// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for the Renesas R-Car I2C unit
 *
 * Copyright (C) 2014-19 Wolfram Sang <wsa@sang-engineering.com>
 * Copyright (C) 2011-2019 Renesas Electronics Corporation
 *
 * Copyright (C) 2012-14 Renesas Solutions Corp.
 * Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
 *
 * This file is based on the drivers/i2c/busses/i2c-sh7760.c
 * (c) 2005-2008 MSC Vertriebsges.m.b.H, Manuel Lauss <mlau@msc-ge.com>
 */
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/slab.h>

/* register offsets */
#define ICSCR   0x00    /* slave ctrl */
#define ICMCR   0x04    /* master ctrl */
#define ICSSR   0x08    /* slave status */
#define ICMSR   0x0C    /* master status */
#define ICSIER  0x10    /* slave irq enable */
#define ICMIER  0x14    /* master irq enable */
#define ICCCR   0x18    /* clock dividers */
#define ICSAR   0x1C    /* slave address */
#define ICMAR   0x20    /* master address */
#define ICRXTX  0x24    /* data port */
#define ICFBSCR 0x38    /* first bit setup cycle (Gen3) */
#define ICDMAER 0x3c    /* DMA enable (Gen3) */

/* ICSCR */
#define SDBS    (1 << 3)        /* slave data buffer select */
#define SIE     (1 << 2)        /* slave interface enable */
#define GCAE    (1 << 1)        /* general call address enable */
#define FNA     (1 << 0)        /* forced non acknowledgment */

/* ICMCR */
#define MDBS    (1 << 7)        /* non-fifo mode switch */
#define FSCL    (1 << 6)        /* override SCL pin */
#define FSDA    (1 << 5)        /* override SDA pin */
#define OBPC    (1 << 4)        /* override pins */
#define MIE     (1 << 3)        /* master if enable */
#define TSBE    (1 << 2)
#define FSB     (1 << 1)        /* force stop bit */
#define ESG     (1 << 0)        /* enable start bit gen */

/* ICSSR (also for ICSIER) */
#define GCAR    (1 << 6)        /* general call received */
#define STM     (1 << 5)        /* slave transmit mode */
#define SSR     (1 << 4)        /* stop received */
#define SDE     (1 << 3)        /* slave data empty */
#define SDT     (1 << 2)        /* slave data transmitted */
#define SDR     (1 << 1)        /* slave data received */
#define SAR     (1 << 0)        /* slave addr received */

/* ICMSR (also for ICMIE) */
#define MNR     (1 << 6)        /* nack received */
#define MAL     (1 << 5)        /* arbitration lost */
#define MST     (1 << 4)        /* sent a stop */
#define MDE     (1 << 3)
#define MDT     (1 << 2)
#define MDR     (1 << 1)
#define MAT     (1 << 0)        /* slave addr xfer done */

/* ICDMAER */
#define RSDMAE  (1 << 3)        /* DMA Slave Received Enable */
#define TSDMAE  (1 << 2)        /* DMA Slave Transmitted Enable */
#define RMDMAE  (1 << 1)        /* DMA Master Received Enable */
#define TMDMAE  (1 << 0)        /* DMA Master Transmitted Enable */

/* ICFBSCR */
#define TCYC17  0x0f            /* 17*Tcyc delay 1st bit between SDA and SCL */

#define RCAR_MIN_DMA_LEN        8

#define RCAR_BUS_PHASE_START    (MDBS | MIE | ESG)
#define RCAR_BUS_PHASE_DATA     (MDBS | MIE)
#define RCAR_BUS_PHASE_STOP     (MDBS | MIE | FSB)

#define RCAR_IRQ_SEND   (MNR | MAL | MST | MAT | MDE)
#define RCAR_IRQ_RECV   (MNR | MAL | MST | MAT | MDR)
#define RCAR_IRQ_STOP   (MST)

#define RCAR_IRQ_ACK_SEND       (~(MAT | MDE) & 0x7F)
#define RCAR_IRQ_ACK_RECV       (~(MAT | MDR) & 0x7F)

#define ID_LAST_MSG     (1 << 0)
#define ID_FIRST_MSG    (1 << 1)
#define ID_DONE         (1 << 2)
#define ID_ARBLOST      (1 << 3)
#define ID_NACK         (1 << 4)
/* persistent flags */
#define ID_P_HOST_NOTIFY        BIT(28)
#define ID_P_REP_AFTER_RD       BIT(29)
#define ID_P_NO_RXDMA           BIT(30) /* HW forbids RXDMA sometimes */
#define ID_P_PM_BLOCKED         BIT(31)
#define ID_P_MASK               GENMASK(31, 28)

enum rcar_i2c_type {
        I2C_RCAR_GEN1,
        I2C_RCAR_GEN2,
        I2C_RCAR_GEN3,
};

struct rcar_i2c_priv {
        u32 flags;
        void __iomem *io;
        struct i2c_adapter adap;
        struct i2c_msg *msg;
        int msgs_left;
        struct clk *clk;

        wait_queue_head_t wait;

        int pos;
        u32 icccr;
        u8 recovery_icmcr;      /* protected by adapter lock */
        enum rcar_i2c_type devtype;
        struct i2c_client *slave;

        struct resource *res;
        struct dma_chan *dma_tx;
        struct dma_chan *dma_rx;
        struct scatterlist sg;
        enum dma_data_direction dma_direction;

        struct reset_control *rstc;
        bool atomic_xfer;
        int irq;

        struct i2c_client *host_notify_client;
};

#define rcar_i2c_priv_to_dev(p)         ((p)->adap.dev.parent)
#define rcar_i2c_is_recv(p)             ((p)->msg->flags & I2C_M_RD)

static void rcar_i2c_write(struct rcar_i2c_priv *priv, int reg, u32 val)
{
        writel(val, priv->io + reg);
}

static u32 rcar_i2c_read(struct rcar_i2c_priv *priv, int reg)
{
        return readl(priv->io + reg);
}

static int rcar_i2c_get_scl(struct i2c_adapter *adap)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);

        return !!(rcar_i2c_read(priv, ICMCR) & FSCL);

};

static void rcar_i2c_set_scl(struct i2c_adapter *adap, int val)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);

        if (val)
                priv->recovery_icmcr |= FSCL;
        else
                priv->recovery_icmcr &= ~FSCL;

        rcar_i2c_write(priv, ICMCR, priv->recovery_icmcr);
};

static void rcar_i2c_set_sda(struct i2c_adapter *adap, int val)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);

        if (val)
                priv->recovery_icmcr |= FSDA;
        else
                priv->recovery_icmcr &= ~FSDA;

        rcar_i2c_write(priv, ICMCR, priv->recovery_icmcr);
};

static int rcar_i2c_get_bus_free(struct i2c_adapter *adap)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);

        return !(rcar_i2c_read(priv, ICMCR) & FSDA);

};

static struct i2c_bus_recovery_info rcar_i2c_bri = {
        .get_scl = rcar_i2c_get_scl,
        .set_scl = rcar_i2c_set_scl,
        .set_sda = rcar_i2c_set_sda,
        .get_bus_free = rcar_i2c_get_bus_free,
        .recover_bus = i2c_generic_scl_recovery,
};
static void rcar_i2c_init(struct rcar_i2c_priv *priv)
{
        /* reset master mode */
        rcar_i2c_write(priv, ICMIER, 0);
        rcar_i2c_write(priv, ICMCR, MDBS);
        rcar_i2c_write(priv, ICMSR, 0);
        /* start clock */
        rcar_i2c_write(priv, ICCCR, priv->icccr);

        if (priv->devtype == I2C_RCAR_GEN3)
                rcar_i2c_write(priv, ICFBSCR, TCYC17);

}

static int rcar_i2c_bus_barrier(struct rcar_i2c_priv *priv)
{
        int ret;
        u32 val;

        ret = readl_poll_timeout(priv->io + ICMCR, val, !(val & FSDA), 10,
                                 priv->adap.timeout);
        if (ret) {
                /* Waiting did not help, try to recover */
                priv->recovery_icmcr = MDBS | OBPC | FSDA | FSCL;
                ret = i2c_recover_bus(&priv->adap);
        }

        return ret;
}

static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv)
{
        u32 scgd, cdf, round, ick, sum, scl, cdf_width;
        unsigned long rate;
        struct device *dev = rcar_i2c_priv_to_dev(priv);
        struct i2c_timings t = {
                .bus_freq_hz            = I2C_MAX_STANDARD_MODE_FREQ,
                .scl_fall_ns            = 35,
                .scl_rise_ns            = 200,
                .scl_int_delay_ns       = 50,
        };

        /* Fall back to previously used values if not supplied */
        i2c_parse_fw_timings(dev, &t, false);

        switch (priv->devtype) {
        case I2C_RCAR_GEN1:
                cdf_width = 2;
                break;
        case I2C_RCAR_GEN2:
        case I2C_RCAR_GEN3:
                cdf_width = 3;
                break;
        default:
                dev_err(dev, "device type error\n");
                return -EIO;
        }

        /*
         * calculate SCL clock
         * see
         *      ICCCR
         *
         * ick  = clkp / (1 + CDF)
         * SCL  = ick / (20 + SCGD * 8 + F[(ticf + tr + intd) * ick])
         *
         * ick  : I2C internal clock < 20 MHz
         * ticf : I2C SCL falling time
         * tr   : I2C SCL rising  time
         * intd : LSI internal delay
         * clkp : peripheral_clk
         * F[]  : integer up-valuation
         */
        rate = clk_get_rate(priv->clk);
        cdf = rate / 20000000;
        if (cdf >= 1U << cdf_width) {
                dev_err(dev, "Input clock %lu too high\n", rate);
                return -EIO;
        }
        ick = rate / (cdf + 1);

        /*
         * it is impossible to calculate large scale
         * number on u32. separate it
         *
         * F[(ticf + tr + intd) * ick] with sum = (ticf + tr + intd)
         *  = F[sum * ick / 1000000000]
         *  = F[(ick / 1000000) * sum / 1000]
         */
        sum = t.scl_fall_ns + t.scl_rise_ns + t.scl_int_delay_ns;
        round = (ick + 500000) / 1000000 * sum;
        round = (round + 500) / 1000;

        /*
         * SCL  = ick / (20 + SCGD * 8 + F[(ticf + tr + intd) * ick])
         *
         * Calculation result (= SCL) should be less than
         * bus_speed for hardware safety
         *
         * We could use something along the lines of
         *      div = ick / (bus_speed + 1) + 1;
         *      scgd = (div - 20 - round + 7) / 8;
         *      scl = ick / (20 + (scgd * 8) + round);
         * (not fully verified) but that would get pretty involved
         */
        for (scgd = 0; scgd < 0x40; scgd++) {
                scl = ick / (20 + (scgd * 8) + round);
                if (scl <= t.bus_freq_hz)
                        goto scgd_find;
        }
        dev_err(dev, "it is impossible to calculate best SCL\n");
        return -EIO;

scgd_find:
        dev_dbg(dev, "clk %d/%d(%lu), round %u, CDF:0x%x, SCGD: 0x%x\n",
                scl, t.bus_freq_hz, rate, round, cdf, scgd);

        /* keep icccr value */
        priv->icccr = scgd << cdf_width | cdf;

        return 0;
}

static void rcar_i2c_prepare_msg(struct rcar_i2c_priv *priv)
{
        int read = !!rcar_i2c_is_recv(priv);

        priv->pos = 0;
        if (priv->msgs_left == 1)
                priv->flags |= ID_LAST_MSG;

        rcar_i2c_write(priv, ICMAR, i2c_8bit_addr_from_msg(priv->msg));
        /*
         * We don't have a test case but the HW engineers say that the write order
         * of ICMSR and ICMCR depends on whether we issue START or REP_START. Since
         * it didn't cause a drawback for me, let's rather be safe than sorry.
         */
        if (priv->flags & ID_FIRST_MSG) {
                rcar_i2c_write(priv, ICMSR, 0);
                rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_START);
        } else {
                if (priv->flags & ID_P_REP_AFTER_RD)
                        priv->flags &= ~ID_P_REP_AFTER_RD;
                else
                        rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_START);
                rcar_i2c_write(priv, ICMSR, 0);
        }

        if (!priv->atomic_xfer)
                rcar_i2c_write(priv, ICMIER, read ? RCAR_IRQ_RECV : RCAR_IRQ_SEND);
}

static void rcar_i2c_next_msg(struct rcar_i2c_priv *priv)
{
        priv->msg++;
        priv->msgs_left--;
        priv->flags &= ID_P_MASK;
        rcar_i2c_prepare_msg(priv);
}

static void rcar_i2c_dma_unmap(struct rcar_i2c_priv *priv)
{
        struct dma_chan *chan = priv->dma_direction == DMA_FROM_DEVICE
                ? priv->dma_rx : priv->dma_tx;

        dma_unmap_single(chan->device->dev, sg_dma_address(&priv->sg),
                         sg_dma_len(&priv->sg), priv->dma_direction);

        /* Gen3 can only do one RXDMA per transfer and we just completed it */
        if (priv->devtype == I2C_RCAR_GEN3 &&
            priv->dma_direction == DMA_FROM_DEVICE)
                priv->flags |= ID_P_NO_RXDMA;

        priv->dma_direction = DMA_NONE;

        /* Disable DMA Master Received/Transmitted, must be last! */
        rcar_i2c_write(priv, ICDMAER, 0);
}

static void rcar_i2c_cleanup_dma(struct rcar_i2c_priv *priv)
{
        if (priv->dma_direction == DMA_NONE)
                return;
        else if (priv->dma_direction == DMA_FROM_DEVICE)
                dmaengine_terminate_all(priv->dma_rx);
        else if (priv->dma_direction == DMA_TO_DEVICE)
                dmaengine_terminate_all(priv->dma_tx);

        rcar_i2c_dma_unmap(priv);
}

static void rcar_i2c_dma_callback(void *data)
{
        struct rcar_i2c_priv *priv = data;

        priv->pos += sg_dma_len(&priv->sg);

        rcar_i2c_dma_unmap(priv);
}

static bool rcar_i2c_dma(struct rcar_i2c_priv *priv)
{
        struct device *dev = rcar_i2c_priv_to_dev(priv);
        struct i2c_msg *msg = priv->msg;
        bool read = msg->flags & I2C_M_RD;
        enum dma_data_direction dir = read ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
        struct dma_chan *chan = read ? priv->dma_rx : priv->dma_tx;
        struct dma_async_tx_descriptor *txdesc;
        dma_addr_t dma_addr;
        dma_cookie_t cookie;
        unsigned char *buf;
        int len;

        /* Do various checks to see if DMA is feasible at all */
        if (priv->atomic_xfer || IS_ERR(chan) || msg->len < RCAR_MIN_DMA_LEN ||
            !(msg->flags & I2C_M_DMA_SAFE) || (read && priv->flags & ID_P_NO_RXDMA))
                return false;

        if (read) {
                /*
                 * The last two bytes needs to be fetched using PIO in
                 * order for the STOP phase to work.
                 */
                buf = priv->msg->buf;
                len = priv->msg->len - 2;
        } else {
                /*
                 * First byte in message was sent using PIO.
                 */
                buf = priv->msg->buf + 1;
                len = priv->msg->len - 1;
        }

        dma_addr = dma_map_single(chan->device->dev, buf, len, dir);
        if (dma_mapping_error(chan->device->dev, dma_addr)) {
                dev_dbg(dev, "dma map failed, using PIO\n");
                return false;
        }

        sg_dma_len(&priv->sg) = len;
        sg_dma_address(&priv->sg) = dma_addr;

        priv->dma_direction = dir;

        txdesc = dmaengine_prep_slave_sg(chan, &priv->sg, 1,
                                         read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV,
                                         DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!txdesc) {
                dev_dbg(dev, "dma prep slave sg failed, using PIO\n");
                rcar_i2c_cleanup_dma(priv);
                return false;
        }

        txdesc->callback = rcar_i2c_dma_callback;
        txdesc->callback_param = priv;

        cookie = dmaengine_submit(txdesc);
        if (dma_submit_error(cookie)) {
                dev_dbg(dev, "submitting dma failed, using PIO\n");
                rcar_i2c_cleanup_dma(priv);
                return false;
        }

        /* Enable DMA Master Received/Transmitted */
        if (read)
                rcar_i2c_write(priv, ICDMAER, RMDMAE);
        else
                rcar_i2c_write(priv, ICDMAER, TMDMAE);

        dma_async_issue_pending(chan);
        return true;
}

static void rcar_i2c_irq_send(struct rcar_i2c_priv *priv, u32 msr)
{
        struct i2c_msg *msg = priv->msg;

        /* FIXME: sometimes, unknown interrupt happened. Do nothing */
        if (!(msr & MDE))
                return;

        /* Check if DMA can be enabled and take over */
        if (priv->pos == 1 && rcar_i2c_dma(priv))
                return;

        if (priv->pos < msg->len) {
                /*
                 * Prepare next data to ICRXTX register.
                 * This data will go to _SHIFT_ register.
                 *
                 *    *
                 * [ICRXTX] -> [SHIFT] -> [I2C bus]
                 */
                rcar_i2c_write(priv, ICRXTX, msg->buf[priv->pos]);
                priv->pos++;
        } else {
                /*
                 * The last data was pushed to ICRXTX on _PREV_ empty irq.
                 * It is on _SHIFT_ register, and will sent to I2C bus.
                 *
                 *                *
                 * [ICRXTX] -> [SHIFT] -> [I2C bus]
                 */

                if (priv->flags & ID_LAST_MSG) {
                        /*
                         * If current msg is the _LAST_ msg,
                         * prepare stop condition here.
                         * ID_DONE will be set on STOP irq.
                         */
                        rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
                } else {
                        rcar_i2c_next_msg(priv);
                        return;
                }
        }

        rcar_i2c_write(priv, ICMSR, RCAR_IRQ_ACK_SEND);
}

static void rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
{
        struct i2c_msg *msg = priv->msg;

        /* FIXME: sometimes, unknown interrupt happened. Do nothing */
        if (!(msr & MDR))
                return;

        if (msr & MAT) {
                /*
                 * Address transfer phase finished, but no data at this point.
                 * Try to use DMA to receive data.
                 */
                rcar_i2c_dma(priv);
        } else if (priv->pos < msg->len) {
                /* get received data */
                msg->buf[priv->pos] = rcar_i2c_read(priv, ICRXTX);
                priv->pos++;
        }

        /* If next received data is the _LAST_, go to new phase. */
        if (priv->pos + 1 == msg->len) {
                if (priv->flags & ID_LAST_MSG) {
                        rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
                } else {
                        rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_START);
                        priv->flags |= ID_P_REP_AFTER_RD;
                }
        }

        if (priv->pos == msg->len && !(priv->flags & ID_LAST_MSG))
                rcar_i2c_next_msg(priv);
        else
                rcar_i2c_write(priv, ICMSR, RCAR_IRQ_ACK_RECV);
}

static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
{
        u32 ssr_raw, ssr_filtered;
        u8 value;

        ssr_raw = rcar_i2c_read(priv, ICSSR) & 0xff;
        ssr_filtered = ssr_raw & rcar_i2c_read(priv, ICSIER);

        if (!ssr_filtered)
                return false;

        /* address detected */
        if (ssr_filtered & SAR) {
                /* read or write request */
                if (ssr_raw & STM) {
                        i2c_slave_event(priv->slave, I2C_SLAVE_READ_REQUESTED, &value);
                        rcar_i2c_write(priv, ICRXTX, value);
                        rcar_i2c_write(priv, ICSIER, SDE | SSR | SAR);
                } else {
                        i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
                        rcar_i2c_read(priv, ICRXTX);    /* dummy read */
                        rcar_i2c_write(priv, ICSIER, SDR | SSR | SAR);
                }

                /* Clear SSR, too, because of old STOPs to other clients than us */
                rcar_i2c_write(priv, ICSSR, ~(SAR | SSR) & 0xff);
        }

        /* master sent stop */
        if (ssr_filtered & SSR) {
                i2c_slave_event(priv->slave, I2C_SLAVE_STOP, &value);
                rcar_i2c_write(priv, ICSCR, SIE | SDBS); /* clear our NACK */
                rcar_i2c_write(priv, ICSIER, SAR);
                rcar_i2c_write(priv, ICSSR, ~SSR & 0xff);
        }

        /* master wants to write to us */
        if (ssr_filtered & SDR) {
                int ret;

                value = rcar_i2c_read(priv, ICRXTX);
                ret = i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
                /* Send NACK in case of error */
                rcar_i2c_write(priv, ICSCR, SIE | SDBS | (ret < 0 ? FNA : 0));
                rcar_i2c_write(priv, ICSSR, ~SDR & 0xff);
        }

        /* master wants to read from us */
        if (ssr_filtered & SDE) {
                i2c_slave_event(priv->slave, I2C_SLAVE_READ_PROCESSED, &value);
                rcar_i2c_write(priv, ICRXTX, value);
                rcar_i2c_write(priv, ICSSR, ~SDE & 0xff);
        }

        return true;
}

/*
 * This driver has a lock-free design because there are IP cores (at least
 * R-Car Gen2) which have an inherent race condition in their hardware design.
 * There, we need to switch to RCAR_BUS_PHASE_DATA as soon as possible after
 * the interrupt was generated, otherwise an unwanted repeated message gets
 * generated. It turned out that taking a spinlock at the beginning of the ISR
 * was already causing repeated messages. Thus, this driver was converted to
 * the now lockless behaviour. Please keep this in mind when hacking the driver.
 * R-Car Gen3 seems to have this fixed but earlier versions than R-Car Gen2 are
 * likely affected. Therefore, we have different interrupt handler entries.
 */
static irqreturn_t rcar_i2c_irq(int irq, struct rcar_i2c_priv *priv, u32 msr)
{
        if (!msr) {
                if (rcar_i2c_slave_irq(priv))
                        return IRQ_HANDLED;

                return IRQ_NONE;
        }

        /* Arbitration lost */
        if (msr & MAL) {
                priv->flags |= ID_DONE | ID_ARBLOST;
                goto out;
        }

        /* Nack */
        if (msr & MNR) {
                /* HW automatically sends STOP after received NACK */
                if (!priv->atomic_xfer)
                        rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
                priv->flags |= ID_NACK;
                goto out;
        }

        /* Stop */
        if (msr & MST) {
                priv->msgs_left--; /* The last message also made it */
                priv->flags |= ID_DONE;
                goto out;
        }

        if (rcar_i2c_is_recv(priv))
                rcar_i2c_irq_recv(priv, msr);
        else
                rcar_i2c_irq_send(priv, msr);

out:
        if (priv->flags & ID_DONE) {
                rcar_i2c_write(priv, ICMIER, 0);
                rcar_i2c_write(priv, ICMSR, 0);
                if (!priv->atomic_xfer)
                        wake_up(&priv->wait);
        }

        return IRQ_HANDLED;
}

static irqreturn_t rcar_i2c_gen2_irq(int irq, void *ptr)
{
        struct rcar_i2c_priv *priv = ptr;
        u32 msr;

        /* Clear START or STOP immediately, except for REPSTART after read */
        if (likely(!(priv->flags & ID_P_REP_AFTER_RD)))
                rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);

        /* Only handle interrupts that are currently enabled */
        msr = rcar_i2c_read(priv, ICMSR);
        if (!priv->atomic_xfer)
                msr &= rcar_i2c_read(priv, ICMIER);

        return rcar_i2c_irq(irq, priv, msr);
}

static irqreturn_t rcar_i2c_gen3_irq(int irq, void *ptr)
{
        struct rcar_i2c_priv *priv = ptr;
        u32 msr;

        /* Only handle interrupts that are currently enabled */
        msr = rcar_i2c_read(priv, ICMSR);
        if (!priv->atomic_xfer)
                msr &= rcar_i2c_read(priv, ICMIER);

        /*
         * Clear START or STOP immediately, except for REPSTART after read or
         * if a spurious interrupt was detected.
         */
        if (likely(!(priv->flags & ID_P_REP_AFTER_RD) && msr))
                rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);

        return rcar_i2c_irq(irq, priv, msr);
}

static struct dma_chan *rcar_i2c_request_dma_chan(struct device *dev,
                                        enum dma_transfer_direction dir,
                                        dma_addr_t port_addr)
{
        struct dma_chan *chan;
        struct dma_slave_config cfg;
        char *chan_name = dir == DMA_MEM_TO_DEV ? "tx" : "rx";
        int ret;

        chan = dma_request_chan(dev, chan_name);
        if (IS_ERR(chan)) {
                dev_dbg(dev, "request_channel failed for %s (%ld)\n",
                        chan_name, PTR_ERR(chan));
                return chan;
        }

        memset(&cfg, 0, sizeof(cfg));
        cfg.direction = dir;
        if (dir == DMA_MEM_TO_DEV) {
                cfg.dst_addr = port_addr;
                cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
        } else {
                cfg.src_addr = port_addr;
                cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
        }

        ret = dmaengine_slave_config(chan, &cfg);
        if (ret) {
                dev_dbg(dev, "slave_config failed for %s (%d)\n",
                        chan_name, ret);
                dma_release_channel(chan);
                return ERR_PTR(ret);
        }

        dev_dbg(dev, "got DMA channel for %s\n", chan_name);
        return chan;
}

static void rcar_i2c_request_dma(struct rcar_i2c_priv *priv,
                                 struct i2c_msg *msg)
{
        struct device *dev = rcar_i2c_priv_to_dev(priv);
        bool read;
        struct dma_chan *chan;
        enum dma_transfer_direction dir;

        read = msg->flags & I2C_M_RD;

        chan = read ? priv->dma_rx : priv->dma_tx;
        if (PTR_ERR(chan) != -EPROBE_DEFER)
                return;

        dir = read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
        chan = rcar_i2c_request_dma_chan(dev, dir, priv->res->start + ICRXTX);

        if (read)
                priv->dma_rx = chan;
        else
                priv->dma_tx = chan;
}

static void rcar_i2c_release_dma(struct rcar_i2c_priv *priv)
{
        if (!IS_ERR(priv->dma_tx)) {
                dma_release_channel(priv->dma_tx);
                priv->dma_tx = ERR_PTR(-EPROBE_DEFER);
        }

        if (!IS_ERR(priv->dma_rx)) {
                dma_release_channel(priv->dma_rx);
                priv->dma_rx = ERR_PTR(-EPROBE_DEFER);
        }
}

/* I2C is a special case, we need to poll the status of a reset */
static int rcar_i2c_do_reset(struct rcar_i2c_priv *priv)
{
        int ret;

        ret = reset_control_reset(priv->rstc);
        if (ret)
                return ret;

        return read_poll_timeout_atomic(reset_control_status, ret, ret == 0, 1,
                                        100, false, priv->rstc);
}

static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
                                struct i2c_msg *msgs,
                                int num)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);
        struct device *dev = rcar_i2c_priv_to_dev(priv);
        int i, ret;
        long time_left;

        priv->atomic_xfer = false;

        pm_runtime_get_sync(dev);

        /* Check bus state before init otherwise bus busy info will be lost */
        ret = rcar_i2c_bus_barrier(priv);
        if (ret < 0)
                goto out;

        /* Gen3 needs a reset before allowing RXDMA once */
        if (priv->devtype == I2C_RCAR_GEN3) {
                priv->flags |= ID_P_NO_RXDMA;
                if (!IS_ERR(priv->rstc)) {
                        ret = rcar_i2c_do_reset(priv);
                        if (ret == 0)
                                priv->flags &= ~ID_P_NO_RXDMA;
                }
        }

        rcar_i2c_init(priv);

        for (i = 0; i < num; i++)
                rcar_i2c_request_dma(priv, msgs + i);

        /* init first message */
        priv->msg = msgs;
        priv->msgs_left = num;
        priv->flags = (priv->flags & ID_P_MASK) | ID_FIRST_MSG;
        rcar_i2c_prepare_msg(priv);

        time_left = wait_event_timeout(priv->wait, priv->flags & ID_DONE,
                                     num * adap->timeout);

        /* cleanup DMA if it couldn't complete properly due to an error */
        if (priv->dma_direction != DMA_NONE)
                rcar_i2c_cleanup_dma(priv);

        if (!time_left) {
                rcar_i2c_init(priv);
                ret = -ETIMEDOUT;
        } else if (priv->flags & ID_NACK) {
                ret = -ENXIO;
        } else if (priv->flags & ID_ARBLOST) {
                ret = -EAGAIN;
        } else {
                ret = num - priv->msgs_left; /* The number of transfer */
        }
out:
        pm_runtime_put(dev);

        if (ret < 0 && ret != -ENXIO)
                dev_err(dev, "error %d : %x\n", ret, priv->flags);

        return ret;
}

static int rcar_i2c_master_xfer_atomic(struct i2c_adapter *adap,
                                struct i2c_msg *msgs,
                                int num)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);
        struct device *dev = rcar_i2c_priv_to_dev(priv);
        unsigned long j;
        bool time_left;
        int ret;

        priv->atomic_xfer = true;

        pm_runtime_get_sync(dev);

        /* Check bus state before init otherwise bus busy info will be lost */
        ret = rcar_i2c_bus_barrier(priv);
        if (ret < 0)
                goto out;

        rcar_i2c_init(priv);

        /* init first message */
        priv->msg = msgs;
        priv->msgs_left = num;
        priv->flags = (priv->flags & ID_P_MASK) | ID_FIRST_MSG;
        rcar_i2c_prepare_msg(priv);

        j = jiffies + num * adap->timeout;
        do {
                u32 msr = rcar_i2c_read(priv, ICMSR);

                msr &= (rcar_i2c_is_recv(priv) ? RCAR_IRQ_RECV : RCAR_IRQ_SEND) | RCAR_IRQ_STOP;

                if (msr) {
                        if (priv->devtype < I2C_RCAR_GEN3)
                                rcar_i2c_gen2_irq(0, priv);
                        else
                                rcar_i2c_gen3_irq(0, priv);
                }

                time_left = time_before_eq(jiffies, j);
        } while (!(priv->flags & ID_DONE) && time_left);

        if (!time_left) {
                rcar_i2c_init(priv);
                ret = -ETIMEDOUT;
        } else if (priv->flags & ID_NACK) {
                ret = -ENXIO;
        } else if (priv->flags & ID_ARBLOST) {
                ret = -EAGAIN;
        } else {
                ret = num - priv->msgs_left; /* The number of transfer */
        }
out:
        pm_runtime_put(dev);

        if (ret < 0 && ret != -ENXIO)
                dev_err(dev, "error %d : %x\n", ret, priv->flags);

        return ret;
}

static int rcar_reg_slave(struct i2c_client *slave)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(slave->adapter);

        if (priv->slave)
                return -EBUSY;

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

        /* Keep device active for slave address detection logic */
        pm_runtime_get_sync(rcar_i2c_priv_to_dev(priv));

        priv->slave = slave;
        rcar_i2c_write(priv, ICSAR, slave->addr);
        rcar_i2c_write(priv, ICSSR, 0);
        rcar_i2c_write(priv, ICSIER, SAR);
        rcar_i2c_write(priv, ICSCR, SIE | SDBS);

        return 0;
}

static int rcar_unreg_slave(struct i2c_client *slave)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(slave->adapter);

        WARN_ON(!priv->slave);

        /* ensure no irq is running before clearing ptr */
        disable_irq(priv->irq);
        rcar_i2c_write(priv, ICSIER, 0);
        rcar_i2c_write(priv, ICSSR, 0);
        enable_irq(priv->irq);
        rcar_i2c_write(priv, ICSCR, SDBS);
        rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */

        priv->slave = NULL;

        pm_runtime_put(rcar_i2c_priv_to_dev(priv));

        return 0;
}

static u32 rcar_i2c_func(struct i2c_adapter *adap)
{
        struct rcar_i2c_priv *priv = i2c_get_adapdata(adap);

        /*
         * This HW can't do:
         * I2C_SMBUS_QUICK (setting FSB during START didn't work)
         * I2C_M_NOSTART (automatically sends address after START)
         * I2C_M_IGNORE_NAK (automatically sends STOP after NAK)
         */
        u32 func = I2C_FUNC_I2C | I2C_FUNC_SLAVE |
                   (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);

        if (priv->flags & ID_P_HOST_NOTIFY)
                func |= I2C_FUNC_SMBUS_HOST_NOTIFY;

        return func;
}

static const struct i2c_algorithm rcar_i2c_algo = {
        .master_xfer    = rcar_i2c_master_xfer,
        .master_xfer_atomic = rcar_i2c_master_xfer_atomic,
        .functionality  = rcar_i2c_func,
        .reg_slave      = rcar_reg_slave,
        .unreg_slave    = rcar_unreg_slave,
};

static const struct i2c_adapter_quirks rcar_i2c_quirks = {
        .flags = I2C_AQ_NO_ZERO_LEN,
};

static const struct of_device_id rcar_i2c_dt_ids[] = {
        { .compatible = "renesas,i2c-r8a7778", .data = (void *)I2C_RCAR_GEN1 },
        { .compatible = "renesas,i2c-r8a7779", .data = (void *)I2C_RCAR_GEN1 },
        { .compatible = "renesas,i2c-r8a7790", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,i2c-r8a7791", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,i2c-r8a7792", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,i2c-r8a7793", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,i2c-r8a7794", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,i2c-r8a7795", .data = (void *)I2C_RCAR_GEN3 },
        { .compatible = "renesas,i2c-r8a7796", .data = (void *)I2C_RCAR_GEN3 },
        { .compatible = "renesas,rcar-gen1-i2c", .data = (void *)I2C_RCAR_GEN1 },
        { .compatible = "renesas,rcar-gen2-i2c", .data = (void *)I2C_RCAR_GEN2 },
        { .compatible = "renesas,rcar-gen3-i2c", .data = (void *)I2C_RCAR_GEN3 },
        {},
};
MODULE_DEVICE_TABLE(of, rcar_i2c_dt_ids);

static int rcar_i2c_probe(struct platform_device *pdev)
{
        struct rcar_i2c_priv *priv;
        struct i2c_adapter *adap;
        struct device *dev = &pdev->dev;
        unsigned long irqflags = 0;
        irqreturn_t (*irqhandler)(int irq, void *ptr) = rcar_i2c_gen3_irq;
        int ret;

        /* Otherwise logic will break because some bytes must always use PIO */
        BUILD_BUG_ON_MSG(RCAR_MIN_DMA_LEN < 3, "Invalid min DMA length");

        priv = devm_kzalloc(dev, sizeof(struct rcar_i2c_priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(priv->clk)) {
                dev_err(dev, "cannot get clock\n");
                return PTR_ERR(priv->clk);
        }

        priv->io = devm_platform_get_and_ioremap_resource(pdev, 0, &priv->res);
        if (IS_ERR(priv->io))
                return PTR_ERR(priv->io);

        priv->devtype = (enum rcar_i2c_type)of_device_get_match_data(dev);
        init_waitqueue_head(&priv->wait);

        adap = &priv->adap;
        adap->nr = pdev->id;
        adap->algo = &rcar_i2c_algo;
        adap->class = I2C_CLASS_DEPRECATED;
        adap->retries = 3;
        adap->dev.parent = dev;
        adap->dev.of_node = dev->of_node;
        adap->bus_recovery_info = &rcar_i2c_bri;
        adap->quirks = &rcar_i2c_quirks;
        i2c_set_adapdata(adap, priv);
        strlcpy(adap->name, pdev->name, sizeof(adap->name));

        /* Init DMA */
        sg_init_table(&priv->sg, 1);
        priv->dma_direction = DMA_NONE;
        priv->dma_rx = priv->dma_tx = ERR_PTR(-EPROBE_DEFER);

        /* Activate device for clock calculation */
        pm_runtime_enable(dev);
        pm_runtime_get_sync(dev);
        ret = rcar_i2c_clock_calculate(priv);
        if (ret < 0)
                goto out_pm_put;

        rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */

        if (priv->devtype < I2C_RCAR_GEN3) {
                irqflags |= IRQF_NO_THREAD;
                irqhandler = rcar_i2c_gen2_irq;
        }

        if (priv->devtype == I2C_RCAR_GEN3) {
                priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
                if (!IS_ERR(priv->rstc)) {
                        ret = reset_control_status(priv->rstc);
                        if (ret < 0)
                                priv->rstc = ERR_PTR(-ENOTSUPP);
                }
        }

        /* Stay always active when multi-master to keep arbitration working */
        if (of_property_read_bool(dev->of_node, "multi-master"))
                priv->flags |= ID_P_PM_BLOCKED;
        else
                pm_runtime_put(dev);

        if (of_property_read_bool(dev->of_node, "smbus"))
                priv->flags |= ID_P_HOST_NOTIFY;

        ret = platform_get_irq(pdev, 0);
        if (ret < 0)
                goto out_pm_disable;
        priv->irq = ret;
        ret = devm_request_irq(dev, priv->irq, irqhandler, irqflags, dev_name(dev), priv);
        if (ret < 0) {
                dev_err(dev, "cannot get irq %d\n", priv->irq);
                goto out_pm_disable;
        }

        platform_set_drvdata(pdev, priv);

        ret = i2c_add_numbered_adapter(adap);
        if (ret < 0)
                goto out_pm_disable;

        if (priv->flags & ID_P_HOST_NOTIFY) {
                priv->host_notify_client = i2c_new_slave_host_notify_device(adap);
                if (IS_ERR(priv->host_notify_client)) {
                        ret = PTR_ERR(priv->host_notify_client);
                        goto out_del_device;
                }
        }

        dev_info(dev, "probed\n");

        return 0;

 out_del_device:
        i2c_del_adapter(&priv->adap);
 out_pm_put:
        pm_runtime_put(dev);
 out_pm_disable:
        pm_runtime_disable(dev);
        return ret;
}

static int rcar_i2c_remove(struct platform_device *pdev)
{
        struct rcar_i2c_priv *priv = platform_get_drvdata(pdev);
        struct device *dev = &pdev->dev;

        if (priv->host_notify_client)
                i2c_free_slave_host_notify_device(priv->host_notify_client);
        i2c_del_adapter(&priv->adap);
        rcar_i2c_release_dma(priv);
        if (priv->flags & ID_P_PM_BLOCKED)
                pm_runtime_put(dev);
        pm_runtime_disable(dev);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int rcar_i2c_suspend(struct device *dev)
{
        struct rcar_i2c_priv *priv = dev_get_drvdata(dev);

        i2c_mark_adapter_suspended(&priv->adap);
        return 0;
}

static int rcar_i2c_resume(struct device *dev)
{
        struct rcar_i2c_priv *priv = dev_get_drvdata(dev);

        i2c_mark_adapter_resumed(&priv->adap);
        return 0;
}

static const struct dev_pm_ops rcar_i2c_pm_ops = {
        SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(rcar_i2c_suspend, rcar_i2c_resume)
};

#define DEV_PM_OPS (&rcar_i2c_pm_ops)
#else
#define DEV_PM_OPS NULL
#endif /* CONFIG_PM_SLEEP */

static struct platform_driver rcar_i2c_driver = {
        .driver = {
                .name   = "i2c-rcar",
                .of_match_table = rcar_i2c_dt_ids,
                .pm     = DEV_PM_OPS,
        },
        .probe          = rcar_i2c_probe,
        .remove         = rcar_i2c_remove,
};

module_platform_driver(rcar_i2c_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Renesas R-Car I2C bus driver");
MODULE_AUTHOR("Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>");