// SPDX-License-Identifier: GPL-2.0
/*
 * MDIO I2C bridge
 *
 * Copyright (C) 2015-2016 Russell King
 * Copyright (C) 2021 Marek Behun
 *
 * 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>
#include <linux/sfp.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_default_c45(struct mii_bus *bus, int phy_id, int devad,
                                    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 (devad >= 0) {
                *p++ = 0x20 | devad;
                *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_default_c45(struct mii_bus *bus, int phy_id,
                                     int devad, 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 (devad >= 0) {
                *p++ = devad;
                *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;
}

static int i2c_mii_read_default_c22(struct mii_bus *bus, int phy_id, int reg)
{
        return i2c_mii_read_default_c45(bus, phy_id, -1, reg);
}

static int i2c_mii_write_default_c22(struct mii_bus *bus, int phy_id, int reg,
                                     u16 val)
{
        return i2c_mii_write_default_c45(bus, phy_id, -1, reg, val);
}

static int smbus_byte_mii_read_default_c22(struct mii_bus *bus, int phy_id,
                                           int reg)
{
        struct i2c_adapter *i2c = bus->priv;
        union i2c_smbus_data smbus_data;
        int val = 0, ret;

        if (!i2c_mii_valid_phy_id(phy_id))
                return 0;

        i2c_lock_bus(i2c, I2C_LOCK_SEGMENT);

        ret = __i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
                               I2C_SMBUS_READ, reg,
                               I2C_SMBUS_BYTE_DATA, &smbus_data);
        if (ret < 0)
                goto unlock;

        val = (smbus_data.byte & 0xff) << 8;

        ret = __i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
                               I2C_SMBUS_READ, reg,
                               I2C_SMBUS_BYTE_DATA, &smbus_data);

unlock:
        i2c_unlock_bus(i2c, I2C_LOCK_SEGMENT);

        if (ret < 0)
                return ret;

        val |= smbus_data.byte & 0xff;

        return val;
}

static int smbus_byte_mii_write_default_c22(struct mii_bus *bus, int phy_id,
                                            int reg, u16 val)
{
        struct i2c_adapter *i2c = bus->priv;
        union i2c_smbus_data smbus_data;
        int ret;

        if (!i2c_mii_valid_phy_id(phy_id))
                return 0;

        smbus_data.byte = (val & 0xff00) >> 8;

        i2c_lock_bus(i2c, I2C_LOCK_SEGMENT);

        ret = __i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
                               I2C_SMBUS_WRITE, reg,
                               I2C_SMBUS_BYTE_DATA, &smbus_data);
        if (ret < 0)
                goto unlock;

        smbus_data.byte = val & 0xff;

        ret = __i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
                               I2C_SMBUS_WRITE, reg,
                               I2C_SMBUS_BYTE_DATA, &smbus_data);

unlock:
        i2c_unlock_bus(i2c, I2C_LOCK_SEGMENT);

        return ret < 0 ? ret : 0;
}

/* RollBall SFPs do not access internal PHY via I2C address 0x56, but
 * instead via address 0x51, when SFP page is set to 0x03 and password to
 * 0xffffffff.
 *
 * address  size  contents  description
 * -------  ----  --------  -----------
 * 0x80     1     CMD       0x01/0x02/0x04 for write/read/done
 * 0x81     1     DEV       Clause 45 device
 * 0x82     2     REG       Clause 45 register
 * 0x84     2     VAL       Register value
 */
#define ROLLBALL_PHY_I2C_ADDR           0x51

#define ROLLBALL_PASSWORD               (SFP_VSL + 3)

#define ROLLBALL_CMD_ADDR               0x80
#define ROLLBALL_DATA_ADDR              0x81

#define ROLLBALL_CMD_WRITE              0x01
#define ROLLBALL_CMD_READ               0x02
#define ROLLBALL_CMD_DONE               0x04

#define SFP_PAGE_ROLLBALL_MDIO          3

static int __i2c_transfer_err(struct i2c_adapter *i2c, struct i2c_msg *msgs,
                              int num)
{
        int ret;

        ret = __i2c_transfer(i2c, msgs, num);
        if (ret < 0)
                return ret;
        else if (ret != num)
                return -EIO;
        else
                return 0;
}

static int __i2c_rollball_get_page(struct i2c_adapter *i2c, int bus_addr,
                                   u8 *page)
{
        struct i2c_msg msgs[2];
        u8 addr = SFP_PAGE;

        msgs[0].addr = bus_addr;
        msgs[0].flags = 0;
        msgs[0].len = 1;
        msgs[0].buf = &addr;

        msgs[1].addr = bus_addr;
        msgs[1].flags = I2C_M_RD;
        msgs[1].len = 1;
        msgs[1].buf = page;

        return __i2c_transfer_err(i2c, msgs, 2);
}

static int __i2c_rollball_set_page(struct i2c_adapter *i2c, int bus_addr,
                                   u8 page)
{
        struct i2c_msg msg;
        u8 buf[2];

        buf[0] = SFP_PAGE;
        buf[1] = page;

        msg.addr = bus_addr;
        msg.flags = 0;
        msg.len = 2;
        msg.buf = buf;

        return __i2c_transfer_err(i2c, &msg, 1);
}

/* In order to not interfere with other SFP code (which possibly may manipulate
 * SFP_PAGE), for every transfer we do this:
 *   1. lock the bus
 *   2. save content of SFP_PAGE
 *   3. set SFP_PAGE to 3
 *   4. do the transfer
 *   5. restore original SFP_PAGE
 *   6. unlock the bus
 * Note that one might think that steps 2 to 5 could be theoretically done all
 * in one call to i2c_transfer (by constructing msgs array in such a way), but
 * unfortunately tests show that this does not work :-( Changed SFP_PAGE does
 * not take into account until i2c_transfer() is done.
 */
static int i2c_transfer_rollball(struct i2c_adapter *i2c,
                                 struct i2c_msg *msgs, int num)
{
        int ret, main_err = 0;
        u8 saved_page;

        i2c_lock_bus(i2c, I2C_LOCK_SEGMENT);

        /* save original page */
        ret = __i2c_rollball_get_page(i2c, msgs->addr, &saved_page);
        if (ret)
                goto unlock;

        /* change to RollBall MDIO page */
        ret = __i2c_rollball_set_page(i2c, msgs->addr, SFP_PAGE_ROLLBALL_MDIO);
        if (ret)
                goto unlock;

        /* do the transfer; we try to restore original page if this fails */
        ret = __i2c_transfer_err(i2c, msgs, num);
        if (ret)
                main_err = ret;

        /* restore original page */
        ret = __i2c_rollball_set_page(i2c, msgs->addr, saved_page);

unlock:
        i2c_unlock_bus(i2c, I2C_LOCK_SEGMENT);

        return main_err ? : ret;
}

static int i2c_rollball_mii_poll(struct mii_bus *bus, int bus_addr, u8 *buf,
                                 size_t len)
{
        struct i2c_adapter *i2c = bus->priv;
        struct i2c_msg msgs[2];
        u8 cmd_addr, tmp, *res;
        int i, ret;

        cmd_addr = ROLLBALL_CMD_ADDR;

        res = buf ? buf : &tmp;
        len = buf ? len : 1;

        msgs[0].addr = bus_addr;
        msgs[0].flags = 0;
        msgs[0].len = 1;
        msgs[0].buf = &cmd_addr;

        msgs[1].addr = bus_addr;
        msgs[1].flags = I2C_M_RD;
        msgs[1].len = len;
        msgs[1].buf = res;

        /* By experiment it takes up to 70 ms to access a register for these
         * SFPs. Sleep 20ms between iterations and try 10 times.
         */
        i = 10;
        do {
                msleep(20);

                ret = i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
                if (ret)
                        return ret;

                if (*res == ROLLBALL_CMD_DONE)
                        return 0;
        } while (i-- > 0);

        dev_dbg(&bus->dev, "poll timed out\n");

        return -ETIMEDOUT;
}

static int i2c_rollball_mii_cmd(struct mii_bus *bus, int bus_addr, u8 cmd,
                                u8 *data, size_t len)
{
        struct i2c_adapter *i2c = bus->priv;
        struct i2c_msg msgs[2];
        u8 cmdbuf[2];

        cmdbuf[0] = ROLLBALL_CMD_ADDR;
        cmdbuf[1] = cmd;

        msgs[0].addr = bus_addr;
        msgs[0].flags = 0;
        msgs[0].len = len;
        msgs[0].buf = data;

        msgs[1].addr = bus_addr;
        msgs[1].flags = 0;
        msgs[1].len = sizeof(cmdbuf);
        msgs[1].buf = cmdbuf;

        return i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
}

static int i2c_mii_read_rollball(struct mii_bus *bus, int phy_id, int devad,
                                 int reg)
{
        u8 buf[4], res[6];
        int bus_addr, ret;
        u16 val;

        bus_addr = i2c_mii_phy_addr(phy_id);
        if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
                return 0xffff;

        buf[0] = ROLLBALL_DATA_ADDR;
        buf[1] = devad;
        buf[2] = (reg >> 8) & 0xff;
        buf[3] = reg & 0xff;

        ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_READ, buf,
                                   sizeof(buf));
        if (ret < 0)
                return ret;

        ret = i2c_rollball_mii_poll(bus, bus_addr, res, sizeof(res));
        if (ret == -ETIMEDOUT)
                return 0xffff;
        else if (ret < 0)
                return ret;

        val = res[4] << 8 | res[5];

        return val;
}

static int i2c_mii_write_rollball(struct mii_bus *bus, int phy_id, int devad,
                                  int reg, u16 val)
{
        int bus_addr, ret;
        u8 buf[6];

        bus_addr = i2c_mii_phy_addr(phy_id);
        if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
                return 0;

        buf[0] = ROLLBALL_DATA_ADDR;
        buf[1] = devad;
        buf[2] = (reg >> 8) & 0xff;
        buf[3] = reg & 0xff;
        buf[4] = val >> 8;
        buf[5] = val & 0xff;

        ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_WRITE, buf,
                                   sizeof(buf));
        if (ret < 0)
                return ret;

        ret = i2c_rollball_mii_poll(bus, bus_addr, NULL, 0);
        if (ret < 0)
                return ret;

        return 0;
}

static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
{
        struct i2c_msg msg;
        u8 pw[5];
        int ret;

        pw[0] = ROLLBALL_PASSWORD;
        pw[1] = 0xff;
        pw[2] = 0xff;
        pw[3] = 0xff;
        pw[4] = 0xff;

        msg.addr = ROLLBALL_PHY_I2C_ADDR;
        msg.flags = 0;
        msg.len = sizeof(pw);
        msg.buf = pw;

        ret = i2c_transfer(i2c, &msg, 1);
        if (ret < 0)
                return ret;
        else if (ret != 1)
                return -EIO;
        else
                return 0;
}

static bool mdio_i2c_check_functionality(struct i2c_adapter *i2c,
                                         enum mdio_i2c_proto protocol)
{
        if (i2c_check_functionality(i2c, I2C_FUNC_I2C))
                return true;

        if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA) &&
            protocol == MDIO_I2C_MARVELL_C22)
                return true;

        return false;
}

struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
                               enum mdio_i2c_proto protocol)
{
        struct mii_bus *mii;
        int ret;

        if (!mdio_i2c_check_functionality(i2c, protocol))
                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->priv = i2c;

        /* Only use SMBus if we have no other choice */
        if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA) &&
            !i2c_check_functionality(i2c, I2C_FUNC_I2C)) {
                mii->read = smbus_byte_mii_read_default_c22;
                mii->write = smbus_byte_mii_write_default_c22;
                return mii;
        }

        switch (protocol) {
        case MDIO_I2C_ROLLBALL:
                ret = i2c_mii_init_rollball(i2c);
                if (ret < 0) {
                        dev_err(parent,
                                "Cannot initialize RollBall MDIO I2C protocol: %d\n",
                                ret);
                        mdiobus_free(mii);
                        return ERR_PTR(ret);
                }

                mii->read_c45 = i2c_mii_read_rollball;
                mii->write_c45 = i2c_mii_write_rollball;
                break;
        default:
                mii->read = i2c_mii_read_default_c22;
                mii->write = i2c_mii_write_default_c22;
                mii->read_c45 = i2c_mii_read_default_c45;
                mii->write_c45 = i2c_mii_write_default_c45;
                break;
        }

        return mii;
}
EXPORT_SYMBOL_GPL(mdio_i2c_alloc);

MODULE_AUTHOR("Russell King");
MODULE_DESCRIPTION("MDIO I2C bridge library");
MODULE_LICENSE("GPL v2");