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