net: dsa: microchip: add support for side MDIO interface in LAN937x

Implement side MDIO channel support for LAN937x switches, providing an
alternative to SPI for PHY management alongside existing SPI-based
switch configuration. This is needed to reduce SPI load, as SPI can be
relatively expensive for small packets compared to MDIO support.

Also, implemented static mappings for PHY addresses for various LAN937x
models to support different internal PHY configurations. Since the PHY
address mappings are not equal to the port indexes, this patch also
provides PHY address calculation based on hardware strapping
configuration.

Signed-off-by: Oleksij Rempel <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/dsa/microchip/ksz_common.c

···
 	.flush_dyn_mac_table = ksz9477_flush_dyn_mac_table,
 	.port_setup = lan937x_port_setup,
 	.set_ageing_time = lan937x_set_ageing_time,
+	.mdio_bus_preinit = lan937x_mdio_bus_preinit,
+	.create_phy_addr_map = lan937x_create_phy_addr_map,
 	.r_phy = lan937x_r_phy,
 	.w_phy = lan937x_w_phy,
 	.r_mib_cnt = ksz9477_r_mib_cnt,
···
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
···
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
···
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
···
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
···
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,

drivers/net/dsa/microchip/lan937x.h

···
 void lan937x_config_cpu_port(struct dsa_switch *ds);
 int lan937x_switch_init(struct ksz_device *dev);
 void lan937x_switch_exit(struct ksz_device *dev);
+int lan937x_mdio_bus_preinit(struct ksz_device *dev, bool side_mdio);
+int lan937x_create_phy_addr_map(struct ksz_device *dev, bool side_mdio);
 int lan937x_r_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 *data);
 int lan937x_w_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 val);
 int lan937x_change_mtu(struct ksz_device *dev, int port, int new_mtu);

drivers/net/dsa/microchip/lan937x_main.c

···
 #include "ksz9477.h"
 #include "lan937x.h"
 
+/* marker for ports without built-in PHY */
+#define LAN937X_NO_PHY U8_MAX
+
+/*
+ * lan9370_phy_addr - Mapping of LAN9370 switch ports to PHY addresses.
+ *
+ * Each entry corresponds to a specific port on the LAN9370 switch,
+ * where ports 1-4 are connected to integrated 100BASE-T1 PHYs, and
+ * Port 5 is connected to an RGMII interface without a PHY. The values
+ * are based on the documentation (DS00003108E, section 3.3).
+ */
+static const u8 lan9370_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 6, /* Port 4, T1 AFE4 */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+};
+
+/*
+ * lan9371_phy_addr - Mapping of LAN9371 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003109E, section 3.3).
+ */
+static const u8 lan9371_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 8, /* Port 4, TX PHY */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+};
+
+/*
+ * lan9372_phy_addr - Mapping of LAN9372 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9372_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 8, /* Port 4, TX PHY */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
+/*
+ * lan9373_phy_addr - Mapping of LAN9373 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9373_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = LAN937X_NO_PHY, /* Port 4, SGMII */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
+/*
+ * lan9374_phy_addr - Mapping of LAN9374 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9374_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 7, /* Port 4, T1 AFE5 */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
 static int lan937x_cfg(struct ksz_device *dev, u32 addr, u8 bits, bool set)
 {
 	return regmap_update_bits(ksz_regmap_8(dev), addr, bits, set ? bits : 0);
···
 				  bits, set ? bits : 0);
 }
 
-static int lan937x_enable_spi_indirect_access(struct ksz_device *dev)
+/**
+ * lan937x_create_phy_addr_map - Create port-to-PHY address map for MDIO bus.
+ * @dev: Pointer to device structure.
+ * @side_mdio: Boolean indicating if the PHYs are accessed over a side MDIO bus.
+ *
+ * This function sets up the PHY address mapping for the LAN937x switches,
+ * which support two access modes for internal PHYs:
+ * 1. **SPI Access**: A straightforward one-to-one port-to-PHY address
+ *    mapping is applied.
+ * 2. **MDIO Access**: The PHY address mapping varies based on chip variant
+ *    and strap configuration. An offset is calculated based on strap settings
+ *    to ensure correct PHY addresses are assigned. The offset calculation logic
+ *    is based on Microchip's Article Number 000015828, available at:
+ *    https://microchip.my.site.com/s/article/LAN9374-Virtual-PHY-PHY-Address-Mapping
+ *
+ * The function first checks if side MDIO access is disabled, in which case a
+ * simple direct mapping (port number = PHY address) is applied. If side MDIO
+ * access is enabled, it reads the strap configuration to determine the correct
+ * offset for PHY addresses.
+ *
+ * The appropriate mapping table is selected based on the chip ID, and the
+ * `phy_addr_map` is populated with the correct addresses for each port. Any
+ * port with no PHY is assigned a `LAN937X_NO_PHY` marker.
+ *
+ * Return: 0 on success, error code on failure.
+ */
+int lan937x_create_phy_addr_map(struct ksz_device *dev, bool side_mdio)
+{
+	static const u8 *phy_addr_map;
+	u32 strap_val;
+	u8 offset = 0;
+	size_t size;
+	int ret, i;
+
+	if (!side_mdio) {
+		/* simple direct mapping */
+		for (i = 0; i < dev->info->port_cnt; i++)
+			dev->phy_addr_map[i] = i;
+
+		return 0;
+	}
+
+	ret = ksz_read32(dev, REG_SW_CFG_STRAP_VAL, &strap_val);
+	if (ret < 0)
+		return ret;
+
+	if (!(strap_val & SW_CASCADE_ID_CFG) && !(strap_val & SW_VPHY_ADD_CFG))
+		offset = 0;
+	else if (!(strap_val & SW_CASCADE_ID_CFG) && (strap_val & SW_VPHY_ADD_CFG))
+		offset = 7;
+	else if ((strap_val & SW_CASCADE_ID_CFG) && !(strap_val & SW_VPHY_ADD_CFG))
+		offset = 15;
+	else
+		offset = 22;
+
+	switch (dev->info->chip_id) {
+	case LAN9370_CHIP_ID:
+		phy_addr_map = lan9370_phy_addr;
+		size = ARRAY_SIZE(lan9370_phy_addr);
+		break;
+	case LAN9371_CHIP_ID:
+		phy_addr_map = lan9371_phy_addr;
+		size = ARRAY_SIZE(lan9371_phy_addr);
+		break;
+	case LAN9372_CHIP_ID:
+		phy_addr_map = lan9372_phy_addr;
+		size = ARRAY_SIZE(lan9372_phy_addr);
+		break;
+	case LAN9373_CHIP_ID:
+		phy_addr_map = lan9373_phy_addr;
+		size = ARRAY_SIZE(lan9373_phy_addr);
+		break;
+	case LAN9374_CHIP_ID:
+		phy_addr_map = lan9374_phy_addr;
+		size = ARRAY_SIZE(lan9374_phy_addr);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (size < dev->info->port_cnt)
+		return -EINVAL;
+
+	for (i = 0; i < dev->info->port_cnt; i++) {
+		if (phy_addr_map[i] == LAN937X_NO_PHY)
+			dev->phy_addr_map[i] = phy_addr_map[i];
+		else
+			dev->phy_addr_map[i] = phy_addr_map[i] + offset;
+	}
+
+	return 0;
+}
+
+/**
+ * lan937x_mdio_bus_preinit - Pre-initialize MDIO bus for accessing PHYs.
+ * @dev: Pointer to device structure.
+ * @side_mdio: Boolean indicating if the PHYs are accessed over a side MDIO bus.
+ *
+ * This function configures the LAN937x switch for PHY access either through
+ * SPI or the side MDIO bus, unlocking the necessary registers for each access
+ * mode.
+ *
+ * Operation Modes:
+ * 1. **SPI Access**: Enables SPI indirect access to address clock domain
+ *    crossing issues when SPI is used for PHY access.
+ * 2. **MDIO Access**: Grants access to internal PHYs over the side MDIO bus,
+ *    required when using the MDIO bus for PHY management.
+ *
+ * Return: 0 on success, error code on failure.
+ */
+int lan937x_mdio_bus_preinit(struct ksz_device *dev, bool side_mdio)
 {
 	u16 data16;
 	int ret;
 
-	/* Enable Phy access through SPI */
+	/* Unlock access to the PHYs, needed for SPI and side MDIO access */
 	ret = lan937x_cfg(dev, REG_GLOBAL_CTRL_0, SW_PHY_REG_BLOCK, false);
 	if (ret < 0)
-		return ret;
+		goto print_error;
 
-	ret = ksz_read16(dev, REG_VPHY_SPECIAL_CTRL__2, &data16);
+	if (side_mdio)
+		/* Allow access to internal PHYs over MDIO bus */
+		data16 = VPHY_MDIO_INTERNAL_ENABLE;
+	else
+		/* Enable SPI indirect access to address clock domain crossing
+		 * issue
+		 */
+		data16 = VPHY_SPI_INDIRECT_ENABLE;
+
+	ret = ksz_rmw16(dev, REG_VPHY_SPECIAL_CTRL__2,
+			VPHY_SPI_INDIRECT_ENABLE | VPHY_MDIO_INTERNAL_ENABLE,
+			data16);
+
+print_error:
 	if (ret < 0)
-		return ret;
+		dev_err(dev->dev, "failed to preinit the MDIO bus\n");
 
-	/* Allow SPI access */
-	data16 |= VPHY_SPI_INDIRECT_ENABLE;
-
-	return ksz_write16(dev, REG_VPHY_SPECIAL_CTRL__2, data16);
+	return ret;
 }
 
 static int lan937x_vphy_ind_addr_wr(struct ksz_device *dev, int addr, int reg)
···
 {
 	struct ksz_device *dev = ds->priv;
 	int ret;
-
-	/* enable Indirect Access from SPI to the VPHY registers */
-	ret = lan937x_enable_spi_indirect_access(dev);
-	if (ret < 0) {
-		dev_err(dev->dev, "failed to enable spi indirect access");
-		return ret;
-	}
 
 	/* The VLAN aware is a global setting. Mixed vlan
 	 * filterings are not supported.

drivers/net/dsa/microchip/lan937x_reg.h

···
 #define SW_CLK125_ENB			BIT(1)
 #define SW_CLK25_ENB			BIT(0)
 
+#define REG_SW_CFG_STRAP_VAL		0x0200
+#define SW_CASCADE_ID_CFG		BIT(15)
+#define SW_VPHY_ADD_CFG			BIT(0)
+
 /* 2 - PHY Control */
 #define REG_SW_CFG_STRAP_OVR		0x0214
 #define SW_VPHY_DISABLE			BIT(31)