drivers/net/phy/mdio-i2c.c

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