net: phy: add marvell usb to mdio controller

An MDIO controller present on development boards for Marvell switches
from the Link Street (88E6xxx) family.

Using this module, you can use the following setup as a development
platform for switchdev and DSA related work.

   .-------.      .-----------------.
   |      USB----USB                |
   |  SoC  |      |  88E6390X-DB  ETH1-10
   |      ETH----ETH0               |
   '-------'      '-----------------'
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -10110,6 +10110,7 @@ MARVELL USB MDIO CONTROLLER DRIVER
 M:	Tobias Waldekranz <tobias@waldekranz.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
+F:	drivers/net/phy/mdio-mvusb.c
 F:	Documentation/devicetree/bindings/net/marvell,mvusb.yaml
 
 MARVELL XENON MMC/SD/SDIO HOST CONTROLLER DRIVER

drivers/net/phy/Kconfig

@@ -179,6 +179,13 @@ config MDIO_MSCC_MIIM
 	  This driver supports the MIIM (MDIO) interface found in the network
 	  switches of the Microsemi SoCs
 
+config MDIO_MVUSB
+	tristate "Marvell USB to MDIO Adapter"
+	depends on USB
+	help
+	  A USB to MDIO converter present on development boards for
+	  Marvell's Link Street family of Ethernet switches.
+
 config MDIO_OCTEON
 	tristate "Octeon and some ThunderX SOCs MDIO buses"
 	depends on (64BIT && OF_MDIO) || COMPILE_TEST

drivers/net/phy/Makefile

@@ -40,6 +40,7 @@ obj-$(CONFIG_MDIO_I2C)		+= mdio-i2c.o
 obj-$(CONFIG_MDIO_IPQ8064)	+= mdio-ipq8064.o
 obj-$(CONFIG_MDIO_MOXART)	+= mdio-moxart.o
 obj-$(CONFIG_MDIO_MSCC_MIIM)	+= mdio-mscc-miim.o
+obj-$(CONFIG_MDIO_MVUSB)	+= mdio-mvusb.o
 obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
 obj-$(CONFIG_MDIO_SUN4I)	+= mdio-sun4i.o
 obj-$(CONFIG_MDIO_THUNDER)	+= mdio-thunder.o

drivers/net/phy/mdio-mvusb.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/usb.h>
+
+#define USB_MARVELL_VID	0x1286
+
+static const struct usb_device_id mvusb_mdio_table[] = {
+	{ USB_DEVICE(USB_MARVELL_VID, 0x1fa4) },
+
+	{}
+};
+MODULE_DEVICE_TABLE(usb, mvusb_mdio_table);
+
+enum {
+	MVUSB_CMD_PREAMBLE0,
+	MVUSB_CMD_PREAMBLE1,
+	MVUSB_CMD_ADDR,
+	MVUSB_CMD_VAL,
+};
+
+struct mvusb_mdio {
+	struct usb_device *udev;
+	struct mii_bus *mdio;
+
+	__le16 buf[4];
+};
+
+static int mvusb_mdio_read(struct mii_bus *mdio, int dev, int reg)
+{
+	struct mvusb_mdio *mvusb = mdio->priv;
+	int err, alen;
+
+	if (dev & MII_ADDR_C45)
+		return -EOPNOTSUPP;
+
+	mvusb->buf[MVUSB_CMD_ADDR] = cpu_to_le16(0xa400 | (dev << 5) | reg);
+
+	err = usb_bulk_msg(mvusb->udev, usb_sndbulkpipe(mvusb->udev, 2),
+			   mvusb->buf, 6, &alen, 100);
+	if (err)
+		return err;
+
+	err = usb_bulk_msg(mvusb->udev, usb_rcvbulkpipe(mvusb->udev, 6),
+			   &mvusb->buf[MVUSB_CMD_VAL], 2, &alen, 100);
+	if (err)
+		return err;
+
+	return le16_to_cpu(mvusb->buf[MVUSB_CMD_VAL]);
+}
+
+static int mvusb_mdio_write(struct mii_bus *mdio, int dev, int reg, u16 val)
+{
+	struct mvusb_mdio *mvusb = mdio->priv;
+	int alen;
+
+	if (dev & MII_ADDR_C45)
+		return -EOPNOTSUPP;
+
+	mvusb->buf[MVUSB_CMD_ADDR] = cpu_to_le16(0x8000 | (dev << 5) | reg);
+	mvusb->buf[MVUSB_CMD_VAL]  = cpu_to_le16(val);
+
+	return usb_bulk_msg(mvusb->udev, usb_sndbulkpipe(mvusb->udev, 2),
+			    mvusb->buf, 8, &alen, 100);
+}
+
+static int mvusb_mdio_probe(struct usb_interface *interface,
+			    const struct usb_device_id *id)
+{
+	struct device *dev = &interface->dev;
+	struct mvusb_mdio *mvusb;
+	struct mii_bus *mdio;
+
+	mdio = devm_mdiobus_alloc_size(dev, sizeof(*mvusb));
+	if (!mdio)
+		return -ENOMEM;
+
+	mvusb = mdio->priv;
+	mvusb->mdio = mdio;
+	mvusb->udev = usb_get_dev(interface_to_usbdev(interface));
+
+	/* Reversed from USB PCAPs, no idea what these mean. */
+	mvusb->buf[MVUSB_CMD_PREAMBLE0] = cpu_to_le16(0xe800);
+	mvusb->buf[MVUSB_CMD_PREAMBLE1] = cpu_to_le16(0x0001);
+
+	snprintf(mdio->id, MII_BUS_ID_SIZE, "mvusb-%s", dev_name(dev));
+	mdio->name = mdio->id;
+	mdio->parent = dev;
+	mdio->read = mvusb_mdio_read;
+	mdio->write = mvusb_mdio_write;
+
+	usb_set_intfdata(interface, mvusb);
+	return of_mdiobus_register(mdio, dev->of_node);
+}
+
+static void mvusb_mdio_disconnect(struct usb_interface *interface)
+{
+	struct mvusb_mdio *mvusb = usb_get_intfdata(interface);
+	struct usb_device *udev = mvusb->udev;
+
+	mdiobus_unregister(mvusb->mdio);
+	usb_set_intfdata(interface, NULL);
+	usb_put_dev(udev);
+}
+
+static struct usb_driver mvusb_mdio_driver = {
+	.name       = "mvusb_mdio",
+	.id_table   = mvusb_mdio_table,
+	.probe      = mvusb_mdio_probe,
+	.disconnect = mvusb_mdio_disconnect,
+};
+
+module_usb_driver(mvusb_mdio_driver);
+
+MODULE_AUTHOR("Tobias Waldekranz <tobias@waldekranz.com>");
+MODULE_DESCRIPTION("Marvell USB MDIO Adapter");
+MODULE_LICENSE("GPL");