// SPDX-License-Identifier: GPL-2.0-only
/*
 * i2c-xiic.c
 * Copyright (c) 2002-2007 Xilinx Inc.
 * Copyright (c) 2009-2010 Intel Corporation
 *
 * This code was implemented by Mocean Laboratories AB when porting linux
 * to the automotive development board Russellville. The copyright holder
 * as seen in the header is Intel corporation.
 * Mocean Laboratories forked off the GNU/Linux platform work into a
 * separate company called Pelagicore AB, which committed the code to the
 * kernel.
 */

/* Supports:
 * Xilinx IIC
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/platform_data/i2c-xiic.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/clk.h>
#include <linux/pm_runtime.h>

#define DRIVER_NAME "xiic-i2c"

enum xilinx_i2c_state {
        STATE_DONE,
        STATE_ERROR,
        STATE_START
};

enum xiic_endian {
        LITTLE,
        BIG
};

/**
 * struct xiic_i2c - Internal representation of the XIIC I2C bus
 * @dev: Pointer to device structure
 * @base: Memory base of the HW registers
 * @wait: Wait queue for callers
 * @adap: Kernel adapter representation
 * @tx_msg: Messages from above to be sent
 * @lock: Mutual exclusion
 * @tx_pos: Current pos in TX message
 * @nmsgs: Number of messages in tx_msg
 * @rx_msg: Current RX message
 * @rx_pos: Position within current RX message
 * @endianness: big/little-endian byte order
 * @clk: Pointer to AXI4-lite input clock
 * @state: See STATE_
 * @singlemaster: Indicates bus is single master
 */
struct xiic_i2c {
        struct device *dev;
        void __iomem *base;
        wait_queue_head_t wait;
        struct i2c_adapter adap;
        struct i2c_msg *tx_msg;
        struct mutex lock;
        unsigned int tx_pos;
        unsigned int nmsgs;
        struct i2c_msg *rx_msg;
        int rx_pos;
        enum xiic_endian endianness;
        struct clk *clk;
        enum xilinx_i2c_state state;
        bool singlemaster;
};


#define XIIC_MSB_OFFSET 0
#define XIIC_REG_OFFSET (0x100+XIIC_MSB_OFFSET)

/*
 * Register offsets in bytes from RegisterBase. Three is added to the
 * base offset to access LSB (IBM style) of the word
 */
#define XIIC_CR_REG_OFFSET   (0x00+XIIC_REG_OFFSET)     /* Control Register   */
#define XIIC_SR_REG_OFFSET   (0x04+XIIC_REG_OFFSET)     /* Status Register    */
#define XIIC_DTR_REG_OFFSET  (0x08+XIIC_REG_OFFSET)     /* Data Tx Register   */
#define XIIC_DRR_REG_OFFSET  (0x0C+XIIC_REG_OFFSET)     /* Data Rx Register   */
#define XIIC_ADR_REG_OFFSET  (0x10+XIIC_REG_OFFSET)     /* Address Register   */
#define XIIC_TFO_REG_OFFSET  (0x14+XIIC_REG_OFFSET)     /* Tx FIFO Occupancy  */
#define XIIC_RFO_REG_OFFSET  (0x18+XIIC_REG_OFFSET)     /* Rx FIFO Occupancy  */
#define XIIC_TBA_REG_OFFSET  (0x1C+XIIC_REG_OFFSET)     /* 10 Bit Address reg */
#define XIIC_RFD_REG_OFFSET  (0x20+XIIC_REG_OFFSET)     /* Rx FIFO Depth reg  */
#define XIIC_GPO_REG_OFFSET  (0x24+XIIC_REG_OFFSET)     /* Output Register    */

/* Control Register masks */
#define XIIC_CR_ENABLE_DEVICE_MASK        0x01  /* Device enable = 1      */
#define XIIC_CR_TX_FIFO_RESET_MASK        0x02  /* Transmit FIFO reset=1  */
#define XIIC_CR_MSMS_MASK                 0x04  /* Master starts Txing=1  */
#define XIIC_CR_DIR_IS_TX_MASK            0x08  /* Dir of tx. Txing=1     */
#define XIIC_CR_NO_ACK_MASK               0x10  /* Tx Ack. NO ack = 1     */
#define XIIC_CR_REPEATED_START_MASK       0x20  /* Repeated start = 1     */
#define XIIC_CR_GENERAL_CALL_MASK         0x40  /* Gen Call enabled = 1   */

/* Status Register masks */
#define XIIC_SR_GEN_CALL_MASK             0x01  /* 1=a mstr issued a GC   */
#define XIIC_SR_ADDR_AS_SLAVE_MASK        0x02  /* 1=when addr as slave   */
#define XIIC_SR_BUS_BUSY_MASK             0x04  /* 1 = bus is busy        */
#define XIIC_SR_MSTR_RDING_SLAVE_MASK     0x08  /* 1=Dir: mstr <-- slave  */
#define XIIC_SR_TX_FIFO_FULL_MASK         0x10  /* 1 = Tx FIFO full       */
#define XIIC_SR_RX_FIFO_FULL_MASK         0x20  /* 1 = Rx FIFO full       */
#define XIIC_SR_RX_FIFO_EMPTY_MASK        0x40  /* 1 = Rx FIFO empty      */
#define XIIC_SR_TX_FIFO_EMPTY_MASK        0x80  /* 1 = Tx FIFO empty      */

/* Interrupt Status Register masks    Interrupt occurs when...       */
#define XIIC_INTR_ARB_LOST_MASK           0x01  /* 1 = arbitration lost   */
#define XIIC_INTR_TX_ERROR_MASK           0x02  /* 1=Tx error/msg complete */
#define XIIC_INTR_TX_EMPTY_MASK           0x04  /* 1 = Tx FIFO/reg empty  */
#define XIIC_INTR_RX_FULL_MASK            0x08  /* 1=Rx FIFO/reg=OCY level */
#define XIIC_INTR_BNB_MASK                0x10  /* 1 = Bus not busy       */
#define XIIC_INTR_AAS_MASK                0x20  /* 1 = when addr as slave */
#define XIIC_INTR_NAAS_MASK               0x40  /* 1 = not addr as slave  */
#define XIIC_INTR_TX_HALF_MASK            0x80  /* 1 = TX FIFO half empty */

/* The following constants specify the depth of the FIFOs */
#define IIC_RX_FIFO_DEPTH         16    /* Rx fifo capacity               */
#define IIC_TX_FIFO_DEPTH         16    /* Tx fifo capacity               */

/* The following constants specify groups of interrupts that are typically
 * enabled or disables at the same time
 */
#define XIIC_TX_INTERRUPTS                           \
(XIIC_INTR_TX_ERROR_MASK | XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)

#define XIIC_TX_RX_INTERRUPTS (XIIC_INTR_RX_FULL_MASK | XIIC_TX_INTERRUPTS)

/*
 * Tx Fifo upper bit masks.
 */
#define XIIC_TX_DYN_START_MASK            0x0100 /* 1 = Set dynamic start */
#define XIIC_TX_DYN_STOP_MASK             0x0200 /* 1 = Set dynamic stop */

/*
 * The following constants define the register offsets for the Interrupt
 * registers. There are some holes in the memory map for reserved addresses
 * to allow other registers to be added and still match the memory map of the
 * interrupt controller registers
 */
#define XIIC_DGIER_OFFSET    0x1C /* Device Global Interrupt Enable Register */
#define XIIC_IISR_OFFSET     0x20 /* Interrupt Status Register */
#define XIIC_IIER_OFFSET     0x28 /* Interrupt Enable Register */
#define XIIC_RESETR_OFFSET   0x40 /* Reset Register */

#define XIIC_RESET_MASK             0xAUL

#define XIIC_PM_TIMEOUT         1000    /* ms */
/* timeout waiting for the controller to respond */
#define XIIC_I2C_TIMEOUT        (msecs_to_jiffies(1000))
/*
 * The following constant is used for the device global interrupt enable
 * register, to enable all interrupts for the device, this is the only bit
 * in the register
 */
#define XIIC_GINTR_ENABLE_MASK      0x80000000UL

#define xiic_tx_space(i2c) ((i2c)->tx_msg->len - (i2c)->tx_pos)
#define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)

static int xiic_start_xfer(struct xiic_i2c *i2c);
static void __xiic_start_xfer(struct xiic_i2c *i2c);

/*
 * For the register read and write functions, a little-endian and big-endian
 * version are necessary. Endianness is detected during the probe function.
 * Only the least significant byte [doublet] of the register are ever
 * accessed. This requires an offset of 3 [2] from the base address for
 * big-endian systems.
 */

static inline void xiic_setreg8(struct xiic_i2c *i2c, int reg, u8 value)
{
        if (i2c->endianness == LITTLE)
                iowrite8(value, i2c->base + reg);
        else
                iowrite8(value, i2c->base + reg + 3);
}

static inline u8 xiic_getreg8(struct xiic_i2c *i2c, int reg)
{
        u8 ret;

        if (i2c->endianness == LITTLE)
                ret = ioread8(i2c->base + reg);
        else
                ret = ioread8(i2c->base + reg + 3);
        return ret;
}

static inline void xiic_setreg16(struct xiic_i2c *i2c, int reg, u16 value)
{
        if (i2c->endianness == LITTLE)
                iowrite16(value, i2c->base + reg);
        else
                iowrite16be(value, i2c->base + reg + 2);
}

static inline void xiic_setreg32(struct xiic_i2c *i2c, int reg, int value)
{
        if (i2c->endianness == LITTLE)
                iowrite32(value, i2c->base + reg);
        else
                iowrite32be(value, i2c->base + reg);
}

static inline int xiic_getreg32(struct xiic_i2c *i2c, int reg)
{
        u32 ret;

        if (i2c->endianness == LITTLE)
                ret = ioread32(i2c->base + reg);
        else
                ret = ioread32be(i2c->base + reg);
        return ret;
}

static inline void xiic_irq_dis(struct xiic_i2c *i2c, u32 mask)
{
        u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
        xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier & ~mask);
}

static inline void xiic_irq_en(struct xiic_i2c *i2c, u32 mask)
{
        u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
        xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier | mask);
}

static inline void xiic_irq_clr(struct xiic_i2c *i2c, u32 mask)
{
        u32 isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
        xiic_setreg32(i2c, XIIC_IISR_OFFSET, isr & mask);
}

static inline void xiic_irq_clr_en(struct xiic_i2c *i2c, u32 mask)
{
        xiic_irq_clr(i2c, mask);
        xiic_irq_en(i2c, mask);
}

static int xiic_clear_rx_fifo(struct xiic_i2c *i2c)
{
        u8 sr;
        unsigned long timeout;

        timeout = jiffies + XIIC_I2C_TIMEOUT;
        for (sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
                !(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
                sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET)) {
                xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
                if (time_after(jiffies, timeout)) {
                        dev_err(i2c->dev, "Failed to clear rx fifo\n");
                        return -ETIMEDOUT;
                }
        }

        return 0;
}

static int xiic_reinit(struct xiic_i2c *i2c)
{
        int ret;

        xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);

        /* Set receive Fifo depth to maximum (zero based). */
        xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, IIC_RX_FIFO_DEPTH - 1);

        /* Reset Tx Fifo. */
        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);

        /* Enable IIC Device, remove Tx Fifo reset & disable general call. */
        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_ENABLE_DEVICE_MASK);

        /* make sure RX fifo is empty */
        ret = xiic_clear_rx_fifo(i2c);
        if (ret)
                return ret;

        /* Enable interrupts */
        xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);

        xiic_irq_clr_en(i2c, XIIC_INTR_ARB_LOST_MASK);

        return 0;
}

static void xiic_deinit(struct xiic_i2c *i2c)
{
        u8 cr;

        xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);

        /* Disable IIC Device. */
        cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr & ~XIIC_CR_ENABLE_DEVICE_MASK);
}

static void xiic_read_rx(struct xiic_i2c *i2c)
{
        u8 bytes_in_fifo;
        int i;

        bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;

        dev_dbg(i2c->adap.dev.parent,
                "%s entry, bytes in fifo: %d, msg: %d, SR: 0x%x, CR: 0x%x\n",
                __func__, bytes_in_fifo, xiic_rx_space(i2c),
                xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
                xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));

        if (bytes_in_fifo > xiic_rx_space(i2c))
                bytes_in_fifo = xiic_rx_space(i2c);

        for (i = 0; i < bytes_in_fifo; i++)
                i2c->rx_msg->buf[i2c->rx_pos++] =
                        xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);

        xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET,
                (xiic_rx_space(i2c) > IIC_RX_FIFO_DEPTH) ?
                IIC_RX_FIFO_DEPTH - 1 :  xiic_rx_space(i2c) - 1);
}

static int xiic_tx_fifo_space(struct xiic_i2c *i2c)
{
        /* return the actual space left in the FIFO */
        return IIC_TX_FIFO_DEPTH - xiic_getreg8(i2c, XIIC_TFO_REG_OFFSET) - 1;
}

static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
{
        u8 fifo_space = xiic_tx_fifo_space(i2c);
        int len = xiic_tx_space(i2c);

        len = (len > fifo_space) ? fifo_space : len;

        dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
                __func__, len, fifo_space);

        while (len--) {
                u16 data = i2c->tx_msg->buf[i2c->tx_pos++];
                if ((xiic_tx_space(i2c) == 0) && (i2c->nmsgs == 1)) {
                        /* last message in transfer -> STOP */
                        data |= XIIC_TX_DYN_STOP_MASK;
                        dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
                }
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
        }
}

static void xiic_wakeup(struct xiic_i2c *i2c, int code)
{
        i2c->tx_msg = NULL;
        i2c->rx_msg = NULL;
        i2c->nmsgs = 0;
        i2c->state = code;
        wake_up(&i2c->wait);
}

static irqreturn_t xiic_process(int irq, void *dev_id)
{
        struct xiic_i2c *i2c = dev_id;
        u32 pend, isr, ier;
        u32 clr = 0;

        /* Get the interrupt Status from the IPIF. There is no clearing of
         * interrupts in the IPIF. Interrupts must be cleared at the source.
         * To find which interrupts are pending; AND interrupts pending with
         * interrupts masked.
         */
        mutex_lock(&i2c->lock);
        isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
        ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
        pend = isr & ier;

        dev_dbg(i2c->adap.dev.parent, "%s: IER: 0x%x, ISR: 0x%x, pend: 0x%x\n",
                __func__, ier, isr, pend);
        dev_dbg(i2c->adap.dev.parent, "%s: SR: 0x%x, msg: %p, nmsgs: %d\n",
                __func__, xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
                i2c->tx_msg, i2c->nmsgs);


        /* Service requesting interrupt */
        if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
                ((pend & XIIC_INTR_TX_ERROR_MASK) &&
                !(pend & XIIC_INTR_RX_FULL_MASK))) {
                /* bus arbritration lost, or...
                 * Transmit error _OR_ RX completed
                 * if this happens when RX_FULL is not set
                 * this is probably a TX error
                 */

                dev_dbg(i2c->adap.dev.parent, "%s error\n", __func__);

                /* dynamic mode seem to suffer from problems if we just flushes
                 * fifos and the next message is a TX with len 0 (only addr)
                 * reset the IP instead of just flush fifos
                 */
                xiic_reinit(i2c);

                if (i2c->rx_msg)
                        xiic_wakeup(i2c, STATE_ERROR);
                if (i2c->tx_msg)
                        xiic_wakeup(i2c, STATE_ERROR);
        }
        if (pend & XIIC_INTR_RX_FULL_MASK) {
                /* Receive register/FIFO is full */

                clr |= XIIC_INTR_RX_FULL_MASK;
                if (!i2c->rx_msg) {
                        dev_dbg(i2c->adap.dev.parent,
                                "%s unexpected RX IRQ\n", __func__);
                        xiic_clear_rx_fifo(i2c);
                        goto out;
                }

                xiic_read_rx(i2c);
                if (xiic_rx_space(i2c) == 0) {
                        /* this is the last part of the message */
                        i2c->rx_msg = NULL;

                        /* also clear TX error if there (RX complete) */
                        clr |= (isr & XIIC_INTR_TX_ERROR_MASK);

                        dev_dbg(i2c->adap.dev.parent,
                                "%s end of message, nmsgs: %d\n",
                                __func__, i2c->nmsgs);

                        /* send next message if this wasn't the last,
                         * otherwise the transfer will be finialise when
                         * receiving the bus not busy interrupt
                         */
                        if (i2c->nmsgs > 1) {
                                i2c->nmsgs--;
                                i2c->tx_msg++;
                                dev_dbg(i2c->adap.dev.parent,
                                        "%s will start next...\n", __func__);

                                __xiic_start_xfer(i2c);
                        }
                }
        }
        if (pend & XIIC_INTR_BNB_MASK) {
                /* IIC bus has transitioned to not busy */
                clr |= XIIC_INTR_BNB_MASK;

                /* The bus is not busy, disable BusNotBusy interrupt */
                xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);

                if (!i2c->tx_msg)
                        goto out;

                if ((i2c->nmsgs == 1) && !i2c->rx_msg &&
                        xiic_tx_space(i2c) == 0)
                        xiic_wakeup(i2c, STATE_DONE);
                else
                        xiic_wakeup(i2c, STATE_ERROR);
        }
        if (pend & (XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)) {
                /* Transmit register/FIFO is empty or ½ empty */

                clr |= (pend &
                        (XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK));

                if (!i2c->tx_msg) {
                        dev_dbg(i2c->adap.dev.parent,
                                "%s unexpected TX IRQ\n", __func__);
                        goto out;
                }

                xiic_fill_tx_fifo(i2c);

                /* current message sent and there is space in the fifo */
                if (!xiic_tx_space(i2c) && xiic_tx_fifo_space(i2c) >= 2) {
                        dev_dbg(i2c->adap.dev.parent,
                                "%s end of message sent, nmsgs: %d\n",
                                __func__, i2c->nmsgs);
                        if (i2c->nmsgs > 1) {
                                i2c->nmsgs--;
                                i2c->tx_msg++;
                                __xiic_start_xfer(i2c);
                        } else {
                                xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);

                                dev_dbg(i2c->adap.dev.parent,
                                        "%s Got TX IRQ but no more to do...\n",
                                        __func__);
                        }
                } else if (!xiic_tx_space(i2c) && (i2c->nmsgs == 1))
                        /* current frame is sent and is last,
                         * make sure to disable tx half
                         */
                        xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
        }
out:
        dev_dbg(i2c->adap.dev.parent, "%s clr: 0x%x\n", __func__, clr);

        xiic_setreg32(i2c, XIIC_IISR_OFFSET, clr);
        mutex_unlock(&i2c->lock);
        return IRQ_HANDLED;
}

static int xiic_bus_busy(struct xiic_i2c *i2c)
{
        u8 sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);

        return (sr & XIIC_SR_BUS_BUSY_MASK) ? -EBUSY : 0;
}

static int xiic_busy(struct xiic_i2c *i2c)
{
        int tries = 3;
        int err;

        if (i2c->tx_msg)
                return -EBUSY;

        /* In single master mode bus can only be busy, when in use by this
         * driver. If the register indicates bus being busy for some reason we
         * should ignore it, since bus will never be released and i2c will be
         * stuck forever.
         */
        if (i2c->singlemaster) {
                return 0;
        }

        /* for instance if previous transfer was terminated due to TX error
         * it might be that the bus is on it's way to become available
         * give it at most 3 ms to wake
         */
        err = xiic_bus_busy(i2c);
        while (err && tries--) {
                msleep(1);
                err = xiic_bus_busy(i2c);
        }

        return err;
}

static void xiic_start_recv(struct xiic_i2c *i2c)
{
        u8 rx_watermark;
        struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;
        unsigned long flags;

        /* Clear and enable Rx full interrupt. */
        xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK | XIIC_INTR_TX_ERROR_MASK);

        /* we want to get all but last byte, because the TX_ERROR IRQ is used
         * to inidicate error ACK on the address, and negative ack on the last
         * received byte, so to not mix them receive all but last.
         * In the case where there is only one byte to receive
         * we can check if ERROR and RX full is set at the same time
         */
        rx_watermark = msg->len;
        if (rx_watermark > IIC_RX_FIFO_DEPTH)
                rx_watermark = IIC_RX_FIFO_DEPTH;
        xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, rx_watermark - 1);

        local_irq_save(flags);
        if (!(msg->flags & I2C_M_NOSTART))
                /* write the address */
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
                        i2c_8bit_addr_from_msg(msg) | XIIC_TX_DYN_START_MASK);

        xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);

        xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
                msg->len | ((i2c->nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0));
        local_irq_restore(flags);

        if (i2c->nmsgs == 1)
                /* very last, enable bus not busy as well */
                xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);

        /* the message is tx:ed */
        i2c->tx_pos = msg->len;
}

static void xiic_start_send(struct xiic_i2c *i2c)
{
        struct i2c_msg *msg = i2c->tx_msg;

        xiic_irq_clr(i2c, XIIC_INTR_TX_ERROR_MASK);

        dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
                __func__, msg, msg->len);
        dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
                __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
                xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));

        if (!(msg->flags & I2C_M_NOSTART)) {
                /* write the address */
                u16 data = i2c_8bit_addr_from_msg(msg) |
                        XIIC_TX_DYN_START_MASK;
                if ((i2c->nmsgs == 1) && msg->len == 0)
                        /* no data and last message -> add STOP */
                        data |= XIIC_TX_DYN_STOP_MASK;

                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
        }

        xiic_fill_tx_fifo(i2c);

        /* Clear any pending Tx empty, Tx Error and then enable them. */
        xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
                XIIC_INTR_BNB_MASK);
}

static irqreturn_t xiic_isr(int irq, void *dev_id)
{
        struct xiic_i2c *i2c = dev_id;
        u32 pend, isr, ier;
        irqreturn_t ret = IRQ_NONE;
        /* Do not processes a devices interrupts if the device has no
         * interrupts pending
         */

        dev_dbg(i2c->adap.dev.parent, "%s entry\n", __func__);

        isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
        ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
        pend = isr & ier;
        if (pend)
                ret = IRQ_WAKE_THREAD;

        return ret;
}

static void __xiic_start_xfer(struct xiic_i2c *i2c)
{
        int first = 1;
        int fifo_space = xiic_tx_fifo_space(i2c);
        dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
                __func__, i2c->tx_msg, fifo_space);

        if (!i2c->tx_msg)
                return;

        i2c->rx_pos = 0;
        i2c->tx_pos = 0;
        i2c->state = STATE_START;
        while ((fifo_space >= 2) && (first || (i2c->nmsgs > 1))) {
                if (!first) {
                        i2c->nmsgs--;
                        i2c->tx_msg++;
                        i2c->tx_pos = 0;
                } else
                        first = 0;

                if (i2c->tx_msg->flags & I2C_M_RD) {
                        /* we dont date putting several reads in the FIFO */
                        xiic_start_recv(i2c);
                        return;
                } else {
                        xiic_start_send(i2c);
                        if (xiic_tx_space(i2c) != 0) {
                                /* the message could not be completely sent */
                                break;
                        }
                }

                fifo_space = xiic_tx_fifo_space(i2c);
        }

        /* there are more messages or the current one could not be completely
         * put into the FIFO, also enable the half empty interrupt
         */
        if (i2c->nmsgs > 1 || xiic_tx_space(i2c))
                xiic_irq_clr_en(i2c, XIIC_INTR_TX_HALF_MASK);

}

static int xiic_start_xfer(struct xiic_i2c *i2c)
{
        int ret;
        mutex_lock(&i2c->lock);

        ret = xiic_reinit(i2c);
        if (!ret)
                __xiic_start_xfer(i2c);

        mutex_unlock(&i2c->lock);

        return ret;
}

static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
        struct xiic_i2c *i2c = i2c_get_adapdata(adap);
        int err;

        dev_dbg(adap->dev.parent, "%s entry SR: 0x%x\n", __func__,
                xiic_getreg8(i2c, XIIC_SR_REG_OFFSET));

        err = pm_runtime_resume_and_get(i2c->dev);
        if (err < 0)
                return err;

        err = xiic_busy(i2c);
        if (err)
                goto out;

        i2c->tx_msg = msgs;
        i2c->nmsgs = num;

        err = xiic_start_xfer(i2c);
        if (err < 0) {
                dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
                goto out;
        }

        if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
                (i2c->state == STATE_DONE), HZ)) {
                err = (i2c->state == STATE_DONE) ? num : -EIO;
                goto out;
        } else {
                i2c->tx_msg = NULL;
                i2c->rx_msg = NULL;
                i2c->nmsgs = 0;
                err = -ETIMEDOUT;
                goto out;
        }
out:
        pm_runtime_mark_last_busy(i2c->dev);
        pm_runtime_put_autosuspend(i2c->dev);
        return err;
}

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

static const struct i2c_algorithm xiic_algorithm = {
        .master_xfer = xiic_xfer,
        .functionality = xiic_func,
};

static const struct i2c_adapter_quirks xiic_quirks = {
        .max_read_len = 255,
};

static const struct i2c_adapter xiic_adapter = {
        .owner = THIS_MODULE,
        .name = DRIVER_NAME,
        .class = I2C_CLASS_DEPRECATED,
        .algo = &xiic_algorithm,
        .quirks = &xiic_quirks,
};


static int xiic_i2c_probe(struct platform_device *pdev)
{
        struct xiic_i2c *i2c;
        struct xiic_i2c_platform_data *pdata;
        struct resource *res;
        int ret, irq;
        u8 i;
        u32 sr;

        i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
        if (!i2c)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        i2c->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(i2c->base))
                return PTR_ERR(i2c->base);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        pdata = dev_get_platdata(&pdev->dev);

        /* hook up driver to tree */
        platform_set_drvdata(pdev, i2c);
        i2c->adap = xiic_adapter;
        i2c_set_adapdata(&i2c->adap, i2c);
        i2c->adap.dev.parent = &pdev->dev;
        i2c->adap.dev.of_node = pdev->dev.of_node;

        mutex_init(&i2c->lock);
        init_waitqueue_head(&i2c->wait);

        i2c->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(i2c->clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(i2c->clk),
                                     "input clock not found.\n");

        ret = clk_prepare_enable(i2c->clk);
        if (ret) {
                dev_err(&pdev->dev, "Unable to enable clock.\n");
                return ret;
        }
        i2c->dev = &pdev->dev;
        pm_runtime_set_autosuspend_delay(i2c->dev, XIIC_PM_TIMEOUT);
        pm_runtime_use_autosuspend(i2c->dev);
        pm_runtime_set_active(i2c->dev);
        pm_runtime_enable(i2c->dev);
        ret = devm_request_threaded_irq(&pdev->dev, irq, xiic_isr,
                                        xiic_process, IRQF_ONESHOT,
                                        pdev->name, i2c);

        if (ret < 0) {
                dev_err(&pdev->dev, "Cannot claim IRQ\n");
                goto err_clk_dis;
        }

        i2c->singlemaster =
                of_property_read_bool(pdev->dev.of_node, "single-master");

        /*
         * Detect endianness
         * Try to reset the TX FIFO. Then check the EMPTY flag. If it is not
         * set, assume that the endianness was wrong and swap.
         */
        i2c->endianness = LITTLE;
        xiic_setreg32(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);
        /* Reset is cleared in xiic_reinit */
        sr = xiic_getreg32(i2c, XIIC_SR_REG_OFFSET);
        if (!(sr & XIIC_SR_TX_FIFO_EMPTY_MASK))
                i2c->endianness = BIG;

        ret = xiic_reinit(i2c);
        if (ret < 0) {
                dev_err(&pdev->dev, "Cannot xiic_reinit\n");
                goto err_clk_dis;
        }

        /* add i2c adapter to i2c tree */
        ret = i2c_add_adapter(&i2c->adap);
        if (ret) {
                xiic_deinit(i2c);
                goto err_clk_dis;
        }

        if (pdata) {
                /* add in known devices to the bus */
                for (i = 0; i < pdata->num_devices; i++)
                        i2c_new_client_device(&i2c->adap, pdata->devices + i);
        }

        return 0;

err_clk_dis:
        pm_runtime_set_suspended(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        clk_disable_unprepare(i2c->clk);
        return ret;
}

static int xiic_i2c_remove(struct platform_device *pdev)
{
        struct xiic_i2c *i2c = platform_get_drvdata(pdev);
        int ret;

        /* remove adapter & data */
        i2c_del_adapter(&i2c->adap);

        ret = pm_runtime_resume_and_get(i2c->dev);
        if (ret < 0)
                return ret;

        xiic_deinit(i2c);
        pm_runtime_put_sync(i2c->dev);
        clk_disable_unprepare(i2c->clk);
        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(&pdev->dev);
        pm_runtime_dont_use_autosuspend(&pdev->dev);

        return 0;
}

#if defined(CONFIG_OF)
static const struct of_device_id xiic_of_match[] = {
        { .compatible = "xlnx,xps-iic-2.00.a", },
        {},
};
MODULE_DEVICE_TABLE(of, xiic_of_match);
#endif

static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
{
        struct xiic_i2c *i2c = dev_get_drvdata(dev);

        clk_disable(i2c->clk);

        return 0;
}

static int __maybe_unused xiic_i2c_runtime_resume(struct device *dev)
{
        struct xiic_i2c *i2c = dev_get_drvdata(dev);
        int ret;

        ret = clk_enable(i2c->clk);
        if (ret) {
                dev_err(dev, "Cannot enable clock.\n");
                return ret;
        }

        return 0;
}

static const struct dev_pm_ops xiic_dev_pm_ops = {
        SET_RUNTIME_PM_OPS(xiic_i2c_runtime_suspend,
                           xiic_i2c_runtime_resume, NULL)
};
static struct platform_driver xiic_i2c_driver = {
        .probe   = xiic_i2c_probe,
        .remove  = xiic_i2c_remove,
        .driver  = {
                .name = DRIVER_NAME,
                .of_match_table = of_match_ptr(xiic_of_match),
                .pm = &xiic_dev_pm_ops,
        },
};

module_platform_driver(xiic_i2c_driver);

MODULE_AUTHOR("info@mocean-labs.com");
MODULE_DESCRIPTION("Xilinx I2C bus driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:"DRIVER_NAME);