tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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");