drivers/net/phy/mdio-i2c.c

   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  */
  22 static bool i2c_mii_valid_phy_id(int phy_id)
  23 {
  24         return phy_id != 0x10 && phy_id != 0x11;
  25 }
  26
  27 static unsigned int i2c_mii_phy_addr(int phy_id)
  28 {
  29         return phy_id + 0x40;
  30 }
  31
  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 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
  66 static 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
  95 struct 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 }
 114 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
 115
 116 MODULE_AUTHOR("Russell King");
 117 MODULE_DESCRIPTION("MDIO I2C bridge library");
 118 MODULE_LICENSE("GPL v2");