net: dsa: microchip: Refactor MDIO handling for side MDIO access

Add support for accessing PHYs via a side MDIO interface in LAN937x
switches. The existing code already supports accessing PHYs via main
management interfaces, which can be SPI, I2C, or MDIO, depending on the
chip variant. This patch enables using a side MDIO bus, where SPI is
used for the main switch configuration and MDIO for managing the
integrated PHYs. On LAN937x, this is optional, allowing them to operate
in both configurations: SPI only, or SPI + MDIO. Typically, the SPI
interface is used for switch configuration, while MDIO handles PHY
management.

Additionally, update interrupt controller code to support non-linear
port to PHY address mapping, enabling correct interrupt handling for
configurations where PHY addresses do not directly correspond to port
indexes. This change ensures that the interrupt mechanism properly
aligns with the new, flexible PHY address mappings introduced by side
MDIO support.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241106075942.1636998-4-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 165 insertions, 10 deletions

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index f73833e24622..e9460650d46e 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -2236,16 +2236,100 @@ static int ksz_sw_mdio_write(struct mii_bus *bus, int addr, int regnum,
 	return dev->dev_ops->w_phy(dev, addr, regnum, val);
 }
 
+/**
+ * ksz_parent_mdio_read - Read data from a PHY register on the parent MDIO bus.
+ * @bus: MDIO bus structure.
+ * @addr: PHY address on the parent MDIO bus.
+ * @regnum: Register number to read.
+ *
+ * This function provides a direct read operation on the parent MDIO bus for
+ * accessing PHY registers. By bypassing SPI or I2C, it uses the parent MDIO bus
+ * to retrieve data from the PHY registers at the specified address and register
+ * number.
+ *
+ * Return: Value of the PHY register, or a negative error code on failure.
+ */
+static int ksz_parent_mdio_read(struct mii_bus *bus, int addr, int regnum)
+{
+	struct ksz_device *dev = bus->priv;
+
+	return mdiobus_read_nested(dev->parent_mdio_bus, addr, regnum);
+}
+
+/**
+ * ksz_parent_mdio_write - Write data to a PHY register on the parent MDIO bus.
+ * @bus: MDIO bus structure.
+ * @addr: PHY address on the parent MDIO bus.
+ * @regnum: Register number to write to.
+ * @val: Value to write to the PHY register.
+ *
+ * This function provides a direct write operation on the parent MDIO bus for
+ * accessing PHY registers. Bypassing SPI or I2C, it uses the parent MDIO bus
+ * to modify the PHY register values at the specified address.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+static int ksz_parent_mdio_write(struct mii_bus *bus, int addr, int regnum,
+				 u16 val)
+{
+	struct ksz_device *dev = bus->priv;
+
+	return mdiobus_write_nested(dev->parent_mdio_bus, addr, regnum, val);
+}
+
+/**
+ * ksz_phy_addr_to_port - Map a PHY address to the corresponding switch port.
+ * @dev: Pointer to device structure.
+ * @addr: PHY address to map to a port.
+ *
+ * This function finds the corresponding switch port for a given PHY address by
+ * iterating over all user ports on the device. It checks if a port's PHY
+ * address in `phy_addr_map` matches the specified address and if the port
+ * contains an internal PHY. If a match is found, the index of the port is
+ * returned.
+ *
+ * Return: Port index on success, or -EINVAL if no matching port is found.
+ */
+static int ksz_phy_addr_to_port(struct ksz_device *dev, int addr)
+{
+	struct dsa_switch *ds = dev->ds;
+	struct dsa_port *dp;
+
+	dsa_switch_for_each_user_port(dp, ds) {
+		if (dev->info->internal_phy[dp->index] &&
+		    dev->phy_addr_map[dp->index] == addr)
+			return dp->index;
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * ksz_irq_phy_setup - Configure IRQs for PHYs in the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * Sets up IRQs for each active PHY connected to the KSZ switch by mapping the
+ * appropriate IRQs for each PHY and assigning them to the `user_mii_bus` in
+ * the DSA switch structure. Each IRQ is mapped based on the port's IRQ domain.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
 static int ksz_irq_phy_setup(struct ksz_device *dev)
 {
 	struct dsa_switch *ds = dev->ds;
-	int phy;
+	int phy, port;
 	int irq;
 	int ret;
 
-	for (phy = 0; phy < KSZ_MAX_NUM_PORTS; phy++) {
+	for (phy = 0; phy < PHY_MAX_ADDR; phy++) {
 		if (BIT(phy) & ds->phys_mii_mask) {
-			irq = irq_find_mapping(dev->ports[phy].pirq.domain,
+			port = ksz_phy_addr_to_port(dev, phy);
+			if (port < 0) {
+				ret = port;
+				goto out;
+			}
+
+			irq = irq_find_mapping(dev->ports[port].pirq.domain,
 					       PORT_SRC_PHY_INT);
 			if (irq < 0) {
 				ret = irq;
@@ -2263,40 +2347,109 @@ out:
 	return ret;
 }
 
+/**
+ * ksz_irq_phy_free - Release IRQ mappings for PHYs in the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * Releases any IRQ mappings previously assigned to active PHYs in the KSZ
+ * switch by disposing of each mapped IRQ in the `user_mii_bus` structure.
+ */
 static void ksz_irq_phy_free(struct ksz_device *dev)
 {
 	struct dsa_switch *ds = dev->ds;
 	int phy;
 
-	for (phy = 0; phy < KSZ_MAX_NUM_PORTS; phy++)
+	for (phy = 0; phy < PHY_MAX_ADDR; phy++)
 		if (BIT(phy) & ds->phys_mii_mask)
 			irq_dispose_mapping(ds->user_mii_bus->irq[phy]);
 }
 
+/**
+ * ksz_mdio_register - Register and configure the MDIO bus for the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * This function sets up and registers an MDIO bus for the KSZ switch device,
+ * allowing access to its internal PHYs. If the device supports side MDIO,
+ * the function will configure the external MDIO controller specified by the
+ * "mdio-parent-bus" device tree property to directly manage internal PHYs.
+ * Otherwise, SPI or I2C access is set up for PHY access.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
 static int ksz_mdio_register(struct ksz_device *dev)
 {
+	struct device_node *parent_bus_node;
+	struct mii_bus *parent_bus = NULL;
 	struct dsa_switch *ds = dev->ds;
 	struct device_node *mdio_np;
 	struct mii_bus *bus;
-	int ret;
+	struct dsa_port *dp;
+	int ret, i;
 
 	mdio_np = of_get_child_by_name(dev->dev->of_node, "mdio");
 	if (!mdio_np)
 		return 0;
 
+	parent_bus_node = of_parse_phandle(mdio_np, "mdio-parent-bus", 0);
+	if (parent_bus_node && !dev->info->phy_side_mdio_supported) {
+		dev_err(dev->dev, "Side MDIO bus is not supported for this HW, ignoring 'mdio-parent-bus' property.\n");
+		ret = -EINVAL;
+
+		goto put_mdio_node;
+	} else if (parent_bus_node) {
+		parent_bus = of_mdio_find_bus(parent_bus_node);
+		if (!parent_bus) {
+			ret = -EPROBE_DEFER;
+
+			goto put_mdio_node;
+		}
+
+		dev->parent_mdio_bus = parent_bus;
+	}
+
 	bus = devm_mdiobus_alloc(ds->dev);
 	if (!bus) {
 		of_node_put(mdio_np);
 		return -ENOMEM;
 	}
 
+	if (dev->dev_ops->mdio_bus_preinit) {
+		ret = dev->dev_ops->mdio_bus_preinit(dev, !!parent_bus);
+		if (ret)
+			goto put_mdio_node;
+	}
+
+	if (dev->dev_ops->create_phy_addr_map) {
+		ret = dev->dev_ops->create_phy_addr_map(dev, !!parent_bus);
+		if (ret)
+			goto put_mdio_node;
+	} else {
+		for (i = 0; i < dev->info->port_cnt; i++)
+			dev->phy_addr_map[i] = i;
+	}
+
 	bus->priv = dev;
-	bus->read = ksz_sw_mdio_read;
-	bus->write = ksz_sw_mdio_write;
-	bus->name = "ksz user smi";
-	snprintf(bus->id, MII_BUS_ID_SIZE, "SMI-%d", ds->index);
+	if (parent_bus) {
+		bus->read = ksz_parent_mdio_read;
+		bus->write = ksz_parent_mdio_write;
+		bus->name = "KSZ side MDIO";
+		snprintf(bus->id, MII_BUS_ID_SIZE, "ksz-side-mdio-%d",
+			 ds->index);
+	} else {
+		bus->read = ksz_sw_mdio_read;
+		bus->write = ksz_sw_mdio_write;
+		bus->name = "ksz user smi";
+		snprintf(bus->id, MII_BUS_ID_SIZE, "SMI-%d", ds->index);
+	}
+
+	dsa_switch_for_each_user_port(dp, dev->ds) {
+		if (dev->info->internal_phy[dp->index] &&
+		    dev->phy_addr_map[dp->index] < PHY_MAX_ADDR)
+			bus->phy_mask |= BIT(dev->phy_addr_map[dp->index]);
+	}
+
+	ds->phys_mii_mask = bus->phy_mask;
 	bus->parent = ds->dev;
-	bus->phy_mask = ~ds->phys_mii_mask;
 
 	ds->user_mii_bus = bus;
 
@@ -2316,7 +2469,9 @@ static int ksz_mdio_register(struct ksz_device *dev)
 			ksz_irq_phy_free(dev);
 	}
 
+put_mdio_node:
 	of_node_put(mdio_np);
+	of_node_put(parent_bus_node);
 
 	return ret;
 }