net: mdio: Add ACPI support code for mdio

Define acpi_mdiobus_register() to Register mii_bus and create PHYs for
each ACPI child node.

Signed-off-by: Calvin Johnson <[e-mail]>
Signed-off-by: Ioana Ciornei <[e-mail]>
Acked-by: Rafael J. Wysocki <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

MAINTAINERS

···
 F:	Documentation/devicetree/bindings/net/qca,ar803x.yaml
 F:	Documentation/networking/phy.rst
 F:	drivers/net/mdio/
+F:	drivers/net/mdio/acpi_mdio.c
 F:	drivers/net/mdio/fwnode_mdio.c
 F:	drivers/net/mdio/of_mdio.c
 F:	drivers/net/pcs/

drivers/net/mdio/Kconfig

···
 	help
 	  OpenFirmware MDIO bus (Ethernet PHY) accessors
 
+config ACPI_MDIO
+	def_tristate PHYLIB
+	depends on ACPI
+	depends on PHYLIB
+	help
+	  ACPI MDIO bus (Ethernet PHY) accessors
+
 if MDIO_BUS
 
 config MDIO_DEVRES

drivers/net/mdio/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Linux MDIO bus drivers
 
+obj-$(CONFIG_ACPI_MDIO)		+= acpi_mdio.o
 obj-$(CONFIG_FWNODE_MDIO)	+= fwnode_mdio.o
 obj-$(CONFIG_OF_MDIO)		+= of_mdio.o
 

drivers/net/mdio/acpi_mdio.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ACPI helpers for the MDIO (Ethernet PHY) API
+ *
+ * This file provides helper functions for extracting PHY device information
+ * out of the ACPI ASL and using it to populate an mii_bus.
+ */
+
+#include <linux/acpi.h>
+#include <linux/acpi_mdio.h>
+#include <linux/bits.h>
+#include <linux/dev_printk.h>
+#include <linux/fwnode_mdio.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+MODULE_AUTHOR("Calvin Johnson <[e-mail]>");
+MODULE_LICENSE("GPL");
+
+/**
+ * acpi_mdiobus_register - Register mii_bus and create PHYs from the ACPI ASL.
+ * @mdio: pointer to mii_bus structure
+ * @fwnode: pointer to fwnode of MDIO bus. This fwnode is expected to represent
+ * an ACPI device object corresponding to the MDIO bus and its children are
+ * expected to correspond to the PHY devices on that bus.
+ *
+ * This function registers the mii_bus structure and registers a phy_device
+ * for each child node of @fwnode.
+ */
+int acpi_mdiobus_register(struct mii_bus *mdio, struct fwnode_handle *fwnode)
+{
+	struct fwnode_handle *child;
+	u32 addr;
+	int ret;
+
+	/* Mask out all PHYs from auto probing. */
+	mdio->phy_mask = GENMASK(31, 0);
+	ret = mdiobus_register(mdio);
+	if (ret)
+		return ret;
+
+	ACPI_COMPANION_SET(&mdio->dev, to_acpi_device_node(fwnode));
+
+	/* Loop over the child nodes and register a phy_device for each PHY */
+	fwnode_for_each_child_node(fwnode, child) {
+		ret = acpi_get_local_address(ACPI_HANDLE_FWNODE(child), &addr);
+		if (ret || addr >= PHY_MAX_ADDR)
+			continue;
+
+		ret = fwnode_mdiobus_register_phy(mdio, child, addr);
+		if (ret == -ENODEV)
+			dev_err(&mdio->dev,
+				"MDIO device at address %d is missing.\n",
+				addr);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(acpi_mdiobus_register);

include/linux/acpi_mdio.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * ACPI helper for the MDIO (Ethernet PHY) API
+ */
+
+#ifndef __LINUX_ACPI_MDIO_H
+#define __LINUX_ACPI_MDIO_H
+
+#include <linux/phy.h>
+
+#if IS_ENABLED(CONFIG_ACPI_MDIO)
+int acpi_mdiobus_register(struct mii_bus *mdio, struct fwnode_handle *fwnode);
+#else /* CONFIG_ACPI_MDIO */
+static inline int
+acpi_mdiobus_register(struct mii_bus *mdio, struct fwnode_handle *fwnode)
+{
+	/*
+	 * Fall back to mdiobus_register() function to register a bus.
+	 * This way, we don't have to keep compat bits around in drivers.
+	 */
+
+	return mdiobus_register(mdio);
+}
+#endif
+
+#endif /* __LINUX_ACPI_MDIO_H */