+static int tsnep_ethtool_get_regs_len(struct net_device *netdev)
+{
+	struct tsnep_adapter *adapter = netdev_priv(netdev);
+	int len;
+	int num_queues;
+
+	len = TSNEP_MAC_SIZE;
+	num_queues = max(adapter->num_tx_queues, adapter->num_rx_queues);
+	len += TSNEP_QUEUE_SIZE * (num_queues - 1);

Why the num_queues - 1 ? A comment here might be good explaining it.

+
+	return len;
+}
+
+static void tsnep_ethtool_get_regs(struct net_device *netdev,
+				   struct ethtool_regs *regs,
+				   void *p)
+{
+	struct tsnep_adapter *adapter = netdev_priv(netdev);
+
+	regs->version = 1;
+
+	memcpy_fromio(p, adapter->addr, regs->len);
+}

So the registers and the queues are contiguous?

+static int tsnep_ethtool_get_ts_info(struct net_device *dev,
+				     struct ethtool_ts_info *info)
+{
+	struct tsnep_adapter *adapter = netdev_priv(dev);
+
+	info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
+				SOF_TIMESTAMPING_RX_SOFTWARE |
+				SOF_TIMESTAMPING_SOFTWARE |
+				SOF_TIMESTAMPING_TX_HARDWARE |
+				SOF_TIMESTAMPING_RX_HARDWARE |
+				SOF_TIMESTAMPING_RAW_HARDWARE;
+
+	if (adapter->ptp_clock)
+		info->phc_index = ptp_clock_index(adapter->ptp_clock);
+	else
+		info->phc_index = -1;
+
+	info->tx_types = BIT(HWTSTAMP_TX_OFF) |
+			 BIT(HWTSTAMP_TX_ON);
+	info->rx_filters = BIT(HWTSTAMP_FILTER_NONE) |
+			   BIT(HWTSTAMP_FILTER_ALL);
+
+	return 0;
+}

You should Cc: Richard Cochran [off-list ref] for the PTP
parts.

+static int tsnep_mdio_init(struct tsnep_adapter *adapter)
+{
+	struct device_node *np = adapter->pdev->dev.of_node;
+	int retval;
+
+	if (np) {
+		np = of_get_child_by_name(np, "mdio");
+		if (!np)
+			return 0;
+
+		adapter->suppress_preamble =
+			of_property_read_bool(np, "suppress-preamble");
+	}
+
+	adapter->mdiobus = devm_mdiobus_alloc(&adapter->pdev->dev);
+	if (!adapter->mdiobus) {
+		retval = -ENOMEM;
+
+		goto out;
+	}
+
+	adapter->mdiobus->priv = (void *)adapter;
+	adapter->mdiobus->parent = &adapter->pdev->dev;
+	adapter->mdiobus->read = tsnep_mdiobus_read;
+	adapter->mdiobus->write = tsnep_mdiobus_write;
+	adapter->mdiobus->name = TSNEP "-mdiobus";
+	snprintf(adapter->mdiobus->id, MII_BUS_ID_SIZE, "%s",
+		 adapter->pdev->name);
+
+	if (np) {
+		retval = of_mdiobus_register(adapter->mdiobus, np);
+
+		of_node_put(np);
+	} else {
+		/* do not scan broadcast address */
+		adapter->mdiobus->phy_mask = 0x0000001;
+
+		retval = mdiobus_register(adapter->mdiobus);

You can probably simply this. of_mdiobus_register() is happy to take a
NULL pointer for np, and will fall back to mdiobus_register().

You have quite a lot of code in this file. Could it either be

1) A loadable module which extends the base driver?
2) A build time configuration option?

What percentage of the overall driver binary does this test code take
up?

Apart from the minor comments above, ethtool, mdio, phy all looks
good.

	Andrew