/*
 * Synopsys DesignWare I2C adapter driver (master only).
 *
 * Based on the TI DAVINCI I2C adapter driver.
 *
 * Copyright (C) 2006 Texas Instruments.
 * Copyright (C) 2007 MontaVista Software Inc.
 * Copyright (C) 2009 Provigent Ltd.
 *
 * ----------------------------------------------------------------------------
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * ----------------------------------------------------------------------------
 *
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/clk.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/slab.h>

/*
 * Registers offset
 */
#define DW_IC_CON               0x0
#define DW_IC_TAR               0x4
#define DW_IC_DATA_CMD          0x10
#define DW_IC_SS_SCL_HCNT       0x14
#define DW_IC_SS_SCL_LCNT       0x18
#define DW_IC_FS_SCL_HCNT       0x1c
#define DW_IC_FS_SCL_LCNT       0x20
#define DW_IC_INTR_STAT         0x2c
#define DW_IC_INTR_MASK         0x30
#define DW_IC_RAW_INTR_STAT     0x34
#define DW_IC_RX_TL             0x38
#define DW_IC_TX_TL             0x3c
#define DW_IC_CLR_INTR          0x40
#define DW_IC_CLR_RX_UNDER      0x44
#define DW_IC_CLR_RX_OVER       0x48
#define DW_IC_CLR_TX_OVER       0x4c
#define DW_IC_CLR_RD_REQ        0x50
#define DW_IC_CLR_TX_ABRT       0x54
#define DW_IC_CLR_RX_DONE       0x58
#define DW_IC_CLR_ACTIVITY      0x5c
#define DW_IC_CLR_STOP_DET      0x60
#define DW_IC_CLR_START_DET     0x64
#define DW_IC_CLR_GEN_CALL      0x68
#define DW_IC_ENABLE            0x6c
#define DW_IC_STATUS            0x70
#define DW_IC_TXFLR             0x74
#define DW_IC_RXFLR             0x78
#define DW_IC_COMP_PARAM_1      0xf4
#define DW_IC_TX_ABRT_SOURCE    0x80

#define DW_IC_CON_MASTER                0x1
#define DW_IC_CON_SPEED_STD             0x2
#define DW_IC_CON_SPEED_FAST            0x4
#define DW_IC_CON_10BITADDR_MASTER      0x10
#define DW_IC_CON_RESTART_EN            0x20
#define DW_IC_CON_SLAVE_DISABLE         0x40

#define DW_IC_INTR_RX_UNDER     0x001
#define DW_IC_INTR_RX_OVER      0x002
#define DW_IC_INTR_RX_FULL      0x004
#define DW_IC_INTR_TX_OVER      0x008
#define DW_IC_INTR_TX_EMPTY     0x010
#define DW_IC_INTR_RD_REQ       0x020
#define DW_IC_INTR_TX_ABRT      0x040
#define DW_IC_INTR_RX_DONE      0x080
#define DW_IC_INTR_ACTIVITY     0x100
#define DW_IC_INTR_STOP_DET     0x200
#define DW_IC_INTR_START_DET    0x400
#define DW_IC_INTR_GEN_CALL     0x800

#define DW_IC_INTR_DEFAULT_MASK         (DW_IC_INTR_RX_FULL | \
                                         DW_IC_INTR_TX_EMPTY | \
                                         DW_IC_INTR_TX_ABRT | \
                                         DW_IC_INTR_STOP_DET)

#define DW_IC_STATUS_ACTIVITY   0x1

#define DW_IC_ERR_TX_ABRT       0x1

/*
 * status codes
 */
#define STATUS_IDLE                     0x0
#define STATUS_WRITE_IN_PROGRESS        0x1
#define STATUS_READ_IN_PROGRESS         0x2

#define TIMEOUT                 20 /* ms */

/*
 * hardware abort codes from the DW_IC_TX_ABRT_SOURCE register
 *
 * only expected abort codes are listed here
 * refer to the datasheet for the full list
 */
#define ABRT_7B_ADDR_NOACK      0
#define ABRT_10ADDR1_NOACK      1
#define ABRT_10ADDR2_NOACK      2
#define ABRT_TXDATA_NOACK       3
#define ABRT_GCALL_NOACK        4
#define ABRT_GCALL_READ         5
#define ABRT_SBYTE_ACKDET       7
#define ABRT_SBYTE_NORSTRT      9
#define ABRT_10B_RD_NORSTRT     10
#define ABRT_MASTER_DIS         11
#define ARB_LOST                12

#define DW_IC_TX_ABRT_7B_ADDR_NOACK     (1UL << ABRT_7B_ADDR_NOACK)
#define DW_IC_TX_ABRT_10ADDR1_NOACK     (1UL << ABRT_10ADDR1_NOACK)
#define DW_IC_TX_ABRT_10ADDR2_NOACK     (1UL << ABRT_10ADDR2_NOACK)
#define DW_IC_TX_ABRT_TXDATA_NOACK      (1UL << ABRT_TXDATA_NOACK)
#define DW_IC_TX_ABRT_GCALL_NOACK       (1UL << ABRT_GCALL_NOACK)
#define DW_IC_TX_ABRT_GCALL_READ        (1UL << ABRT_GCALL_READ)
#define DW_IC_TX_ABRT_SBYTE_ACKDET      (1UL << ABRT_SBYTE_ACKDET)
#define DW_IC_TX_ABRT_SBYTE_NORSTRT     (1UL << ABRT_SBYTE_NORSTRT)
#define DW_IC_TX_ABRT_10B_RD_NORSTRT    (1UL << ABRT_10B_RD_NORSTRT)
#define DW_IC_TX_ABRT_MASTER_DIS        (1UL << ABRT_MASTER_DIS)
#define DW_IC_TX_ARB_LOST               (1UL << ARB_LOST)

#define DW_IC_TX_ABRT_NOACK             (DW_IC_TX_ABRT_7B_ADDR_NOACK | \
                                         DW_IC_TX_ABRT_10ADDR1_NOACK | \
                                         DW_IC_TX_ABRT_10ADDR2_NOACK | \
                                         DW_IC_TX_ABRT_TXDATA_NOACK | \
                                         DW_IC_TX_ABRT_GCALL_NOACK)

static char *abort_sources[] = {
        [ABRT_7B_ADDR_NOACK] =
                "slave address not acknowledged (7bit mode)",
        [ABRT_10ADDR1_NOACK] =
                "first address byte not acknowledged (10bit mode)",
        [ABRT_10ADDR2_NOACK] =
                "second address byte not acknowledged (10bit mode)",
        [ABRT_TXDATA_NOACK] =
                "data not acknowledged",
        [ABRT_GCALL_NOACK] =
                "no acknowledgement for a general call",
        [ABRT_GCALL_READ] =
                "read after general call",
        [ABRT_SBYTE_ACKDET] =
                "start byte acknowledged",
        [ABRT_SBYTE_NORSTRT] =
                "trying to send start byte when restart is disabled",
        [ABRT_10B_RD_NORSTRT] =
                "trying to read when restart is disabled (10bit mode)",
        [ABRT_MASTER_DIS] =
                "trying to use disabled adapter",
        [ARB_LOST] =
                "lost arbitration",
};

/**
 * struct dw_i2c_dev - private i2c-designware data
 * @dev: driver model device node
 * @base: IO registers pointer
 * @cmd_complete: tx completion indicator
 * @lock: protect this struct and IO registers
 * @clk: input reference clock
 * @cmd_err: run time hadware error code
 * @msgs: points to an array of messages currently being transfered
 * @msgs_num: the number of elements in msgs
 * @msg_write_idx: the element index of the current tx message in the msgs
 *      array
 * @tx_buf_len: the length of the current tx buffer
 * @tx_buf: the current tx buffer
 * @msg_read_idx: the element index of the current rx message in the msgs
 *      array
 * @rx_buf_len: the length of the current rx buffer
 * @rx_buf: the current rx buffer
 * @msg_err: error status of the current transfer
 * @status: i2c master status, one of STATUS_*
 * @abort_source: copy of the TX_ABRT_SOURCE register
 * @irq: interrupt number for the i2c master
 * @adapter: i2c subsystem adapter node
 * @tx_fifo_depth: depth of the hardware tx fifo
 * @rx_fifo_depth: depth of the hardware rx fifo
 */
struct dw_i2c_dev {
        struct device           *dev;
        void __iomem            *base;
        struct completion       cmd_complete;
        struct mutex            lock;
        struct clk              *clk;
        int                     cmd_err;
        struct i2c_msg          *msgs;
        int                     msgs_num;
        int                     msg_write_idx;
        u32                     tx_buf_len;
        u8                      *tx_buf;
        int                     msg_read_idx;
        u32                     rx_buf_len;
        u8                      *rx_buf;
        int                     msg_err;
        unsigned int            status;
        u32                     abort_source;
        int                     irq;
        struct i2c_adapter      adapter;
        unsigned int            tx_fifo_depth;
        unsigned int            rx_fifo_depth;
};

static u32
i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset)
{
        /*
         * DesignWare I2C core doesn't seem to have solid strategy to meet
         * the tHD;STA timing spec.  Configuring _HCNT based on tHIGH spec
         * will result in violation of the tHD;STA spec.
         */
        if (cond)
                /*
                 * Conditional expression:
                 *
                 *   IC_[FS]S_SCL_HCNT + (1+4+3) >= IC_CLK * tHIGH
                 *
                 * This is based on the DW manuals, and represents an ideal
                 * configuration.  The resulting I2C bus speed will be
                 * faster than any of the others.
                 *
                 * If your hardware is free from tHD;STA issue, try this one.
                 */
                return (ic_clk * tSYMBOL + 5000) / 10000 - 8 + offset;
        else
                /*
                 * Conditional expression:
                 *
                 *   IC_[FS]S_SCL_HCNT + 3 >= IC_CLK * (tHD;STA + tf)
                 *
                 * This is just experimental rule; the tHD;STA period turned
                 * out to be proportinal to (_HCNT + 3).  With this setting,
                 * we could meet both tHIGH and tHD;STA timing specs.
                 *
                 * If unsure, you'd better to take this alternative.
                 *
                 * The reason why we need to take into account "tf" here,
                 * is the same as described in i2c_dw_scl_lcnt().
                 */
                return (ic_clk * (tSYMBOL + tf) + 5000) / 10000 - 3 + offset;
}

static u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset)
{
        /*
         * Conditional expression:
         *
         *   IC_[FS]S_SCL_LCNT + 1 >= IC_CLK * (tLOW + tf)
         *
         * DW I2C core starts counting the SCL CNTs for the LOW period
         * of the SCL clock (tLOW) as soon as it pulls the SCL line.
         * In order to meet the tLOW timing spec, we need to take into
         * account the fall time of SCL signal (tf).  Default tf value
         * should be 0.3 us, for safety.
         */
        return ((ic_clk * (tLOW + tf) + 5000) / 10000) - 1 + offset;
}

/**
 * i2c_dw_init() - initialize the designware i2c master hardware
 * @dev: device private data
 *
 * This functions configures and enables the I2C master.
 * This function is called during I2C init function, and in case of timeout at
 * run time.
 */
static void i2c_dw_init(struct dw_i2c_dev *dev)
{
        u32 input_clock_khz = clk_get_rate(dev->clk) / 1000;
        u32 ic_con, hcnt, lcnt;

        /* Disable the adapter */
        writel(0, dev->base + DW_IC_ENABLE);

        /* set standard and fast speed deviders for high/low periods */

        /* Standard-mode */
        hcnt = i2c_dw_scl_hcnt(input_clock_khz,
                                40,     /* tHD;STA = tHIGH = 4.0 us */
                                3,      /* tf = 0.3 us */
                                0,      /* 0: DW default, 1: Ideal */
                                0);     /* No offset */
        lcnt = i2c_dw_scl_lcnt(input_clock_khz,
                                47,     /* tLOW = 4.7 us */
                                3,      /* tf = 0.3 us */
                                0);     /* No offset */
        writel(hcnt, dev->base + DW_IC_SS_SCL_HCNT);
        writel(lcnt, dev->base + DW_IC_SS_SCL_LCNT);
        dev_dbg(dev->dev, "Standard-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);

        /* Fast-mode */
        hcnt = i2c_dw_scl_hcnt(input_clock_khz,
                                6,      /* tHD;STA = tHIGH = 0.6 us */
                                3,      /* tf = 0.3 us */
                                0,      /* 0: DW default, 1: Ideal */
                                0);     /* No offset */
        lcnt = i2c_dw_scl_lcnt(input_clock_khz,
                                13,     /* tLOW = 1.3 us */
                                3,      /* tf = 0.3 us */
                                0);     /* No offset */
        writel(hcnt, dev->base + DW_IC_FS_SCL_HCNT);
        writel(lcnt, dev->base + DW_IC_FS_SCL_LCNT);
        dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);

        /* Configure Tx/Rx FIFO threshold levels */
        writel(dev->tx_fifo_depth - 1, dev->base + DW_IC_TX_TL);
        writel(0, dev->base + DW_IC_RX_TL);

        /* configure the i2c master */
        ic_con = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
                DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
        writel(ic_con, dev->base + DW_IC_CON);
}

/*
 * Waiting for bus not busy
 */
static int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev)
{
        int timeout = TIMEOUT;

        while (readl(dev->base + DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
                if (timeout <= 0) {
                        dev_warn(dev->dev, "timeout waiting for bus ready\n");
                        return -ETIMEDOUT;
                }
                timeout--;
                mdelay(1);
        }

        return 0;
}

static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        u32 ic_con;

        /* Disable the adapter */
        writel(0, dev->base + DW_IC_ENABLE);

        /* set the slave (target) address */
        writel(msgs[dev->msg_write_idx].addr, dev->base + DW_IC_TAR);

        /* if the slave address is ten bit address, enable 10BITADDR */
        ic_con = readl(dev->base + DW_IC_CON);
        if (msgs[dev->msg_write_idx].flags & I2C_M_TEN)
                ic_con |= DW_IC_CON_10BITADDR_MASTER;
        else
                ic_con &= ~DW_IC_CON_10BITADDR_MASTER;
        writel(ic_con, dev->base + DW_IC_CON);

        /* Enable the adapter */
        writel(1, dev->base + DW_IC_ENABLE);

        /* Enable interrupts */
        writel(DW_IC_INTR_DEFAULT_MASK, dev->base + DW_IC_INTR_MASK);
}

/*
 * Initiate (and continue) low level master read/write transaction.
 * This function is only called from i2c_dw_isr, and pumping i2c_msg
 * messages into the tx buffer.  Even if the size of i2c_msg data is
 * longer than the size of the tx buffer, it handles everything.
 */
static void
i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        u32 intr_mask;
        int tx_limit, rx_limit;
        u32 addr = msgs[dev->msg_write_idx].addr;
        u32 buf_len = dev->tx_buf_len;
        u8 *buf = dev->tx_buf;;

        intr_mask = DW_IC_INTR_DEFAULT_MASK;

        for (; dev->msg_write_idx < dev->msgs_num; dev->msg_write_idx++) {
                /*
                 * if target address has changed, we need to
                 * reprogram the target address in the i2c
                 * adapter when we are done with this transfer
                 */
                if (msgs[dev->msg_write_idx].addr != addr) {
                        dev_err(dev->dev,
                                "%s: invalid target address\n", __func__);
                        dev->msg_err = -EINVAL;
                        break;
                }

                if (msgs[dev->msg_write_idx].len == 0) {
                        dev_err(dev->dev,
                                "%s: invalid message length\n", __func__);
                        dev->msg_err = -EINVAL;
                        break;
                }

                if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) {
                        /* new i2c_msg */
                        buf = msgs[dev->msg_write_idx].buf;
                        buf_len = msgs[dev->msg_write_idx].len;
                }

                tx_limit = dev->tx_fifo_depth - readl(dev->base + DW_IC_TXFLR);
                rx_limit = dev->rx_fifo_depth - readl(dev->base + DW_IC_RXFLR);

                while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
                        if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
                                writel(0x100, dev->base + DW_IC_DATA_CMD);
                                rx_limit--;
                        } else
                                writel(*buf++, dev->base + DW_IC_DATA_CMD);
                        tx_limit--; buf_len--;
                }

                dev->tx_buf = buf;
                dev->tx_buf_len = buf_len;

                if (buf_len > 0) {
                        /* more bytes to be written */
                        dev->status |= STATUS_WRITE_IN_PROGRESS;
                        break;
                } else
                        dev->status &= ~STATUS_WRITE_IN_PROGRESS;
        }

        /*
         * If i2c_msg index search is completed, we don't need TX_EMPTY
         * interrupt any more.
         */
        if (dev->msg_write_idx == dev->msgs_num)
                intr_mask &= ~DW_IC_INTR_TX_EMPTY;

        if (dev->msg_err)
                intr_mask = 0;

        writel(intr_mask, dev->base + DW_IC_INTR_MASK);
}

static void
i2c_dw_read(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        int rx_valid;

        for (; dev->msg_read_idx < dev->msgs_num; dev->msg_read_idx++) {
                u32 len;
                u8 *buf;

                if (!(msgs[dev->msg_read_idx].flags & I2C_M_RD))
                        continue;

                if (!(dev->status & STATUS_READ_IN_PROGRESS)) {
                        len = msgs[dev->msg_read_idx].len;
                        buf = msgs[dev->msg_read_idx].buf;
                } else {
                        len = dev->rx_buf_len;
                        buf = dev->rx_buf;
                }

                rx_valid = readl(dev->base + DW_IC_RXFLR);

                for (; len > 0 && rx_valid > 0; len--, rx_valid--)
                        *buf++ = readl(dev->base + DW_IC_DATA_CMD);

                if (len > 0) {
                        dev->status |= STATUS_READ_IN_PROGRESS;
                        dev->rx_buf_len = len;
                        dev->rx_buf = buf;
                        return;
                } else
                        dev->status &= ~STATUS_READ_IN_PROGRESS;
        }
}

static int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev)
{
        unsigned long abort_source = dev->abort_source;
        int i;

        if (abort_source & DW_IC_TX_ABRT_NOACK) {
                for_each_set_bit(i, &abort_source, ARRAY_SIZE(abort_sources))
                        dev_dbg(dev->dev,
                                "%s: %s\n", __func__, abort_sources[i]);
                return -EREMOTEIO;
        }

        for_each_set_bit(i, &abort_source, ARRAY_SIZE(abort_sources))
                dev_err(dev->dev, "%s: %s\n", __func__, abort_sources[i]);

        if (abort_source & DW_IC_TX_ARB_LOST)
                return -EAGAIN;
        else if (abort_source & DW_IC_TX_ABRT_GCALL_READ)
                return -EINVAL; /* wrong msgs[] data */
        else
                return -EIO;
}

/*
 * Prepare controller for a transaction and call i2c_dw_xfer_msg
 */
static int
i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
{
        struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
        int ret;

        dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);

        mutex_lock(&dev->lock);

        INIT_COMPLETION(dev->cmd_complete);
        dev->msgs = msgs;
        dev->msgs_num = num;
        dev->cmd_err = 0;
        dev->msg_write_idx = 0;
        dev->msg_read_idx = 0;
        dev->msg_err = 0;
        dev->status = STATUS_IDLE;
        dev->abort_source = 0;

        ret = i2c_dw_wait_bus_not_busy(dev);
        if (ret < 0)
                goto done;

        /* start the transfers */
        i2c_dw_xfer_init(dev);

        /* wait for tx to complete */
        ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete, HZ);
        if (ret == 0) {
                dev_err(dev->dev, "controller timed out\n");
                i2c_dw_init(dev);
                ret = -ETIMEDOUT;
                goto done;
        } else if (ret < 0)
                goto done;

        if (dev->msg_err) {
                ret = dev->msg_err;
                goto done;
        }

        /* no error */
        if (likely(!dev->cmd_err)) {
                /* Disable the adapter */
                writel(0, dev->base + DW_IC_ENABLE);
                ret = num;
                goto done;
        }

        /* We have an error */
        if (dev->cmd_err == DW_IC_ERR_TX_ABRT) {
                ret = i2c_dw_handle_tx_abort(dev);
                goto done;
        }
        ret = -EIO;

done:
        mutex_unlock(&dev->lock);

        return ret;
}

static u32 i2c_dw_func(struct i2c_adapter *adap)
{
        return  I2C_FUNC_I2C |
                I2C_FUNC_10BIT_ADDR |
                I2C_FUNC_SMBUS_BYTE |
                I2C_FUNC_SMBUS_BYTE_DATA |
                I2C_FUNC_SMBUS_WORD_DATA |
                I2C_FUNC_SMBUS_I2C_BLOCK;
}

static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
{
        u32 stat;

        /*
         * The IC_INTR_STAT register just indicates "enabled" interrupts.
         * Ths unmasked raw version of interrupt status bits are available
         * in the IC_RAW_INTR_STAT register.
         *
         * That is,
         *   stat = readl(IC_INTR_STAT);
         * equals to,
         *   stat = readl(IC_RAW_INTR_STAT) & readl(IC_INTR_MASK);
         *
         * The raw version might be useful for debugging purposes.
         */
        stat = readl(dev->base + DW_IC_INTR_STAT);

        /*
         * Do not use the IC_CLR_INTR register to clear interrupts, or
         * you'll miss some interrupts, triggered during the period from
         * readl(IC_INTR_STAT) to readl(IC_CLR_INTR).
         *
         * Instead, use the separately-prepared IC_CLR_* registers.
         */
        if (stat & DW_IC_INTR_RX_UNDER)
                readl(dev->base + DW_IC_CLR_RX_UNDER);
        if (stat & DW_IC_INTR_RX_OVER)
                readl(dev->base + DW_IC_CLR_RX_OVER);
        if (stat & DW_IC_INTR_TX_OVER)
                readl(dev->base + DW_IC_CLR_TX_OVER);
        if (stat & DW_IC_INTR_RD_REQ)
                readl(dev->base + DW_IC_CLR_RD_REQ);
        if (stat & DW_IC_INTR_TX_ABRT) {
                /*
                 * The IC_TX_ABRT_SOURCE register is cleared whenever
                 * the IC_CLR_TX_ABRT is read.  Preserve it beforehand.
                 */
                dev->abort_source = readl(dev->base + DW_IC_TX_ABRT_SOURCE);
                readl(dev->base + DW_IC_CLR_TX_ABRT);
        }
        if (stat & DW_IC_INTR_RX_DONE)
                readl(dev->base + DW_IC_CLR_RX_DONE);
        if (stat & DW_IC_INTR_ACTIVITY)
                readl(dev->base + DW_IC_CLR_ACTIVITY);
        if (stat & DW_IC_INTR_STOP_DET)
                readl(dev->base + DW_IC_CLR_STOP_DET);
        if (stat & DW_IC_INTR_START_DET)
                readl(dev->base + DW_IC_CLR_START_DET);
        if (stat & DW_IC_INTR_GEN_CALL)
                readl(dev->base + DW_IC_CLR_GEN_CALL);

        return stat;
}

/*
 * Interrupt service routine. This gets called whenever an I2C interrupt
 * occurs.
 */
static irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
{
        struct dw_i2c_dev *dev = dev_id;
        u32 stat;

        stat = i2c_dw_read_clear_intrbits(dev);
        dev_dbg(dev->dev, "%s: stat=0x%x\n", __func__, stat);

        if (stat & DW_IC_INTR_TX_ABRT) {
                dev->cmd_err |= DW_IC_ERR_TX_ABRT;
                dev->status = STATUS_IDLE;

                /*
                 * Anytime TX_ABRT is set, the contents of the tx/rx
                 * buffers are flushed.  Make sure to skip them.
                 */
                writel(0, dev->base + DW_IC_INTR_MASK);
                goto tx_aborted;
        }

        if (stat & DW_IC_INTR_RX_FULL)
                i2c_dw_read(dev);

        if (stat & DW_IC_INTR_TX_EMPTY)
                i2c_dw_xfer_msg(dev);

        /*
         * No need to modify or disable the interrupt mask here.
         * i2c_dw_xfer_msg() will take care of it according to
         * the current transmit status.
         */

tx_aborted:
        if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
                complete(&dev->cmd_complete);

        return IRQ_HANDLED;
}

static struct i2c_algorithm i2c_dw_algo = {
        .master_xfer    = i2c_dw_xfer,
        .functionality  = i2c_dw_func,
};

static int __devinit dw_i2c_probe(struct platform_device *pdev)
{
        struct dw_i2c_dev *dev;
        struct i2c_adapter *adap;
        struct resource *mem, *ioarea;
        int irq, r;

        /* NOTE: driver uses the static register mapping */
        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!mem) {
                dev_err(&pdev->dev, "no mem resource?\n");
                return -EINVAL;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(&pdev->dev, "no irq resource?\n");
                return irq; /* -ENXIO */
        }

        ioarea = request_mem_region(mem->start, resource_size(mem),
                        pdev->name);
        if (!ioarea) {
                dev_err(&pdev->dev, "I2C region already claimed\n");
                return -EBUSY;
        }

        dev = kzalloc(sizeof(struct dw_i2c_dev), GFP_KERNEL);
        if (!dev) {
                r = -ENOMEM;
                goto err_release_region;
        }

        init_completion(&dev->cmd_complete);
        mutex_init(&dev->lock);
        dev->dev = get_device(&pdev->dev);
        dev->irq = irq;
        platform_set_drvdata(pdev, dev);

        dev->clk = clk_get(&pdev->dev, NULL);
        if (IS_ERR(dev->clk)) {
                r = -ENODEV;
                goto err_free_mem;
        }
        clk_enable(dev->clk);

        dev->base = ioremap(mem->start, resource_size(mem));
        if (dev->base == NULL) {
                dev_err(&pdev->dev, "failure mapping io resources\n");
                r = -EBUSY;
                goto err_unuse_clocks;
        }
        {
                u32 param1 = readl(dev->base + DW_IC_COMP_PARAM_1);

                dev->tx_fifo_depth = ((param1 >> 16) & 0xff) + 1;
                dev->rx_fifo_depth = ((param1 >> 8)  & 0xff) + 1;
        }
        i2c_dw_init(dev);

        writel(0, dev->base + DW_IC_INTR_MASK); /* disable IRQ */
        r = request_irq(dev->irq, i2c_dw_isr, IRQF_DISABLED, pdev->name, dev);
        if (r) {
                dev_err(&pdev->dev, "failure requesting irq %i\n", dev->irq);
                goto err_iounmap;
        }

        adap = &dev->adapter;
        i2c_set_adapdata(adap, dev);
        adap->owner = THIS_MODULE;
        adap->class = I2C_CLASS_HWMON;
        strlcpy(adap->name, "Synopsys DesignWare I2C adapter",
                        sizeof(adap->name));
        adap->algo = &i2c_dw_algo;
        adap->dev.parent = &pdev->dev;

        adap->nr = pdev->id;
        r = i2c_add_numbered_adapter(adap);
        if (r) {
                dev_err(&pdev->dev, "failure adding adapter\n");
                goto err_free_irq;
        }

        return 0;

err_free_irq:
        free_irq(dev->irq, dev);
err_iounmap:
        iounmap(dev->base);
err_unuse_clocks:
        clk_disable(dev->clk);
        clk_put(dev->clk);
        dev->clk = NULL;
err_free_mem:
        platform_set_drvdata(pdev, NULL);
        put_device(&pdev->dev);
        kfree(dev);
err_release_region:
        release_mem_region(mem->start, resource_size(mem));

        return r;
}

static int __devexit dw_i2c_remove(struct platform_device *pdev)
{
        struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
        struct resource *mem;

        platform_set_drvdata(pdev, NULL);
        i2c_del_adapter(&dev->adapter);
        put_device(&pdev->dev);

        clk_disable(dev->clk);
        clk_put(dev->clk);
        dev->clk = NULL;

        writel(0, dev->base + DW_IC_ENABLE);
        free_irq(dev->irq, dev);
        kfree(dev);

        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        release_mem_region(mem->start, resource_size(mem));
        return 0;
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:i2c_designware");

static struct platform_driver dw_i2c_driver = {
        .remove         = __devexit_p(dw_i2c_remove),
        .driver         = {
                .name   = "i2c_designware",
                .owner  = THIS_MODULE,
        },
};

static int __init dw_i2c_init_driver(void)
{
        return platform_driver_probe(&dw_i2c_driver, dw_i2c_probe);
}
module_init(dw_i2c_init_driver);

static void __exit dw_i2c_exit_driver(void)
{
        platform_driver_unregister(&dw_i2c_driver);
}
module_exit(dw_i2c_exit_driver);

MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
MODULE_DESCRIPTION("Synopsys DesignWare I2C bus adapter");
MODULE_LICENSE("GPL");