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 */
i2c_mii_valid_phy_id(int phy_id)22 static bool i2c_mii_valid_phy_id(int phy_id)
23 {
24 return phy_id != 0x10 && phy_id != 0x11;
25 }
26
i2c_mii_phy_addr(int phy_id)27 static unsigned int i2c_mii_phy_addr(int phy_id)
28 {
29 return phy_id + 0x40;
30 }
31
i2c_mii_read(struct mii_bus * bus,int phy_id,int reg)32 static 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 data[2], dev_addr = reg;
37 int bus_addr, ret;
38
39 if (!i2c_mii_valid_phy_id(phy_id))
40 return 0xffff;
41
42 bus_addr = i2c_mii_phy_addr(phy_id);
43 msgs[0].addr = bus_addr;
44 msgs[0].flags = 0;
45 msgs[0].len = 1;
46 msgs[0].buf = &dev_addr;
47 msgs[1].addr = bus_addr;
48 msgs[1].flags = I2C_M_RD;
49 msgs[1].len = sizeof(data);
50 msgs[1].buf = data;
51
52 ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
53 if (ret != ARRAY_SIZE(msgs))
54 return 0xffff;
55
56 return data[0] << 8 | data[1];
57 }
58
i2c_mii_write(struct mii_bus * bus,int phy_id,int reg,u16 val)59 static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
60 {
61 struct i2c_adapter *i2c = bus->priv;
62 struct i2c_msg msg;
63 int ret;
64 u8 data[3];
65
66 if (!i2c_mii_valid_phy_id(phy_id))
67 return 0;
68
69 data[0] = reg;
70 data[1] = val >> 8;
71 data[2] = val;
72
73 msg.addr = i2c_mii_phy_addr(phy_id);
74 msg.flags = 0;
75 msg.len = 3;
76 msg.buf = data;
77
78 ret = i2c_transfer(i2c, &msg, 1);
79
80 return ret < 0 ? ret : 0;
81 }
82
mdio_i2c_alloc(struct device * parent,struct i2c_adapter * i2c)83 struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
84 {
85 struct mii_bus *mii;
86
87 if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
88 return ERR_PTR(-EINVAL);
89
90 mii = mdiobus_alloc();
91 if (!mii)
92 return ERR_PTR(-ENOMEM);
93
94 snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
95 mii->parent = parent;
96 mii->read = i2c_mii_read;
97 mii->write = i2c_mii_write;
98 mii->priv = i2c;
99
100 return mii;
101 }
102 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
103
104 MODULE_AUTHOR("Russell King");
105 MODULE_DESCRIPTION("MDIO I2C bridge library");
106 MODULE_LICENSE("GPL v2");
107
