phy: bcm-ns-usb3: add MDIO driver using proper bus layer

As USB 3.0 PHY is attached to the MDIO bus this module should provide a
MDIO driver and use a proper bus layer. This is a proper (cleaner)
solution which doesn't require code to know this specific MDIO bus
details. It also allows reusing the driver with other MDIO buses.

For now keep platform device support in place. We may consider dropping
it once MDIO bindings gets used "everywhere".

Signed-off-by: Rafał Miłecki <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

drivers/phy/broadcom/Kconfig

···
 	depends on ARCH_BCM_IPROC || COMPILE_TEST
 	depends on HAS_IOMEM && OF
 	select GENERIC_PHY
+	select MDIO_DEVICE
 	help
 	  Enable this to support Broadcom USB 3.0 PHY connected to the USB
 	  controller on Northstar family.

drivers/phy/broadcom/phy-bcm-ns-usb3.c

···
 #include <linux/bcma/bcma.h>
 #include <linux/delay.h>
 #include <linux/err.h>
+#include <linux/mdio.h>
 #include <linux/module.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/phy/phy.h>
···
 	enum bcm_ns_family family;
 	void __iomem *dmp;
 	void __iomem *ccb_mii;
+	struct mdio_device *mdiodev;
 	struct phy *phy;
 
 	int (*phy_write)(struct bcm_ns_usb3 *usb3, u16 reg, u16 value);
···
 };
 
 /**************************************************
+ * MDIO driver code
+ **************************************************/
+
+static int bcm_ns_usb3_mdiodev_phy_write(struct bcm_ns_usb3 *usb3, u16 reg,
+					 u16 value)
+{
+	struct mdio_device *mdiodev = usb3->mdiodev;
+
+	return mdiobus_write(mdiodev->bus, mdiodev->addr, reg, value);
+}
+
+static int bcm_ns_usb3_mdio_probe(struct mdio_device *mdiodev)
+{
+	struct device *dev = &mdiodev->dev;
+	const struct of_device_id *of_id;
+	struct phy_provider *phy_provider;
+	struct device_node *syscon_np;
+	struct bcm_ns_usb3 *usb3;
+	struct resource res;
+	int err;
+
+	usb3 = devm_kzalloc(dev, sizeof(*usb3), GFP_KERNEL);
+	if (!usb3)
+		return -ENOMEM;
+
+	usb3->dev = dev;
+	usb3->mdiodev = mdiodev;
+
+	of_id = of_match_device(bcm_ns_usb3_id_table, dev);
+	if (!of_id)
+		return -EINVAL;
+	usb3->family = (enum bcm_ns_family)of_id->data;
+
+	syscon_np = of_parse_phandle(dev->of_node, "usb3-dmp-syscon", 0);
+	err = of_address_to_resource(syscon_np, 0, &res);
+	of_node_put(syscon_np);
+	if (err)
+		return err;
+
+	usb3->dmp = devm_ioremap_resource(dev, &res);
+	if (IS_ERR(usb3->dmp)) {
+		dev_err(dev, "Failed to map DMP regs\n");
+		return PTR_ERR(usb3->dmp);
+	}
+
+	usb3->phy_write = bcm_ns_usb3_mdiodev_phy_write;
+
+	usb3->phy = devm_phy_create(dev, NULL, &ops);
+	if (IS_ERR(usb3->phy)) {
+		dev_err(dev, "Failed to create PHY\n");
+		return PTR_ERR(usb3->phy);
+	}
+
+	phy_set_drvdata(usb3->phy, usb3);
+
+	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
+
+	return PTR_ERR_OR_ZERO(phy_provider);
+}
+
+static struct mdio_driver bcm_ns_usb3_mdio_driver = {
+	.mdiodrv = {
+		.driver = {
+			.name = "bcm_ns_mdio_usb3",
+			.of_match_table = bcm_ns_usb3_id_table,
+		},
+	},
+	.probe = bcm_ns_usb3_mdio_probe,
+};
+
+/**************************************************
  * Platform driver code
  **************************************************/
 
···
 		.of_match_table = bcm_ns_usb3_id_table,
 	},
 };
-module_platform_driver(bcm_ns_usb3_driver);
+
+static int __init bcm_ns_usb3_module_init(void)
+{
+	int err;
+
+	/*
+	 * For backward compatibility we register as MDIO and platform driver.
+	 * After getting MDIO binding commonly used (e.g. switching all DT files
+	 * to use it) we should deprecate the old binding and eventually drop
+	 * support for it.
+	 */
+
+	err = mdio_driver_register(&bcm_ns_usb3_mdio_driver);
+	if (err)
+		return err;
+
+	err = platform_driver_register(&bcm_ns_usb3_driver);
+	if (err)
+		mdio_driver_unregister(&bcm_ns_usb3_mdio_driver);
+
+	return err;
+}
+module_init(bcm_ns_usb3_module_init);
+
+static void __exit bcm_ns_usb3_module_exit(void)
+{
+	platform_driver_unregister(&bcm_ns_usb3_driver);
+	mdio_driver_unregister(&bcm_ns_usb3_mdio_driver);
+}
+module_exit(bcm_ns_usb3_module_exit)
 
 MODULE_LICENSE("GPL v2");