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// SPDX-License-Identifier: GPL-2.0
/*
* MDIO I2C bridge
*
* Copyright (C) 2015-2016 Russell King
*
* Network PHYs can appear on I2C buses when they are part of SFP module.
* This driver exposes these PHYs to the networking PHY code, allowing
* our PHY drivers access to these PHYs, and so allowing configuration
* of their settings.
*/
#include <linux/i2c.h>
#include <linux/mdio/mdio-i2c.h>
#include <linux/phy.h>
/*
* I2C bus addresses 0x50 and 0x51 are normally an EEPROM, which is
* specified to be present in SFP modules. These correspond with PHY
* addresses 16 and 17. Disallow access to these "phy" addresses.
*/
static bool i2c_mii_valid_phy_id(int phy_id)
{
return phy_id != 0x10 && phy_id != 0x11;
}
static unsigned int i2c_mii_phy_addr(int phy_id)
{
return phy_id + 0x40;
}
static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
{
struct i2c_adapter *i2c = bus->priv;
struct i2c_msg msgs[2];
u8 addr[3], data[2], *p;
int bus_addr, ret;
if (!i2c_mii_valid_phy_id(phy_id))
return 0xffff;
p = addr;
if (reg & MII_ADDR_C45) {
*p++ = 0x20 | ((reg >> 16) & 31);
*p++ = reg >> 8;
}
*p++ = reg;
bus_addr = i2c_mii_phy_addr(phy_id);
msgs[0].addr = bus_addr;
msgs[0].flags = 0;
msgs[0].len = p - addr;
msgs[0].buf = addr;
msgs[1].addr = bus_addr;
msgs[1].flags = I2C_M_RD;
msgs[1].len = sizeof(data);
msgs[1].buf = data;
ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
if (ret != ARRAY_SIZE(msgs))
return 0xffff;
return data[0] << 8 | data[1];
}
static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
{
struct i2c_adapter *i2c = bus->priv;
struct i2c_msg msg;
int ret;
u8 data[5], *p;
if (!i2c_mii_valid_phy_id(phy_id))
return 0;
p = data;
if (reg & MII_ADDR_C45) {
*p++ = (reg >> 16) & 31;
*p++ = reg >> 8;
}
*p++ = reg;
*p++ = val >> 8;
*p++ = val;
msg.addr = i2c_mii_phy_addr(phy_id);
msg.flags = 0;
msg.len = p - data;
msg.buf = data;
ret = i2c_transfer(i2c, &msg, 1);
return ret < 0 ? ret : 0;
}
struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
{
struct mii_bus *mii;
if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
return ERR_PTR(-EINVAL);
mii = mdiobus_alloc();
if (!mii)
return ERR_PTR(-ENOMEM);
snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
mii->parent = parent;
mii->read = i2c_mii_read;
mii->write = i2c_mii_write;
mii->priv = i2c;
return mii;
}
EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
MODULE_AUTHOR("Russell King");
MODULE_DESCRIPTION("MDIO I2C bridge library");
MODULE_LICENSE("GPL v2");
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