net/mdio/mdio-i2c.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * MDIO I2C bridge
0004  *
0005  * Copyright (C) 2015-2016 Russell King
0006  *
0007  * Network PHYs can appear on I2C buses when they are part of SFP module.
0008  * This driver exposes these PHYs to the networking PHY code, allowing
0009  * our PHY drivers access to these PHYs, and so allowing configuration
0010  * of their settings.
0011  */
0012 #include <linux/i2c.h>
0013 #include <linux/mdio/mdio-i2c.h>
0014 #include <linux/phy.h>
0015
0016 /*
0017  * I2C bus addresses 0x50 and 0x51 are normally an EEPROM, which is
0018  * specified to be present in SFP modules.  These correspond with PHY
0019  * addresses 16 and 17.  Disallow access to these "phy" addresses.
0020  */
0021 static bool i2c_mii_valid_phy_id(int phy_id)
0022 {
0023     return phy_id != 0x10 && phy_id != 0x11;
0024 }
0025
0026 static unsigned int i2c_mii_phy_addr(int phy_id)
0027 {
0028     return phy_id + 0x40;
0029 }
0030
0031 static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
0032 {
0033     struct i2c_adapter *i2c = bus->priv;
0034     struct i2c_msg msgs[2];
0035     u8 addr[3], data[2], *p;
0036     int bus_addr, ret;
0037
0038     if (!i2c_mii_valid_phy_id(phy_id))
0039         return 0xffff;
0040
0041     p = addr;
0042     if (reg & MII_ADDR_C45) {
0043         *p++ = 0x20 | ((reg >> 16) & 31);
0044         *p++ = reg >> 8;
0045     }
0046     *p++ = reg;
0047
0048     bus_addr = i2c_mii_phy_addr(phy_id);
0049     msgs[0].addr = bus_addr;
0050     msgs[0].flags = 0;
0051     msgs[0].len = p - addr;
0052     msgs[0].buf = addr;
0053     msgs[1].addr = bus_addr;
0054     msgs[1].flags = I2C_M_RD;
0055     msgs[1].len = sizeof(data);
0056     msgs[1].buf = data;
0057
0058     ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
0059     if (ret != ARRAY_SIZE(msgs))
0060         return 0xffff;
0061
0062     return data[0] << 8 | data[1];
0063 }
0064
0065 static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
0066 {
0067     struct i2c_adapter *i2c = bus->priv;
0068     struct i2c_msg msg;
0069     int ret;
0070     u8 data[5], *p;
0071
0072     if (!i2c_mii_valid_phy_id(phy_id))
0073         return 0;
0074
0075     p = data;
0076     if (reg & MII_ADDR_C45) {
0077         *p++ = (reg >> 16) & 31;
0078         *p++ = reg >> 8;
0079     }
0080     *p++ = reg;
0081     *p++ = val >> 8;
0082     *p++ = val;
0083
0084     msg.addr = i2c_mii_phy_addr(phy_id);
0085     msg.flags = 0;
0086     msg.len = p - data;
0087     msg.buf = data;
0088
0089     ret = i2c_transfer(i2c, &msg, 1);
0090
0091     return ret < 0 ? ret : 0;
0092 }
0093
0094 struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
0095 {
0096     struct mii_bus *mii;
0097
0098     if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
0099         return ERR_PTR(-EINVAL);
0100
0101     mii = mdiobus_alloc();
0102     if (!mii)
0103         return ERR_PTR(-ENOMEM);
0104
0105     snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
0106     mii->parent = parent;
0107     mii->read = i2c_mii_read;
0108     mii->write = i2c_mii_write;
0109     mii->priv = i2c;
0110
0111     return mii;
0112 }
0113 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
0114
0115 MODULE_AUTHOR("Russell King");
0116 MODULE_DESCRIPTION("MDIO I2C bridge library");
0117 MODULE_LICENSE("GPL v2");