII_SEL:
> +	default:
> +		/* Interface is MII */
> +		interface = PHY_INTERFACE_MODE_MII;
> +		break;
> +	}
> +
> +	return interface;
> +}
> +
> +static void lan937x_config_cpu_port(struct dsa_switch *ds)
> +{
> +	struct ksz_device *dev = ds->priv;
> +	struct ksz_port *p;
> +	int i;
> +
> +	ds->num_ports = dev->port_cnt;
> +
> +	for (i = 0; i < dev->port_cnt; i++) {
> +		if (dsa_is_cpu_port(ds, i) && (dev->cpu_ports & (1 << i))) {
> +			phy_interface_t interface;
> +
> +			dev->cpu_port = i;
> +			dev->host_mask = (1 << dev->cpu_port);
> +			dev->port_mask |= dev->host_mask;
> +			p = &dev->ports[i];
> +
> +			/* Check if the device tree have specific interface
> +			 * setting otherwise read & assign from XMII register
> +			 * for host port interface
> +			 */
> +			interface = lan937x_get_interface(dev, i);

What does the CPU port have so special that you override it here?
Again some compatibility with out-of-tree DT bindings?

> +			if (!p->interface)
> +				p->interface = interface;
> +
> +			dev_info(dev->dev,
> +				 "Port%d: using phy mode %s\n",
> +				 i,
> +				 phy_modes(p->interface));
> +
> +			/* enable cpu port */
> +			lan937x_port_setup(dev, i, true);
> +			p->vid_member = dev->port_mask;
> +		}
> +	}
> +
> +static u8 lan937x_rgmii_dly_reg_val(int port, u32 val)
> +{
> +	u8 reg_val;
> +
> +	/* force minimum delay if delay is less than min delay */
> +	if (val && val < 2170)
> +		val = 2170;
> +
> +	/* maximum delay is 4ns */
> +	if (val > 4000)
> +		val = 4000;

These bindings are new. Given that you also document their min and max
values, why don't you just error out on out-of-range values instead of
silently doing what you think is going to be fine?