// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * I2C bus driver for the Cadence I2C controller.
 *
 * Copyright (C) 2009 - 2014 Xilinx, Inc.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/pm_runtime.h>
#include <linux/pinctrl/consumer.h>
#include <linux/reset.h>

/* Register offsets for the I2C device. */
#define CDNS_I2C_CR_OFFSET              0x00 /* Control Register, RW */
#define CDNS_I2C_SR_OFFSET              0x04 /* Status Register, RO */
#define CDNS_I2C_ADDR_OFFSET            0x08 /* I2C Address Register, RW */
#define CDNS_I2C_DATA_OFFSET            0x0C /* I2C Data Register, RW */
#define CDNS_I2C_ISR_OFFSET             0x10 /* IRQ Status Register, RW */
#define CDNS_I2C_XFER_SIZE_OFFSET       0x14 /* Transfer Size Register, RW */
#define CDNS_I2C_TIME_OUT_OFFSET        0x1C /* Time Out Register, RW */
#define CDNS_I2C_IMR_OFFSET             0x20 /* IRQ Mask Register, RO */
#define CDNS_I2C_IER_OFFSET             0x24 /* IRQ Enable Register, WO */
#define CDNS_I2C_IDR_OFFSET             0x28 /* IRQ Disable Register, WO */

/* Control Register Bit mask definitions */
#define CDNS_I2C_CR_HOLD                BIT(4) /* Hold Bus bit */
#define CDNS_I2C_CR_ACK_EN              BIT(3)
#define CDNS_I2C_CR_NEA                 BIT(2)
#define CDNS_I2C_CR_MS                  BIT(1)
/* Read or Write Master transfer 0 = Transmitter, 1 = Receiver */
#define CDNS_I2C_CR_RW                  BIT(0)
/* 1 = Auto init FIFO to zeroes */
#define CDNS_I2C_CR_CLR_FIFO            BIT(6)
#define CDNS_I2C_CR_DIVA_SHIFT          14
#define CDNS_I2C_CR_DIVA_MASK           (3 << CDNS_I2C_CR_DIVA_SHIFT)
#define CDNS_I2C_CR_DIVB_SHIFT          8
#define CDNS_I2C_CR_DIVB_MASK           (0x3f << CDNS_I2C_CR_DIVB_SHIFT)

#define CDNS_I2C_CR_MASTER_EN_MASK      (CDNS_I2C_CR_NEA | \
                                         CDNS_I2C_CR_ACK_EN | \
                                         CDNS_I2C_CR_MS)

#define CDNS_I2C_CR_SLAVE_EN_MASK       ~CDNS_I2C_CR_MASTER_EN_MASK

/* Status Register Bit mask definitions */
#define CDNS_I2C_SR_BA          BIT(8)
#define CDNS_I2C_SR_TXDV        BIT(6)
#define CDNS_I2C_SR_RXDV        BIT(5)
#define CDNS_I2C_SR_RXRW        BIT(3)

/*
 * I2C Address Register Bit mask definitions
 * Normal addressing mode uses [6:0] bits. Extended addressing mode uses [9:0]
 * bits. A write access to this register always initiates a transfer if the I2C
 * is in master mode.
 */
#define CDNS_I2C_ADDR_MASK      0x000003FF /* I2C Address Mask */

/*
 * I2C Interrupt Registers Bit mask definitions
 * All the four interrupt registers (Status/Mask/Enable/Disable) have the same
 * bit definitions.
 */
#define CDNS_I2C_IXR_ARB_LOST           BIT(9)
#define CDNS_I2C_IXR_RX_UNF             BIT(7)
#define CDNS_I2C_IXR_TX_OVF             BIT(6)
#define CDNS_I2C_IXR_RX_OVF             BIT(5)
#define CDNS_I2C_IXR_SLV_RDY            BIT(4)
#define CDNS_I2C_IXR_TO                 BIT(3)
#define CDNS_I2C_IXR_NACK               BIT(2)
#define CDNS_I2C_IXR_DATA               BIT(1)
#define CDNS_I2C_IXR_COMP               BIT(0)

#define CDNS_I2C_IXR_ALL_INTR_MASK      (CDNS_I2C_IXR_ARB_LOST | \
                                         CDNS_I2C_IXR_RX_UNF | \
                                         CDNS_I2C_IXR_TX_OVF | \
                                         CDNS_I2C_IXR_RX_OVF | \
                                         CDNS_I2C_IXR_SLV_RDY | \
                                         CDNS_I2C_IXR_TO | \
                                         CDNS_I2C_IXR_NACK | \
                                         CDNS_I2C_IXR_DATA | \
                                         CDNS_I2C_IXR_COMP)

#define CDNS_I2C_IXR_ERR_INTR_MASK      (CDNS_I2C_IXR_ARB_LOST | \
                                         CDNS_I2C_IXR_RX_UNF | \
                                         CDNS_I2C_IXR_TX_OVF | \
                                         CDNS_I2C_IXR_RX_OVF | \
                                         CDNS_I2C_IXR_NACK)

#define CDNS_I2C_ENABLED_INTR_MASK      (CDNS_I2C_IXR_ARB_LOST | \
                                         CDNS_I2C_IXR_RX_UNF | \
                                         CDNS_I2C_IXR_TX_OVF | \
                                         CDNS_I2C_IXR_RX_OVF | \
                                         CDNS_I2C_IXR_NACK | \
                                         CDNS_I2C_IXR_DATA | \
                                         CDNS_I2C_IXR_COMP)

#define CDNS_I2C_IXR_SLAVE_INTR_MASK    (CDNS_I2C_IXR_RX_UNF | \
                                         CDNS_I2C_IXR_TX_OVF | \
                                         CDNS_I2C_IXR_RX_OVF | \
                                         CDNS_I2C_IXR_TO | \
                                         CDNS_I2C_IXR_NACK | \
                                         CDNS_I2C_IXR_DATA | \
                                         CDNS_I2C_IXR_COMP)

#define CDNS_I2C_TIMEOUT                msecs_to_jiffies(1000)
/* timeout for pm runtime autosuspend */
#define CNDS_I2C_PM_TIMEOUT             1000    /* ms */

#define CDNS_I2C_FIFO_DEPTH_DEFAULT     16
#define CDNS_I2C_MAX_TRANSFER_SIZE      255
/* Transfer size in multiples of data interrupt depth */
#define CDNS_I2C_TRANSFER_SIZE(max)     ((max) - 3)

#define DRIVER_NAME             "cdns-i2c"

#define CDNS_I2C_DIVA_MAX       4
#define CDNS_I2C_DIVB_MAX       64

#define CDNS_I2C_TIMEOUT_MAX    0xFF

#define CDNS_I2C_BROKEN_HOLD_BIT        BIT(0)
#define CDNS_I2C_POLL_US        100000
#define CDNS_I2C_POLL_US_ATOMIC 10
#define CDNS_I2C_TIMEOUT_US     500000

#define cdns_i2c_readreg(offset)       readl_relaxed(id->membase + offset)
#define cdns_i2c_writereg(val, offset) writel_relaxed(val, id->membase + offset)

#if IS_ENABLED(CONFIG_I2C_SLAVE)
/**
 * enum cdns_i2c_mode - I2C Controller current operating mode
 *
 * @CDNS_I2C_MODE_SLAVE:       I2C controller operating in slave mode
 * @CDNS_I2C_MODE_MASTER:      I2C Controller operating in master mode
 */
enum cdns_i2c_mode {
        CDNS_I2C_MODE_SLAVE,
        CDNS_I2C_MODE_MASTER,
};

/**
 * enum cdns_i2c_slave_state - Slave state when I2C is operating in slave mode
 *
 * @CDNS_I2C_SLAVE_STATE_IDLE: I2C slave idle
 * @CDNS_I2C_SLAVE_STATE_SEND: I2C slave sending data to master
 * @CDNS_I2C_SLAVE_STATE_RECV: I2C slave receiving data from master
 */
enum cdns_i2c_slave_state {
        CDNS_I2C_SLAVE_STATE_IDLE,
        CDNS_I2C_SLAVE_STATE_SEND,
        CDNS_I2C_SLAVE_STATE_RECV,
};
#endif

/**
 * struct cdns_i2c - I2C device private data structure
 *
 * @dev:                Pointer to device structure
 * @membase:            Base address of the I2C device
 * @adap:               I2C adapter instance
 * @p_msg:              Message pointer
 * @err_status:         Error status in Interrupt Status Register
 * @xfer_done:          Transfer complete status
 * @p_send_buf:         Pointer to transmit buffer
 * @p_recv_buf:         Pointer to receive buffer
 * @send_count:         Number of bytes still expected to send
 * @recv_count:         Number of bytes still expected to receive
 * @curr_recv_count:    Number of bytes to be received in current transfer
 * @input_clk:          Input clock to I2C controller
 * @i2c_clk:            Maximum I2C clock speed
 * @bus_hold_flag:      Flag used in repeated start for clearing HOLD bit
 * @clk:                Pointer to struct clk
 * @clk_rate_change_nb: Notifier block for clock rate changes
 * @reset:              Reset control for the device
 * @quirks:             flag for broken hold bit usage in r1p10
 * @ctrl_reg:           Cached value of the control register.
 * @rinfo:              I2C GPIO recovery information
 * @ctrl_reg_diva_divb: value of fields DIV_A and DIV_B from CR register
 * @slave:              Registered slave instance.
 * @dev_mode:           I2C operating role(master/slave).
 * @slave_state:        I2C Slave state(idle/read/write).
 * @fifo_depth:         The depth of the transfer FIFO
 * @transfer_size:      The maximum number of bytes in one transfer
 * @atomic:             Mode of transfer
 * @err_status_atomic:  Error status in atomic mode
 */
struct cdns_i2c {
        struct device           *dev;
        void __iomem *membase;
        struct i2c_adapter adap;
        struct i2c_msg *p_msg;
        int err_status;
        struct completion xfer_done;
        unsigned char *p_send_buf;
        unsigned char *p_recv_buf;
        unsigned int send_count;
        unsigned int recv_count;
        unsigned int curr_recv_count;
        unsigned long input_clk;
        unsigned int i2c_clk;
        unsigned int bus_hold_flag;
        struct clk *clk;
        struct notifier_block clk_rate_change_nb;
        struct reset_control *reset;
        u32 quirks;
        u32 ctrl_reg;
        struct i2c_bus_recovery_info rinfo;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        u16 ctrl_reg_diva_divb;
        struct i2c_client *slave;
        enum cdns_i2c_mode dev_mode;
        enum cdns_i2c_slave_state slave_state;
#endif
        u32 fifo_depth;
        unsigned int transfer_size;
        bool atomic;
        int err_status_atomic;
};

struct cdns_platform_data {
        u32 quirks;
};

#define to_cdns_i2c(_nb)        container_of(_nb, struct cdns_i2c, \
                                             clk_rate_change_nb)

/**
 * cdns_i2c_init -  Controller initialisation
 * @id:         Device private data structure
 *
 * Initialise the i2c controller.
 *
 */
static void cdns_i2c_init(struct cdns_i2c *id)
{
        cdns_i2c_writereg(id->ctrl_reg, CDNS_I2C_CR_OFFSET);
        /*
         * Cadence I2C controller has a bug wherein it generates
         * invalid read transaction after HW timeout in master receiver mode.
         * HW timeout is not used by this driver and the interrupt is disabled.
         * But the feature itself cannot be disabled. Hence maximum value
         * is written to this register to reduce the chances of error.
         */
        cdns_i2c_writereg(CDNS_I2C_TIMEOUT_MAX, CDNS_I2C_TIME_OUT_OFFSET);
}

/**
 * cdns_i2c_runtime_suspend -  Runtime suspend method for the driver
 * @dev:        Address of the platform_device structure
 *
 * Put the driver into low power mode.
 *
 * Return: 0 always
 */
static int cdns_i2c_runtime_suspend(struct device *dev)
{
        struct cdns_i2c *xi2c = dev_get_drvdata(dev);

        clk_disable(xi2c->clk);

        return 0;
}

/**
 * cdns_i2c_runtime_resume - Runtime resume
 * @dev:        Address of the platform_device structure
 *
 * Runtime resume callback.
 *
 * Return: 0 on success and error value on error
 */
static int cdns_i2c_runtime_resume(struct device *dev)
{
        struct cdns_i2c *xi2c = dev_get_drvdata(dev);
        int ret;

        ret = clk_enable(xi2c->clk);
        if (ret) {
                dev_err(dev, "Cannot enable clock.\n");
                return ret;
        }
        cdns_i2c_init(xi2c);

        return 0;
}

/**
 * cdns_i2c_clear_bus_hold - Clear bus hold bit
 * @id: Pointer to driver data struct
 *
 * Helper to clear the controller's bus hold bit.
 */
static void cdns_i2c_clear_bus_hold(struct cdns_i2c *id)
{
        u32 reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
        if (reg & CDNS_I2C_CR_HOLD)
                cdns_i2c_writereg(reg & ~CDNS_I2C_CR_HOLD, CDNS_I2C_CR_OFFSET);
}

static inline bool cdns_is_holdquirk(struct cdns_i2c *id, bool hold_wrkaround)
{
        return (hold_wrkaround &&
                (id->curr_recv_count == id->fifo_depth + 1));
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static void cdns_i2c_set_mode(enum cdns_i2c_mode mode, struct cdns_i2c *id)
{
        /* Disable all interrupts */
        cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK, CDNS_I2C_IDR_OFFSET);

        /* Clear FIFO and transfer size */
        cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);

        /* Update device mode and state */
        id->dev_mode = mode;
        id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;

        switch (mode) {
        case CDNS_I2C_MODE_MASTER:
                /* Enable i2c master */
                cdns_i2c_writereg(id->ctrl_reg_diva_divb |
                                  CDNS_I2C_CR_MASTER_EN_MASK,
                                  CDNS_I2C_CR_OFFSET);
                /*
                 * This delay is needed to give the IP some time to switch to
                 * the master mode. With lower values(like 110 us) i2cdetect
                 * will not detect any slave and without this delay, the IP will
                 * trigger a timeout interrupt.
                 */
                usleep_range(115, 125);
                break;
        case CDNS_I2C_MODE_SLAVE:
                /* Enable i2c slave */
                cdns_i2c_writereg(id->ctrl_reg_diva_divb &
                                  CDNS_I2C_CR_SLAVE_EN_MASK,
                                  CDNS_I2C_CR_OFFSET);

                /* Setting slave address */
                cdns_i2c_writereg(id->slave->addr & CDNS_I2C_ADDR_MASK,
                                  CDNS_I2C_ADDR_OFFSET);

                /* Enable slave send/receive interrupts */
                cdns_i2c_writereg(CDNS_I2C_IXR_SLAVE_INTR_MASK,
                                  CDNS_I2C_IER_OFFSET);
                break;
        }
}

static void cdns_i2c_slave_rcv_data(struct cdns_i2c *id)
{
        u8 bytes;
        unsigned char data;

        /* Prepare backend for data reception */
        if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
                id->slave_state = CDNS_I2C_SLAVE_STATE_RECV;
                i2c_slave_event(id->slave, I2C_SLAVE_WRITE_REQUESTED, NULL);
        }

        /* Fetch number of bytes to receive */
        bytes = cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);

        /* Read data and send to backend */
        while (bytes--) {
                data = cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
                i2c_slave_event(id->slave, I2C_SLAVE_WRITE_RECEIVED, &data);
        }
}

static void cdns_i2c_slave_send_data(struct cdns_i2c *id)
{
        u8 data;

        /* Prepare backend for data transmission */
        if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
                id->slave_state = CDNS_I2C_SLAVE_STATE_SEND;
                i2c_slave_event(id->slave, I2C_SLAVE_READ_REQUESTED, &data);
        } else {
                i2c_slave_event(id->slave, I2C_SLAVE_READ_PROCESSED, &data);
        }

        /* Send data over bus */
        cdns_i2c_writereg(data, CDNS_I2C_DATA_OFFSET);
}

/**
 * cdns_i2c_slave_isr - Interrupt handler for the I2C device in slave role
 * @ptr:       Pointer to I2C device private data
 *
 * This function handles the data interrupt and transfer complete interrupt of
 * the I2C device in slave role.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_slave_isr(void *ptr)
{
        struct cdns_i2c *id = ptr;
        unsigned int isr_status, i2c_status;

        /* Fetch the interrupt status */
        isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

        /* Ignore masked interrupts */
        isr_status &= ~cdns_i2c_readreg(CDNS_I2C_IMR_OFFSET);

        /* Fetch transfer mode (send/receive) */
        i2c_status = cdns_i2c_readreg(CDNS_I2C_SR_OFFSET);

        /* Handle data send/receive */
        if (i2c_status & CDNS_I2C_SR_RXRW) {
                /* Send data to master */
                if (isr_status & CDNS_I2C_IXR_DATA)
                        cdns_i2c_slave_send_data(id);

                if (isr_status & CDNS_I2C_IXR_COMP) {
                        id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
                        i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
                }
        } else {
                /* Receive data from master */
                if (isr_status & CDNS_I2C_IXR_DATA)
                        cdns_i2c_slave_rcv_data(id);

                if (isr_status & CDNS_I2C_IXR_COMP) {
                        cdns_i2c_slave_rcv_data(id);
                        id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
                        i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
                }
        }

        /* Master indicated xfer stop or fifo underflow/overflow */
        if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_RX_OVF |
                          CDNS_I2C_IXR_RX_UNF | CDNS_I2C_IXR_TX_OVF)) {
                id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
                i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
                cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);
        }

        return IRQ_HANDLED;
}
#endif

/**
 * cdns_i2c_master_isr - Interrupt handler for the I2C device in master role
 * @ptr:       Pointer to I2C device private data
 *
 * This function handles the data interrupt, transfer complete interrupt and
 * the error interrupts of the I2C device in master role.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_master_isr(void *ptr)
{
        unsigned int isr_status, avail_bytes;
        unsigned int bytes_to_send;
        bool updatetx;
        struct cdns_i2c *id = ptr;
        /* Signal completion only after everything is updated */
        int done_flag = 0;
        irqreturn_t status = IRQ_NONE;

        isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);
        id->err_status = 0;

        /* Handling nack and arbitration lost interrupt */
        if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_ARB_LOST)) {
                done_flag = 1;
                status = IRQ_HANDLED;
        }

        /*
         * Check if transfer size register needs to be updated again for a
         * large data receive operation.
         */
        updatetx = id->recv_count > id->curr_recv_count;

        /* When receiving, handle data interrupt and completion interrupt */
        if (id->p_recv_buf &&
            ((isr_status & CDNS_I2C_IXR_COMP) ||
             (isr_status & CDNS_I2C_IXR_DATA))) {
                /* Read data if receive data valid is set */
                while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
                       CDNS_I2C_SR_RXDV) {
                        if (id->recv_count > 0) {
                                *(id->p_recv_buf)++ =
                                        cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
                                id->recv_count--;
                                id->curr_recv_count--;

                                /*
                                 * Clear hold bit that was set for FIFO control
                                 * if RX data left is less than or equal to
                                 * FIFO DEPTH unless repeated start is selected
                                 */
                                if (id->recv_count <= id->fifo_depth &&
                                    !id->bus_hold_flag)
                                        cdns_i2c_clear_bus_hold(id);

                        } else {
                                dev_err(id->adap.dev.parent,
                                        "xfer_size reg rollover. xfer aborted!\n");
                                id->err_status |= CDNS_I2C_IXR_TO;
                                break;
                        }

                        if (cdns_is_holdquirk(id, updatetx))
                                break;
                }

                /*
                 * The controller sends NACK to the slave when transfer size
                 * register reaches zero without considering the HOLD bit.
                 * This workaround is implemented for large data transfers to
                 * maintain transfer size non-zero while performing a large
                 * receive operation.
                 */
                if (cdns_is_holdquirk(id, updatetx)) {
                        /* wait while fifo is full */
                        while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
                               (id->curr_recv_count - id->fifo_depth))
                                ;

                        /*
                         * Check number of bytes to be received against maximum
                         * transfer size and update register accordingly.
                         */
                        if (((int)(id->recv_count) - id->fifo_depth) >
                            id->transfer_size) {
                                cdns_i2c_writereg(id->transfer_size,
                                                  CDNS_I2C_XFER_SIZE_OFFSET);
                                id->curr_recv_count = id->transfer_size +
                                                      id->fifo_depth;
                        } else {
                                cdns_i2c_writereg(id->recv_count -
                                                  id->fifo_depth,
                                                  CDNS_I2C_XFER_SIZE_OFFSET);
                                id->curr_recv_count = id->recv_count;
                        }
                }

                /* Clear hold (if not repeated start) and signal completion */
                if ((isr_status & CDNS_I2C_IXR_COMP) && !id->recv_count) {
                        if (!id->bus_hold_flag)
                                cdns_i2c_clear_bus_hold(id);
                        done_flag = 1;
                }

                status = IRQ_HANDLED;
        }

        /* When sending, handle transfer complete interrupt */
        if ((isr_status & CDNS_I2C_IXR_COMP) && !id->p_recv_buf) {
                /*
                 * If there is more data to be sent, calculate the
                 * space available in FIFO and fill with that many bytes.
                 */
                if (id->send_count) {
                        avail_bytes = id->fifo_depth -
                            cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
                        if (id->send_count > avail_bytes)
                                bytes_to_send = avail_bytes;
                        else
                                bytes_to_send = id->send_count;

                        while (bytes_to_send--) {
                                cdns_i2c_writereg(
                                        (*(id->p_send_buf)++),
                                         CDNS_I2C_DATA_OFFSET);
                                id->send_count--;
                        }
                } else {
                        /*
                         * Signal the completion of transaction and
                         * clear the hold bus bit if there are no
                         * further messages to be processed.
                         */
                        done_flag = 1;
                }
                if (!id->send_count && !id->bus_hold_flag)
                        cdns_i2c_clear_bus_hold(id);

                status = IRQ_HANDLED;
        }

        /* Update the status for errors */
        id->err_status |= isr_status & CDNS_I2C_IXR_ERR_INTR_MASK;
        if (id->err_status)
                status = IRQ_HANDLED;

        if (done_flag)
                complete(&id->xfer_done);

        return status;
}

/**
 * cdns_i2c_isr - Interrupt handler for the I2C device
 * @irq:        irq number for the I2C device
 * @ptr:        void pointer to cdns_i2c structure
 *
 * This function passes the control to slave/master based on current role of
 * i2c controller.
 *
 * Return: IRQ_HANDLED always
 */
static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
{
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        struct cdns_i2c *id = ptr;

        if (id->dev_mode == CDNS_I2C_MODE_SLAVE)
                return cdns_i2c_slave_isr(ptr);
#endif
        return cdns_i2c_master_isr(ptr);
}

static bool cdns_i2c_error_check(struct cdns_i2c *id)
{
        unsigned int isr_status;

        id->err_status = 0;

        isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(isr_status & CDNS_I2C_IXR_ERR_INTR_MASK, CDNS_I2C_ISR_OFFSET);

        id->err_status = isr_status & CDNS_I2C_IXR_ERR_INTR_MASK;

        return !!id->err_status;
}

static void cdns_i2c_mrecv_atomic(struct cdns_i2c *id)
{
        while (id->recv_count > 0) {
                bool updatetx;

                /*
                 * Check if transfer size register needs to be updated again for a
                 * large data receive operation.
                 */
                updatetx = id->recv_count > id->curr_recv_count;

                while (id->curr_recv_count > 0) {
                        if (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) & CDNS_I2C_SR_RXDV) {
                                *id->p_recv_buf = cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
                                id->p_recv_buf++;
                                id->recv_count--;
                                id->curr_recv_count--;

                                /*
                                 * Clear the hold bit that was set for FIFO control,
                                 * if the remaining RX data is less than or equal to
                                 * the FIFO depth, unless a repeated start is selected.
                                 */
                                if (id->recv_count <= id->fifo_depth && !id->bus_hold_flag)
                                        cdns_i2c_clear_bus_hold(id);
                        }
                        if (cdns_i2c_error_check(id))
                                return;
                        if (cdns_is_holdquirk(id, updatetx))
                                break;
                }

                /*
                 * The controller sends NACK to the slave/target when transfer size
                 * register reaches zero without considering the HOLD bit.
                 * This workaround is implemented for large data transfers to
                 * maintain transfer size non-zero while performing a large
                 * receive operation.
                 */
                if (cdns_is_holdquirk(id, updatetx)) {
                        /* wait while fifo is full */
                        while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
                               (id->curr_recv_count - id->fifo_depth))
                                ;

                        /*
                         * Check number of bytes to be received against maximum
                         * transfer size and update register accordingly.
                         */
                        if ((id->recv_count - id->fifo_depth) >
                            id->transfer_size) {
                                cdns_i2c_writereg(id->transfer_size,
                                                  CDNS_I2C_XFER_SIZE_OFFSET);
                                id->curr_recv_count = id->transfer_size +
                                                      id->fifo_depth;
                        } else {
                                cdns_i2c_writereg(id->recv_count -
                                                  id->fifo_depth,
                                                  CDNS_I2C_XFER_SIZE_OFFSET);
                                id->curr_recv_count = id->recv_count;
                        }
                }
        }

        /* Clear hold (if not repeated start) */
        if (!id->recv_count && !id->bus_hold_flag)
                cdns_i2c_clear_bus_hold(id);
}

/**
 * cdns_i2c_mrecv - Prepare and start a master receive operation
 * @id:         pointer to the i2c device structure
 */
static void cdns_i2c_mrecv(struct cdns_i2c *id)
{
        unsigned int ctrl_reg;
        unsigned int isr_status;
        unsigned long flags;
        bool hold_clear = false;
        bool irq_save = false;

        u32 addr;

        id->p_recv_buf = id->p_msg->buf;
        id->recv_count = id->p_msg->len;

        /* Put the controller in master receive mode and clear the FIFO */
        ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
        ctrl_reg |= CDNS_I2C_CR_RW | CDNS_I2C_CR_CLR_FIFO;

        /*
         * Receive up to I2C_SMBUS_BLOCK_MAX data bytes, plus one message length
         * byte, plus one checksum byte if PEC is enabled. p_msg->len will be 2 if
         * PEC is enabled, otherwise 1.
         */
        if (id->p_msg->flags & I2C_M_RECV_LEN)
                id->recv_count = I2C_SMBUS_BLOCK_MAX + id->p_msg->len;

        id->curr_recv_count = id->recv_count;

        /*
         * Check for the message size against FIFO depth and set the
         * 'hold bus' bit if it is greater than FIFO depth.
         */
        if (id->recv_count > id->fifo_depth)
                ctrl_reg |= CDNS_I2C_CR_HOLD;

        cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);

        /* Clear the interrupts in interrupt status register */
        isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

        /*
         * The no. of bytes to receive is checked against the limit of
         * max transfer size. Set transfer size register with no of bytes
         * receive if it is less than transfer size and transfer size if
         * it is more. Enable the interrupts.
         */
        if (id->recv_count > id->transfer_size) {
                cdns_i2c_writereg(id->transfer_size,
                                  CDNS_I2C_XFER_SIZE_OFFSET);
                id->curr_recv_count = id->transfer_size;
        } else {
                cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
        }

        /* Determine hold_clear based on number of bytes to receive and hold flag */
        if (!id->bus_hold_flag && id->recv_count <= id->fifo_depth) {
                if (ctrl_reg & CDNS_I2C_CR_HOLD) {
                        hold_clear = true;
                        if (id->quirks & CDNS_I2C_BROKEN_HOLD_BIT)
                                irq_save = true;
                }
        }

        addr = id->p_msg->addr;
        addr &= CDNS_I2C_ADDR_MASK;

        if (hold_clear) {
                ctrl_reg &= ~CDNS_I2C_CR_HOLD;
                ctrl_reg &= ~CDNS_I2C_CR_CLR_FIFO;
                /*
                 * In case of Xilinx Zynq SOC, clear the HOLD bit before transfer size
                 * register reaches '0'. This is an IP bug which causes transfer size
                 * register overflow to 0xFF. To satisfy this timing requirement,
                 * disable the interrupts on current processor core between register
                 * writes to slave address register and control register.
                 */
                if (irq_save)
                        local_irq_save(flags);

                cdns_i2c_writereg(addr, CDNS_I2C_ADDR_OFFSET);
                cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
                /* Read it back to avoid bufferring and make sure write happens */
                cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);

                if (irq_save)
                        local_irq_restore(flags);
        } else {
                cdns_i2c_writereg(addr, CDNS_I2C_ADDR_OFFSET);
        }

        if (!id->atomic)
                cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
        else
                cdns_i2c_mrecv_atomic(id);
}

static void cdns_i2c_msend_rem_atomic(struct cdns_i2c *id)
{
        while (id->send_count) {
                unsigned int avail_bytes;
                unsigned int bytes_to_send;

                avail_bytes = id->fifo_depth - cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
                if (id->send_count > avail_bytes)
                        bytes_to_send = avail_bytes;
                else
                        bytes_to_send = id->send_count;

                while (bytes_to_send--) {
                        cdns_i2c_writereg((*id->p_send_buf++), CDNS_I2C_DATA_OFFSET);
                        id->send_count--;
                }
                if (cdns_i2c_error_check(id))
                        return;
        }

        if (!id->send_count && !id->bus_hold_flag)
                cdns_i2c_clear_bus_hold(id);
}

/**
 * cdns_i2c_msend - Prepare and start a master send operation
 * @id:         pointer to the i2c device
 */
static void cdns_i2c_msend(struct cdns_i2c *id)
{
        unsigned int avail_bytes;
        unsigned int bytes_to_send;
        unsigned int ctrl_reg;
        unsigned int isr_status;

        id->p_recv_buf = NULL;
        id->p_send_buf = id->p_msg->buf;
        id->send_count = id->p_msg->len;

        /* Set the controller in Master transmit mode and clear the FIFO. */
        ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
        ctrl_reg &= ~CDNS_I2C_CR_RW;
        ctrl_reg |= CDNS_I2C_CR_CLR_FIFO;

        /*
         * Check for the message size against FIFO depth and set the
         * 'hold bus' bit if it is greater than FIFO depth.
         */
        if (id->send_count > id->fifo_depth)
                ctrl_reg |= CDNS_I2C_CR_HOLD;
        cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);

        /* Clear the interrupts in interrupt status register. */
        isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);

        /*
         * Calculate the space available in FIFO. Check the message length
         * against the space available, and fill the FIFO accordingly.
         * Enable the interrupts.
         */
        avail_bytes = id->fifo_depth -
                                cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);

        if (id->send_count > avail_bytes)
                bytes_to_send = avail_bytes;
        else
                bytes_to_send = id->send_count;

        while (bytes_to_send--) {
                cdns_i2c_writereg((*(id->p_send_buf)++), CDNS_I2C_DATA_OFFSET);
                id->send_count--;
        }

        /*
         * Clear the bus hold flag if there is no more data
         * and if it is the last message.
         */
        if (!id->bus_hold_flag && !id->send_count)
                cdns_i2c_clear_bus_hold(id);
        /* Set the slave address in address register - triggers operation. */
        cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
                                                CDNS_I2C_ADDR_OFFSET);

        if (!id->atomic)
                cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
        else if (id->send_count > 0)
                cdns_i2c_msend_rem_atomic(id);
}

/**
 * cdns_i2c_master_reset - Reset the interface
 * @adap:       pointer to the i2c adapter driver instance
 *
 * This function cleanup the fifos, clear the hold bit and status
 * and disable the interrupts.
 */
static void cdns_i2c_master_reset(struct i2c_adapter *adap)
{
        struct cdns_i2c *id = adap->algo_data;
        u32 regval;

        /* Disable the interrupts */
        cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK, CDNS_I2C_IDR_OFFSET);
        /* Clear the hold bit and fifos */
        regval = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
        regval &= ~CDNS_I2C_CR_HOLD;
        regval |= CDNS_I2C_CR_CLR_FIFO;
        cdns_i2c_writereg(regval, CDNS_I2C_CR_OFFSET);
        /* Update the transfercount register to zero */
        cdns_i2c_writereg(0, CDNS_I2C_XFER_SIZE_OFFSET);
        /* Clear the interrupt status register */
        regval = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
        cdns_i2c_writereg(regval, CDNS_I2C_ISR_OFFSET);
        /* Clear the status register */
        regval = cdns_i2c_readreg(CDNS_I2C_SR_OFFSET);
        cdns_i2c_writereg(regval, CDNS_I2C_SR_OFFSET);
}

static int cdns_i2c_process_msg(struct cdns_i2c *id, struct i2c_msg *msg,
                struct i2c_adapter *adap)
{
        unsigned long time_left, msg_timeout;
        u32 reg;

        id->p_msg = msg;
        id->err_status = 0;
        if (!id->atomic)
                reinit_completion(&id->xfer_done);

        /* Check for the TEN Bit mode on each msg */
        reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
        if (msg->flags & I2C_M_TEN) {
                if (reg & CDNS_I2C_CR_NEA)
                        cdns_i2c_writereg(reg & ~CDNS_I2C_CR_NEA,
                                        CDNS_I2C_CR_OFFSET);
        } else {
                if (!(reg & CDNS_I2C_CR_NEA))
                        cdns_i2c_writereg(reg | CDNS_I2C_CR_NEA,
                                        CDNS_I2C_CR_OFFSET);
        }

        /* Check for the R/W flag on each msg */
        if (msg->flags & I2C_M_RD)
                cdns_i2c_mrecv(id);
        else
                cdns_i2c_msend(id);

        /* Minimal time to execute this message */
        msg_timeout = msecs_to_jiffies((1000 * msg->len * BITS_PER_BYTE) / id->i2c_clk);

        /*
         * Plus some wiggle room.
         * For non-atomic contexts, 500 ms is added to the timeout.
         * For atomic contexts, 2000 ms is added because transfers happen in polled
         * mode, requiring more time to account for the polling overhead.
         */
        if (!id->atomic)
                msg_timeout += msecs_to_jiffies(500);
        else
                msg_timeout += msecs_to_jiffies(2000);

        if (msg_timeout < adap->timeout)
                msg_timeout = adap->timeout;

        if (!id->atomic) {
                /* Wait for the signal of completion */
                time_left = wait_for_completion_timeout(&id->xfer_done, msg_timeout);
        } else {
                /* 0 is success, -ETIMEDOUT is error */
                time_left = !readl_poll_timeout_atomic(id->membase + CDNS_I2C_ISR_OFFSET,
                                                       reg, (reg & CDNS_I2C_IXR_COMP),
                                                       CDNS_I2C_POLL_US_ATOMIC, msg_timeout);
        }

        if (time_left == 0) {
                cdns_i2c_master_reset(adap);
                return -ETIMEDOUT;
        }

        cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK,
                          CDNS_I2C_IDR_OFFSET);

        /* If it is bus arbitration error, try again */
        if (id->err_status & CDNS_I2C_IXR_ARB_LOST)
                return -EAGAIN;

        if (msg->flags & I2C_M_RECV_LEN)
                msg->len += min_t(unsigned int, msg->buf[0], I2C_SMBUS_BLOCK_MAX);

        return 0;
}

static int cdns_i2c_master_common_xfer(struct i2c_adapter *adap,
                                       struct i2c_msg *msgs,
                                       int num)
{
        int ret, count;
        u32 reg;
        struct cdns_i2c *id = adap->algo_data;
        bool hold_quirk;

        /* Check if the bus is free */
        if (!id->atomic)
                ret = readl_relaxed_poll_timeout(id->membase + CDNS_I2C_SR_OFFSET,
                                                 reg,
                                                 !(reg & CDNS_I2C_SR_BA),
                                                 CDNS_I2C_POLL_US, CDNS_I2C_TIMEOUT_US);
        else
                ret = readl_poll_timeout_atomic(id->membase + CDNS_I2C_SR_OFFSET,
                                                reg,
                                                !(reg & CDNS_I2C_SR_BA),
                                                CDNS_I2C_POLL_US_ATOMIC, CDNS_I2C_TIMEOUT_US);
        if (ret) {
                ret = -EAGAIN;
                if (id->adap.bus_recovery_info)
                        i2c_recover_bus(adap);
                return ret;
        }

        hold_quirk = !!(id->quirks & CDNS_I2C_BROKEN_HOLD_BIT);
        /*
         * Set the flag to one when multiple messages are to be
         * processed with a repeated start.
         */
        if (num > 1) {
                /*
                 * This controller does not give completion interrupt after a
                 * master receive message if HOLD bit is set (repeated start),
                 * resulting in SW timeout. Hence, if a receive message is
                 * followed by any other message, an error is returned
                 * indicating that this sequence is not supported.
                 */
                for (count = 0; (count < num - 1 && hold_quirk); count++) {
                        if (msgs[count].flags & I2C_M_RD) {
                                dev_warn(adap->dev.parent,
                                         "Can't do repeated start after a receive message\n");
                                return -EOPNOTSUPP;
                        }
                }
                id->bus_hold_flag = 1;
                reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
                reg |= CDNS_I2C_CR_HOLD;
                cdns_i2c_writereg(reg, CDNS_I2C_CR_OFFSET);
        } else {
                id->bus_hold_flag = 0;
        }

        /* Process the msg one by one */
        for (count = 0; count < num; count++, msgs++) {
                if (count == (num - 1))
                        id->bus_hold_flag = 0;

                ret = cdns_i2c_process_msg(id, msgs, adap);
                if (ret)
                        return ret;

                /* Report the other error interrupts to application */
                if (id->err_status || id->err_status_atomic) {
                        cdns_i2c_master_reset(adap);

                        if (id->err_status & CDNS_I2C_IXR_NACK)
                                return -ENXIO;

                        return -EIO;
                }
        }
        return 0;
}

/**
 * cdns_i2c_master_xfer - The main i2c transfer function
 * @adap:       pointer to the i2c adapter driver instance
 * @msgs:       pointer to the i2c message structure
 * @num:        the number of messages to transfer
 *
 * Initiates the send/recv activity based on the transfer message received.
 *
 * Return: number of msgs processed on success, negative error otherwise
 */
static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                                int num)
{
        int ret;
        struct cdns_i2c *id = adap->algo_data;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        bool change_role = false;
#endif

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

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        /* Check i2c operating mode and switch if possible */
        if (id->dev_mode == CDNS_I2C_MODE_SLAVE) {
                if (id->slave_state != CDNS_I2C_SLAVE_STATE_IDLE) {
                        ret = -EAGAIN;
                        goto out;
                }

                /* Set mode to master */
                cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);

                /* Mark flag to change role once xfer is completed */
                change_role = true;
        }
#endif

        ret = cdns_i2c_master_common_xfer(adap, msgs, num);
        if (!ret)
                ret = num;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
out:
        /* Switch i2c mode to slave */
        if (change_role)
                cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);
#endif

        pm_runtime_put_autosuspend(id->dev);
        return ret;
}

/**
 * cdns_i2c_master_xfer_atomic - The i2c transfer function in atomic mode
 * @adap:       pointer to the i2c adapter driver instance
 * @msgs:       pointer to the i2c message structure
 * @num:        the number of messages to transfer
 *
 * Return: number of msgs processed on success, negative error otherwise
 */
static int cdns_i2c_master_xfer_atomic(struct i2c_adapter *adap, struct i2c_msg *msgs,
                                       int num)
{
        int ret;
        struct cdns_i2c *id = adap->algo_data;

        ret = cdns_i2c_runtime_resume(id->dev);
        if (ret)
                return ret;

        if (id->quirks & CDNS_I2C_BROKEN_HOLD_BIT) {
                dev_warn(id->adap.dev.parent,
                         "Atomic xfer not supported for version 1.0\n");
                return 0;
        }

        id->atomic = true;
        ret = cdns_i2c_master_common_xfer(adap, msgs, num);
        if (!ret)
                ret = num;

        id->atomic = false;
        cdns_i2c_runtime_suspend(id->dev);

        return ret;
}

/**
 * cdns_i2c_func - Returns the supported features of the I2C driver
 * @adap:       pointer to the i2c adapter structure
 *
 * Return: 32 bit value, each bit corresponding to a feature
 */
static u32 cdns_i2c_func(struct i2c_adapter *adap)
{
        u32 func = I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR |
                        (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) |
                        I2C_FUNC_SMBUS_BLOCK_DATA;

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        func |= I2C_FUNC_SLAVE;
#endif

        return func;
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static int cdns_reg_slave(struct i2c_client *slave)
{
        int ret;
        struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
                                                                        adap);

        if (id->slave)
                return -EBUSY;

        if (slave->flags & I2C_CLIENT_TEN)
                return -EAFNOSUPPORT;

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

        /* Store slave information */
        id->slave = slave;

        /* Enable I2C slave */
        cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);

        return 0;
}

static int cdns_unreg_slave(struct i2c_client *slave)
{
        struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
                                                                        adap);

        pm_runtime_put(id->dev);

        /* Remove slave information */
        id->slave = NULL;

        /* Enable I2C master */
        cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);

        return 0;
}
#endif

static const struct i2c_algorithm cdns_i2c_algo = {
        .xfer = cdns_i2c_master_xfer,
        .xfer_atomic = cdns_i2c_master_xfer_atomic,
        .functionality = cdns_i2c_func,
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        .reg_slave = cdns_reg_slave,
        .unreg_slave = cdns_unreg_slave,
#endif
};

/**
 * cdns_i2c_calc_divs - Calculate clock dividers
 * @f:          I2C clock frequency
 * @input_clk:  Input clock frequency
 * @a:          First divider (return value)
 * @b:          Second divider (return value)
 *
 * f is used as input and output variable. As input it is used as target I2C
 * frequency. On function exit f holds the actually resulting I2C frequency.
 *
 * Return: 0 on success, negative errno otherwise.
 */
static int cdns_i2c_calc_divs(unsigned long *f, unsigned long input_clk,
                unsigned int *a, unsigned int *b)
{
        unsigned long fscl = *f, best_fscl = *f, actual_fscl, temp;
        unsigned int div_a, div_b, calc_div_a = 0, calc_div_b = 0;
        unsigned int last_error, current_error;

        /* calculate (divisor_a+1) x (divisor_b+1) */
        temp = input_clk / (22 * fscl);

        /*
         * If the calculated value is negative or 0, the fscl input is out of
         * range. Return error.
         */
        if (!temp || (temp > (CDNS_I2C_DIVA_MAX * CDNS_I2C_DIVB_MAX)))
                return -EINVAL;

        last_error = -1;
        for (div_a = 0; div_a < CDNS_I2C_DIVA_MAX; div_a++) {
                div_b = DIV_ROUND_UP(input_clk, 22 * fscl * (div_a + 1));

                if ((div_b < 1) || (div_b > CDNS_I2C_DIVB_MAX))
                        continue;
                div_b--;

                actual_fscl = input_clk / (22 * (div_a + 1) * (div_b + 1));

                if (actual_fscl > fscl)
                        continue;

                current_error = fscl - actual_fscl;

                if (last_error > current_error) {
                        calc_div_a = div_a;
                        calc_div_b = div_b;
                        best_fscl = actual_fscl;
                        last_error = current_error;
                }
        }

        *a = calc_div_a;
        *b = calc_div_b;
        *f = best_fscl;

        return 0;
}

/**
 * cdns_i2c_setclk - This function sets the serial clock rate for the I2C device
 * @clk_in:     I2C clock input frequency in Hz
 * @id:         Pointer to the I2C device structure
 *
 * The device must be idle rather than busy transferring data before setting
 * these device options.
 * The data rate is set by values in the control register.
 * The formula for determining the correct register values is
 *      Fscl = Fpclk/(22 x (divisor_a+1) x (divisor_b+1))
 * See the hardware data sheet for a full explanation of setting the serial
 * clock rate. The clock can not be faster than the input clock divide by 22.
 * The two most common clock rates are 100KHz and 400KHz.
 *
 * Return: 0 on success, negative error otherwise
 */
static int cdns_i2c_setclk(unsigned long clk_in, struct cdns_i2c *id)
{
        unsigned int div_a, div_b;
        unsigned int ctrl_reg;
        int ret = 0;
        unsigned long fscl = id->i2c_clk;

        ret = cdns_i2c_calc_divs(&fscl, clk_in, &div_a, &div_b);
        if (ret)
                return ret;

        ctrl_reg = id->ctrl_reg;
        ctrl_reg &= ~(CDNS_I2C_CR_DIVA_MASK | CDNS_I2C_CR_DIVB_MASK);
        ctrl_reg |= ((div_a << CDNS_I2C_CR_DIVA_SHIFT) |
                        (div_b << CDNS_I2C_CR_DIVB_SHIFT));
        id->ctrl_reg = ctrl_reg;
        cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        id->ctrl_reg_diva_divb = ctrl_reg & (CDNS_I2C_CR_DIVA_MASK |
                                 CDNS_I2C_CR_DIVB_MASK);
#endif
        return 0;
}

/**
 * cdns_i2c_clk_notifier_cb - Clock rate change callback
 * @nb:         Pointer to notifier block
 * @event:      Notification reason
 * @data:       Pointer to notification data object
 *
 * This function is called when the cdns_i2c input clock frequency changes.
 * The callback checks whether a valid bus frequency can be generated after the
 * change. If so, the change is acknowledged, otherwise the change is aborted.
 * New dividers are written to the HW in the pre- or post change notification
 * depending on the scaling direction.
 *
 * Return:      NOTIFY_STOP if the rate change should be aborted, NOTIFY_OK
 *              to acknowledge the change, NOTIFY_DONE if the notification is
 *              considered irrelevant.
 */
static int cdns_i2c_clk_notifier_cb(struct notifier_block *nb, unsigned long
                event, void *data)
{
        struct clk_notifier_data *ndata = data;
        struct cdns_i2c *id = to_cdns_i2c(nb);

        if (pm_runtime_suspended(id->dev))
                return NOTIFY_OK;

        switch (event) {
        case PRE_RATE_CHANGE:
        {
                unsigned long input_clk = ndata->new_rate;
                unsigned long fscl = id->i2c_clk;
                unsigned int div_a, div_b;
                int ret;

                ret = cdns_i2c_calc_divs(&fscl, input_clk, &div_a, &div_b);
                if (ret) {
                        dev_warn(id->adap.dev.parent,
                                        "clock rate change rejected\n");
                        return NOTIFY_STOP;
                }

                /* scale up */
                if (ndata->new_rate > ndata->old_rate)
                        cdns_i2c_setclk(ndata->new_rate, id);

                return NOTIFY_OK;
        }
        case POST_RATE_CHANGE:
                id->input_clk = ndata->new_rate;
                /* scale down */
                if (ndata->new_rate < ndata->old_rate)
                        cdns_i2c_setclk(ndata->new_rate, id);
                return NOTIFY_OK;
        case ABORT_RATE_CHANGE:
                /* scale up */
                if (ndata->new_rate > ndata->old_rate)
                        cdns_i2c_setclk(ndata->old_rate, id);
                return NOTIFY_OK;
        default:
                return NOTIFY_DONE;
        }
}

static int __maybe_unused cdns_i2c_suspend(struct device *dev)
{
        struct cdns_i2c *xi2c = dev_get_drvdata(dev);

        i2c_mark_adapter_suspended(&xi2c->adap);

        if (!pm_runtime_status_suspended(dev))
                return cdns_i2c_runtime_suspend(dev);

        return 0;
}

static int __maybe_unused cdns_i2c_resume(struct device *dev)
{
        struct cdns_i2c *xi2c = dev_get_drvdata(dev);
        int err;

        err = cdns_i2c_runtime_resume(dev);
        if (err)
                return err;

        if (pm_runtime_status_suspended(dev)) {
                err = cdns_i2c_runtime_suspend(dev);
                if (err)
                        return err;
        }

        i2c_mark_adapter_resumed(&xi2c->adap);

        return 0;
}

static const struct dev_pm_ops cdns_i2c_dev_pm_ops = {
        SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(cdns_i2c_suspend, cdns_i2c_resume)
        SET_RUNTIME_PM_OPS(cdns_i2c_runtime_suspend,
                           cdns_i2c_runtime_resume, NULL)
};

static const struct cdns_platform_data r1p10_i2c_def = {
        .quirks = CDNS_I2C_BROKEN_HOLD_BIT,
};

static const struct of_device_id cdns_i2c_of_match[] = {
        { .compatible = "cdns,i2c-r1p10", .data = &r1p10_i2c_def },
        { .compatible = "cdns,i2c-r1p14",},
        { /* end of table */ }
};
MODULE_DEVICE_TABLE(of, cdns_i2c_of_match);

/**
 * cdns_i2c_detect_transfer_size - Detect the maximum transfer size supported
 * @id: Device private data structure
 *
 * Detect the maximum transfer size that is supported by this instance of the
 * Cadence I2C controller.
 */
static void cdns_i2c_detect_transfer_size(struct cdns_i2c *id)
{
        u32 val;

        /*
         * Writing to the transfer size register is only possible if these two bits
         * are set in the control register.
         */
        cdns_i2c_writereg(CDNS_I2C_CR_MS | CDNS_I2C_CR_RW, CDNS_I2C_CR_OFFSET);

        /*
         * The number of writable bits of the transfer size register can be between
         * 4 and 8. This is a controlled through a synthesis parameter of the IP
         * core and can vary from instance to instance. The unused MSBs always read
         * back as 0. Writing 0xff and then reading the value back will report the
         * maximum supported transfer size.
         */
        cdns_i2c_writereg(CDNS_I2C_MAX_TRANSFER_SIZE, CDNS_I2C_XFER_SIZE_OFFSET);
        val = cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
        id->transfer_size = CDNS_I2C_TRANSFER_SIZE(val);
        cdns_i2c_writereg(0, CDNS_I2C_XFER_SIZE_OFFSET);
        cdns_i2c_writereg(0, CDNS_I2C_CR_OFFSET);
}

/**
 * cdns_i2c_probe - Platform registration call
 * @pdev:       Handle to the platform device structure
 *
 * This function does all the memory allocation and registration for the i2c
 * device. User can modify the address mode to 10 bit address mode using the
 * ioctl call with option I2C_TENBIT.
 *
 * Return: 0 on success, negative error otherwise
 */
static int cdns_i2c_probe(struct platform_device *pdev)
{
        struct resource *r_mem;
        struct cdns_i2c *id;
        int ret, irq;
        const struct of_device_id *match;

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

        id->dev = &pdev->dev;
        platform_set_drvdata(pdev, id);

        match = of_match_node(cdns_i2c_of_match, pdev->dev.of_node);
        if (match && match->data) {
                const struct cdns_platform_data *data = match->data;
                id->quirks = data->quirks;
        }

        id->rinfo.pinctrl = devm_pinctrl_get(&pdev->dev);
        if (IS_ERR(id->rinfo.pinctrl)) {
                int err = PTR_ERR(id->rinfo.pinctrl);

                dev_info(&pdev->dev, "can't get pinctrl, bus recovery not supported\n");
                if (err != -ENODEV)
                        return err;
        } else {
                id->adap.bus_recovery_info = &id->rinfo;
        }

        id->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r_mem);
        if (IS_ERR(id->membase))
                return PTR_ERR(id->membase);

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

        id->adap.owner = THIS_MODULE;
        id->adap.dev.of_node = pdev->dev.of_node;
        id->adap.algo = &cdns_i2c_algo;
        id->adap.timeout = CDNS_I2C_TIMEOUT;
        id->adap.retries = 3;           /* Default retry value. */
        id->adap.algo_data = id;
        id->adap.dev.parent = &pdev->dev;
        init_completion(&id->xfer_done);
        snprintf(id->adap.name, sizeof(id->adap.name),
                 "Cadence I2C at %08lx", (unsigned long)r_mem->start);

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

        id->reset = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
        if (IS_ERR(id->reset))
                return dev_err_probe(&pdev->dev, PTR_ERR(id->reset),
                                     "Failed to request reset.\n");

        ret = reset_control_deassert(id->reset);
        if (ret)
                return dev_err_probe(&pdev->dev, ret,
                                     "Failed to de-assert reset.\n");

        pm_runtime_set_autosuspend_delay(id->dev, CNDS_I2C_PM_TIMEOUT);
        pm_runtime_use_autosuspend(id->dev);
        pm_runtime_set_active(id->dev);
        pm_runtime_enable(id->dev);

        id->clk_rate_change_nb.notifier_call = cdns_i2c_clk_notifier_cb;
        if (clk_notifier_register(id->clk, &id->clk_rate_change_nb))
                dev_warn(&pdev->dev, "Unable to register clock notifier.\n");
        id->input_clk = clk_get_rate(id->clk);

        ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
                        &id->i2c_clk);
        if (ret || (id->i2c_clk > I2C_MAX_FAST_MODE_FREQ))
                id->i2c_clk = I2C_MAX_STANDARD_MODE_FREQ;

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        /* Set initial mode to master */
        id->dev_mode = CDNS_I2C_MODE_MASTER;
        id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
#endif
        id->ctrl_reg = CDNS_I2C_CR_ACK_EN | CDNS_I2C_CR_NEA | CDNS_I2C_CR_MS;

        id->fifo_depth = CDNS_I2C_FIFO_DEPTH_DEFAULT;
        of_property_read_u32(pdev->dev.of_node, "fifo-depth", &id->fifo_depth);

        cdns_i2c_detect_transfer_size(id);

        ret = cdns_i2c_setclk(id->input_clk, id);
        if (ret) {
                dev_err(&pdev->dev, "invalid SCL clock: %u Hz\n", id->i2c_clk);
                ret = -EINVAL;
                goto err_clk_notifier_unregister;
        }

        ret = devm_request_irq(&pdev->dev, irq, cdns_i2c_isr, 0,
                                 DRIVER_NAME, id);
        if (ret) {
                dev_err(&pdev->dev, "cannot get irq %d\n", irq);
                goto err_clk_notifier_unregister;
        }
        cdns_i2c_init(id);

        ret = i2c_add_adapter(&id->adap);
        if (ret < 0)
                goto err_clk_notifier_unregister;

        dev_info(&pdev->dev, "%u kHz mmio %08lx irq %d\n",
                 id->i2c_clk / 1000, (unsigned long)r_mem->start, irq);

        return 0;

err_clk_notifier_unregister:
        clk_notifier_unregister(id->clk, &id->clk_rate_change_nb);
        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(&pdev->dev);
        reset_control_assert(id->reset);
        return ret;
}

/**
 * cdns_i2c_remove - Unregister the device after releasing the resources
 * @pdev:       Handle to the platform device structure
 *
 * This function frees all the resources allocated to the device.
 *
 * Return: 0 always
 */
static void cdns_i2c_remove(struct platform_device *pdev)
{
        struct cdns_i2c *id = platform_get_drvdata(pdev);

        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(&pdev->dev);
        pm_runtime_dont_use_autosuspend(&pdev->dev);

        i2c_del_adapter(&id->adap);
        clk_notifier_unregister(id->clk, &id->clk_rate_change_nb);
        reset_control_assert(id->reset);
}

static struct platform_driver cdns_i2c_drv = {
        .driver = {
                .name  = DRIVER_NAME,
                .of_match_table = cdns_i2c_of_match,
                .pm = &cdns_i2c_dev_pm_ops,
        },
        .probe  = cdns_i2c_probe,
        .remove = cdns_i2c_remove,
};

module_platform_driver(cdns_i2c_drv);

MODULE_AUTHOR("Xilinx Inc.");
MODULE_DESCRIPTION("Cadence I2C bus driver");
MODULE_LICENSE("GPL");