1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * MDIO I2C bridge 4 * 5 * Copyright (C) 2015-2016 Russell King 6 * 7 * Network PHYs can appear on I2C buses when they are part of SFP module. 8 * This driver exposes these PHYs to the networking PHY code, allowing 9 * our PHY drivers access to these PHYs, and so allowing configuration 10 * of their settings. 11 */ 12 #include <linux/i2c.h> 13 #include <linux/mdio/mdio-i2c.h> 14 #include <linux/phy.h> 15 16 /* 17 * I2C bus addresses 0x50 and 0x51 are normally an EEPROM, which is 18 * specified to be present in SFP modules. These correspond with PHY 19 * addresses 16 and 17. Disallow access to these "phy" addresses. 20 */ 21 static bool i2c_mii_valid_phy_id(int phy_id) 22 { 23 return phy_id != 0x10 && phy_id != 0x11; 24 } 25 26 static unsigned int i2c_mii_phy_addr(int phy_id) 27 { 28 return phy_id + 0x40; 29 } 30 31 static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg) 32 { 33 struct i2c_adapter *i2c = bus->priv; 34 struct i2c_msg msgs[2]; 35 u8 addr[3], data[2], *p; 36 int bus_addr, ret; 37 38 if (!i2c_mii_valid_phy_id(phy_id)) 39 return 0xffff; 40 41 p = addr; 42 if (reg & MII_ADDR_C45) { 43 *p++ = 0x20 | ((reg >> 16) & 31); 44 *p++ = reg >> 8; 45 } 46 *p++ = reg; 47 48 bus_addr = i2c_mii_phy_addr(phy_id); 49 msgs[0].addr = bus_addr; 50 msgs[0].flags = 0; 51 msgs[0].len = p - addr; 52 msgs[0].buf = addr; 53 msgs[1].addr = bus_addr; 54 msgs[1].flags = I2C_M_RD; 55 msgs[1].len = sizeof(data); 56 msgs[1].buf = data; 57 58 ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs)); 59 if (ret != ARRAY_SIZE(msgs)) 60 return 0xffff; 61 62 return data[0] << 8 | data[1]; 63 } 64 65 static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val) 66 { 67 struct i2c_adapter *i2c = bus->priv; 68 struct i2c_msg msg; 69 int ret; 70 u8 data[5], *p; 71 72 if (!i2c_mii_valid_phy_id(phy_id)) 73 return 0; 74 75 p = data; 76 if (reg & MII_ADDR_C45) { 77 *p++ = (reg >> 16) & 31; 78 *p++ = reg >> 8; 79 } 80 *p++ = reg; 81 *p++ = val >> 8; 82 *p++ = val; 83 84 msg.addr = i2c_mii_phy_addr(phy_id); 85 msg.flags = 0; 86 msg.len = p - data; 87 msg.buf = data; 88 89 ret = i2c_transfer(i2c, &msg, 1); 90 91 return ret < 0 ? ret : 0; 92 } 93 94 struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c) 95 { 96 struct mii_bus *mii; 97 98 if (!i2c_check_functionality(i2c, I2C_FUNC_I2C)) 99 return ERR_PTR(-EINVAL); 100 101 mii = mdiobus_alloc(); 102 if (!mii) 103 return ERR_PTR(-ENOMEM); 104 105 snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent)); 106 mii->parent = parent; 107 mii->read = i2c_mii_read; 108 mii->write = i2c_mii_write; 109 mii->priv = i2c; 110 111 return mii; 112 } 113 EXPORT_SYMBOL_GPL(mdio_i2c_alloc); 114 115 MODULE_AUTHOR("Russell King"); 116 MODULE_DESCRIPTION("MDIO I2C bridge library"); 117 MODULE_LICENSE("GPL v2"); 118