// SPDX-License-Identifier: GPL-2.0-or-later
/* linux/drivers/i2c/busses/i2c-s3c2410.c
 *
 * Copyright (C) 2004,2005,2009 Simtec Electronics
 *      Ben Dooks <ben@simtec.co.uk>
 *
 * S3C2410 I2C Controller
*/

#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/gpio/consumer.h>
#include <linux/pinctrl/consumer.h>
#include <linux/mfd/syscon.h>
#include <linux/regmap.h>

#include <asm/irq.h>

#include <linux/platform_data/i2c-s3c2410.h>

/* see s3c2410x user guide, v1.1, section 9 (p447) for more info */

#define S3C2410_IICCON                  0x00
#define S3C2410_IICSTAT                 0x04
#define S3C2410_IICADD                  0x08
#define S3C2410_IICDS                   0x0C
#define S3C2440_IICLC                   0x10

#define S3C2410_IICCON_ACKEN            (1 << 7)
#define S3C2410_IICCON_TXDIV_16         (0 << 6)
#define S3C2410_IICCON_TXDIV_512        (1 << 6)
#define S3C2410_IICCON_IRQEN            (1 << 5)
#define S3C2410_IICCON_IRQPEND          (1 << 4)
#define S3C2410_IICCON_SCALE(x)         ((x) & 0xf)
#define S3C2410_IICCON_SCALEMASK        (0xf)

#define S3C2410_IICSTAT_MASTER_RX       (2 << 6)
#define S3C2410_IICSTAT_MASTER_TX       (3 << 6)
#define S3C2410_IICSTAT_SLAVE_RX        (0 << 6)
#define S3C2410_IICSTAT_SLAVE_TX        (1 << 6)
#define S3C2410_IICSTAT_MODEMASK        (3 << 6)

#define S3C2410_IICSTAT_START           (1 << 5)
#define S3C2410_IICSTAT_BUSBUSY         (1 << 5)
#define S3C2410_IICSTAT_TXRXEN          (1 << 4)
#define S3C2410_IICSTAT_ARBITR          (1 << 3)
#define S3C2410_IICSTAT_ASSLAVE         (1 << 2)
#define S3C2410_IICSTAT_ADDR0           (1 << 1)
#define S3C2410_IICSTAT_LASTBIT         (1 << 0)

#define S3C2410_IICLC_SDA_DELAY0        (0 << 0)
#define S3C2410_IICLC_SDA_DELAY5        (1 << 0)
#define S3C2410_IICLC_SDA_DELAY10       (2 << 0)
#define S3C2410_IICLC_SDA_DELAY15       (3 << 0)
#define S3C2410_IICLC_SDA_DELAY_MASK    (3 << 0)

#define S3C2410_IICLC_FILTER_ON         (1 << 2)

/* Treat S3C2410 as baseline hardware, anything else is supported via quirks */
#define QUIRK_S3C2440           (1 << 0)
#define QUIRK_HDMIPHY           (1 << 1)
#define QUIRK_NO_GPIO           (1 << 2)
#define QUIRK_POLL              (1 << 3)
#define QUIRK_ATOMIC            (1 << 4)

/* Max time to wait for bus to become idle after a xfer (in us) */
#define S3C2410_IDLE_TIMEOUT    5000

/* Exynos5 Sysreg offset */
#define EXYNOS5_SYS_I2C_CFG     0x0234

/* i2c controller state */
enum s3c24xx_i2c_state {
        STATE_IDLE,
        STATE_START,
        STATE_READ,
        STATE_WRITE,
        STATE_STOP
};

struct s3c24xx_i2c {
        wait_queue_head_t       wait;
        kernel_ulong_t          quirks;

        struct i2c_msg          *msg;
        unsigned int            msg_num;
        unsigned int            msg_idx;
        unsigned int            msg_ptr;

        unsigned int            tx_setup;
        unsigned int            irq;

        enum s3c24xx_i2c_state  state;
        unsigned long           clkrate;

        void __iomem            *regs;
        struct clk              *clk;
        struct device           *dev;
        struct i2c_adapter      adap;

        struct s3c2410_platform_i2c     *pdata;
        struct gpio_desc        *gpios[2];
        struct pinctrl          *pctrl;
        struct regmap           *sysreg;
        unsigned int            sys_i2c_cfg;
};

static const struct platform_device_id s3c24xx_driver_ids[] = {
        {
                .name           = "s3c2410-i2c",
                .driver_data    = 0,
        }, {
                .name           = "s3c2440-i2c",
                .driver_data    = QUIRK_S3C2440,
        }, {
                .name           = "s3c2440-hdmiphy-i2c",
                .driver_data    = QUIRK_S3C2440 | QUIRK_HDMIPHY | QUIRK_NO_GPIO,
        }, { }
};
MODULE_DEVICE_TABLE(platform, s3c24xx_driver_ids);

static void i2c_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat);

#ifdef CONFIG_OF
static const struct of_device_id s3c24xx_i2c_match[] = {
        { .compatible = "samsung,s3c2440-i2c", .data = (void *)QUIRK_S3C2440 },
        { .compatible = "samsung,s3c2440-hdmiphy-i2c",
          .data = (void *)(QUIRK_S3C2440 | QUIRK_HDMIPHY | QUIRK_NO_GPIO) },
        { .compatible = "samsung,exynos5-sata-phy-i2c",
          .data = (void *)(QUIRK_S3C2440 | QUIRK_POLL | QUIRK_NO_GPIO) },
        {},
};
MODULE_DEVICE_TABLE(of, s3c24xx_i2c_match);
#endif

/*
 * Get controller type either from device tree or platform device variant.
 */
static inline kernel_ulong_t s3c24xx_get_device_quirks(struct platform_device *pdev)
{
        if (pdev->dev.of_node)
                return (kernel_ulong_t)of_device_get_match_data(&pdev->dev);

        return platform_get_device_id(pdev)->driver_data;
}

/*
 * Complete the message and wake up the caller, using the given return code,
 * or zero to mean ok.
 */
static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret)
{
        dev_dbg(i2c->dev, "master_complete %d\n", ret);

        i2c->msg_ptr = 0;
        i2c->msg = NULL;
        i2c->msg_idx++;
        i2c->msg_num = 0;
        if (ret)
                i2c->msg_idx = ret;

        if (!(i2c->quirks & (QUIRK_POLL | QUIRK_ATOMIC)))
                wake_up(&i2c->wait);
}

static inline void s3c24xx_i2c_disable_ack(struct s3c24xx_i2c *i2c)
{
        unsigned long tmp;

        tmp = readl(i2c->regs + S3C2410_IICCON);
        writel(tmp & ~S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);
}

static inline void s3c24xx_i2c_enable_ack(struct s3c24xx_i2c *i2c)
{
        unsigned long tmp;

        tmp = readl(i2c->regs + S3C2410_IICCON);
        writel(tmp | S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);
}

/* irq enable/disable functions */
static inline void s3c24xx_i2c_disable_irq(struct s3c24xx_i2c *i2c)
{
        unsigned long tmp;

        tmp = readl(i2c->regs + S3C2410_IICCON);
        writel(tmp & ~S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}

static inline void s3c24xx_i2c_enable_irq(struct s3c24xx_i2c *i2c)
{
        unsigned long tmp;

        tmp = readl(i2c->regs + S3C2410_IICCON);
        writel(tmp | S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}

static bool is_ack(struct s3c24xx_i2c *i2c)
{
        int tries;

        for (tries = 50; tries; --tries) {
                unsigned long tmp = readl(i2c->regs + S3C2410_IICCON);

                if (!(tmp & S3C2410_IICCON_ACKEN)) {
                        /*
                         * Wait a bit for the bus to stabilize,
                         * delay estimated experimentally.
                         */
                        usleep_range(100, 200);
                        return true;
                }
                if (tmp & S3C2410_IICCON_IRQPEND) {
                        if (!(readl(i2c->regs + S3C2410_IICSTAT)
                                & S3C2410_IICSTAT_LASTBIT))
                                return true;
                }
                usleep_range(1000, 2000);
        }
        dev_err(i2c->dev, "ack was not received\n");
        return false;
}

/*
 * put the start of a message onto the bus
 */
static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c,
                                      struct i2c_msg *msg)
{
        unsigned int addr = (msg->addr & 0x7f) << 1;
        unsigned long stat;
        unsigned long iiccon;

        stat = 0;
        stat |=  S3C2410_IICSTAT_TXRXEN;

        if (msg->flags & I2C_M_RD) {
                stat |= S3C2410_IICSTAT_MASTER_RX;
                addr |= 1;
        } else
                stat |= S3C2410_IICSTAT_MASTER_TX;

        if (msg->flags & I2C_M_REV_DIR_ADDR)
                addr ^= 1;

        /* todo - check for whether ack wanted or not */
        s3c24xx_i2c_enable_ack(i2c);

        iiccon = readl(i2c->regs + S3C2410_IICCON);
        writel(stat, i2c->regs + S3C2410_IICSTAT);

        dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr);
        writeb(addr, i2c->regs + S3C2410_IICDS);

        /*
         * delay here to ensure the data byte has gotten onto the bus
         * before the transaction is started
         */
        ndelay(i2c->tx_setup);

        dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
        writel(iiccon, i2c->regs + S3C2410_IICCON);

        stat |= S3C2410_IICSTAT_START;
        writel(stat, i2c->regs + S3C2410_IICSTAT);
}

static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret)
{
        unsigned long iicstat = readl(i2c->regs + S3C2410_IICSTAT);

        dev_dbg(i2c->dev, "STOP\n");

        /*
         * The datasheet says that the STOP sequence should be:
         *  1) I2CSTAT.5 = 0    - Clear BUSY (or 'generate STOP')
         *  2) I2CCON.4 = 0     - Clear IRQPEND
         *  3) Wait until the stop condition takes effect.
         *  4*) I2CSTAT.4 = 0   - Clear TXRXEN
         *
         * Where, step "4*" is only for buses with the "HDMIPHY" quirk.
         *
         * However, after much experimentation, it appears that:
         * a) normal buses automatically clear BUSY and transition from
         *    Master->Slave when they complete generating a STOP condition.
         *    Therefore, step (3) can be done in doxfer() by polling I2CCON.4
         *    after starting the STOP generation here.
         * b) HDMIPHY bus does neither, so there is no way to do step 3.
         *    There is no indication when this bus has finished generating
         *    STOP.
         *
         * In fact, we have found that as soon as the IRQPEND bit is cleared in
         * step 2, the HDMIPHY bus generates the STOP condition, and then
         * immediately starts transferring another data byte, even though the
         * bus is supposedly stopped.  This is presumably because the bus is
         * still in "Master" mode, and its BUSY bit is still set.
         *
         * To avoid these extra post-STOP transactions on HDMI phy devices, we
         * just disable Serial Output on the bus (I2CSTAT.4 = 0) directly,
         * instead of first generating a proper STOP condition.  This should
         * float SDA & SCK terminating the transfer.  Subsequent transfers
         *  start with a proper START condition, and proceed normally.
         *
         * The HDMIPHY bus is an internal bus that always has exactly two
         * devices, the host as Master and the HDMIPHY device as the slave.
         * Skipping the STOP condition has been tested on this bus and works.
         */
        if (i2c->quirks & QUIRK_HDMIPHY) {
                /* Stop driving the I2C pins */
                iicstat &= ~S3C2410_IICSTAT_TXRXEN;
        } else {
                /* stop the transfer */
                iicstat &= ~S3C2410_IICSTAT_START;
        }
        writel(iicstat, i2c->regs + S3C2410_IICSTAT);

        i2c->state = STATE_STOP;

        s3c24xx_i2c_master_complete(i2c, ret);
        s3c24xx_i2c_disable_irq(i2c);
}

/*
 * helper functions to determine the current state in the set of
 * messages we are sending
 */

/*
 * returns TRUE if the current message is the last in the set
 */
static inline int is_lastmsg(struct s3c24xx_i2c *i2c)
{
        return i2c->msg_idx >= (i2c->msg_num - 1);
}

/*
 * returns TRUE if we this is the last byte in the current message
 */
static inline int is_msglast(struct s3c24xx_i2c *i2c)
{
        /*
         * msg->len is always 1 for the first byte of smbus block read.
         * Actual length will be read from slave. More bytes will be
         * read according to the length then.
         */
        if (i2c->msg->flags & I2C_M_RECV_LEN && i2c->msg->len == 1)
                return 0;

        return i2c->msg_ptr == i2c->msg->len-1;
}

/*
 * returns TRUE if we reached the end of the current message
 */
static inline int is_msgend(struct s3c24xx_i2c *i2c)
{
        return i2c->msg_ptr >= i2c->msg->len;
}

/*
 * process an interrupt and work out what to do
 */
static void i2c_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
{
        unsigned long tmp;
        unsigned char byte;

        switch (i2c->state) {

        case STATE_IDLE:
                dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __func__);
                goto out;

        case STATE_STOP:
                dev_err(i2c->dev, "%s: called in STATE_STOP\n", __func__);
                s3c24xx_i2c_disable_irq(i2c);
                goto out_ack;

        case STATE_START:
                /*
                 * last thing we did was send a start condition on the
                 * bus, or started a new i2c message
                 */
                if (iicstat & S3C2410_IICSTAT_LASTBIT &&
                    !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
                        /* ack was not received... */
                        dev_dbg(i2c->dev, "ack was not received\n");
                        s3c24xx_i2c_stop(i2c, -ENXIO);
                        goto out_ack;
                }

                if (i2c->msg->flags & I2C_M_RD)
                        i2c->state = STATE_READ;
                else
                        i2c->state = STATE_WRITE;

                /*
                 * Terminate the transfer if there is nothing to do
                 * as this is used by the i2c probe to find devices.
                 */
                if (is_lastmsg(i2c) && i2c->msg->len == 0) {
                        s3c24xx_i2c_stop(i2c, 0);
                        goto out_ack;
                }

                if (i2c->state == STATE_READ)
                        goto prepare_read;

                /*
                 * fall through to the write state, as we will need to
                 * send a byte as well
                 */
                fallthrough;
        case STATE_WRITE:
                /*
                 * we are writing data to the device... check for the
                 * end of the message, and if so, work out what to do
                 */
                if (!(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
                        if (iicstat & S3C2410_IICSTAT_LASTBIT) {
                                dev_dbg(i2c->dev, "WRITE: No Ack\n");

                                s3c24xx_i2c_stop(i2c, -ECONNREFUSED);
                                goto out_ack;
                        }
                }

 retry_write:

                if (!is_msgend(i2c)) {
                        byte = i2c->msg->buf[i2c->msg_ptr++];
                        writeb(byte, i2c->regs + S3C2410_IICDS);

                        /*
                         * delay after writing the byte to allow the
                         * data setup time on the bus, as writing the
                         * data to the register causes the first bit
                         * to appear on SDA, and SCL will change as
                         * soon as the interrupt is acknowledged
                         */
                        ndelay(i2c->tx_setup);

                } else if (!is_lastmsg(i2c)) {
                        /* we need to go to the next i2c message */

                        dev_dbg(i2c->dev, "WRITE: Next Message\n");

                        i2c->msg_ptr = 0;
                        i2c->msg_idx++;
                        i2c->msg++;

                        /* check to see if we need to do another message */
                        if (i2c->msg->flags & I2C_M_NOSTART) {

                                if (i2c->msg->flags & I2C_M_RD) {
                                        /*
                                         * cannot do this, the controller
                                         * forces us to send a new START
                                         * when we change direction
                                         */
                                        dev_dbg(i2c->dev,
                                                "missing START before write->read\n");
                                        s3c24xx_i2c_stop(i2c, -EINVAL);
                                        break;
                                }

                                goto retry_write;
                        } else {
                                /* send the new start */
                                s3c24xx_i2c_message_start(i2c, i2c->msg);
                                i2c->state = STATE_START;
                        }

                } else {
                        /* send stop */
                        s3c24xx_i2c_stop(i2c, 0);
                }
                break;

        case STATE_READ:
                /*
                 * we have a byte of data in the data register, do
                 * something with it, and then work out whether we are
                 * going to do any more read/write
                 */
                byte = readb(i2c->regs + S3C2410_IICDS);
                i2c->msg->buf[i2c->msg_ptr++] = byte;

                /* Add actual length to read for smbus block read */
                if (i2c->msg->flags & I2C_M_RECV_LEN && i2c->msg->len == 1)
                        i2c->msg->len += byte;
 prepare_read:
                if (is_msglast(i2c)) {
                        /* last byte of buffer */

                        if (is_lastmsg(i2c))
                                s3c24xx_i2c_disable_ack(i2c);

                } else if (is_msgend(i2c)) {
                        /*
                         * ok, we've read the entire buffer, see if there
                         * is anything else we need to do
                         */
                        if (is_lastmsg(i2c)) {
                                /* last message, send stop and complete */
                                dev_dbg(i2c->dev, "READ: Send Stop\n");

                                s3c24xx_i2c_stop(i2c, 0);
                        } else {
                                /* go to the next transfer */
                                dev_dbg(i2c->dev, "READ: Next Transfer\n");

                                i2c->msg_ptr = 0;
                                i2c->msg_idx++;
                                i2c->msg++;
                        }
                }

                break;
        }

        /* acknowlegde the IRQ and get back on with the work */

 out_ack:
        tmp = readl(i2c->regs + S3C2410_IICCON);
        tmp &= ~S3C2410_IICCON_IRQPEND;
        writel(tmp, i2c->regs + S3C2410_IICCON);
 out:
        return;
}

/*
 * top level IRQ servicing routine
 */
static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id)
{
        struct s3c24xx_i2c *i2c = dev_id;
        unsigned long status;
        unsigned long tmp;

        status = readl(i2c->regs + S3C2410_IICSTAT);

        if (status & S3C2410_IICSTAT_ARBITR) {
                /* deal with arbitration loss */
                dev_err(i2c->dev, "deal with arbitration loss\n");
        }

        if (i2c->state == STATE_IDLE) {
                dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE\n");

                tmp = readl(i2c->regs + S3C2410_IICCON);
                tmp &= ~S3C2410_IICCON_IRQPEND;
                writel(tmp, i2c->regs +  S3C2410_IICCON);
                goto out;
        }

        /*
         * pretty much this leaves us with the fact that we've
         * transmitted or received whatever byte we last sent
         */
        i2c_s3c_irq_nextbyte(i2c, status);

 out:
        return IRQ_HANDLED;
}

/*
 * Disable the bus so that we won't get any interrupts from now on, or try
 * to drive any lines. This is the default state when we don't have
 * anything to send/receive.
 *
 * If there is an event on the bus, or we have a pre-existing event at
 * kernel boot time, we may not notice the event and the I2C controller
 * will lock the bus with the I2C clock line low indefinitely.
 */
static inline void s3c24xx_i2c_disable_bus(struct s3c24xx_i2c *i2c)
{
        unsigned long tmp;

        /* Stop driving the I2C pins */
        tmp = readl(i2c->regs + S3C2410_IICSTAT);
        tmp &= ~S3C2410_IICSTAT_TXRXEN;
        writel(tmp, i2c->regs + S3C2410_IICSTAT);

        /* We don't expect any interrupts now, and don't want send acks */
        tmp = readl(i2c->regs + S3C2410_IICCON);
        tmp &= ~(S3C2410_IICCON_IRQEN | S3C2410_IICCON_IRQPEND |
                S3C2410_IICCON_ACKEN);
        writel(tmp, i2c->regs + S3C2410_IICCON);
}


/*
 * get the i2c bus for a master transaction
 */
static int s3c24xx_i2c_set_master(struct s3c24xx_i2c *i2c)
{
        unsigned long iicstat;
        int timeout = 400;

        while (timeout-- > 0) {
                iicstat = readl(i2c->regs + S3C2410_IICSTAT);

                if (!(iicstat & S3C2410_IICSTAT_BUSBUSY))
                        return 0;

                msleep(1);
        }

        return -ETIMEDOUT;
}

/*
 * wait for the i2c bus to become idle.
 */
static void s3c24xx_i2c_wait_idle(struct s3c24xx_i2c *i2c)
{
        unsigned long iicstat;
        ktime_t start, now;
        unsigned long delay;
        int spins;

        /* ensure the stop has been through the bus */

        dev_dbg(i2c->dev, "waiting for bus idle\n");

        start = now = ktime_get();

        /*
         * Most of the time, the bus is already idle within a few usec of the
         * end of a transaction.  However, really slow i2c devices can stretch
         * the clock, delaying STOP generation.
         *
         * On slower SoCs this typically happens within a very small number of
         * instructions so busy wait briefly to avoid scheduling overhead.
         */
        spins = 3;
        iicstat = readl(i2c->regs + S3C2410_IICSTAT);
        while ((iicstat & S3C2410_IICSTAT_START) && --spins) {
                cpu_relax();
                iicstat = readl(i2c->regs + S3C2410_IICSTAT);
        }

        /*
         * If we do get an appreciable delay as a compromise between idle
         * detection latency for the normal, fast case, and system load in the
         * slow device case, use an exponential back off in the polling loop,
         * up to 1/10th of the total timeout, then continue to poll at a
         * constant rate up to the timeout.
         */
        delay = 1;
        while ((iicstat & S3C2410_IICSTAT_START) &&
               ktime_us_delta(now, start) < S3C2410_IDLE_TIMEOUT) {
                usleep_range(delay, 2 * delay);
                if (delay < S3C2410_IDLE_TIMEOUT / 10)
                        delay <<= 1;
                now = ktime_get();
                iicstat = readl(i2c->regs + S3C2410_IICSTAT);
        }

        if (iicstat & S3C2410_IICSTAT_START)
                dev_warn(i2c->dev, "timeout waiting for bus idle\n");
}

/*
 * this starts an i2c transfer
 */
static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
                              struct i2c_msg *msgs, int num)
{
        long time_left = 0;
        int ret;

        ret = s3c24xx_i2c_set_master(i2c);
        if (ret != 0) {
                dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
                ret = -EAGAIN;
                goto out;
        }

        i2c->msg     = msgs;
        i2c->msg_num = num;
        i2c->msg_ptr = 0;
        i2c->msg_idx = 0;
        i2c->state   = STATE_START;

        s3c24xx_i2c_enable_irq(i2c);
        s3c24xx_i2c_message_start(i2c, msgs);

        if (i2c->quirks & (QUIRK_POLL | QUIRK_ATOMIC)) {
                while ((i2c->msg_num != 0) && is_ack(i2c)) {
                        unsigned long stat = readl(i2c->regs + S3C2410_IICSTAT);

                        i2c_s3c_irq_nextbyte(i2c, stat);

                        stat = readl(i2c->regs + S3C2410_IICSTAT);
                        if (stat & S3C2410_IICSTAT_ARBITR)
                                dev_err(i2c->dev, "deal with arbitration loss\n");
                }
        } else {
                time_left = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);
        }

        ret = i2c->msg_idx;

        /*
         * Having these next two as dev_err() makes life very
         * noisy when doing an i2cdetect
         */
        if (time_left == 0)
                dev_dbg(i2c->dev, "timeout\n");
        else if (ret != num)
                dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);

        /* For QUIRK_HDMIPHY, bus is already disabled */
        if (i2c->quirks & QUIRK_HDMIPHY)
                goto out;

        s3c24xx_i2c_wait_idle(i2c);

        s3c24xx_i2c_disable_bus(i2c);

 out:
        i2c->state = STATE_IDLE;

        return ret;
}

/*
 * first port of call from the i2c bus code when an message needs
 * transferring across the i2c bus.
 */
static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
                        struct i2c_msg *msgs, int num)
{
        struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
        int retry;
        int ret;

        ret = clk_enable(i2c->clk);
        if (ret)
                return ret;

        for (retry = 0; retry < adap->retries; retry++) {

                ret = s3c24xx_i2c_doxfer(i2c, msgs, num);

                if (ret != -EAGAIN) {
                        clk_disable(i2c->clk);
                        return ret;
                }

                dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry);

                udelay(100);
        }

        clk_disable(i2c->clk);
        return -EREMOTEIO;
}

static int s3c24xx_i2c_xfer_atomic(struct i2c_adapter *adap,
                                   struct i2c_msg *msgs, int num)
{
        struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
        int ret;

        disable_irq(i2c->irq);
        i2c->quirks |= QUIRK_ATOMIC;
        ret = s3c24xx_i2c_xfer(adap, msgs, num);
        i2c->quirks &= ~QUIRK_ATOMIC;
        enable_irq(i2c->irq);

        return ret;
}

/* declare our i2c functionality */
static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL_ALL | I2C_FUNC_NOSTART |
                I2C_FUNC_PROTOCOL_MANGLING;
}

/* i2c bus registration info */
static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
        .xfer = s3c24xx_i2c_xfer,
        .xfer_atomic = s3c24xx_i2c_xfer_atomic,
        .functionality = s3c24xx_i2c_func,
};

/*
 * return the divisor settings for a given frequency
 */
static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted,
                                   unsigned int *div1, unsigned int *divs)
{
        unsigned int calc_divs = clkin / wanted;
        unsigned int calc_div1;

        if (calc_divs > (16*16))
                calc_div1 = 512;
        else
                calc_div1 = 16;

        calc_divs += calc_div1-1;
        calc_divs /= calc_div1;

        if (calc_divs == 0)
                calc_divs = 1;
        if (calc_divs > 17)
                calc_divs = 17;

        *divs = calc_divs;
        *div1 = calc_div1;

        return clkin / (calc_divs * calc_div1);
}

/*
 * work out a divisor for the user requested frequency setting,
 * either by the requested frequency, or scanning the acceptable
 * range of frequencies until something is found
 */
static int s3c24xx_i2c_clockrate(struct s3c24xx_i2c *i2c, unsigned int *got)
{
        struct s3c2410_platform_i2c *pdata = i2c->pdata;
        unsigned long clkin = clk_get_rate(i2c->clk);
        unsigned int divs, div1;
        unsigned long target_frequency;
        u32 iiccon;
        int freq;

        i2c->clkrate = clkin;
        clkin /= 1000;  /* clkin now in KHz */

        dev_dbg(i2c->dev, "pdata desired frequency %lu\n", pdata->frequency);

        target_frequency = pdata->frequency ?: I2C_MAX_STANDARD_MODE_FREQ;

        target_frequency /= 1000; /* Target frequency now in KHz */

        freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);

        if (freq > target_frequency) {
                dev_err(i2c->dev,
                        "Unable to achieve desired frequency %luKHz."   \
                        " Lowest achievable %dKHz\n", target_frequency, freq);
                return -EINVAL;
        }

        *got = freq;

        iiccon = readl(i2c->regs + S3C2410_IICCON);
        iiccon &= ~(S3C2410_IICCON_SCALEMASK | S3C2410_IICCON_TXDIV_512);
        iiccon |= (divs-1);

        if (div1 == 512)
                iiccon |= S3C2410_IICCON_TXDIV_512;

        if (i2c->quirks & QUIRK_POLL)
                iiccon |= S3C2410_IICCON_SCALE(2);

        writel(iiccon, i2c->regs + S3C2410_IICCON);

        if (i2c->quirks & QUIRK_S3C2440) {
                unsigned long sda_delay;

                if (pdata->sda_delay) {
                        sda_delay = clkin * pdata->sda_delay;
                        sda_delay = DIV_ROUND_UP(sda_delay, 1000000);
                        sda_delay = DIV_ROUND_UP(sda_delay, 5);
                        if (sda_delay > 3)
                                sda_delay = 3;
                        sda_delay |= S3C2410_IICLC_FILTER_ON;
                } else
                        sda_delay = 0;

                dev_dbg(i2c->dev, "IICLC=%08lx\n", sda_delay);
                writel(sda_delay, i2c->regs + S3C2440_IICLC);
        }

        return 0;
}

#ifdef CONFIG_OF
static int s3c24xx_i2c_parse_dt_gpio(struct s3c24xx_i2c *i2c)
{
        int i;

        if (i2c->quirks & QUIRK_NO_GPIO)
                return 0;

        for (i = 0; i < 2; i++) {
                i2c->gpios[i] = devm_gpiod_get_index(i2c->dev, NULL,
                                                     i, GPIOD_ASIS);
                if (IS_ERR(i2c->gpios[i])) {
                        dev_err(i2c->dev, "i2c gpio invalid at index %d\n", i);
                        return -EINVAL;
                }
        }
        return 0;
}

#else
static int s3c24xx_i2c_parse_dt_gpio(struct s3c24xx_i2c *i2c)
{
        return 0;
}
#endif

/*
 * initialise the controller, set the IO lines and frequency
 */
static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c)
{
        struct s3c2410_platform_i2c *pdata;
        unsigned int freq;

        /* get the plafrom data */

        pdata = i2c->pdata;

        /* write slave address */

        writeb(pdata->slave_addr, i2c->regs + S3C2410_IICADD);

        dev_info(i2c->dev, "slave address 0x%02x\n", pdata->slave_addr);

        writel(0, i2c->regs + S3C2410_IICCON);
        writel(0, i2c->regs + S3C2410_IICSTAT);

        /* we need to work out the divisors for the clock... */

        if (s3c24xx_i2c_clockrate(i2c, &freq) != 0) {
                dev_err(i2c->dev, "cannot meet bus frequency required\n");
                return -EINVAL;
        }

        /* todo - check that the i2c lines aren't being dragged anywhere */

        dev_info(i2c->dev, "bus frequency set to %d KHz\n", freq);
        dev_dbg(i2c->dev, "S3C2410_IICCON=0x%02x\n",
                readl(i2c->regs + S3C2410_IICCON));

        return 0;
}

#ifdef CONFIG_OF
/*
 * Parse the device tree node and retreive the platform data.
 */
static void
s3c24xx_i2c_parse_dt(struct device_node *np, struct s3c24xx_i2c *i2c)
{
        struct s3c2410_platform_i2c *pdata = i2c->pdata;
        int id;

        if (!np)
                return;

        pdata->bus_num = -1; /* i2c bus number is dynamically assigned */
        of_property_read_u32(np, "samsung,i2c-sda-delay", &pdata->sda_delay);
        of_property_read_u32(np, "samsung,i2c-slave-addr", &pdata->slave_addr);
        of_property_read_u32(np, "samsung,i2c-max-bus-freq",
                                (u32 *)&pdata->frequency);
        /*
         * Exynos5's legacy i2c controller and new high speed i2c
         * controller have muxed interrupt sources. By default the
         * interrupts for 4-channel HS-I2C controller are enabled.
         * If nodes for first four channels of legacy i2c controller
         * are available then re-configure the interrupts via the
         * system register.
         */
        id = of_alias_get_id(np, "i2c");
        i2c->sysreg = syscon_regmap_lookup_by_phandle(np,
                        "samsung,sysreg-phandle");
        if (IS_ERR(i2c->sysreg))
                return;

        regmap_update_bits(i2c->sysreg, EXYNOS5_SYS_I2C_CFG, BIT(id), 0);
}
#else
static void
s3c24xx_i2c_parse_dt(struct device_node *np, struct s3c24xx_i2c *i2c) { }
#endif

static int s3c24xx_i2c_probe(struct platform_device *pdev)
{
        struct s3c24xx_i2c *i2c;
        struct s3c2410_platform_i2c *pdata = NULL;
        struct resource *res;
        int ret;

        if (!pdev->dev.of_node) {
                pdata = dev_get_platdata(&pdev->dev);
                if (!pdata) {
                        dev_err(&pdev->dev, "no platform data\n");
                        return -EINVAL;
                }
        }

        i2c = devm_kzalloc(&pdev->dev, sizeof(struct s3c24xx_i2c), GFP_KERNEL);
        if (!i2c)
                return -ENOMEM;

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

        i2c->quirks = s3c24xx_get_device_quirks(pdev);
        i2c->sysreg = ERR_PTR(-ENOENT);
        if (pdata)
                memcpy(i2c->pdata, pdata, sizeof(*pdata));
        else
                s3c24xx_i2c_parse_dt(pdev->dev.of_node, i2c);

        strscpy(i2c->adap.name, "s3c2410-i2c", sizeof(i2c->adap.name));
        i2c->adap.owner = THIS_MODULE;
        i2c->adap.algo = &s3c24xx_i2c_algorithm;
        i2c->adap.retries = 2;
        i2c->adap.class = I2C_CLASS_DEPRECATED;
        i2c->tx_setup = 50;

        init_waitqueue_head(&i2c->wait);

        /* find the clock and enable it */
        i2c->dev = &pdev->dev;
        i2c->clk = devm_clk_get(&pdev->dev, "i2c");
        if (IS_ERR(i2c->clk)) {
                dev_err(&pdev->dev, "cannot get clock\n");
                return -ENOENT;
        }

        dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk);

        /* map the registers */
        i2c->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(i2c->regs))
                return PTR_ERR(i2c->regs);

        dev_dbg(&pdev->dev, "registers %p (%p)\n",
                i2c->regs, res);

        /* setup info block for the i2c core */
        i2c->adap.algo_data = i2c;
        i2c->adap.dev.parent = &pdev->dev;
        i2c->pctrl = devm_pinctrl_get_select_default(i2c->dev);

        /* inititalise the i2c gpio lines */
        if (i2c->pdata->cfg_gpio)
                i2c->pdata->cfg_gpio(to_platform_device(i2c->dev));
        else if (IS_ERR(i2c->pctrl) && s3c24xx_i2c_parse_dt_gpio(i2c))
                return -EINVAL;

        /* initialise the i2c controller */
        ret = clk_prepare_enable(i2c->clk);
        if (ret) {
                dev_err(&pdev->dev, "I2C clock enable failed\n");
                return ret;
        }

        ret = s3c24xx_i2c_init(i2c);
        clk_disable(i2c->clk);
        if (ret != 0) {
                dev_err(&pdev->dev, "I2C controller init failed\n");
                clk_unprepare(i2c->clk);
                return ret;
        }

        /*
         * find the IRQ for this unit (note, this relies on the init call to
         * ensure no current IRQs pending
         */
        if (!(i2c->quirks & QUIRK_POLL)) {
                i2c->irq = ret = platform_get_irq(pdev, 0);
                if (ret < 0) {
                        clk_unprepare(i2c->clk);
                        return ret;
                }

                ret = devm_request_irq(&pdev->dev, i2c->irq, s3c24xx_i2c_irq,
                                       0, dev_name(&pdev->dev), i2c);
                if (ret != 0) {
                        dev_err(&pdev->dev, "cannot claim IRQ %d\n", i2c->irq);
                        clk_unprepare(i2c->clk);
                        return ret;
                }
        }

        /*
         * Note, previous versions of the driver used i2c_add_adapter()
         * to add the bus at any number. We now pass the bus number via
         * the platform data, so if unset it will now default to always
         * being bus 0.
         */
        i2c->adap.nr = i2c->pdata->bus_num;
        i2c->adap.dev.of_node = pdev->dev.of_node;

        platform_set_drvdata(pdev, i2c);

        pm_runtime_enable(&pdev->dev);

        ret = i2c_add_numbered_adapter(&i2c->adap);
        if (ret < 0) {
                pm_runtime_disable(&pdev->dev);
                clk_unprepare(i2c->clk);
                return ret;
        }

        dev_info(&pdev->dev, "%s: S3C I2C adapter\n", dev_name(&i2c->adap.dev));
        return 0;
}

static void s3c24xx_i2c_remove(struct platform_device *pdev)
{
        struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);

        clk_unprepare(i2c->clk);

        pm_runtime_disable(&pdev->dev);

        i2c_del_adapter(&i2c->adap);
}

static int s3c24xx_i2c_suspend_noirq(struct device *dev)
{
        struct s3c24xx_i2c *i2c = dev_get_drvdata(dev);

        i2c_mark_adapter_suspended(&i2c->adap);

        if (!IS_ERR(i2c->sysreg))
                regmap_read(i2c->sysreg, EXYNOS5_SYS_I2C_CFG, &i2c->sys_i2c_cfg);

        return 0;
}

static int s3c24xx_i2c_resume_noirq(struct device *dev)
{
        struct s3c24xx_i2c *i2c = dev_get_drvdata(dev);
        int ret;

        if (!IS_ERR(i2c->sysreg))
                regmap_write(i2c->sysreg, EXYNOS5_SYS_I2C_CFG, i2c->sys_i2c_cfg);

        ret = clk_enable(i2c->clk);
        if (ret)
                return ret;
        s3c24xx_i2c_init(i2c);
        clk_disable(i2c->clk);
        i2c_mark_adapter_resumed(&i2c->adap);

        return 0;
}

static const struct dev_pm_ops s3c24xx_i2c_dev_pm_ops = {
        NOIRQ_SYSTEM_SLEEP_PM_OPS(s3c24xx_i2c_suspend_noirq,
                                  s3c24xx_i2c_resume_noirq)
};

static struct platform_driver s3c24xx_i2c_driver = {
        .probe          = s3c24xx_i2c_probe,
        .remove         = s3c24xx_i2c_remove,
        .id_table       = s3c24xx_driver_ids,
        .driver         = {
                .name   = "s3c-i2c",
                .pm     = pm_sleep_ptr(&s3c24xx_i2c_dev_pm_ops),
                .of_match_table = of_match_ptr(s3c24xx_i2c_match),
        },
};

static int __init i2c_adap_s3c_init(void)
{
        return platform_driver_register(&s3c24xx_i2c_driver);
}
subsys_initcall(i2c_adap_s3c_init);

static void __exit i2c_adap_s3c_exit(void)
{
        platform_driver_unregister(&s3c24xx_i2c_driver);
}
module_exit(i2c_adap_s3c_exit);

MODULE_DESCRIPTION("S3C24XX I2C Bus driver");
MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");
MODULE_LICENSE("GPL");