/*-
 * Copyright (C) 2008 MARVELL INTERNATIONAL LTD.
 * All rights reserved.
 *
 * Developed by Semihalf.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of MARVELL nor the names of contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Driver for the TWSI (aka I2C, aka IIC) bus controller found on Marvell
 * and Allwinner SoCs. Supports master operation only.
 *
 * Calls to DELAY() are needed per Application Note AN-179 "TWSI Software
 * Guidelines for Discovery(TM), Horizon (TM) and Feroceon(TM) Devices".
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/module.h>
#include <sys/resource.h>
#include <sys/rman.h>
#include <sys/sysctl.h>

#include <machine/_inttypes.h>
#include <machine/bus.h>
#include <machine/resource.h>

#include <dev/iicbus/iiconf.h>
#include <dev/iicbus/iicbus.h>

#include <dev/iicbus/controller/twsi/twsi.h>

#include "iicbus_if.h"

#define TWSI_CONTROL_ACK        (1 << 2)
#define TWSI_CONTROL_IFLG       (1 << 3)
#define TWSI_CONTROL_STOP       (1 << 4)
#define TWSI_CONTROL_START      (1 << 5)
#define TWSI_CONTROL_TWSIEN     (1 << 6)
#define TWSI_CONTROL_INTEN      (1 << 7)

#define TWSI_STATUS_BUS_ERROR           0x00
#define TWSI_STATUS_START               0x08
#define TWSI_STATUS_RPTD_START          0x10
#define TWSI_STATUS_ADDR_W_ACK          0x18
#define TWSI_STATUS_ADDR_W_NACK         0x20
#define TWSI_STATUS_DATA_WR_ACK         0x28
#define TWSI_STATUS_DATA_WR_NACK        0x30
#define TWSI_STATUS_ARBITRATION_LOST    0x38
#define TWSI_STATUS_ADDR_R_ACK          0x40
#define TWSI_STATUS_ADDR_R_NACK         0x48
#define TWSI_STATUS_DATA_RD_ACK         0x50
#define TWSI_STATUS_DATA_RD_NOACK       0x58
#define TWSI_STATUS_IDLE                0xf8

#define TWSI_DEBUG
#undef TWSI_DEBUG

#define debugf(sc, fmt, args...)        if ((sc)->debug)        \
    device_printf((sc)->dev, "%s: " fmt, __func__, ##args)

static struct resource_spec res_spec[] = {
        { SYS_RES_MEMORY, 0, RF_ACTIVE },
        { SYS_RES_IRQ, 0, RF_ACTIVE | RF_SHAREABLE},
        { -1, 0 }
};

static __inline uint32_t
TWSI_READ(struct twsi_softc *sc, bus_size_t off)
{
        uint32_t val;

        val = bus_read_4(sc->res[0], off);
        if (sc->debug > 1)
                debugf(sc, "read %x from %lx\n", val, off);
        return (val);
}

static __inline void
TWSI_WRITE(struct twsi_softc *sc, bus_size_t off, uint32_t val)
{

        if (sc->debug > 1)
                debugf(sc, "Writing %x to %lx\n", val, off);
        bus_write_4(sc->res[0], off, val);
}

static __inline void
twsi_control_clear(struct twsi_softc *sc, uint32_t mask)
{
        uint32_t val;

        val = TWSI_READ(sc, sc->reg_control);
        debugf(sc, "read val=%x\n", val);
        val &= ~(TWSI_CONTROL_STOP | TWSI_CONTROL_START);
        val &= ~mask;
        debugf(sc, "write val=%x\n", val);
        TWSI_WRITE(sc, sc->reg_control, val);
}

static __inline void
twsi_control_set(struct twsi_softc *sc, uint32_t mask)
{
        uint32_t val;

        val = TWSI_READ(sc, sc->reg_control);
        debugf(sc, "read val=%x\n", val);
        val &= ~(TWSI_CONTROL_STOP | TWSI_CONTROL_START);
        val |= mask;
        debugf(sc, "write val=%x\n", val);
        TWSI_WRITE(sc, sc->reg_control, val);
}

static __inline void
twsi_clear_iflg(struct twsi_softc *sc)
{

        DELAY(1000);
        /* There are two ways of clearing IFLAG. */
        if (sc->iflag_w1c)
                twsi_control_set(sc, TWSI_CONTROL_IFLG);
        else
                twsi_control_clear(sc, TWSI_CONTROL_IFLG);
        DELAY(1000);
}


/*
 * timeout given in us
 * returns
 *   0 on successful mask change
 *   non-zero on timeout
 */
static int
twsi_poll_ctrl(struct twsi_softc *sc, int timeout, uint32_t mask)
{

        timeout /= 10;
        debugf(sc, "Waiting for ctrl reg to match mask %x\n", mask);
        while (!(TWSI_READ(sc, sc->reg_control) & mask)) {
                DELAY(10);
                if (--timeout < 0)
                        return (timeout);
        }
        debugf(sc, "done\n");
        return (0);
}


/*
 * 'timeout' is given in us. Note also that timeout handling is not exact --
 * twsi_locked_start() total wait can be more than 2 x timeout
 * (twsi_poll_ctrl() is called twice). 'mask' can be either TWSI_STATUS_START
 * or TWSI_STATUS_RPTD_START
 */
static int
twsi_locked_start(device_t dev, struct twsi_softc *sc, int32_t mask,
    u_char slave, int timeout)
{
        int read_access, iflg_set = 0;
        uint32_t status;

        mtx_assert(&sc->mutex, MA_OWNED);

        if (mask == TWSI_STATUS_RPTD_START)
                /* read IFLG to know if it should be cleared later; from NBSD */
                iflg_set = TWSI_READ(sc, sc->reg_control) & TWSI_CONTROL_IFLG;

        debugf(sc, "send start\n");
        twsi_control_set(sc, TWSI_CONTROL_START);

        if (mask == TWSI_STATUS_RPTD_START && iflg_set) {
                debugf(sc, "IFLG set, clearing (mask=%x)\n", mask);
                twsi_clear_iflg(sc);
        }

        /*
         * Without this delay we timeout checking IFLG if the timeout is 0.
         * NBSD driver always waits here too.
         */
        DELAY(1000);

        if (twsi_poll_ctrl(sc, timeout, TWSI_CONTROL_IFLG)) {
                debugf(sc, "timeout sending %sSTART condition\n",
                    mask == TWSI_STATUS_START ? "" : "repeated ");
                return (IIC_ETIMEOUT);
        }

        status = TWSI_READ(sc, sc->reg_status);
        debugf(sc, "status=%x\n", status);

        if (status != mask) {
                debugf(sc, "wrong status (%02x) after sending %sSTART condition\n",
                    status, mask == TWSI_STATUS_START ? "" : "repeated ");
                return (IIC_ESTATUS);
        }

        TWSI_WRITE(sc, sc->reg_data, slave);
        twsi_clear_iflg(sc);
        DELAY(1000);

        if (twsi_poll_ctrl(sc, timeout, TWSI_CONTROL_IFLG)) {
                debugf(sc, "timeout sending slave address (timeout=%d)\n", timeout);
                return (IIC_ETIMEOUT);
        }

        read_access = (slave & 0x1) ? 1 : 0;
        status = TWSI_READ(sc, sc->reg_status);
        if (status != (read_access ?
            TWSI_STATUS_ADDR_R_ACK : TWSI_STATUS_ADDR_W_ACK)) {
                debugf(sc, "no ACK (status: %02x) after sending slave address\n",
                    status);
                return (IIC_ENOACK);
        }

        return (IIC_NOERR);
}

#define TWSI_BAUD_RATE_RAW(C,M,N)       ((C)/((10*(M+1))<<(N)))
#define ABSSUB(a,b)     (((a) > (b)) ? (a) - (b) : (b) - (a))

static int
twsi_calc_baud_rate(struct twsi_softc *sc, const u_int target,
  int *param)
{
        uint64_t clk;
        uint32_t cur, diff, diff0;
        int m, n, m0, n0;

        /* Calculate baud rate. */
        diff0 = 0xffffffff;

        if (clk_get_freq(sc->clk_core, &clk) < 0)
                return (-1);

        debugf(sc, "Bus clock is at %ju\n", clk);

        for (n = 0; n < 8; n++) {
                for (m = 0; m < 16; m++) {
                        cur = TWSI_BAUD_RATE_RAW(clk,m,n);
                        diff = ABSSUB(target, cur);
                        if (diff < diff0) {
                                m0 = m;
                                n0 = n;
                                diff0 = diff;
                        }
                }
        }
        *param = TWSI_BAUD_RATE_PARAM(m0, n0);

        return (0);
}

/*
 * Only slave mode supported, disregard [old]addr
 */
static int
twsi_reset(device_t dev, u_char speed, u_char addr, u_char *oldaddr)
{
        struct twsi_softc *sc;
        uint32_t param;
        u_int busfreq;

        sc = device_get_softc(dev);

        busfreq = IICBUS_GET_FREQUENCY(sc->iicbus, speed);

        if (twsi_calc_baud_rate(sc, busfreq, &param) == -1) {
                switch (speed) {
                case IIC_SLOW:
                case IIC_FAST:
                        param = sc->baud_rate[speed].param;
                        debugf(sc, "Using IIC_FAST mode with speed param=%x\n", param);
                        break;
                case IIC_FASTEST:
                case IIC_UNKNOWN:
                default:
                        param = sc->baud_rate[IIC_FAST].param;
                        debugf(sc, "Using IIC_FASTEST/UNKNOWN mode with speed param=%x\n", param);
                        break;
                }
        }

        debugf(sc, "Using clock param=%x\n", param);

        mtx_lock(&sc->mutex);
        TWSI_WRITE(sc, sc->reg_soft_reset, 0x1);
        TWSI_WRITE(sc, sc->reg_baud_rate, param);
        TWSI_WRITE(sc, sc->reg_control, TWSI_CONTROL_TWSIEN);
        DELAY(1000);
        mtx_unlock(&sc->mutex);

        return (0);
}

static int
twsi_stop(device_t dev)
{
        struct twsi_softc *sc;

        sc = device_get_softc(dev);

        debugf(sc, "%s\n", __func__);
        mtx_lock(&sc->mutex);
        twsi_control_clear(sc, TWSI_CONTROL_ACK);
        twsi_control_set(sc, TWSI_CONTROL_STOP);
        twsi_clear_iflg(sc);
        DELAY(1000);
        mtx_unlock(&sc->mutex);

        return (IIC_NOERR);
}

/*
 * timeout is given in us
 */
static int
twsi_repeated_start(device_t dev, u_char slave, int timeout)
{
        struct twsi_softc *sc;
        int rv;

        sc = device_get_softc(dev);

        debugf(sc, "%s: slave=%x\n", __func__, slave);
        mtx_lock(&sc->mutex);
        rv = twsi_locked_start(dev, sc, TWSI_STATUS_RPTD_START, slave,
            timeout);
        mtx_unlock(&sc->mutex);

        if (rv) {
                twsi_stop(dev);
                return (rv);
        } else
                return (IIC_NOERR);
}

/*
 * timeout is given in us
 */
static int
twsi_start(device_t dev, u_char slave, int timeout)
{
        struct twsi_softc *sc;
        int rv;

        sc = device_get_softc(dev);

        debugf(sc, "%s: slave=%x\n", __func__, slave);
        mtx_lock(&sc->mutex);
        rv = twsi_locked_start(dev, sc, TWSI_STATUS_START, slave, timeout);
        mtx_unlock(&sc->mutex);

        if (rv) {
                twsi_stop(dev);
                return (rv);
        } else
                return (IIC_NOERR);
}

static int
twsi_read(device_t dev, char *buf, int len, int *read, int last, int delay)
{
        struct twsi_softc *sc;
        uint32_t status;
        int last_byte, rv;

        sc = device_get_softc(dev);

        mtx_lock(&sc->mutex);
        *read = 0;
        while (*read < len) {
                /*
                 * Check if we are reading last byte of the last buffer,
                 * do not send ACK then, per I2C specs
                 */
                last_byte = ((*read == len - 1) && last) ? 1 : 0;
                if (last_byte)
                        twsi_control_clear(sc, TWSI_CONTROL_ACK);
                else
                        twsi_control_set(sc, TWSI_CONTROL_ACK);

                twsi_clear_iflg(sc);
                DELAY(1000);

                if (twsi_poll_ctrl(sc, delay, TWSI_CONTROL_IFLG)) {
                        debugf(sc, "timeout reading data (delay=%d)\n", delay);
                        rv = IIC_ETIMEOUT;
                        goto out;
                }

                status = TWSI_READ(sc, sc->reg_status);
                if (status != (last_byte ?
                    TWSI_STATUS_DATA_RD_NOACK : TWSI_STATUS_DATA_RD_ACK)) {
                        debugf(sc, "wrong status (%02x) while reading\n", status);
                        rv = IIC_ESTATUS;
                        goto out;
                }

                *buf++ = TWSI_READ(sc, sc->reg_data);
                (*read)++;
        }
        rv = IIC_NOERR;
out:
        mtx_unlock(&sc->mutex);
        return (rv);
}

static int
twsi_write(device_t dev, const char *buf, int len, int *sent, int timeout)
{
        struct twsi_softc *sc;
        uint32_t status;
        int rv;

        sc = device_get_softc(dev);

        mtx_lock(&sc->mutex);
        *sent = 0;
        while (*sent < len) {
                TWSI_WRITE(sc, sc->reg_data, *buf++);

                twsi_clear_iflg(sc);
                DELAY(1000);
                if (twsi_poll_ctrl(sc, timeout, TWSI_CONTROL_IFLG)) {
                        debugf(sc, "timeout writing data (timeout=%d)\n", timeout);
                        rv = IIC_ETIMEOUT;
                        goto out;
                }

                status = TWSI_READ(sc, sc->reg_status);
                if (status != TWSI_STATUS_DATA_WR_ACK) {
                        debugf(sc, "wrong status (%02x) while writing\n", status);
                        rv = IIC_ESTATUS;
                        goto out;
                }
                (*sent)++;
        }
        rv = IIC_NOERR;
out:
        mtx_unlock(&sc->mutex);
        return (rv);
}

static void
twsi_error(struct twsi_softc *sc, int err)
{
        /*
         * Must send stop condition to abort the current transfer.
         */
        debugf(sc, "Sending STOP condition for error %d\n", err);
        sc->transfer = 0;
        sc->error = err;
        sc->control_val = 0;
        TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_STOP);
}

static int
twsi_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs)
{
        struct twsi_softc *sc;
        uint32_t status;
        int error;

        sc = device_get_softc(dev);

        if (!sc->have_intr)
                return (iicbus_transfer_gen(dev, msgs, nmsgs));

        mtx_lock(&sc->mutex);
        KASSERT(sc->transfer == 0,
            ("starting a transfer while another is active"));

        debugf(sc, "transmitting %d messages\n", nmsgs);
        status = TWSI_READ(sc, sc->reg_status);
        debugf(sc, "status=0x%x\n", status);
        if (status != TWSI_STATUS_IDLE) {
                debugf(sc, "Bad status at start of transfer\n");
                twsi_error(sc, IIC_ESTATUS);
                goto end;
        }

        sc->nmsgs = nmsgs;
        sc->msgs = msgs;
        sc->msg_idx = 0;
        sc->transfer = 1;
        sc->error = 0;

#ifdef TWSI_DEBUG
        for (int i = 0; i < nmsgs; i++)
                debugf(sc, "msg %d is %d bytes long\n", i, msgs[i].len);
#endif

        /* Send start and re-enable interrupts */
        sc->control_val = TWSI_CONTROL_TWSIEN | TWSI_CONTROL_INTEN;
        TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
        msleep_sbt(sc, &sc->mutex, 0, "twsi", 3000 * SBT_1MS, SBT_1MS, 0);
        debugf(sc, "pause finish\n");
        if (sc->error == 0 && sc->transfer != 0) {
                device_printf(sc->dev, "transfer timeout\n");
                sc->error = IIC_ETIMEOUT;
                sc->transfer = 0;
        }

        if (sc->error != 0)
                debugf(sc, "Error: %d\n", sc->error);

end:
        /* Disable module and interrupts */
        debugf(sc, "status=0x%x\n", TWSI_READ(sc, sc->reg_status));
        TWSI_WRITE(sc, sc->reg_control, 0);
        debugf(sc, "status=0x%x\n", TWSI_READ(sc, sc->reg_status));
        error = sc->error;
        mtx_unlock(&sc->mutex);

        return (error);
}

static void
twsi_intr(void *arg)
{
        struct twsi_softc *sc;
        uint32_t status;
        bool message_done;
        bool send_start;

        sc = arg;
        send_start = false;

        mtx_lock(&sc->mutex);
        debugf(sc, "Got interrupt, current msg=%u\n", sc->msg_idx);

        status = TWSI_READ(sc, sc->reg_status);
        debugf(sc, "reg control = 0x%x, status = 0x%x\n",
            TWSI_READ(sc, sc->reg_control), status);

        if (sc->transfer == 0) {
                device_printf(sc->dev, "interrupt without active transfer, "
                    "status = 0x%x\n", status);
                TWSI_WRITE(sc, sc->reg_control, sc->control_val |
                    TWSI_CONTROL_STOP);
                goto end;
        }

restart:
        message_done = false;

        switch (status) {
        case TWSI_STATUS_START:
        case TWSI_STATUS_RPTD_START:
                /* Transmit the address */
                debugf(sc, "Send address 0x%x\n",
                    sc->msgs[sc->msg_idx].slave);

                if (sc->msgs[sc->msg_idx].flags & IIC_M_RD)
                        TWSI_WRITE(sc, sc->reg_data,
                            sc->msgs[sc->msg_idx].slave | LSB);
                else
                        TWSI_WRITE(sc, sc->reg_data,
                            sc->msgs[sc->msg_idx].slave & ~LSB);
                break;

        case TWSI_STATUS_ADDR_W_ACK:
                debugf(sc, "Address ACK-ed (write)\n");

                if (sc->msgs[sc->msg_idx].len > 0) {
                        /* Directly send the first byte */
                        sc->sent_bytes = 1;
                        debugf(sc, "Sending byte 0 (of %d) = %x\n",
                            sc->msgs[sc->msg_idx].len,
                            sc->msgs[sc->msg_idx].buf[0]);
                        TWSI_WRITE(sc, sc->reg_data,
                            sc->msgs[sc->msg_idx].buf[0]);
                } else {
                        debugf(sc, "Zero-length write, sending STOP\n");
                        TWSI_WRITE(sc, sc->reg_control,
                            sc->control_val | TWSI_CONTROL_STOP);
                }
                break;

        case TWSI_STATUS_ADDR_R_ACK:
                debugf(sc, "Address ACK-ed (read)\n");
                sc->recv_bytes = 0;

                if (sc->msgs[sc->msg_idx].len == 0) {
                        debugf(sc, "Zero-length read, sending STOP\n");
                        TWSI_WRITE(sc, sc->reg_control,
                            sc->control_val | TWSI_CONTROL_STOP);
                } else if (sc->msgs[sc->msg_idx].len == 1) {
                        sc->control_val &= ~TWSI_CONTROL_ACK;
                } else {
                        sc->control_val |= TWSI_CONTROL_ACK;
                }
                break;

        case TWSI_STATUS_ADDR_W_NACK:
        case TWSI_STATUS_ADDR_R_NACK:
                debugf(sc, "Address NACK-ed\n");
                twsi_error(sc, IIC_ENOACK);
                break;
        case TWSI_STATUS_DATA_WR_NACK:
                debugf(sc, "Data byte NACK-ed\n");
                twsi_error(sc, IIC_ENOACK);
                break;
        case TWSI_STATUS_DATA_WR_ACK:
                KASSERT(sc->sent_bytes <= sc->msgs[sc->msg_idx].len,
                    ("sent_bytes beyond message length"));
                debugf(sc, "ACK received after transmitting data\n");
                if (sc->sent_bytes == sc->msgs[sc->msg_idx].len) {
                        debugf(sc, "Done TX data\n");

                        /* Send stop, no interrupts on stop */
                        if (!(sc->msgs[sc->msg_idx].flags & IIC_M_NOSTOP)) {
                                TWSI_WRITE(sc, sc->reg_control,
                                    sc->control_val | TWSI_CONTROL_STOP);
                        } else {
                                debugf(sc, "NOSTOP flag\n");
                        }
                        message_done = true;
                        break;
                }

                debugf(sc, "Sending byte %d (of %d) = 0x%x\n",
                    sc->sent_bytes,
                    sc->msgs[sc->msg_idx].len,
                    sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
                TWSI_WRITE(sc, sc->reg_data,
                    sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
                sc->sent_bytes++;
                break;

        case TWSI_STATUS_DATA_RD_ACK:
                debugf(sc, "Received and ACK-ed data\n");
                KASSERT(sc->recv_bytes < sc->msgs[sc->msg_idx].len,
                    ("receiving beyond the end of buffer"));

                sc->msgs[sc->msg_idx].buf[sc->recv_bytes] =
                    TWSI_READ(sc, sc->reg_data);
                debugf(sc, "Received byte %d (of %d) = 0x%x\n",
                    sc->recv_bytes,
                    sc->msgs[sc->msg_idx].len,
                    sc->msgs[sc->msg_idx].buf[sc->recv_bytes]);
                sc->recv_bytes++;

                /* If we only have one byte left, disable ACK */
                if (sc->msgs[sc->msg_idx].len - sc->recv_bytes == 1) {
                        sc->control_val &= ~TWSI_CONTROL_ACK;
                } else if (sc->msgs[sc->msg_idx].len == sc->recv_bytes) {
                        /*
                         * We should not have ACK-ed the last byte.
                         * The protocol state machine is in invalid state.
                         */
                        debugf(sc, "RX all but asked for more?\n");
                        twsi_error(sc, IIC_ESTATUS);
                }
                break;

        case TWSI_STATUS_DATA_RD_NOACK:
                debugf(sc, "Received and NACK-ed data\n");
                KASSERT(sc->recv_bytes == sc->msgs[sc->msg_idx].len - 1,
                    ("sent NACK before receiving all requested data"));
                sc->msgs[sc->msg_idx].buf[sc->recv_bytes] =
                    TWSI_READ(sc, sc->reg_data);
                debugf(sc, "Received byte %d (of %d) = 0x%x\n",
                    sc->recv_bytes,
                    sc->msgs[sc->msg_idx].len,
                    sc->msgs[sc->msg_idx].buf[sc->recv_bytes]);
                sc->recv_bytes++;

                if (sc->msgs[sc->msg_idx].len == sc->recv_bytes) {
                        debugf(sc, "Done RX data\n");
                        if (!(sc->msgs[sc->msg_idx].flags & IIC_M_NOSTOP)) {
                                debugf(sc, "Send STOP\n");
                                TWSI_WRITE(sc, sc->reg_control,
                                    sc->control_val | TWSI_CONTROL_STOP);
                        }
                        message_done = true;
                } else {
                        /*
                         * We should not have NACK-ed yet.
                         * The protocol state machine is in invalid state.
                         */
                        debugf(sc, "NACK-ed before receving all bytes?\n");
                        twsi_error(sc, IIC_ESTATUS);
                }
                break;

        case TWSI_STATUS_BUS_ERROR:
                debugf(sc, "Bus error\n");
                twsi_error(sc, IIC_EBUSERR);
                break;
        case TWSI_STATUS_ARBITRATION_LOST:
                debugf(sc, "Arbitration lost\n");
                twsi_error(sc, IIC_EBUSBSY);
                break;
        default:
                debugf(sc, "unexpected status 0x%x\n", status);
                twsi_error(sc, IIC_ESTATUS);
                break;
        }

        if (message_done) {
                sc->msg_idx++;
                if (sc->msg_idx == sc->nmsgs) {
                        debugf(sc, "All messages transmitted\n");
                        sc->transfer = 0;
                        sc->error = 0;
                } else if ((sc->msgs[sc->msg_idx].flags & IIC_M_NOSTART) == 0) {
                        debugf(sc, "Send (repeated) start\n");
                        send_start = true;
                } else {
                        /* Just keep transmitting data. */
                        KASSERT((sc->msgs[sc->msg_idx - 1].flags & IIC_M_NOSTOP) != 0,
                            ("NOSTART message after STOP"));
                        KASSERT((sc->msgs[sc->msg_idx].flags & IIC_M_RD) ==
                            (sc->msgs[sc->msg_idx - 1].flags & IIC_M_RD),
                            ("change of transfer direction without a START"));
                        debugf(sc, "NOSTART message after NOSTOP\n");
                        sc->sent_bytes = 0;
                        sc->recv_bytes = 0;
                        if ((sc->msgs[sc->msg_idx].flags & IIC_M_RD) == 0) {
                                status = TWSI_STATUS_ADDR_W_ACK;
                                goto restart;
                        } else {
                                debugf(sc, "Read+NOSTART unsupported\n");
                                twsi_error(sc, IIC_ESTATUS);
                        }
                }
        }
end:
        /*
         * Newer Allwinner chips clear IFLG after writing 1 to it.
         */
        debugf(sc, "Refresh reg_control\n");
        TWSI_WRITE(sc, sc->reg_control, sc->control_val |
            (sc->iflag_w1c ? TWSI_CONTROL_IFLG : 0) |
            (send_start ? TWSI_CONTROL_START : 0));

        debugf(sc, "Done with interrupt, transfer = %d\n", sc->transfer);
        if (sc->transfer == 0)
                wakeup(sc);
        mtx_unlock(&sc->mutex);
}

static void
twsi_intr_start(void *pdev)
{
        struct twsi_softc *sc;

        sc = device_get_softc(pdev);

        if ((bus_setup_intr(pdev, sc->res[1], INTR_TYPE_MISC | INTR_MPSAFE,
              NULL, twsi_intr, sc, &sc->intrhand)))
                device_printf(pdev, "unable to register interrupt handler\n");

        sc->have_intr = true;
}

int
twsi_attach(device_t dev)
{
        struct twsi_softc *sc;
        struct sysctl_ctx_list *ctx;
        struct sysctl_oid *tree_node;
        struct sysctl_oid_list *tree;

        sc = device_get_softc(dev);
        sc->dev = dev;

        mtx_init(&sc->mutex, device_get_nameunit(dev), "twsi", MTX_DEF);

        if (bus_alloc_resources(dev, res_spec, sc->res)) {
                device_printf(dev, "could not allocate resources\n");
                twsi_detach(dev);
                return (ENXIO);
        }

#ifdef TWSI_DEBUG
        sc->debug = 1;
#endif
        ctx = device_get_sysctl_ctx(dev);
        tree_node = device_get_sysctl_tree(dev);
        tree = SYSCTL_CHILDREN(tree_node);
        SYSCTL_ADD_INT(ctx, tree, OID_AUTO, "debug", CTLFLAG_RWTUN,
            &sc->debug, 0, "Set debug level (zero to disable)");

        /* Attach the iicbus. */
        if ((sc->iicbus = device_add_child(dev, "iicbus",
            DEVICE_UNIT_ANY)) == NULL) {
                device_printf(dev, "could not allocate iicbus instance\n");
                twsi_detach(dev);
                return (ENXIO);
        }
        bus_attach_children(dev);

        config_intrhook_oneshot(twsi_intr_start, dev);

        return (0);
}

int
twsi_detach(device_t dev)
{
        struct twsi_softc *sc;
        int rv;

        sc = device_get_softc(dev);

        if ((rv = bus_generic_detach(dev)) != 0)
                return (rv);

        if (sc->intrhand != NULL)
                bus_teardown_intr(sc->dev, sc->res[1], sc->intrhand);

        bus_release_resources(dev, res_spec, sc->res);

        mtx_destroy(&sc->mutex);
        return (0);
}

static device_method_t twsi_methods[] = {
        /* device interface */
        DEVMETHOD(device_detach,        twsi_detach),

        /* Bus interface */
        DEVMETHOD(bus_setup_intr,       bus_generic_setup_intr),
        DEVMETHOD(bus_teardown_intr,    bus_generic_teardown_intr),
        DEVMETHOD(bus_alloc_resource,   bus_generic_alloc_resource),
        DEVMETHOD(bus_release_resource, bus_generic_release_resource),
        DEVMETHOD(bus_activate_resource, bus_generic_activate_resource),
        DEVMETHOD(bus_deactivate_resource, bus_generic_deactivate_resource),
        DEVMETHOD(bus_adjust_resource,  bus_generic_adjust_resource),
        DEVMETHOD(bus_set_resource,     bus_generic_rl_set_resource),
        DEVMETHOD(bus_get_resource,     bus_generic_rl_get_resource),

        /* iicbus interface */
        DEVMETHOD(iicbus_callback, iicbus_null_callback),
        DEVMETHOD(iicbus_repeated_start, twsi_repeated_start),
        DEVMETHOD(iicbus_start,         twsi_start),
        DEVMETHOD(iicbus_stop,          twsi_stop),
        DEVMETHOD(iicbus_write,         twsi_write),
        DEVMETHOD(iicbus_read,          twsi_read),
        DEVMETHOD(iicbus_reset,         twsi_reset),
        DEVMETHOD(iicbus_transfer,      twsi_transfer),
        DEVMETHOD_END
};

DEFINE_CLASS_0(twsi, twsi_driver, twsi_methods,
    sizeof(struct twsi_softc));