// 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/completion.h>
#include <linux/platform_data/i2c-xiic.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/clk.h>
#include <linux/pm_runtime.h>
#include <linux/iopoll.h>
#include <linux/spinlock.h>

#define DRIVER_NAME "xiic-i2c"
#define DYNAMIC_MODE_READ_BROKEN_BIT    BIT(0)
#define SMBUS_BLOCK_READ_MIN_LEN        3

enum xilinx_i2c_state {
        STATE_DONE,
        STATE_ERROR,
        STATE_START
};

enum xiic_endian {
        LITTLE,
        BIG
};

enum i2c_scl_freq {
        REG_VALUES_100KHZ = 0,
        REG_VALUES_400KHZ = 1,
        REG_VALUES_1MHZ = 2
};

/**
 * struct xiic_i2c - Internal representation of the XIIC I2C bus
 * @dev: Pointer to device structure
 * @base: Memory base of the HW registers
 * @completion: Completion 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
 * @dynamic: Mode of controller
 * @prev_msg_tx: Previous message is Tx
 * @quirks: To hold platform specific bug info
 * @smbus_block_read: Flag to handle block read
 * @input_clk: Input clock to I2C controller
 * @i2c_clk: I2C SCL frequency
 * @atomic: Mode of transfer
 * @atomic_lock: Lock for atomic transfer mode
 * @atomic_xfer_state: See STATE_
 */
struct xiic_i2c {
        struct device *dev;
        void __iomem *base;
        struct completion completion;
        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;
        bool dynamic;
        bool prev_msg_tx;
        u32 quirks;
        bool smbus_block_read;
        unsigned long input_clk;
        unsigned int i2c_clk;
        bool atomic;
        spinlock_t atomic_lock;         /* Lock for atomic transfer mode */
        enum xilinx_i2c_state atomic_xfer_state;
};

struct xiic_version_data {
        u32 quirks;
};

/**
 * struct timing_regs - AXI I2C timing registers that depend on I2C spec
 * @tsusta: setup time for a repeated START condition
 * @tsusto: setup time for a STOP condition
 * @thdsta: hold time for a repeated START condition
 * @tsudat: setup time for data
 * @tbuf: bus free time between STOP and START
 */
struct timing_regs {
        unsigned int tsusta;
        unsigned int tsusto;
        unsigned int thdsta;
        unsigned int tsudat;
        unsigned int tbuf;
};

/* Reg values in ns derived from I2C spec and AXI I2C PG for different frequencies */
static const struct timing_regs timing_reg_values[] = {
        { 5700, 5000, 4300, 550, 5000 }, /* Reg values for 100KHz */
        { 900, 900, 900, 400, 1600 },    /* Reg values for 400KHz */
        { 380, 380, 380, 170, 620 },     /* Reg values for 1MHz   */
};

#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    */

/*
 * Timing register offsets from RegisterBase. These are used only for
 * setting i2c clock frequency for the line.
 */
#define XIIC_TSUSTA_REG_OFFSET (0x28 + XIIC_REG_OFFSET) /* TSUSTA Register */
#define XIIC_TSUSTO_REG_OFFSET (0x2C + XIIC_REG_OFFSET) /* TSUSTO Register */
#define XIIC_THDSTA_REG_OFFSET (0x30 + XIIC_REG_OFFSET) /* THDSTA Register */
#define XIIC_TSUDAT_REG_OFFSET (0x34 + XIIC_REG_OFFSET) /* TSUDAT Register */
#define XIIC_TBUF_REG_OFFSET   (0x38 + XIIC_REG_OFFSET) /* TBUF Register */
#define XIIC_THIGH_REG_OFFSET  (0x3C + XIIC_REG_OFFSET) /* THIGH Register */
#define XIIC_TLOW_REG_OFFSET   (0x40 + XIIC_REG_OFFSET) /* TLOW Register */
#define XIIC_THDDAT_REG_OFFSET (0x44 + XIIC_REG_OFFSET) /* THDDAT 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 */

/* Dynamic mode constants */
#define MAX_READ_LENGTH_DYNAMIC                255 /* Max length for dynamic read */

/*
 * 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))
/* timeout waiting for the controller finish transfers */
#define XIIC_XFER_TIMEOUT       (msecs_to_jiffies(10000))
/* timeout waiting for the controller finish transfers in micro seconds */
#define XIIC_XFER_TIMEOUT_US    10000000

/*
 * 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, struct i2c_msg *msgs, int num);
static void __xiic_start_xfer(struct xiic_i2c *i2c);

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

        clk_disable(i2c->clk);

        return 0;
}

static int 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;
}

/*
 * 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_wait_tx_empty(struct xiic_i2c *i2c)
{
        u8 isr;
        unsigned long timeout;

        timeout = jiffies + XIIC_I2C_TIMEOUT;
        for (isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
                !(isr & XIIC_INTR_TX_EMPTY_MASK);
                        isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET)) {
                if (time_after(jiffies, timeout)) {
                        dev_err(i2c->dev, "Timeout waiting at Tx empty\n");
                        return -ETIMEDOUT;
                }
        }

        return 0;
}

/**
 * xiic_setclk - Sets the configured clock rate
 * @i2c: Pointer to the xiic device structure
 *
 * The timing register values are calculated according to the input clock
 * frequency and configured scl frequency. For details, please refer the
 * AXI I2C PG and NXP I2C Spec.
 * Supported frequencies are 100KHz, 400KHz and 1MHz.
 *
 * Return: 0 on success (Supported frequency selected or not configurable in SW)
 *        -EINVAL on failure (scl frequency not supported or THIGH is 0)
 */
static int xiic_setclk(struct xiic_i2c *i2c)
{
        unsigned int clk_in_mhz;
        unsigned int index = 0;
        u32 reg_val;

        if (!i2c->atomic)
                dev_dbg(i2c->adap.dev.parent,
                        "%s entry, i2c->input_clk: %ld, i2c->i2c_clk: %d\n",
                        __func__, i2c->input_clk, i2c->i2c_clk);

        /* If not specified in DT, do not configure in SW. Rely only on Vivado design */
        if (!i2c->i2c_clk || !i2c->input_clk)
                return 0;

        clk_in_mhz = DIV_ROUND_UP(i2c->input_clk, 1000000);

        switch (i2c->i2c_clk) {
        case I2C_MAX_FAST_MODE_PLUS_FREQ:
                index = REG_VALUES_1MHZ;
                break;
        case I2C_MAX_FAST_MODE_FREQ:
                index = REG_VALUES_400KHZ;
                break;
        case I2C_MAX_STANDARD_MODE_FREQ:
                index = REG_VALUES_100KHZ;
                break;
        default:
                dev_warn(i2c->adap.dev.parent, "Unsupported scl frequency\n");
                return -EINVAL;
        }

        /*
         * Value to be stored in a register is the number of clock cycles required
         * for the time duration. So the time is divided by the input clock time
         * period to get the number of clock cycles required. Refer Xilinx AXI I2C
         * PG document and I2C specification for further details.
         */

        /* THIGH - Depends on SCL clock frequency(i2c_clk) as below */
        reg_val = (DIV_ROUND_UP(i2c->input_clk, 2 * i2c->i2c_clk)) - 7;
        if (reg_val == 0)
                return -EINVAL;

        xiic_setreg32(i2c, XIIC_THIGH_REG_OFFSET, reg_val - 1);

        /* TLOW - Value same as THIGH */
        xiic_setreg32(i2c, XIIC_TLOW_REG_OFFSET, reg_val - 1);

        /* TSUSTA */
        reg_val = (timing_reg_values[index].tsusta * clk_in_mhz) / 1000;
        xiic_setreg32(i2c, XIIC_TSUSTA_REG_OFFSET, reg_val - 1);

        /* TSUSTO */
        reg_val = (timing_reg_values[index].tsusto * clk_in_mhz) / 1000;
        xiic_setreg32(i2c, XIIC_TSUSTO_REG_OFFSET, reg_val - 1);

        /* THDSTA */
        reg_val = (timing_reg_values[index].thdsta * clk_in_mhz) / 1000;
        xiic_setreg32(i2c, XIIC_THDSTA_REG_OFFSET, reg_val - 1);

        /* TSUDAT */
        reg_val = (timing_reg_values[index].tsudat * clk_in_mhz) / 1000;
        xiic_setreg32(i2c, XIIC_TSUDAT_REG_OFFSET, reg_val - 1);

        /* TBUF */
        reg_val = (timing_reg_values[index].tbuf * clk_in_mhz) / 1000;
        xiic_setreg32(i2c, XIIC_TBUF_REG_OFFSET, reg_val - 1);

        /* THDDAT */
        xiic_setreg32(i2c, XIIC_THDDAT_REG_OFFSET, 1);

        return 0;
}

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

        xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);

        ret = xiic_setclk(i2c);
        if (ret)
                return ret;

        /* 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 */
        if (!i2c->atomic)
                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_smbus_block_read_setup(struct xiic_i2c *i2c)
{
        u8 rxmsg_len, rfd_set = 0;

        /*
         * Clear the I2C_M_RECV_LEN flag to avoid setting
         * message length again
         */
        i2c->rx_msg->flags &= ~I2C_M_RECV_LEN;

        /* Set smbus_block_read flag to identify in isr */
        i2c->smbus_block_read = true;

        /* Read byte from rx fifo and set message length */
        rxmsg_len = xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);

        i2c->rx_msg->buf[i2c->rx_pos++] = rxmsg_len;

        /* Check if received length is valid */
        if (rxmsg_len <= I2C_SMBUS_BLOCK_MAX) {
                /* Set Receive fifo depth */
                if (rxmsg_len > IIC_RX_FIFO_DEPTH) {
                        /*
                         * When Rx msg len greater than or equal to Rx fifo capacity
                         * Receive fifo depth should set to Rx fifo capacity minus 1
                         */
                        rfd_set = IIC_RX_FIFO_DEPTH - 1;
                        i2c->rx_msg->len = rxmsg_len + 1;
                } else if ((rxmsg_len == 1) ||
                        (rxmsg_len == 0)) {
                        /*
                         * Minimum of 3 bytes required to exit cleanly. 1 byte
                         * already received, Second byte is being received. Have
                         * to set NACK in read_rx before receiving the last byte
                         */
                        rfd_set = 0;
                        i2c->rx_msg->len = SMBUS_BLOCK_READ_MIN_LEN;
                } else {
                        /*
                         * When Rx msg len less than Rx fifo capacity
                         * Receive fifo depth should set to Rx msg len minus 2
                         */
                        rfd_set = rxmsg_len - 2;
                        i2c->rx_msg->len = rxmsg_len + 1;
                }
                xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, rfd_set);

                return;
        }

        /* Invalid message length, trigger STATE_ERROR with tx_msg_len in ISR */
        i2c->tx_msg->len = 3;
        i2c->smbus_block_read = false;
        dev_err(i2c->adap.dev.parent, "smbus_block_read Invalid msg length\n");
}

static void xiic_read_rx(struct xiic_i2c *i2c)
{
        u8 bytes_in_fifo, cr = 0, bytes_to_read = 0;
        u32 bytes_rem = 0;
        int i;

        bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;

        if (!i2c->atomic)
                dev_dbg(i2c->adap.dev.parent,
                        "%s entry, bytes in fifo: %d, rem: %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);

        bytes_to_read = bytes_in_fifo;

        if (!i2c->dynamic) {
                bytes_rem = xiic_rx_space(i2c) - bytes_in_fifo;

                /* Set msg length if smbus_block_read */
                if (i2c->rx_msg->flags & I2C_M_RECV_LEN) {
                        xiic_smbus_block_read_setup(i2c);
                        return;
                }

                if (bytes_rem > IIC_RX_FIFO_DEPTH) {
                        bytes_to_read = bytes_in_fifo;
                } else if (bytes_rem > 1) {
                        bytes_to_read = bytes_rem - 1;
                } else if (bytes_rem == 1) {
                        bytes_to_read = 1;
                        /* Set NACK in CR to indicate slave transmitter */
                        cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr |
                                        XIIC_CR_NO_ACK_MASK);
                } else if (bytes_rem == 0) {
                        bytes_to_read = bytes_in_fifo;

                        /* Generate stop on the bus if it is last message */
                        if (i2c->nmsgs == 1) {
                                cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                                xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
                                                ~XIIC_CR_MSMS_MASK);
                        }

                        /* Make TXACK=0, clean up for next transaction */
                        cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
                                        ~XIIC_CR_NO_ACK_MASK);
                }
        }

        /* Read the fifo */
        for (i = 0; i < bytes_to_read; i++) {
                i2c->rx_msg->buf[i2c->rx_pos++] =
                        xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
        }

        if (i2c->dynamic) {
                u8 bytes;

                /* Receive remaining bytes if less than fifo depth */
                bytes = min_t(u8, xiic_rx_space(i2c), IIC_RX_FIFO_DEPTH);
                bytes--;
                xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, bytes);
        }
}

static bool xiic_error_check(struct xiic_i2c *i2c)
{
        bool status = false;
        u32 pend, isr, ier;

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

        if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
            ((pend & XIIC_INTR_TX_ERROR_MASK) &&
            !(pend & XIIC_INTR_RX_FULL_MASK))) {
                xiic_reinit(i2c);
                status = true;
                if (i2c->tx_msg || i2c->rx_msg)
                        i2c->atomic_xfer_state = STATE_ERROR;
        }
        return status;
}

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;

        if (!i2c->atomic)
                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) && i2c->nmsgs == 1) {
                        /* last message in transfer -> STOP */
                        if (i2c->dynamic) {
                                data |= XIIC_TX_DYN_STOP_MASK;
                        } else {
                                u8 cr;
                                int status;

                                /* Wait till FIFO is empty so STOP is sent last */
                                status = xiic_wait_tx_empty(i2c);
                                if (status)
                                        return;

                                /* Write to CR to stop */
                                cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                                xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
                                             ~XIIC_CR_MSMS_MASK);
                        }
                        if (!i2c->atomic)
                                dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
                }
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);

                if (i2c->atomic && xiic_error_check(i2c))
                        return;
        }
}

static void xiic_wakeup(struct xiic_i2c *i2c, enum xilinx_i2c_state code)
{
        i2c->tx_msg = NULL;
        i2c->rx_msg = NULL;
        i2c->nmsgs = 0;
        i2c->state = code;
        complete(&i2c->completion);
}

static irqreturn_t xiic_process(int irq, void *dev_id)
{
        struct xiic_i2c *i2c = dev_id;
        u32 pend, isr, ier;
        u32 clr = 0;
        int xfer_more = 0;
        int wakeup_req = 0;
        enum xilinx_i2c_state wakeup_code = STATE_DONE;
        int ret;

        /* 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);
        dev_dbg(i2c->adap.dev.parent, "%s, ISR: 0x%x, CR: 0x%x\n",
                __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
                xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));

        /* 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
                 */
                ret = xiic_reinit(i2c);
                if (ret < 0)
                        dev_dbg(i2c->adap.dev.parent, "reinit failed\n");

                if (i2c->rx_msg) {
                        wakeup_req = 1;
                        wakeup_code = STATE_ERROR;
                }
                if (i2c->tx_msg) {
                        wakeup_req = 1;
                        wakeup_code = STATE_ERROR;
                }
                /* don't try to handle other events */
                goto out;
        }
        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__);
                                xfer_more = 1;
                        }
                }
        }
        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;
                }

                if (xiic_tx_space(i2c)) {
                        xiic_fill_tx_fifo(i2c);
                } else {
                        /* current message fully written */
                        dev_dbg(i2c->adap.dev.parent,
                                "%s end of message sent, nmsgs: %d\n",
                                __func__, i2c->nmsgs);
                        /* Don't move onto the next message until the TX FIFO empties,
                         * to ensure that a NAK is not missed.
                         */
                        if (i2c->nmsgs > 1 && (pend & XIIC_INTR_TX_EMPTY_MASK)) {
                                i2c->nmsgs--;
                                i2c->tx_msg++;
                                xfer_more = 1;
                        } 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__);
                        }
                }
        }

        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 && i2c->smbus_block_read) {
                        i2c->smbus_block_read = false;
                        /* Set requested message len=1 to indicate STATE_DONE */
                        i2c->tx_msg->len = 1;
                }

                if (!i2c->tx_msg)
                        goto out;

                wakeup_req = 1;

                if (i2c->nmsgs == 1 && !i2c->rx_msg &&
                    xiic_tx_space(i2c) == 0)
                        wakeup_code = STATE_DONE;
                else
                        wakeup_code = STATE_ERROR;
        }

out:
        dev_dbg(i2c->adap.dev.parent, "%s clr: 0x%x\n", __func__, clr);

        xiic_setreg32(i2c, XIIC_IISR_OFFSET, clr);
        if (xfer_more)
                __xiic_start_xfer(i2c);
        if (wakeup_req)
                xiic_wakeup(i2c, wakeup_code);

        WARN_ON(xfer_more && wakeup_req);

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

        /* 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--) {
                if (i2c->atomic)
                        udelay(1000);
                else
                        usleep_range(1000, 1100);
                err = xiic_bus_busy(i2c);
        }

        return err;
}

static void xiic_recv_atomic(struct xiic_i2c *i2c)
{
        while (xiic_rx_space(i2c)) {
                if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
                        xiic_read_rx(i2c);

                        /* Clear Rx full and Tx error interrupts. */
                        xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK |
                                        XIIC_INTR_TX_ERROR_MASK);
                }
                if (xiic_error_check(i2c))
                        return;
        }

        i2c->rx_msg = NULL;
        xiic_irq_clr_en(i2c, XIIC_INTR_TX_ERROR_MASK);

        /* send next message if this wasn't the last. */
        if (i2c->nmsgs > 1) {
                i2c->nmsgs--;
                i2c->tx_msg++;
                __xiic_start_xfer(i2c);
        }
}

static void xiic_start_recv(struct xiic_i2c *i2c)
{
        u16 rx_watermark;
        u8 cr = 0, rfd_set = 0;
        struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;

        if (!i2c->atomic)
                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));

        /* Disable Tx interrupts */
        xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK | XIIC_INTR_TX_EMPTY_MASK);

        if (i2c->dynamic) {
                u8 bytes;
                u16 val;

                /* 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 indicate 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;
                bytes = min_t(u8, rx_watermark, IIC_RX_FIFO_DEPTH);

                if (rx_watermark > 0)
                        bytes--;
                xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, bytes);

                /* write the address */
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
                              i2c_8bit_addr_from_msg(msg) |
                              XIIC_TX_DYN_START_MASK);

                /* If last message, include dynamic stop bit with length */
                val = (i2c->nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0;
                val |= msg->len;

                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, val);

                xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
        } else {
                /*
                 * If previous message is Tx, make sure that Tx FIFO is empty
                 * before starting a new transfer as the repeated start in
                 * standard mode can corrupt the transaction if there are
                 * still bytes to be transmitted in FIFO
                 */
                if (i2c->prev_msg_tx) {
                        int status;

                        status = xiic_wait_tx_empty(i2c);
                        if (status)
                                return;
                }

                cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);

                /* Set Receive fifo depth */
                rx_watermark = msg->len;
                if (rx_watermark > IIC_RX_FIFO_DEPTH) {
                        rfd_set = IIC_RX_FIFO_DEPTH - 1;
                } else if (rx_watermark == 1) {
                        rfd_set = rx_watermark - 1;

                        /* Set No_ACK, except for smbus_block_read */
                        if (!(i2c->rx_msg->flags & I2C_M_RECV_LEN)) {
                                /* Handle single byte transfer separately */
                                cr |= XIIC_CR_NO_ACK_MASK;
                        }
                } else if (rx_watermark == 0) {
                        rfd_set = rx_watermark;
                } else {
                        rfd_set = rx_watermark - 2;
                }
                /* Check if RSTA should be set */
                if (cr & XIIC_CR_MSMS_MASK) {
                        /* Already a master, RSTA should be set */
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, (cr |
                                        XIIC_CR_REPEATED_START_MASK) &
                                        ~(XIIC_CR_DIR_IS_TX_MASK));
                }

                xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, rfd_set);

                /* Clear and enable Rx full and transmit complete interrupts */
                xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK |
                                XIIC_INTR_TX_ERROR_MASK);

                /* Write the address */
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
                              i2c_8bit_addr_from_msg(msg));

                /* Write to Control Register,to start transaction in Rx mode */
                if ((cr & XIIC_CR_MSMS_MASK) == 0) {
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, (cr |
                                        XIIC_CR_MSMS_MASK)
                                        & ~(XIIC_CR_DIR_IS_TX_MASK));
                }
                if (!i2c->atomic)
                        dev_dbg(i2c->adap.dev.parent, "%s end, ISR: 0x%x, CR: 0x%x\n",
                                __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
                                xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
        }

        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;

        i2c->prev_msg_tx = false;

        /* Enable interrupts */
        if (!i2c->atomic)
                xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
        else
                xiic_recv_atomic(i2c);
}

static void xiic_send_rem_atomic(struct xiic_i2c *i2c)
{
        while (xiic_tx_space(i2c)) {
                if (xiic_tx_fifo_space(i2c)) {
                        u16 data;

                        data = i2c->tx_msg->buf[i2c->tx_pos];
                        i2c->tx_pos++;
                        if (!xiic_tx_space(i2c) && i2c->nmsgs == 1) {
                                /* last message in transfer -> STOP */
                                if (i2c->dynamic) {
                                        data |= XIIC_TX_DYN_STOP_MASK;
                                } else {
                                        u8 cr;
                                        int status;

                                        /* Wait till FIFO is empty so STOP is sent last */
                                        status = xiic_wait_tx_empty(i2c);
                                        if (status)
                                                return;

                                        /* Write to CR to stop */
                                        cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
                                                     ~XIIC_CR_MSMS_MASK);
                                }
                        }
                        xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
                }
                if (xiic_error_check(i2c))
                        return;
        }

        if (i2c->nmsgs > 1) {
                i2c->nmsgs--;
                i2c->tx_msg++;
                __xiic_start_xfer(i2c);
        } else {
                xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
        }
}

static void xiic_start_send(struct xiic_i2c *i2c)
{
        u8 cr = 0;
        u16 data;
        struct i2c_msg *msg = i2c->tx_msg;

        if (!i2c->atomic) {
                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 (i2c->dynamic) {
                /* write the address */
                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);

                /* 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 |
                                ((i2c->nmsgs > 1 || xiic_tx_space(i2c)) ?
                                XIIC_INTR_TX_HALF_MASK : 0));

                xiic_fill_tx_fifo(i2c);
        } else {
                /*
                 * If previous message is Tx, make sure that Tx FIFO is empty
                 * before starting a new transfer as the repeated start in
                 * standard mode can corrupt the transaction if there are
                 * still bytes to be transmitted in FIFO
                 */
                if (i2c->prev_msg_tx) {
                        int status;

                        status = xiic_wait_tx_empty(i2c);
                        if (status)
                                return;
                }
                /* Check if RSTA should be set */
                cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                if (cr & XIIC_CR_MSMS_MASK) {
                        /* Already a master, RSTA should be set */
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, (cr |
                                        XIIC_CR_REPEATED_START_MASK |
                                        XIIC_CR_DIR_IS_TX_MASK) &
                                        ~(XIIC_CR_NO_ACK_MASK));
                }

                /* Write address to FIFO */
                data = i2c_8bit_addr_from_msg(msg);
                xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);

                /* Fill fifo */
                xiic_fill_tx_fifo(i2c);

                if ((cr & XIIC_CR_MSMS_MASK) == 0) {
                        /* Start Tx by writing to CR */
                        cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
                        xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr |
                                        XIIC_CR_MSMS_MASK |
                                        XIIC_CR_DIR_IS_TX_MASK);
                }

                /* 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);
        }

        i2c->prev_msg_tx = true;

        if (i2c->atomic && !i2c->atomic_xfer_state)
                xiic_send_rem_atomic(i2c);
}

static void __xiic_start_xfer(struct xiic_i2c *i2c)
{
        int fifo_space = xiic_tx_fifo_space(i2c);

        if (!i2c->atomic)
                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;

        if (i2c->atomic && xiic_error_check(i2c))
                return;

        i2c->rx_pos = 0;
        i2c->tx_pos = 0;
        i2c->state = STATE_START;
        if (i2c->tx_msg->flags & I2C_M_RD) {
                /* we dont date putting several reads in the FIFO */
                xiic_start_recv(i2c);
        } else {
                xiic_start_send(i2c);
        }
}

static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
{
        bool broken_read, max_read_len, smbus_blk_read;
        int ret, count;

        if (i2c->atomic)
                spin_lock(&i2c->atomic_lock);
        else
                mutex_lock(&i2c->lock);

        if (i2c->tx_msg || i2c->rx_msg) {
                dev_err(i2c->adap.dev.parent,
                        "cannot start a transfer while busy\n");
                ret = -EBUSY;
                goto out;
        }

        i2c->atomic_xfer_state = STATE_DONE;

        /* 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) {
                ret = xiic_wait_not_busy(i2c);
                if (ret) {
                        /* If the bus is stuck in a busy state, such as due to spurious low
                         * pulses on the bus causing a false start condition to be detected,
                         * then try to recover by re-initializing the controller and check
                         * again if the bus is still busy.
                         */
                        dev_warn(i2c->adap.dev.parent, "I2C bus busy timeout, reinitializing\n");
                        ret = xiic_reinit(i2c);
                        if (ret)
                                goto out;
                        ret = xiic_wait_not_busy(i2c);
                        if (ret)
                                goto out;
                }
        }

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

        if (!i2c->atomic)
                init_completion(&i2c->completion);

        /* Decide standard mode or Dynamic mode */
        i2c->dynamic = true;

        /* Initialize prev message type */
        i2c->prev_msg_tx = false;

        /*
         * Scan through nmsgs, use dynamic mode when none of the below three
         * conditions occur. We need standard mode even if one condition holds
         * true in the entire array of messages in a single transfer.
         * If read transaction as dynamic mode is broken for delayed reads
         * in xlnx,axi-iic-2.0 / xlnx,xps-iic-2.00.a IP versions.
         * If read length is > 255 bytes.
         * If smbus_block_read transaction.
         */
        for (count = 0; count < i2c->nmsgs; count++) {
                broken_read = (i2c->quirks & DYNAMIC_MODE_READ_BROKEN_BIT) &&
                                (i2c->tx_msg[count].flags & I2C_M_RD);
                max_read_len = (i2c->tx_msg[count].flags & I2C_M_RD) &&
                                (i2c->tx_msg[count].len > MAX_READ_LENGTH_DYNAMIC);
                smbus_blk_read = (i2c->tx_msg[count].flags & I2C_M_RECV_LEN);

                if (broken_read || max_read_len || smbus_blk_read) {
                        i2c->dynamic = false;
                        break;
                }
        }

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

out:
        if (i2c->atomic)
                spin_unlock(&i2c->atomic_lock);
        else
                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_start_xfer(i2c, msgs, num);
        if (err < 0)
                goto out;

        err = wait_for_completion_timeout(&i2c->completion, XIIC_XFER_TIMEOUT);
        mutex_lock(&i2c->lock);
        if (err == 0) { /* Timeout */
                i2c->tx_msg = NULL;
                i2c->rx_msg = NULL;
                i2c->nmsgs = 0;
                err = -ETIMEDOUT;
        } else {
                err = (i2c->state == STATE_DONE) ? num : -EIO;
        }
        mutex_unlock(&i2c->lock);

out:
        pm_runtime_put_autosuspend(i2c->dev);
        return err;
}

static int xiic_xfer_atomic(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
        struct xiic_i2c *i2c = i2c_get_adapdata(adap);
        u32 status_reg;
        int err;

        err = xiic_i2c_runtime_resume(i2c->dev);
        if (err)
                return err;

        i2c->atomic = true;
        err = xiic_start_xfer(i2c, msgs, num);
        if (err < 0)
                return err;

        err = readl_poll_timeout_atomic(i2c->base + XIIC_SR_REG_OFFSET,
                                        status_reg, !(status_reg & XIIC_SR_BUS_BUSY_MASK),
                                        1, XIIC_XFER_TIMEOUT_US);

        if (err) /* Timeout */
                err = -ETIMEDOUT;

        spin_lock(&i2c->atomic_lock);
        if (err || i2c->state) {
                i2c->tx_msg = NULL;
                i2c->rx_msg = NULL;
                i2c->nmsgs = 0;
        }

        err = (i2c->atomic_xfer_state == STATE_DONE) ? num : -EIO;
        spin_unlock(&i2c->atomic_lock);

        i2c->atomic = false;
        xiic_i2c_runtime_suspend(i2c->dev);

        return err;
}

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

static const struct i2c_algorithm xiic_algorithm = {
        .xfer = xiic_xfer,
        .xfer_atomic = xiic_xfer_atomic,
        .functionality = xiic_func,
};

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

static const struct xiic_version_data xiic_2_00 = {
        .quirks = DYNAMIC_MODE_READ_BROKEN_BIT,
};

static const struct of_device_id xiic_of_match[] = {
        { .compatible = "xlnx,xps-iic-2.00.a", .data = &xiic_2_00 },
        { .compatible = "xlnx,axi-iic-2.1", },
        {},
};
MODULE_DEVICE_TABLE(of, xiic_of_match);

static int xiic_i2c_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct fwnode_handle *fwnode = dev_fwnode(dev);
        struct xiic_i2c *i2c;
        struct xiic_i2c_platform_data *pdata;
        const struct xiic_version_data *data;
        struct resource *res;
        int ret, irq;
        u8 i;
        u32 sr;

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

        data = device_get_match_data(dev);
        if (data)
                i2c->quirks = data->quirks;

        i2c->base = devm_platform_get_and_ioremap_resource(pdev, 0, &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(dev);

        /* hook up driver to tree */
        platform_set_drvdata(pdev, i2c);
        i2c->adap = xiic_adapter;
        i2c->adap.nr = pdev->id;
        i2c_set_adapdata(&i2c->adap, i2c);
        i2c->adap.dev.parent = &pdev->dev;
        device_set_node(&i2c->adap.dev, fwnode);
        snprintf(i2c->adap.name, sizeof(i2c->adap.name),
                 DRIVER_NAME " %s", pdev->name);

        ret = devm_mutex_init(dev, &i2c->lock);
        if (ret)
                return ret;

        spin_lock_init(&i2c->atomic_lock);

        if (is_of_node(fwnode)) {
                i2c->clk = devm_clk_get_enabled(dev, NULL);
                if (IS_ERR(i2c->clk))
                        return dev_err_probe(dev, PTR_ERR(i2c->clk),
                                        "failed to enable input clock.\n");
        }

        i2c->dev = dev;

        pm_runtime_set_autosuspend_delay(dev, XIIC_PM_TIMEOUT);
        pm_runtime_use_autosuspend(dev);
        ret = devm_pm_runtime_set_active_enabled(dev);
        if (ret)
                return ret;

        /* SCL frequency configuration */
        i2c->input_clk = clk_get_rate(i2c->clk);
        ret = device_property_read_u32(dev, "clock-frequency", &i2c->i2c_clk);
        /* If clock-frequency not specified in DT, do not configure in SW */
        if (ret || i2c->i2c_clk > I2C_MAX_FAST_MODE_PLUS_FREQ)
                i2c->i2c_clk = 0;

        ret = devm_request_threaded_irq(dev, irq, NULL, xiic_process,
                                        IRQF_ONESHOT, pdev->name, i2c);
        if (ret)
                return ret;

        i2c->singlemaster = device_property_read_bool(dev, "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)
                return dev_err_probe(dev, ret, "Cannot xiic_reinit\n");

        /* add i2c adapter to i2c tree */
        ret = i2c_add_numbered_adapter(&i2c->adap);
        if (ret) {
                xiic_deinit(i2c);
                return ret;
        }

        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);
        }

        dev_dbg(dev, "mmio %pR irq %d scl clock frequency %d\n",
                res, irq, i2c->i2c_clk);

        return 0;
}

static void xiic_i2c_remove(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct xiic_i2c *i2c = platform_get_drvdata(pdev);
        int ret;

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

        ret = pm_runtime_get_sync(dev);
        if (ret < 0)
                dev_warn(dev, "Failed to activate device for removal (%pe)\n",
                         ERR_PTR(ret));
        else
                xiic_deinit(i2c);

        pm_runtime_put_sync(dev);
}

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