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 */
 21static bool i2c_mii_valid_phy_id(int phy_id)
 22{
 23	return phy_id != 0x10 && phy_id != 0x11;
 24}
 25
 26static unsigned int i2c_mii_phy_addr(int phy_id)
 27{
 28	return phy_id + 0x40;
 29}
 30
 31static 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
 65static 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
 94struct 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}
113EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
114
115MODULE_AUTHOR("Russell King");
116MODULE_DESCRIPTION("MDIO I2C bridge library");
117MODULE_LICENSE("GPL v2");