1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * MDIO I2C bridge
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (C) 2015-2016 Russell King
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * Network PHYs can appear on I2C buses when they are part of SFP module.
8*4882a593Smuzhiyun * This driver exposes these PHYs to the networking PHY code, allowing
9*4882a593Smuzhiyun * our PHY drivers access to these PHYs, and so allowing configuration
10*4882a593Smuzhiyun * of their settings.
11*4882a593Smuzhiyun */
12*4882a593Smuzhiyun #include <linux/i2c.h>
13*4882a593Smuzhiyun #include <linux/mdio/mdio-i2c.h>
14*4882a593Smuzhiyun #include <linux/phy.h>
15*4882a593Smuzhiyun
16*4882a593Smuzhiyun /*
17*4882a593Smuzhiyun * I2C bus addresses 0x50 and 0x51 are normally an EEPROM, which is
18*4882a593Smuzhiyun * specified to be present in SFP modules. These correspond with PHY
19*4882a593Smuzhiyun * addresses 16 and 17. Disallow access to these "phy" addresses.
20*4882a593Smuzhiyun */
i2c_mii_valid_phy_id(int phy_id)21*4882a593Smuzhiyun static bool i2c_mii_valid_phy_id(int phy_id)
22*4882a593Smuzhiyun {
23*4882a593Smuzhiyun return phy_id != 0x10 && phy_id != 0x11;
24*4882a593Smuzhiyun }
25*4882a593Smuzhiyun
i2c_mii_phy_addr(int phy_id)26*4882a593Smuzhiyun static unsigned int i2c_mii_phy_addr(int phy_id)
27*4882a593Smuzhiyun {
28*4882a593Smuzhiyun return phy_id + 0x40;
29*4882a593Smuzhiyun }
30*4882a593Smuzhiyun
i2c_mii_read(struct mii_bus * bus,int phy_id,int reg)31*4882a593Smuzhiyun static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
32*4882a593Smuzhiyun {
33*4882a593Smuzhiyun struct i2c_adapter *i2c = bus->priv;
34*4882a593Smuzhiyun struct i2c_msg msgs[2];
35*4882a593Smuzhiyun u8 addr[3], data[2], *p;
36*4882a593Smuzhiyun int bus_addr, ret;
37*4882a593Smuzhiyun
38*4882a593Smuzhiyun if (!i2c_mii_valid_phy_id(phy_id))
39*4882a593Smuzhiyun return 0xffff;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun p = addr;
42*4882a593Smuzhiyun if (reg & MII_ADDR_C45) {
43*4882a593Smuzhiyun *p++ = 0x20 | ((reg >> 16) & 31);
44*4882a593Smuzhiyun *p++ = reg >> 8;
45*4882a593Smuzhiyun }
46*4882a593Smuzhiyun *p++ = reg;
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun bus_addr = i2c_mii_phy_addr(phy_id);
49*4882a593Smuzhiyun msgs[0].addr = bus_addr;
50*4882a593Smuzhiyun msgs[0].flags = 0;
51*4882a593Smuzhiyun msgs[0].len = p - addr;
52*4882a593Smuzhiyun msgs[0].buf = addr;
53*4882a593Smuzhiyun msgs[1].addr = bus_addr;
54*4882a593Smuzhiyun msgs[1].flags = I2C_M_RD;
55*4882a593Smuzhiyun msgs[1].len = sizeof(data);
56*4882a593Smuzhiyun msgs[1].buf = data;
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
59*4882a593Smuzhiyun if (ret != ARRAY_SIZE(msgs))
60*4882a593Smuzhiyun return 0xffff;
61*4882a593Smuzhiyun
62*4882a593Smuzhiyun return data[0] << 8 | data[1];
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun
i2c_mii_write(struct mii_bus * bus,int phy_id,int reg,u16 val)65*4882a593Smuzhiyun static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
66*4882a593Smuzhiyun {
67*4882a593Smuzhiyun struct i2c_adapter *i2c = bus->priv;
68*4882a593Smuzhiyun struct i2c_msg msg;
69*4882a593Smuzhiyun int ret;
70*4882a593Smuzhiyun u8 data[5], *p;
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun if (!i2c_mii_valid_phy_id(phy_id))
73*4882a593Smuzhiyun return 0;
74*4882a593Smuzhiyun
75*4882a593Smuzhiyun p = data;
76*4882a593Smuzhiyun if (reg & MII_ADDR_C45) {
77*4882a593Smuzhiyun *p++ = (reg >> 16) & 31;
78*4882a593Smuzhiyun *p++ = reg >> 8;
79*4882a593Smuzhiyun }
80*4882a593Smuzhiyun *p++ = reg;
81*4882a593Smuzhiyun *p++ = val >> 8;
82*4882a593Smuzhiyun *p++ = val;
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun msg.addr = i2c_mii_phy_addr(phy_id);
85*4882a593Smuzhiyun msg.flags = 0;
86*4882a593Smuzhiyun msg.len = p - data;
87*4882a593Smuzhiyun msg.buf = data;
88*4882a593Smuzhiyun
89*4882a593Smuzhiyun ret = i2c_transfer(i2c, &msg, 1);
90*4882a593Smuzhiyun
91*4882a593Smuzhiyun return ret < 0 ? ret : 0;
92*4882a593Smuzhiyun }
93*4882a593Smuzhiyun
mdio_i2c_alloc(struct device * parent,struct i2c_adapter * i2c)94*4882a593Smuzhiyun struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
95*4882a593Smuzhiyun {
96*4882a593Smuzhiyun struct mii_bus *mii;
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
99*4882a593Smuzhiyun return ERR_PTR(-EINVAL);
100*4882a593Smuzhiyun
101*4882a593Smuzhiyun mii = mdiobus_alloc();
102*4882a593Smuzhiyun if (!mii)
103*4882a593Smuzhiyun return ERR_PTR(-ENOMEM);
104*4882a593Smuzhiyun
105*4882a593Smuzhiyun snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
106*4882a593Smuzhiyun mii->parent = parent;
107*4882a593Smuzhiyun mii->read = i2c_mii_read;
108*4882a593Smuzhiyun mii->write = i2c_mii_write;
109*4882a593Smuzhiyun mii->priv = i2c;
110*4882a593Smuzhiyun
111*4882a593Smuzhiyun return mii;
112*4882a593Smuzhiyun }
113*4882a593Smuzhiyun EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
114*4882a593Smuzhiyun
115*4882a593Smuzhiyun MODULE_AUTHOR("Russell King");
116*4882a593Smuzhiyun MODULE_DESCRIPTION("MDIO I2C bridge library");
117*4882a593Smuzhiyun MODULE_LICENSE("GPL v2");
118