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