Merge tag 'media/v4.10-4' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab...

[mirror_ubuntu-zesty-kernel.git] / drivers / i2c / busses / i2c-octeon-core.c

/*
 * (C) Copyright 2009-2010
 * Nokia Siemens Networks, michael.lawnick.ext@nsn.com
 *
 * Portions Copyright (C) 2010 - 2016 Cavium, Inc.
 *
 * This file contains the shared part of the driver for the i2c adapter in
 * Cavium Networks' OCTEON processors and ThunderX SOCs.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include "i2c-octeon-core.h"

/* interrupt service routine */
irqreturn_t octeon_i2c_isr(int irq, void *dev_id)
{
        struct octeon_i2c *i2c = dev_id;

        i2c->int_disable(i2c);
        wake_up(&i2c->queue);

        return IRQ_HANDLED;
}

static bool octeon_i2c_test_iflg(struct octeon_i2c *i2c)
{
        return (octeon_i2c_ctl_read(i2c) & TWSI_CTL_IFLG);
}

/**
 * octeon_i2c_wait - wait for the IFLG to be set
 * @i2c: The struct octeon_i2c
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_wait(struct octeon_i2c *i2c)
{
        long time_left;

        /*
         * Some chip revisions don't assert the irq in the interrupt
         * controller. So we must poll for the IFLG change.
         */
        if (i2c->broken_irq_mode) {
                u64 end = get_jiffies_64() + i2c->adap.timeout;

                while (!octeon_i2c_test_iflg(i2c) &&
                       time_before64(get_jiffies_64(), end))
                        usleep_range(I2C_OCTEON_EVENT_WAIT / 2, I2C_OCTEON_EVENT_WAIT);

                return octeon_i2c_test_iflg(i2c) ? 0 : -ETIMEDOUT;
        }

        i2c->int_enable(i2c);
        time_left = wait_event_timeout(i2c->queue, octeon_i2c_test_iflg(i2c),
                                       i2c->adap.timeout);
        i2c->int_disable(i2c);

        if (i2c->broken_irq_check && !time_left &&
            octeon_i2c_test_iflg(i2c)) {
                dev_err(i2c->dev, "broken irq connection detected, switching to polling mode.\n");
                i2c->broken_irq_mode = true;
                return 0;
        }

        if (!time_left)
                return -ETIMEDOUT;

        return 0;
}

static bool octeon_i2c_hlc_test_valid(struct octeon_i2c *i2c)
{
        return (__raw_readq(i2c->twsi_base + SW_TWSI(i2c)) & SW_TWSI_V) == 0;
}

static void octeon_i2c_hlc_int_clear(struct octeon_i2c *i2c)
{
        /* clear ST/TS events, listen for neither */
        octeon_i2c_write_int(i2c, TWSI_INT_ST_INT | TWSI_INT_TS_INT);
}

/*
 * Cleanup low-level state & enable high-level controller.
 */
static void octeon_i2c_hlc_enable(struct octeon_i2c *i2c)
{
        int try = 0;
        u64 val;

        if (i2c->hlc_enabled)
                return;
        i2c->hlc_enabled = true;

        while (1) {
                val = octeon_i2c_ctl_read(i2c);
                if (!(val & (TWSI_CTL_STA | TWSI_CTL_STP)))
                        break;

                /* clear IFLG event */
                if (val & TWSI_CTL_IFLG)
                        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);

                if (try++ > 100) {
                        pr_err("%s: giving up\n", __func__);
                        break;
                }

                /* spin until any start/stop has finished */
                udelay(10);
        }
        octeon_i2c_ctl_write(i2c, TWSI_CTL_CE | TWSI_CTL_AAK | TWSI_CTL_ENAB);
}

static void octeon_i2c_hlc_disable(struct octeon_i2c *i2c)
{
        if (!i2c->hlc_enabled)
                return;

        i2c->hlc_enabled = false;
        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
}

/**
 * octeon_i2c_hlc_wait - wait for an HLC operation to complete
 * @i2c: The struct octeon_i2c
 *
 * Returns 0 on success, otherwise -ETIMEDOUT.
 */
static int octeon_i2c_hlc_wait(struct octeon_i2c *i2c)
{
        int time_left;

        /*
         * Some cn38xx boards don't assert the irq in the interrupt
         * controller. So we must poll for the valid bit change.
         */
        if (i2c->broken_irq_mode) {
                u64 end = get_jiffies_64() + i2c->adap.timeout;

                while (!octeon_i2c_hlc_test_valid(i2c) &&
                       time_before64(get_jiffies_64(), end))
                        usleep_range(I2C_OCTEON_EVENT_WAIT / 2, I2C_OCTEON_EVENT_WAIT);

                return octeon_i2c_hlc_test_valid(i2c) ? 0 : -ETIMEDOUT;
        }

        i2c->hlc_int_enable(i2c);
        time_left = wait_event_timeout(i2c->queue,
                                       octeon_i2c_hlc_test_valid(i2c),
                                       i2c->adap.timeout);
        i2c->hlc_int_disable(i2c);
        if (!time_left)
                octeon_i2c_hlc_int_clear(i2c);

        if (i2c->broken_irq_check && !time_left &&
            octeon_i2c_hlc_test_valid(i2c)) {
                dev_err(i2c->dev, "broken irq connection detected, switching to polling mode.\n");
                i2c->broken_irq_mode = true;
                return 0;
        }

        if (!time_left)
                return -ETIMEDOUT;
        return 0;
}

static int octeon_i2c_check_status(struct octeon_i2c *i2c, int final_read)
{
        u8 stat;

        /*
         * This is ugly... in HLC mode the status is not in the status register
         * but in the lower 8 bits of SW_TWSI.
         */
        if (i2c->hlc_enabled)
                stat = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
        else
                stat = octeon_i2c_stat_read(i2c);

        switch (stat) {
        /* Everything is fine */
        case STAT_IDLE:
        case STAT_AD2W_ACK:
        case STAT_RXADDR_ACK:
        case STAT_TXADDR_ACK:
        case STAT_TXDATA_ACK:
                return 0;

        /* ACK allowed on pre-terminal bytes only */
        case STAT_RXDATA_ACK:
                if (!final_read)
                        return 0;
                return -EIO;

        /* NAK allowed on terminal byte only */
        case STAT_RXDATA_NAK:
                if (final_read)
                        return 0;
                return -EIO;

        /* Arbitration lost */
        case STAT_LOST_ARB_38:
        case STAT_LOST_ARB_68:
        case STAT_LOST_ARB_78:
        case STAT_LOST_ARB_B0:
                return -EAGAIN;

        /* Being addressed as slave, should back off & listen */
        case STAT_SLAVE_60:
        case STAT_SLAVE_70:
        case STAT_GENDATA_ACK:
        case STAT_GENDATA_NAK:
                return -EOPNOTSUPP;

        /* Core busy as slave */
        case STAT_SLAVE_80:
        case STAT_SLAVE_88:
        case STAT_SLAVE_A0:
        case STAT_SLAVE_A8:
        case STAT_SLAVE_LOST:
        case STAT_SLAVE_NAK:
        case STAT_SLAVE_ACK:
                return -EOPNOTSUPP;

        case STAT_TXDATA_NAK:
                return -EIO;
        case STAT_TXADDR_NAK:
        case STAT_RXADDR_NAK:
        case STAT_AD2W_NAK:
                return -ENXIO;
        default:
                dev_err(i2c->dev, "unhandled state: %d\n", stat);
                return -EIO;
        }
}

static int octeon_i2c_recovery(struct octeon_i2c *i2c)
{
        int ret;

        ret = i2c_recover_bus(&i2c->adap);
        if (ret)
                /* recover failed, try hardware re-init */
                ret = octeon_i2c_init_lowlevel(i2c);
        return ret;
}

/**
 * octeon_i2c_start - send START to the bus
 * @i2c: The struct octeon_i2c
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_start(struct octeon_i2c *i2c)
{
        int ret;
        u8 stat;

        octeon_i2c_hlc_disable(i2c);

        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB | TWSI_CTL_STA);
        ret = octeon_i2c_wait(i2c);
        if (ret)
                goto error;

        stat = octeon_i2c_stat_read(i2c);
        if (stat == STAT_START || stat == STAT_REP_START)
                /* START successful, bail out */
                return 0;

error:
        /* START failed, try to recover */
        ret = octeon_i2c_recovery(i2c);
        return (ret) ? ret : -EAGAIN;
}

/* send STOP to the bus */
static void octeon_i2c_stop(struct octeon_i2c *i2c)
{
        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB | TWSI_CTL_STP);
}

/**
 * octeon_i2c_read - receive data from the bus via low-level controller
 * @i2c: The struct octeon_i2c
 * @target: Target address
 * @data: Pointer to the location to store the data
 * @rlength: Length of the data
 * @recv_len: flag for length byte
 *
 * The address is sent over the bus, then the data is read.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_read(struct octeon_i2c *i2c, int target,
                           u8 *data, u16 *rlength, bool recv_len)
{
        int i, result, length = *rlength;
        bool final_read = false;

        octeon_i2c_data_write(i2c, (target << 1) | 1);
        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);

        result = octeon_i2c_wait(i2c);
        if (result)
                return result;

        /* address OK ? */
        result = octeon_i2c_check_status(i2c, false);
        if (result)
                return result;

        for (i = 0; i < length; i++) {
                /*
                 * For the last byte to receive TWSI_CTL_AAK must not be set.
                 *
                 * A special case is I2C_M_RECV_LEN where we don't know the
                 * additional length yet. If recv_len is set we assume we're
                 * not reading the final byte and therefore need to set
                 * TWSI_CTL_AAK.
                 */
                if ((i + 1 == length) && !(recv_len && i == 0))
                        final_read = true;

                /* clear iflg to allow next event */
                if (final_read)
                        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
                else
                        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB | TWSI_CTL_AAK);

                result = octeon_i2c_wait(i2c);
                if (result)
                        return result;

                data[i] = octeon_i2c_data_read(i2c, &result);
                if (result)
                        return result;
                if (recv_len && i == 0) {
                        if (data[i] > I2C_SMBUS_BLOCK_MAX + 1)
                                return -EPROTO;
                        length += data[i];
                }

                result = octeon_i2c_check_status(i2c, final_read);
                if (result)
                        return result;
        }
        *rlength = length;
        return 0;
}

/**
 * octeon_i2c_write - send data to the bus via low-level controller
 * @i2c: The struct octeon_i2c
 * @target: Target address
 * @data: Pointer to the data to be sent
 * @length: Length of the data
 *
 * The address is sent over the bus, then the data.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_write(struct octeon_i2c *i2c, int target,
                            const u8 *data, int length)
{
        int i, result;

        octeon_i2c_data_write(i2c, target << 1);
        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);

        result = octeon_i2c_wait(i2c);
        if (result)
                return result;

        for (i = 0; i < length; i++) {
                result = octeon_i2c_check_status(i2c, false);
                if (result)
                        return result;

                octeon_i2c_data_write(i2c, data[i]);
                octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);

                result = octeon_i2c_wait(i2c);
                if (result)
                        return result;
        }

        return 0;
}

/* high-level-controller pure read of up to 8 bytes */
static int octeon_i2c_hlc_read(struct octeon_i2c *i2c, struct i2c_msg *msgs)
{
        int i, j, ret = 0;
        u64 cmd;

        octeon_i2c_hlc_enable(i2c);
        octeon_i2c_hlc_int_clear(i2c);

        cmd = SW_TWSI_V | SW_TWSI_R | SW_TWSI_SOVR;
        /* SIZE */
        cmd |= (u64)(msgs[0].len - 1) << SW_TWSI_SIZE_SHIFT;
        /* A */
        cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;

        if (msgs[0].flags & I2C_M_TEN)
                cmd |= SW_TWSI_OP_10;
        else
                cmd |= SW_TWSI_OP_7;

        octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI(i2c));
        ret = octeon_i2c_hlc_wait(i2c);
        if (ret)
                goto err;

        cmd = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
        if ((cmd & SW_TWSI_R) == 0)
                return octeon_i2c_check_status(i2c, false);

        for (i = 0, j = msgs[0].len - 1; i  < msgs[0].len && i < 4; i++, j--)
                msgs[0].buf[j] = (cmd >> (8 * i)) & 0xff;

        if (msgs[0].len > 4) {
                cmd = __raw_readq(i2c->twsi_base + SW_TWSI_EXT(i2c));
                for (i = 0; i  < msgs[0].len - 4 && i < 4; i++, j--)
                        msgs[0].buf[j] = (cmd >> (8 * i)) & 0xff;
        }

err:
        return ret;
}

/* high-level-controller pure write of up to 8 bytes */
static int octeon_i2c_hlc_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
{
        int i, j, ret = 0;
        u64 cmd;

        octeon_i2c_hlc_enable(i2c);
        octeon_i2c_hlc_int_clear(i2c);

        cmd = SW_TWSI_V | SW_TWSI_SOVR;
        /* SIZE */
        cmd |= (u64)(msgs[0].len - 1) << SW_TWSI_SIZE_SHIFT;
        /* A */
        cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;

        if (msgs[0].flags & I2C_M_TEN)
                cmd |= SW_TWSI_OP_10;
        else
                cmd |= SW_TWSI_OP_7;

        for (i = 0, j = msgs[0].len - 1; i  < msgs[0].len && i < 4; i++, j--)
                cmd |= (u64)msgs[0].buf[j] << (8 * i);

        if (msgs[0].len > 4) {
                u64 ext = 0;

                for (i = 0; i < msgs[0].len - 4 && i < 4; i++, j--)
                        ext |= (u64)msgs[0].buf[j] << (8 * i);
                octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT(i2c));
        }

        octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI(i2c));
        ret = octeon_i2c_hlc_wait(i2c);
        if (ret)
                goto err;

        cmd = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
        if ((cmd & SW_TWSI_R) == 0)
                return octeon_i2c_check_status(i2c, false);

err:
        return ret;
}

/* high-level-controller composite write+read, msg0=addr, msg1=data */
static int octeon_i2c_hlc_comp_read(struct octeon_i2c *i2c, struct i2c_msg *msgs)
{
        int i, j, ret = 0;
        u64 cmd;

        octeon_i2c_hlc_enable(i2c);

        cmd = SW_TWSI_V | SW_TWSI_R | SW_TWSI_SOVR;
        /* SIZE */
        cmd |= (u64)(msgs[1].len - 1) << SW_TWSI_SIZE_SHIFT;
        /* A */
        cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;

        if (msgs[0].flags & I2C_M_TEN)
                cmd |= SW_TWSI_OP_10_IA;
        else
                cmd |= SW_TWSI_OP_7_IA;

        if (msgs[0].len == 2) {
                u64 ext = 0;

                cmd |= SW_TWSI_EIA;
                ext = (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
                cmd |= (u64)msgs[0].buf[1] << SW_TWSI_IA_SHIFT;
                octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT(i2c));
        } else {
                cmd |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
        }

        octeon_i2c_hlc_int_clear(i2c);
        octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI(i2c));

        ret = octeon_i2c_hlc_wait(i2c);
        if (ret)
                goto err;

        cmd = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
        if ((cmd & SW_TWSI_R) == 0)
                return octeon_i2c_check_status(i2c, false);

        for (i = 0, j = msgs[1].len - 1; i  < msgs[1].len && i < 4; i++, j--)
                msgs[1].buf[j] = (cmd >> (8 * i)) & 0xff;

        if (msgs[1].len > 4) {
                cmd = __raw_readq(i2c->twsi_base + SW_TWSI_EXT(i2c));
                for (i = 0; i  < msgs[1].len - 4 && i < 4; i++, j--)
                        msgs[1].buf[j] = (cmd >> (8 * i)) & 0xff;
        }

err:
        return ret;
}

/* high-level-controller composite write+write, m[0]len<=2, m[1]len<=8 */
static int octeon_i2c_hlc_comp_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
{
        bool set_ext = false;
        int i, j, ret = 0;
        u64 cmd, ext = 0;

        octeon_i2c_hlc_enable(i2c);

        cmd = SW_TWSI_V | SW_TWSI_SOVR;
        /* SIZE */
        cmd |= (u64)(msgs[1].len - 1) << SW_TWSI_SIZE_SHIFT;
        /* A */
        cmd |= (u64)(msgs[0].addr & 0x7full) << SW_TWSI_ADDR_SHIFT;

        if (msgs[0].flags & I2C_M_TEN)
                cmd |= SW_TWSI_OP_10_IA;
        else
                cmd |= SW_TWSI_OP_7_IA;

        if (msgs[0].len == 2) {
                cmd |= SW_TWSI_EIA;
                ext |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
                set_ext = true;
                cmd |= (u64)msgs[0].buf[1] << SW_TWSI_IA_SHIFT;
        } else {
                cmd |= (u64)msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
        }

        for (i = 0, j = msgs[1].len - 1; i  < msgs[1].len && i < 4; i++, j--)
                cmd |= (u64)msgs[1].buf[j] << (8 * i);

        if (msgs[1].len > 4) {
                for (i = 0; i < msgs[1].len - 4 && i < 4; i++, j--)
                        ext |= (u64)msgs[1].buf[j] << (8 * i);
                set_ext = true;
        }
        if (set_ext)
                octeon_i2c_writeq_flush(ext, i2c->twsi_base + SW_TWSI_EXT(i2c));

        octeon_i2c_hlc_int_clear(i2c);
        octeon_i2c_writeq_flush(cmd, i2c->twsi_base + SW_TWSI(i2c));

        ret = octeon_i2c_hlc_wait(i2c);
        if (ret)
                goto err;

        cmd = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
        if ((cmd & SW_TWSI_R) == 0)
                return octeon_i2c_check_status(i2c, false);

err:
        return ret;
}

/**
 * octeon_i2c_xfer - The driver's master_xfer function
 * @adap: Pointer to the i2c_adapter structure
 * @msgs: Pointer to the messages to be processed
 * @num: Length of the MSGS array
 *
 * Returns the number of messages processed, or a negative errno on failure.
 */
int octeon_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);
        int i, ret = 0;

        if (num == 1) {
                if (msgs[0].len > 0 && msgs[0].len <= 8) {
                        if (msgs[0].flags & I2C_M_RD)
                                ret = octeon_i2c_hlc_read(i2c, msgs);
                        else
                                ret = octeon_i2c_hlc_write(i2c, msgs);
                        goto out;
                }
        } else if (num == 2) {
                if ((msgs[0].flags & I2C_M_RD) == 0 &&
                    (msgs[1].flags & I2C_M_RECV_LEN) == 0 &&
                    msgs[0].len > 0 && msgs[0].len <= 2 &&
                    msgs[1].len > 0 && msgs[1].len <= 8 &&
                    msgs[0].addr == msgs[1].addr) {
                        if (msgs[1].flags & I2C_M_RD)
                                ret = octeon_i2c_hlc_comp_read(i2c, msgs);
                        else
                                ret = octeon_i2c_hlc_comp_write(i2c, msgs);
                        goto out;
                }
        }

        for (i = 0; ret == 0 && i < num; i++) {
                struct i2c_msg *pmsg = &msgs[i];

                /* zero-length messages are not supported */
                if (!pmsg->len) {
                        ret = -EOPNOTSUPP;
                        break;
                }

                ret = octeon_i2c_start(i2c);
                if (ret)
                        return ret;

                if (pmsg->flags & I2C_M_RD)
                        ret = octeon_i2c_read(i2c, pmsg->addr, pmsg->buf,
                                              &pmsg->len, pmsg->flags & I2C_M_RECV_LEN);
                else
                        ret = octeon_i2c_write(i2c, pmsg->addr, pmsg->buf,
                                               pmsg->len);
        }
        octeon_i2c_stop(i2c);
out:
        return (ret != 0) ? ret : num;
}

/* calculate and set clock divisors */
void octeon_i2c_set_clock(struct octeon_i2c *i2c)
{
        int tclk, thp_base, inc, thp_idx, mdiv_idx, ndiv_idx, foscl, diff;
        int thp = 0x18, mdiv = 2, ndiv = 0, delta_hz = 1000000;

        for (ndiv_idx = 0; ndiv_idx < 8 && delta_hz != 0; ndiv_idx++) {
                /*
                 * An mdiv value of less than 2 seems to not work well
                 * with ds1337 RTCs, so we constrain it to larger values.
                 */
                for (mdiv_idx = 15; mdiv_idx >= 2 && delta_hz != 0; mdiv_idx--) {
                        /*
                         * For given ndiv and mdiv values check the
                         * two closest thp values.
                         */
                        tclk = i2c->twsi_freq * (mdiv_idx + 1) * 10;
                        tclk *= (1 << ndiv_idx);
                        thp_base = (i2c->sys_freq / (tclk * 2)) - 1;

                        for (inc = 0; inc <= 1; inc++) {
                                thp_idx = thp_base + inc;
                                if (thp_idx < 5 || thp_idx > 0xff)
                                        continue;

                                foscl = i2c->sys_freq / (2 * (thp_idx + 1));
                                foscl = foscl / (1 << ndiv_idx);
                                foscl = foscl / (mdiv_idx + 1) / 10;
                                diff = abs(foscl - i2c->twsi_freq);
                                if (diff < delta_hz) {
                                        delta_hz = diff;
                                        thp = thp_idx;
                                        mdiv = mdiv_idx;
                                        ndiv = ndiv_idx;
                                }
                        }
                }
        }
        octeon_i2c_reg_write(i2c, SW_TWSI_OP_TWSI_CLK, thp);
        octeon_i2c_reg_write(i2c, SW_TWSI_EOP_TWSI_CLKCTL, (mdiv << 3) | ndiv);
}

int octeon_i2c_init_lowlevel(struct octeon_i2c *i2c)
{
        u8 status = 0;
        int tries;

        /* reset controller */
        octeon_i2c_reg_write(i2c, SW_TWSI_EOP_TWSI_RST, 0);

        for (tries = 10; tries && status != STAT_IDLE; tries--) {
                udelay(1);
                status = octeon_i2c_stat_read(i2c);
                if (status == STAT_IDLE)
                        break;
        }

        if (status != STAT_IDLE) {
                dev_err(i2c->dev, "%s: TWSI_RST failed! (0x%x)\n",
                        __func__, status);
                return -EIO;
        }

        /* toggle twice to force both teardowns */
        octeon_i2c_hlc_enable(i2c);
        octeon_i2c_hlc_disable(i2c);
        return 0;
}

static int octeon_i2c_get_scl(struct i2c_adapter *adap)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);
        u64 state;

        state = octeon_i2c_read_int(i2c);
        return state & TWSI_INT_SCL;
}

static void octeon_i2c_set_scl(struct i2c_adapter *adap, int val)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);

        octeon_i2c_write_int(i2c, val ? 0 : TWSI_INT_SCL_OVR);
}

static int octeon_i2c_get_sda(struct i2c_adapter *adap)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);
        u64 state;

        state = octeon_i2c_read_int(i2c);
        return state & TWSI_INT_SDA;
}

static void octeon_i2c_prepare_recovery(struct i2c_adapter *adap)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);

        octeon_i2c_hlc_disable(i2c);
        octeon_i2c_reg_write(i2c, SW_TWSI_EOP_TWSI_RST, 0);
        /* wait for software reset to settle */
        udelay(5);

        /*
         * Bring control register to a good state regardless
         * of HLC state.
         */
        octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);

        octeon_i2c_write_int(i2c, 0);
}

static void octeon_i2c_unprepare_recovery(struct i2c_adapter *adap)
{
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);

        /*
         * Generate STOP to finish the unfinished transaction.
         * Can't generate STOP via the TWSI CTL register
         * since it could bring the TWSI controller into an inoperable state.
         */
        octeon_i2c_write_int(i2c, TWSI_INT_SDA_OVR | TWSI_INT_SCL_OVR);
        udelay(5);
        octeon_i2c_write_int(i2c, TWSI_INT_SDA_OVR);
        udelay(5);
        octeon_i2c_write_int(i2c, 0);
}

struct i2c_bus_recovery_info octeon_i2c_recovery_info = {
        .recover_bus = i2c_generic_scl_recovery,
        .get_scl = octeon_i2c_get_scl,
        .set_scl = octeon_i2c_set_scl,
        .get_sda = octeon_i2c_get_sda,
        .prepare_recovery = octeon_i2c_prepare_recovery,
        .unprepare_recovery = octeon_i2c_unprepare_recovery,
};