1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2015-2016 Russell King
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
12 #include <linux/i2c.h>
13 #include <linux/mdio/mdio-i2c.h>
14 #include <linux/phy.h>
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.
21 static bool i2c_mii_valid_phy_id(int phy_id)
23 return phy_id != 0x10 && phy_id != 0x11;
26 static unsigned int i2c_mii_phy_addr(int phy_id)
31 static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
33 struct i2c_adapter *i2c = bus->priv;
34 struct i2c_msg msgs[2];
35 u8 addr[3], data[2], *p;
38 if (!i2c_mii_valid_phy_id(phy_id))
42 if (reg & MII_ADDR_C45) {
43 *p++ = 0x20 | ((reg >> 16) & 31);
48 bus_addr = i2c_mii_phy_addr(phy_id);
49 msgs[0].addr = bus_addr;
51 msgs[0].len = p - addr;
53 msgs[1].addr = bus_addr;
54 msgs[1].flags = I2C_M_RD;
55 msgs[1].len = sizeof(data);
58 ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
59 if (ret != ARRAY_SIZE(msgs))
62 return data[0] << 8 | data[1];
65 static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
67 struct i2c_adapter *i2c = bus->priv;
72 if (!i2c_mii_valid_phy_id(phy_id))
76 if (reg & MII_ADDR_C45) {
77 *p++ = (reg >> 16) & 31;
84 msg.addr = i2c_mii_phy_addr(phy_id);
89 ret = i2c_transfer(i2c, &msg, 1);
91 return ret < 0 ? ret : 0;
94 struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
98 if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
99 return ERR_PTR(-EINVAL);
101 mii = mdiobus_alloc();
103 return ERR_PTR(-ENOMEM);
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;
113 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
115 MODULE_AUTHOR("Russell King");
116 MODULE_DESCRIPTION("MDIO I2C bridge library");
117 MODULE_LICENSE("GPL v2");