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