/*
 * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
 * Copyright (c) 2016 Michael Shych <michaels@mellanox.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>

/* General defines */
#define MLXPLAT_CPLD_LPC_I2C_BASE_ADDR  0x2000
#define MLXCPLD_I2C_DEVICE_NAME         "i2c_mlxcpld"
#define MLXCPLD_I2C_VALID_FLAG          (I2C_M_RECV_LEN | I2C_M_RD)
#define MLXCPLD_I2C_BUS_NUM             1
#define MLXCPLD_I2C_DATA_REG_SZ         36
#define MLXCPLD_I2C_MAX_ADDR_LEN        4
#define MLXCPLD_I2C_RETR_NUM            2
#define MLXCPLD_I2C_XFER_TO             500000 /* usec */
#define MLXCPLD_I2C_POLL_TIME           2000   /* usec */

/* LPC I2C registers */
#define MLXCPLD_LPCI2C_LPF_REG          0x0
#define MLXCPLD_LPCI2C_CTRL_REG         0x1
#define MLXCPLD_LPCI2C_HALF_CYC_REG     0x4
#define MLXCPLD_LPCI2C_I2C_HOLD_REG     0x5
#define MLXCPLD_LPCI2C_CMD_REG          0x6
#define MLXCPLD_LPCI2C_NUM_DAT_REG      0x7
#define MLXCPLD_LPCI2C_NUM_ADDR_REG     0x8
#define MLXCPLD_LPCI2C_STATUS_REG       0x9
#define MLXCPLD_LPCI2C_DATA_REG         0xa

/* LPC I2C masks and parametres */
#define MLXCPLD_LPCI2C_RST_SEL_MASK     0x1
#define MLXCPLD_LPCI2C_TRANS_END        0x1
#define MLXCPLD_LPCI2C_STATUS_NACK      0x10
#define MLXCPLD_LPCI2C_NO_IND           0
#define MLXCPLD_LPCI2C_ACK_IND          1
#define MLXCPLD_LPCI2C_NACK_IND         2

struct  mlxcpld_i2c_curr_xfer {
        u8 cmd;
        u8 addr_width;
        u8 data_len;
        u8 msg_num;
        struct i2c_msg *msg;
};

struct mlxcpld_i2c_priv {
        struct i2c_adapter adap;
        u32 base_addr;
        struct mutex lock;
        struct  mlxcpld_i2c_curr_xfer xfer;
        struct device *dev;
};

static void mlxcpld_i2c_lpc_write_buf(u8 *data, u8 len, u32 addr)
{
        int i;

        for (i = 0; i < len - len % 4; i += 4)
                outl(*(u32 *)(data + i), addr + i);
        for (; i < len; ++i)
                outb(*(data + i), addr + i);
}

static void mlxcpld_i2c_lpc_read_buf(u8 *data, u8 len, u32 addr)
{
        int i;

        for (i = 0; i < len - len % 4; i += 4)
                *(u32 *)(data + i) = inl(addr + i);
        for (; i < len; ++i)
                *(data + i) = inb(addr + i);
}

static void mlxcpld_i2c_read_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
                                  u8 *data, u8 datalen)
{
        u32 addr = priv->base_addr + offs;

        switch (datalen) {
        case 1:
                *(data) = inb(addr);
                break;
        case 2:
                *((u16 *)data) = inw(addr);
                break;
        case 3:
                *((u16 *)data) = inw(addr);
                *(data + 2) = inb(addr + 2);
                break;
        case 4:
                *((u32 *)data) = inl(addr);
                break;
        default:
                mlxcpld_i2c_lpc_read_buf(data, datalen, addr);
                break;
        }
}

static void mlxcpld_i2c_write_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
                                   u8 *data, u8 datalen)
{
        u32 addr = priv->base_addr + offs;

        switch (datalen) {
        case 1:
                outb(*(data), addr);
                break;
        case 2:
                outw(*((u16 *)data), addr);
                break;
        case 3:
                outw(*((u16 *)data), addr);
                outb(*(data + 2), addr + 2);
                break;
        case 4:
                outl(*((u32 *)data), addr);
                break;
        default:
                mlxcpld_i2c_lpc_write_buf(data, datalen, addr);
                break;
        }
}

/*
 * Check validity of received i2c messages parameters.
 * Returns 0 if OK, other - in case of invalid parameters.
 */
static int mlxcpld_i2c_check_msg_params(struct mlxcpld_i2c_priv *priv,
                                        struct i2c_msg *msgs, int num)
{
        int i;

        if (!num) {
                dev_err(priv->dev, "Incorrect 0 num of messages\n");
                return -EINVAL;
        }

        if (unlikely(msgs[0].addr > 0x7f)) {
                dev_err(priv->dev, "Invalid address 0x%03x\n",
                        msgs[0].addr);
                return -EINVAL;
        }

        for (i = 0; i < num; ++i) {
                if (unlikely(!msgs[i].buf)) {
                        dev_err(priv->dev, "Invalid buf in msg[%d]\n",
                                i);
                        return -EINVAL;
                }
                if (unlikely(msgs[0].addr != msgs[i].addr)) {
                        dev_err(priv->dev, "Invalid addr in msg[%d]\n",
                                i);
                        return -EINVAL;
                }
        }

        return 0;
}

/*
 * Check if transfer is completed and status of operation.
 * Returns 0 - transfer completed (both ACK or NACK),
 * negative - transfer isn't finished.
 */
static int mlxcpld_i2c_check_status(struct mlxcpld_i2c_priv *priv, int *status)
{
        u8 val;

        mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);

        if (val & MLXCPLD_LPCI2C_TRANS_END) {
                if (val & MLXCPLD_LPCI2C_STATUS_NACK)
                        /*
                         * The slave is unable to accept the data. No such
                         * slave, command not understood, or unable to accept
                         * any more data.
                         */
                        *status = MLXCPLD_LPCI2C_NACK_IND;
                else
                        *status = MLXCPLD_LPCI2C_ACK_IND;
                return 0;
        }
        *status = MLXCPLD_LPCI2C_NO_IND;

        return -EIO;
}

static void mlxcpld_i2c_set_transf_data(struct mlxcpld_i2c_priv *priv,
                                        struct i2c_msg *msgs, int num,
                                        u8 comm_len)
{
        priv->xfer.msg = msgs;
        priv->xfer.msg_num = num;

        /*
         * All upper layers currently are never use transfer with more than
         * 2 messages. Actually, it's also not so relevant in Mellanox systems
         * because of HW limitation. Max size of transfer is not more than 32
         * bytes in the current x86 LPCI2C bridge.
         */
        priv->xfer.cmd = msgs[num - 1].flags & I2C_M_RD;

        if (priv->xfer.cmd == I2C_M_RD && comm_len != msgs[0].len) {
                priv->xfer.addr_width = msgs[0].len;
                priv->xfer.data_len = comm_len - priv->xfer.addr_width;
        } else {
                priv->xfer.addr_width = 0;
                priv->xfer.data_len = comm_len;
        }
}

/* Reset CPLD LPCI2C block */
static void mlxcpld_i2c_reset(struct mlxcpld_i2c_priv *priv)
{
        u8 val;

        mutex_lock(&priv->lock);

        mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
        val &= ~MLXCPLD_LPCI2C_RST_SEL_MASK;
        mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);

        mutex_unlock(&priv->lock);
}

/* Make sure the CPLD is ready to start transmitting. */
static int mlxcpld_i2c_check_busy(struct mlxcpld_i2c_priv *priv)
{
        u8 val;

        mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);

        if (val & MLXCPLD_LPCI2C_TRANS_END)
                return 0;

        return -EIO;
}

static int mlxcpld_i2c_wait_for_free(struct mlxcpld_i2c_priv *priv)
{
        int timeout = 0;

        do {
                if (!mlxcpld_i2c_check_busy(priv))
                        break;
                usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
                timeout += MLXCPLD_I2C_POLL_TIME;
        } while (timeout <= MLXCPLD_I2C_XFER_TO);

        if (timeout > MLXCPLD_I2C_XFER_TO)
                return -ETIMEDOUT;

        return 0;
}

/*
 * Wait for master transfer to complete.
 * It puts current process to sleep until we get interrupt or timeout expires.
 * Returns the number of transferred or read bytes or error (<0).
 */
static int mlxcpld_i2c_wait_for_tc(struct mlxcpld_i2c_priv *priv)
{
        int status, i, timeout = 0;
        u8 datalen;

        do {
                usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
                if (!mlxcpld_i2c_check_status(priv, &status))
                        break;
                timeout += MLXCPLD_I2C_POLL_TIME;
        } while (status == 0 && timeout < MLXCPLD_I2C_XFER_TO);

        switch (status) {
        case MLXCPLD_LPCI2C_NO_IND:
                return -ETIMEDOUT;

        case MLXCPLD_LPCI2C_ACK_IND:
                if (priv->xfer.cmd != I2C_M_RD)
                        return (priv->xfer.addr_width + priv->xfer.data_len);

                if (priv->xfer.msg_num == 1)
                        i = 0;
                else
                        i = 1;

                if (!priv->xfer.msg[i].buf)
                        return -EINVAL;

                /*
                 * Actual read data len will be always the same as
                 * requested len. 0xff (line pull-up) will be returned
                 * if slave has no data to return. Thus don't read
                 * MLXCPLD_LPCI2C_NUM_DAT_REG reg from CPLD.
                 */
                datalen = priv->xfer.data_len;

                mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_DATA_REG,
                                      priv->xfer.msg[i].buf, datalen);

                return datalen;

        case MLXCPLD_LPCI2C_NACK_IND:
                return -ENXIO;

        default:
                return -EINVAL;
        }
}

static void mlxcpld_i2c_xfer_msg(struct mlxcpld_i2c_priv *priv)
{
        int i, len = 0;
        u8 cmd;

        mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_DAT_REG,
                               &priv->xfer.data_len, 1);
        mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_ADDR_REG,
                               &priv->xfer.addr_width, 1);

        for (i = 0; i < priv->xfer.msg_num; i++) {
                if ((priv->xfer.msg[i].flags & I2C_M_RD) != I2C_M_RD) {
                        /* Don't write to CPLD buffer in read transaction */
                        mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_DATA_REG +
                                               len, priv->xfer.msg[i].buf,
                                               priv->xfer.msg[i].len);
                        len += priv->xfer.msg[i].len;
                }
        }

        /*
         * Set target slave address with command for master transfer.
         * It should be latest executed function before CPLD transaction.
         */
        cmd = (priv->xfer.msg[0].addr << 1) | priv->xfer.cmd;
        mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CMD_REG, &cmd, 1);
}

/*
 * Generic lpc-i2c transfer.
 * Returns the number of processed messages or error (<0).
 */
static int mlxcpld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                            int num)
{
        struct mlxcpld_i2c_priv *priv = i2c_get_adapdata(adap);
        u8 comm_len = 0;
        int i, err;

        err = mlxcpld_i2c_check_msg_params(priv, msgs, num);
        if (err) {
                dev_err(priv->dev, "Incorrect message\n");
                return err;
        }

        for (i = 0; i < num; ++i)
                comm_len += msgs[i].len;

        /* Check bus state */
        if (mlxcpld_i2c_wait_for_free(priv)) {
                dev_err(priv->dev, "LPCI2C bridge is busy\n");

                /*
                 * Usually it means something serious has happened.
                 * We can not have unfinished previous transfer
                 * so it doesn't make any sense to try to stop it.
                 * Probably we were not able to recover from the
                 * previous error.
                 * The only reasonable thing - is soft reset.
                 */
                mlxcpld_i2c_reset(priv);
                if (mlxcpld_i2c_check_busy(priv)) {
                        dev_err(priv->dev, "LPCI2C bridge is busy after reset\n");
                        return -EIO;
                }
        }

        mlxcpld_i2c_set_transf_data(priv, msgs, num, comm_len);

        mutex_lock(&priv->lock);

        /* Do real transfer. Can't fail */
        mlxcpld_i2c_xfer_msg(priv);

        /* Wait for transaction complete */
        err = mlxcpld_i2c_wait_for_tc(priv);

        mutex_unlock(&priv->lock);

        return err < 0 ? err : num;
}

static u32 mlxcpld_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA;
}

static const struct i2c_algorithm mlxcpld_i2c_algo = {
        .master_xfer    = mlxcpld_i2c_xfer,
        .functionality  = mlxcpld_i2c_func
};

static struct i2c_adapter_quirks mlxcpld_i2c_quirks = {
        .flags = I2C_AQ_COMB_WRITE_THEN_READ,
        .max_read_len = MLXCPLD_I2C_DATA_REG_SZ - MLXCPLD_I2C_MAX_ADDR_LEN,
        .max_write_len = MLXCPLD_I2C_DATA_REG_SZ,
        .max_comb_1st_msg_len = 4,
};

static struct i2c_adapter mlxcpld_i2c_adapter = {
        .owner          = THIS_MODULE,
        .name           = "i2c-mlxcpld",
        .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
        .algo           = &mlxcpld_i2c_algo,
        .quirks         = &mlxcpld_i2c_quirks,
        .retries        = MLXCPLD_I2C_RETR_NUM,
        .nr             = MLXCPLD_I2C_BUS_NUM,
};

static int mlxcpld_i2c_probe(struct platform_device *pdev)
{
        struct mlxcpld_i2c_priv *priv;
        int err;

        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        mutex_init(&priv->lock);
        platform_set_drvdata(pdev, priv);

        priv->dev = &pdev->dev;

        /* Register with i2c layer */
        mlxcpld_i2c_adapter.timeout = usecs_to_jiffies(MLXCPLD_I2C_XFER_TO);
        priv->adap = mlxcpld_i2c_adapter;
        priv->adap.dev.parent = &pdev->dev;
        priv->base_addr = MLXPLAT_CPLD_LPC_I2C_BASE_ADDR;
        i2c_set_adapdata(&priv->adap, priv);

        err = i2c_add_numbered_adapter(&priv->adap);
        if (err)
                mutex_destroy(&priv->lock);

        return err;
}

static int mlxcpld_i2c_remove(struct platform_device *pdev)
{
        struct mlxcpld_i2c_priv *priv = platform_get_drvdata(pdev);

        i2c_del_adapter(&priv->adap);
        mutex_destroy(&priv->lock);

        return 0;
}

static struct platform_driver mlxcpld_i2c_driver = {
        .probe          = mlxcpld_i2c_probe,
        .remove         = mlxcpld_i2c_remove,
        .driver = {
                .name = MLXCPLD_I2C_DEVICE_NAME,
        },
};

module_platform_driver(mlxcpld_i2c_driver);

MODULE_AUTHOR("Michael Shych <michaels@mellanox.com>");
MODULE_DESCRIPTION("Mellanox I2C-CPLD controller driver");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("platform:i2c-mlxcpld");