1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2015-2016 Russell King
6 * Copyright (C) 2021 Marek Behun
8 * Network PHYs can appear on I2C buses when they are part of SFP module.
9 * This driver exposes these PHYs to the networking PHY code, allowing
10 * our PHY drivers access to these PHYs, and so allowing configuration
13 #include <linux/i2c.h>
14 #include <linux/mdio/mdio-i2c.h>
15 #include <linux/phy.h>
16 #include <linux/sfp.h>
19 * I2C bus addresses 0x50 and 0x51 are normally an EEPROM, which is
20 * specified to be present in SFP modules. These correspond with PHY
21 * addresses 16 and 17. Disallow access to these "phy" addresses.
23 static bool i2c_mii_valid_phy_id(int phy_id)
25 return phy_id != 0x10 && phy_id != 0x11;
28 static unsigned int i2c_mii_phy_addr(int phy_id)
33 static int i2c_mii_read_default(struct mii_bus *bus, int phy_id, int reg)
35 struct i2c_adapter *i2c = bus->priv;
36 struct i2c_msg msgs[2];
37 u8 addr[3], data[2], *p;
40 if (!i2c_mii_valid_phy_id(phy_id))
44 if (reg & MII_ADDR_C45) {
45 *p++ = 0x20 | ((reg >> 16) & 31);
50 bus_addr = i2c_mii_phy_addr(phy_id);
51 msgs[0].addr = bus_addr;
53 msgs[0].len = p - addr;
55 msgs[1].addr = bus_addr;
56 msgs[1].flags = I2C_M_RD;
57 msgs[1].len = sizeof(data);
60 ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
61 if (ret != ARRAY_SIZE(msgs))
64 return data[0] << 8 | data[1];
67 static int i2c_mii_write_default(struct mii_bus *bus, int phy_id, int reg,
70 struct i2c_adapter *i2c = bus->priv;
75 if (!i2c_mii_valid_phy_id(phy_id))
79 if (reg & MII_ADDR_C45) {
80 *p++ = (reg >> 16) & 31;
87 msg.addr = i2c_mii_phy_addr(phy_id);
92 ret = i2c_transfer(i2c, &msg, 1);
94 return ret < 0 ? ret : 0;
97 /* RollBall SFPs do not access internal PHY via I2C address 0x56, but
98 * instead via address 0x51, when SFP page is set to 0x03 and password to
101 * address size contents description
102 * ------- ---- -------- -----------
103 * 0x80 1 CMD 0x01/0x02/0x04 for write/read/done
104 * 0x81 1 DEV Clause 45 device
105 * 0x82 2 REG Clause 45 register
106 * 0x84 2 VAL Register value
108 #define ROLLBALL_PHY_I2C_ADDR 0x51
110 #define ROLLBALL_PASSWORD (SFP_VSL + 3)
112 #define ROLLBALL_CMD_ADDR 0x80
113 #define ROLLBALL_DATA_ADDR 0x81
115 #define ROLLBALL_CMD_WRITE 0x01
116 #define ROLLBALL_CMD_READ 0x02
117 #define ROLLBALL_CMD_DONE 0x04
119 #define SFP_PAGE_ROLLBALL_MDIO 3
121 static int __i2c_transfer_err(struct i2c_adapter *i2c, struct i2c_msg *msgs,
126 ret = __i2c_transfer(i2c, msgs, num);
135 static int __i2c_rollball_get_page(struct i2c_adapter *i2c, int bus_addr,
138 struct i2c_msg msgs[2];
141 msgs[0].addr = bus_addr;
146 msgs[1].addr = bus_addr;
147 msgs[1].flags = I2C_M_RD;
151 return __i2c_transfer_err(i2c, msgs, 2);
154 static int __i2c_rollball_set_page(struct i2c_adapter *i2c, int bus_addr,
168 return __i2c_transfer_err(i2c, &msg, 1);
171 /* In order to not interfere with other SFP code (which possibly may manipulate
172 * SFP_PAGE), for every transfer we do this:
174 * 2. save content of SFP_PAGE
175 * 3. set SFP_PAGE to 3
177 * 5. restore original SFP_PAGE
179 * Note that one might think that steps 2 to 5 could be theoretically done all
180 * in one call to i2c_transfer (by constructing msgs array in such a way), but
181 * unfortunately tests show that this does not work :-( Changed SFP_PAGE does
182 * not take into account until i2c_transfer() is done.
184 static int i2c_transfer_rollball(struct i2c_adapter *i2c,
185 struct i2c_msg *msgs, int num)
187 int ret, main_err = 0;
190 i2c_lock_bus(i2c, I2C_LOCK_SEGMENT);
192 /* save original page */
193 ret = __i2c_rollball_get_page(i2c, msgs->addr, &saved_page);
197 /* change to RollBall MDIO page */
198 ret = __i2c_rollball_set_page(i2c, msgs->addr, SFP_PAGE_ROLLBALL_MDIO);
202 /* do the transfer; we try to restore original page if this fails */
203 ret = __i2c_transfer_err(i2c, msgs, num);
207 /* restore original page */
208 ret = __i2c_rollball_set_page(i2c, msgs->addr, saved_page);
211 i2c_unlock_bus(i2c, I2C_LOCK_SEGMENT);
213 return main_err ? : ret;
216 static int i2c_rollball_mii_poll(struct mii_bus *bus, int bus_addr, u8 *buf,
219 struct i2c_adapter *i2c = bus->priv;
220 struct i2c_msg msgs[2];
221 u8 cmd_addr, tmp, *res;
224 cmd_addr = ROLLBALL_CMD_ADDR;
226 res = buf ? buf : &tmp;
229 msgs[0].addr = bus_addr;
232 msgs[0].buf = &cmd_addr;
234 msgs[1].addr = bus_addr;
235 msgs[1].flags = I2C_M_RD;
239 /* By experiment it takes up to 70 ms to access a register for these
240 * SFPs. Sleep 20ms between iterations and try 10 times.
246 ret = i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
250 if (*res == ROLLBALL_CMD_DONE)
254 dev_dbg(&bus->dev, "poll timed out\n");
259 static int i2c_rollball_mii_cmd(struct mii_bus *bus, int bus_addr, u8 cmd,
260 u8 *data, size_t len)
262 struct i2c_adapter *i2c = bus->priv;
263 struct i2c_msg msgs[2];
266 cmdbuf[0] = ROLLBALL_CMD_ADDR;
269 msgs[0].addr = bus_addr;
274 msgs[1].addr = bus_addr;
276 msgs[1].len = sizeof(cmdbuf);
277 msgs[1].buf = cmdbuf;
279 return i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
282 static int i2c_mii_read_rollball(struct mii_bus *bus, int phy_id, int reg)
288 if (!(reg & MII_ADDR_C45))
291 bus_addr = i2c_mii_phy_addr(phy_id);
292 if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
295 buf[0] = ROLLBALL_DATA_ADDR;
296 buf[1] = (reg >> 16) & 0x1f;
297 buf[2] = (reg >> 8) & 0xff;
300 ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_READ, buf,
305 ret = i2c_rollball_mii_poll(bus, bus_addr, res, sizeof(res));
306 if (ret == -ETIMEDOUT)
311 val = res[4] << 8 | res[5];
316 static int i2c_mii_write_rollball(struct mii_bus *bus, int phy_id, int reg,
322 if (!(reg & MII_ADDR_C45))
325 bus_addr = i2c_mii_phy_addr(phy_id);
326 if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
329 buf[0] = ROLLBALL_DATA_ADDR;
330 buf[1] = (reg >> 16) & 0x1f;
331 buf[2] = (reg >> 8) & 0xff;
336 ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_WRITE, buf,
341 ret = i2c_rollball_mii_poll(bus, bus_addr, NULL, 0);
348 static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
354 pw[0] = ROLLBALL_PASSWORD;
360 msg.addr = ROLLBALL_PHY_I2C_ADDR;
362 msg.len = sizeof(pw);
365 ret = i2c_transfer(i2c, &msg, 1);
374 struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
375 enum mdio_i2c_proto protocol)
380 if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
381 return ERR_PTR(-EINVAL);
383 mii = mdiobus_alloc();
385 return ERR_PTR(-ENOMEM);
387 snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
388 mii->parent = parent;
392 case MDIO_I2C_ROLLBALL:
393 ret = i2c_mii_init_rollball(i2c);
396 "Cannot initialize RollBall MDIO I2C protocol: %d\n",
402 mii->read = i2c_mii_read_rollball;
403 mii->write = i2c_mii_write_rollball;
406 mii->read = i2c_mii_read_default;
407 mii->write = i2c_mii_write_default;
413 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
415 MODULE_AUTHOR("Russell King");
416 MODULE_DESCRIPTION("MDIO I2C bridge library");
417 MODULE_LICENSE("GPL v2");