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");
118