// SPDX-License-Identifier: GPL-2.0-only
/*
 * STMicroelectronics st_lsm6dsx FIFO buffer library driver
 *
 * LSM6DS3/LSM6DS3H/LSM6DSL/LSM6DSM/ISM330DLC/LSM6DS3TR-C:
 * The FIFO buffer can be configured to store data from gyroscope and
 * accelerometer. Samples are queued without any tag according to a
 * specific pattern based on 'FIFO data sets' (6 bytes each):
 *  - 1st data set is reserved for gyroscope data
 *  - 2nd data set is reserved for accelerometer data
 * The FIFO pattern changes depending on the ODRs and decimation factors
 * assigned to the FIFO data sets. The first sequence of data stored in FIFO
 * buffer contains the data of all the enabled FIFO data sets
 * (e.g. Gx, Gy, Gz, Ax, Ay, Az), then data are repeated depending on the
 * value of the decimation factor and ODR set for each FIFO data set.
 *
 * LSM6DSO/LSM6DSOX/ASM330LHH/LSM6DSR/LSM6DSRX/ISM330DHCX/LSM6DST/LSM6DSOP:
 * The FIFO buffer can be configured to store data from gyroscope and
 * accelerometer. Each sample is queued with a tag (1B) indicating data
 * source (gyroscope, accelerometer, hw timer).
 *
 * FIFO supported modes:
 *  - BYPASS: FIFO disabled
 *  - CONTINUOUS: FIFO enabled. When the buffer is full, the FIFO index
 *    restarts from the beginning and the oldest sample is overwritten
 *
 * Copyright 2016 STMicroelectronics Inc.
 *
 * Lorenzo Bianconi <lorenzo.bianconi@st.com>
 * Denis Ciocca <denis.ciocca@st.com>
 */
#include <linux/module.h>
#include <linux/iio/kfifo_buf.h>
#include <linux/iio/iio.h>
#include <linux/iio/buffer.h>
#include <linux/regmap.h>
#include <linux/bitfield.h>

#include <linux/platform_data/st_sensors_pdata.h>

#include "st_lsm6dsx.h"

#define ST_LSM6DSX_REG_FIFO_MODE_ADDR           0x0a
#define ST_LSM6DSX_FIFO_MODE_MASK               GENMASK(2, 0)
#define ST_LSM6DSX_FIFO_ODR_MASK                GENMASK(6, 3)
#define ST_LSM6DSX_FIFO_EMPTY_MASK              BIT(12)
#define ST_LSM6DSX_REG_FIFO_OUTL_ADDR           0x3e
#define ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR        0x78
#define ST_LSM6DSX_REG_TS_RESET_ADDR            0x42

#define ST_LSM6DSX_MAX_FIFO_ODR_VAL             0x08

#define ST_LSM6DSX_TS_RESET_VAL                 0xaa

struct st_lsm6dsx_decimator_entry {
        u8 decimator;
        u8 val;
};

enum st_lsm6dsx_fifo_tag {
        ST_LSM6DSX_GYRO_TAG = 0x01,
        ST_LSM6DSX_ACC_TAG = 0x02,
        ST_LSM6DSX_TS_TAG = 0x04,
        ST_LSM6DSX_EXT0_TAG = 0x0f,
        ST_LSM6DSX_EXT1_TAG = 0x10,
        ST_LSM6DSX_EXT2_TAG = 0x11,
};

static const
struct st_lsm6dsx_decimator_entry st_lsm6dsx_decimator_table[] = {
        {  0, 0x0 },
        {  1, 0x1 },
        {  2, 0x2 },
        {  3, 0x3 },
        {  4, 0x4 },
        {  8, 0x5 },
        { 16, 0x6 },
        { 32, 0x7 },
};

static int
st_lsm6dsx_get_decimator_val(struct st_lsm6dsx_sensor *sensor, u32 max_odr)
{
        const int max_size = ARRAY_SIZE(st_lsm6dsx_decimator_table);
        u32 decimator =  max_odr / sensor->odr;
        int i;

        if (decimator > 1)
                decimator = round_down(decimator, 2);

        for (i = 0; i < max_size; i++) {
                if (st_lsm6dsx_decimator_table[i].decimator == decimator)
                        break;
        }

        sensor->decimator = decimator;
        return i == max_size ? 0 : st_lsm6dsx_decimator_table[i].val;
}

static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
                                       u32 *max_odr, u32 *min_odr)
{
        struct st_lsm6dsx_sensor *sensor;
        int i;

        *max_odr = 0, *min_odr = ~0;
        for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
                if (!hw->iio_devs[i])
                        continue;

                sensor = iio_priv(hw->iio_devs[i]);

                if (!(hw->enable_mask & BIT(sensor->id)))
                        continue;

                *max_odr = max_t(u32, *max_odr, sensor->odr);
                *min_odr = min_t(u32, *min_odr, sensor->odr);
        }
}

static u8 st_lsm6dsx_get_sip(struct st_lsm6dsx_sensor *sensor, u32 min_odr)
{
        u8 sip = sensor->odr / min_odr;

        return sip > 1 ? round_down(sip, 2) : sip;
}

static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
{
        const struct st_lsm6dsx_reg *ts_dec_reg;
        struct st_lsm6dsx_sensor *sensor;
        u16 sip = 0, ts_sip = 0;
        u32 max_odr, min_odr;
        int err = 0, i;
        u8 data;

        st_lsm6dsx_get_max_min_odr(hw, &max_odr, &min_odr);

        for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
                const struct st_lsm6dsx_reg *dec_reg;

                if (!hw->iio_devs[i])
                        continue;

                sensor = iio_priv(hw->iio_devs[i]);
                /* update fifo decimators and sample in pattern */
                if (hw->enable_mask & BIT(sensor->id)) {
                        sensor->sip = st_lsm6dsx_get_sip(sensor, min_odr);
                        data = st_lsm6dsx_get_decimator_val(sensor, max_odr);
                } else {
                        sensor->sip = 0;
                        data = 0;
                }
                ts_sip = max_t(u16, ts_sip, sensor->sip);

                dec_reg = &hw->settings->decimator[sensor->id];
                if (dec_reg->addr) {
                        int val = ST_LSM6DSX_SHIFT_VAL(data, dec_reg->mask);

                        err = st_lsm6dsx_update_bits_locked(hw, dec_reg->addr,
                                                            dec_reg->mask,
                                                            val);
                        if (err < 0)
                                return err;
                }
                sip += sensor->sip;
        }
        hw->sip = sip + ts_sip;
        hw->ts_sip = ts_sip;

        /*
         * update hw ts decimator if necessary. Decimator for hw timestamp
         * is always 1 or 0 in order to have a ts sample for each data
         * sample in FIFO
         */
        ts_dec_reg = &hw->settings->ts_settings.decimator;
        if (ts_dec_reg->addr) {
                int val, ts_dec = !!hw->ts_sip;

                val = ST_LSM6DSX_SHIFT_VAL(ts_dec, ts_dec_reg->mask);
                err = st_lsm6dsx_update_bits_locked(hw, ts_dec_reg->addr,
                                                    ts_dec_reg->mask, val);
        }
        return err;
}

static int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
                                    enum st_lsm6dsx_fifo_mode fifo_mode)
{
        unsigned int data;

        data = FIELD_PREP(ST_LSM6DSX_FIFO_MODE_MASK, fifo_mode);
        return st_lsm6dsx_update_bits_locked(hw, ST_LSM6DSX_REG_FIFO_MODE_ADDR,
                                             ST_LSM6DSX_FIFO_MODE_MASK, data);
}

static int st_lsm6dsx_set_fifo_odr(struct st_lsm6dsx_sensor *sensor,
                                   bool enable)
{
        struct st_lsm6dsx_hw *hw = sensor->hw;
        const struct st_lsm6dsx_reg *batch_reg;
        u8 data;

        batch_reg = &hw->settings->batch[sensor->id];
        if (batch_reg->addr) {
                int val;

                if (enable) {
                        int err;

                        err = st_lsm6dsx_check_odr(sensor, sensor->odr,
                                                   &data);
                        if (err < 0)
                                return err;
                } else {
                        data = 0;
                }
                val = ST_LSM6DSX_SHIFT_VAL(data, batch_reg->mask);
                return st_lsm6dsx_update_bits_locked(hw, batch_reg->addr,
                                                     batch_reg->mask, val);
        } else {
                data = hw->enable_mask ? ST_LSM6DSX_MAX_FIFO_ODR_VAL : 0;
                return st_lsm6dsx_update_bits_locked(hw,
                                        ST_LSM6DSX_REG_FIFO_MODE_ADDR,
                                        ST_LSM6DSX_FIFO_ODR_MASK,
                                        FIELD_PREP(ST_LSM6DSX_FIFO_ODR_MASK,
                                                   data));
        }
}

int st_lsm6dsx_update_watermark(struct st_lsm6dsx_sensor *sensor, u16 watermark)
{
        u16 fifo_watermark = ~0, cur_watermark, fifo_th_mask;
        struct st_lsm6dsx_hw *hw = sensor->hw;
        struct st_lsm6dsx_sensor *cur_sensor;
        int i, err, data;
        __le16 wdata;

        if (!hw->sip)
                return 0;

        for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
                if (!hw->iio_devs[i])
                        continue;

                cur_sensor = iio_priv(hw->iio_devs[i]);

                if (!(hw->enable_mask & BIT(cur_sensor->id)))
                        continue;

                cur_watermark = (cur_sensor == sensor) ? watermark
                                                       : cur_sensor->watermark;

                fifo_watermark = min_t(u16, fifo_watermark, cur_watermark);
        }

        fifo_watermark = max_t(u16, fifo_watermark, hw->sip);
        fifo_watermark = (fifo_watermark / hw->sip) * hw->sip;
        fifo_watermark = fifo_watermark * hw->settings->fifo_ops.th_wl;

        mutex_lock(&hw->page_lock);
        err = regmap_read(hw->regmap, hw->settings->fifo_ops.fifo_th.addr + 1,
                          &data);
        if (err < 0)
                goto out;

        fifo_th_mask = hw->settings->fifo_ops.fifo_th.mask;
        fifo_watermark = ((data << 8) & ~fifo_th_mask) |
                         (fifo_watermark & fifo_th_mask);

        wdata = cpu_to_le16(fifo_watermark);
        err = regmap_bulk_write(hw->regmap,
                                hw->settings->fifo_ops.fifo_th.addr,
                                &wdata, sizeof(wdata));
out:
        mutex_unlock(&hw->page_lock);
        return err;
}

static int st_lsm6dsx_reset_hw_ts(struct st_lsm6dsx_hw *hw)
{
        struct st_lsm6dsx_sensor *sensor;
        int i, err;

        /* reset hw ts counter */
        err = st_lsm6dsx_write_locked(hw, ST_LSM6DSX_REG_TS_RESET_ADDR,
                                      ST_LSM6DSX_TS_RESET_VAL);
        if (err < 0)
                return err;

        for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
                if (!hw->iio_devs[i])
                        continue;

                sensor = iio_priv(hw->iio_devs[i]);
                /*
                 * store enable buffer timestamp as reference for
                 * hw timestamp
                 */
                sensor->ts_ref = iio_get_time_ns(hw->iio_devs[i]);
        }
        return 0;
}

int st_lsm6dsx_resume_fifo(struct st_lsm6dsx_hw *hw)
{
        int err;

        /* reset hw ts counter */
        err = st_lsm6dsx_reset_hw_ts(hw);
        if (err < 0)
                return err;

        return st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
}

/*
 * Set max bulk read to ST_LSM6DSX_MAX_WORD_LEN/ST_LSM6DSX_MAX_TAGGED_WORD_LEN
 * in order to avoid a kmalloc for each bus access
 */
static inline int st_lsm6dsx_read_block(struct st_lsm6dsx_hw *hw, u8 addr,
                                        u8 *data, unsigned int data_len,
                                        unsigned int max_word_len)
{
        unsigned int word_len, read_len = 0;
        int err;

        while (read_len < data_len) {
                word_len = min_t(unsigned int, data_len - read_len,
                                 max_word_len);
                err = st_lsm6dsx_read_locked(hw, addr, data + read_len,
                                             word_len);
                if (err < 0)
                        return err;
                read_len += word_len;
        }
        return 0;
}

#define ST_LSM6DSX_IIO_BUFF_SIZE        (ALIGN(ST_LSM6DSX_SAMPLE_SIZE, \
                                               sizeof(s64)) + sizeof(s64))
/**
 * st_lsm6dsx_read_fifo() - hw FIFO read routine
 * @hw: Pointer to instance of struct st_lsm6dsx_hw.
 *
 * Read samples from the hw FIFO and push them to IIO buffers.
 *
 * Return: Number of bytes read from the FIFO
 */
int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
{
        struct st_lsm6dsx_sensor *acc_sensor, *gyro_sensor, *ext_sensor = NULL;
        int err, sip, acc_sip, gyro_sip, ts_sip, ext_sip, read_len, offset;
        u16 fifo_len, pattern_len = hw->sip * ST_LSM6DSX_SAMPLE_SIZE;
        u16 fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
        bool reset_ts = false;
        __le16 fifo_status;
        s64 ts = 0;

        err = st_lsm6dsx_read_locked(hw,
                                     hw->settings->fifo_ops.fifo_diff.addr,
                                     &fifo_status, sizeof(fifo_status));
        if (err < 0) {
                dev_err(hw->dev, "failed to read fifo status (err=%d)\n",
                        err);
                return err;
        }

        if (fifo_status & cpu_to_le16(ST_LSM6DSX_FIFO_EMPTY_MASK))
                return 0;

        fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
                   ST_LSM6DSX_CHAN_SIZE;
        fifo_len = (fifo_len / pattern_len) * pattern_len;

        acc_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
        gyro_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_GYRO]);
        if (hw->iio_devs[ST_LSM6DSX_ID_EXT0])
                ext_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_EXT0]);

        for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
                err = st_lsm6dsx_read_block(hw, ST_LSM6DSX_REG_FIFO_OUTL_ADDR,
                                            hw->buff, pattern_len,
                                            ST_LSM6DSX_MAX_WORD_LEN);
                if (err < 0) {
                        dev_err(hw->dev,
                                "failed to read pattern from fifo (err=%d)\n",
                                err);
                        return err;
                }

                /*
                 * Data are written to the FIFO with a specific pattern
                 * depending on the configured ODRs. The first sequence of data
                 * stored in FIFO contains the data of all enabled sensors
                 * (e.g. Gx, Gy, Gz, Ax, Ay, Az, Ts), then data are repeated
                 * depending on the value of the decimation factor set for each
                 * sensor.
                 *
                 * Supposing the FIFO is storing data from gyroscope and
                 * accelerometer at different ODRs:
                 *   - gyroscope ODR = 208Hz, accelerometer ODR = 104Hz
                 * Since the gyroscope ODR is twice the accelerometer one, the
                 * following pattern is repeated every 9 samples:
                 *   - Gx, Gy, Gz, Ax, Ay, Az, Ts, Gx, Gy, Gz, Ts, Gx, ..
                 */
                ext_sip = ext_sensor ? ext_sensor->sip : 0;
                gyro_sip = gyro_sensor->sip;
                acc_sip = acc_sensor->sip;
                ts_sip = hw->ts_sip;
                offset = 0;
                sip = 0;

                while (acc_sip > 0 || gyro_sip > 0 || ext_sip > 0) {
                        if (gyro_sip > 0 && !(sip % gyro_sensor->decimator)) {
                                memcpy(hw->scan[ST_LSM6DSX_ID_GYRO].channels,
                                       &hw->buff[offset],
                                       sizeof(hw->scan[ST_LSM6DSX_ID_GYRO].channels));
                                offset += sizeof(hw->scan[ST_LSM6DSX_ID_GYRO].channels);
                        }
                        if (acc_sip > 0 && !(sip % acc_sensor->decimator)) {
                                memcpy(hw->scan[ST_LSM6DSX_ID_ACC].channels,
                                       &hw->buff[offset],
                                       sizeof(hw->scan[ST_LSM6DSX_ID_ACC].channels));
                                offset += sizeof(hw->scan[ST_LSM6DSX_ID_ACC].channels);
                        }
                        if (ext_sip > 0 && !(sip % ext_sensor->decimator)) {
                                memcpy(hw->scan[ST_LSM6DSX_ID_EXT0].channels,
                                       &hw->buff[offset],
                                       sizeof(hw->scan[ST_LSM6DSX_ID_EXT0].channels));
                                offset += sizeof(hw->scan[ST_LSM6DSX_ID_EXT0].channels);
                        }

                        if (ts_sip-- > 0) {
                                u8 data[ST_LSM6DSX_SAMPLE_SIZE];

                                memcpy(data, &hw->buff[offset], sizeof(data));
                                /*
                                 * hw timestamp is 3B long and it is stored
                                 * in FIFO using 6B as 4th FIFO data set
                                 * according to this schema:
                                 * B0 = ts[15:8], B1 = ts[23:16], B3 = ts[7:0]
                                 */
                                ts = data[1] << 16 | data[0] << 8 | data[3];
                                /*
                                 * check if hw timestamp engine is going to
                                 * reset (the sensor generates an interrupt
                                 * to signal the hw timestamp will reset in
                                 * 1.638s)
                                 */
                                if (!reset_ts && ts >= 0xff0000)
                                        reset_ts = true;
                                ts *= hw->ts_gain;

                                offset += ST_LSM6DSX_SAMPLE_SIZE;
                        }

                        if (gyro_sip > 0 && !(sip % gyro_sensor->decimator)) {
                                iio_push_to_buffers_with_timestamp(
                                        hw->iio_devs[ST_LSM6DSX_ID_GYRO],
                                        &hw->scan[ST_LSM6DSX_ID_GYRO],
                                        gyro_sensor->ts_ref + ts);
                                gyro_sip--;
                        }
                        if (acc_sip > 0 && !(sip % acc_sensor->decimator)) {
                                iio_push_to_buffers_with_timestamp(
                                        hw->iio_devs[ST_LSM6DSX_ID_ACC],
                                        &hw->scan[ST_LSM6DSX_ID_ACC],
                                        acc_sensor->ts_ref + ts);
                                acc_sip--;
                        }
                        if (ext_sip > 0 && !(sip % ext_sensor->decimator)) {
                                iio_push_to_buffers_with_timestamp(
                                        hw->iio_devs[ST_LSM6DSX_ID_EXT0],
                                        &hw->scan[ST_LSM6DSX_ID_EXT0],
                                        ext_sensor->ts_ref + ts);
                                ext_sip--;
                        }
                        sip++;
                }
        }

        if (unlikely(reset_ts)) {
                err = st_lsm6dsx_reset_hw_ts(hw);
                if (err < 0) {
                        dev_err(hw->dev, "failed to reset hw ts (err=%d)\n",
                                err);
                        return err;
                }
        }
        return read_len;
}

#define ST_LSM6DSX_INVALID_SAMPLE       0x7ffd
static int
st_lsm6dsx_push_tagged_data(struct st_lsm6dsx_hw *hw, u8 tag,
                            u8 *data, s64 ts)
{
        s16 val = le16_to_cpu(*(__le16 *)data);
        struct st_lsm6dsx_sensor *sensor;
        struct iio_dev *iio_dev;

        /* invalid sample during bootstrap phase */
        if (val >= ST_LSM6DSX_INVALID_SAMPLE)
                return -EINVAL;

        /*
         * EXT_TAG are managed in FIFO fashion so ST_LSM6DSX_EXT0_TAG
         * corresponds to the first enabled channel, ST_LSM6DSX_EXT1_TAG
         * to the second one and ST_LSM6DSX_EXT2_TAG to the last enabled
         * channel
         */
        switch (tag) {
        case ST_LSM6DSX_GYRO_TAG:
                iio_dev = hw->iio_devs[ST_LSM6DSX_ID_GYRO];
                break;
        case ST_LSM6DSX_ACC_TAG:
                iio_dev = hw->iio_devs[ST_LSM6DSX_ID_ACC];
                break;
        case ST_LSM6DSX_EXT0_TAG:
                if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT0))
                        iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT0];
                else if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1))
                        iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];
                else
                        iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
                break;
        case ST_LSM6DSX_EXT1_TAG:
                if ((hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT0)) &&
                    (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1)))
                        iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];
                else
                        iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
                break;
        case ST_LSM6DSX_EXT2_TAG:
                iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
                break;
        default:
                return -EINVAL;
        }

        sensor = iio_priv(iio_dev);
        iio_push_to_buffers_with_timestamp(iio_dev, data,
                                           ts + sensor->ts_ref);

        return 0;
}

/**
 * st_lsm6dsx_read_tagged_fifo() - tagged hw FIFO read routine
 * @hw: Pointer to instance of struct st_lsm6dsx_hw.
 *
 * Read samples from the hw FIFO and push them to IIO buffers.
 *
 * Return: Number of bytes read from the FIFO
 */
int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
{
        u16 pattern_len = hw->sip * ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
        u16 fifo_len, fifo_diff_mask;
        /*
         * Alignment needed as this can ultimately be passed to a
         * call to iio_push_to_buffers_with_timestamp() which
         * must be passed a buffer that is aligned to 8 bytes so
         * as to allow insertion of a naturally aligned timestamp.
         */
        u8 iio_buff[ST_LSM6DSX_IIO_BUFF_SIZE] __aligned(8);
        u8 tag;
        bool reset_ts = false;
        int i, err, read_len;
        __le16 fifo_status;
        s64 ts = 0;

        err = st_lsm6dsx_read_locked(hw,
                                     hw->settings->fifo_ops.fifo_diff.addr,
                                     &fifo_status, sizeof(fifo_status));
        if (err < 0) {
                dev_err(hw->dev, "failed to read fifo status (err=%d)\n",
                        err);
                return err;
        }

        fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
        fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
                   ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
        if (!fifo_len)
                return 0;

        for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
                err = st_lsm6dsx_read_block(hw,
                                            ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR,
                                            hw->buff, pattern_len,
                                            ST_LSM6DSX_MAX_TAGGED_WORD_LEN);
                if (err < 0) {
                        dev_err(hw->dev,
                                "failed to read pattern from fifo (err=%d)\n",
                                err);
                        return err;
                }

                for (i = 0; i < pattern_len;
                     i += ST_LSM6DSX_TAGGED_SAMPLE_SIZE) {
                        memcpy(iio_buff, &hw->buff[i + ST_LSM6DSX_TAG_SIZE],
                               ST_LSM6DSX_SAMPLE_SIZE);

                        tag = hw->buff[i] >> 3;
                        if (tag == ST_LSM6DSX_TS_TAG) {
                                /*
                                 * hw timestamp is 4B long and it is stored
                                 * in FIFO according to this schema:
                                 * B0 = ts[7:0], B1 = ts[15:8], B2 = ts[23:16],
                                 * B3 = ts[31:24]
                                 */
                                ts = le32_to_cpu(*((__le32 *)iio_buff));
                                /*
                                 * check if hw timestamp engine is going to
                                 * reset (the sensor generates an interrupt
                                 * to signal the hw timestamp will reset in
                                 * 1.638s)
                                 */
                                if (!reset_ts && ts >= 0xffff0000)
                                        reset_ts = true;
                                ts *= hw->ts_gain;
                        } else {
                                st_lsm6dsx_push_tagged_data(hw, tag, iio_buff,
                                                            ts);
                        }
                }
        }

        if (unlikely(reset_ts)) {
                err = st_lsm6dsx_reset_hw_ts(hw);
                if (err < 0)
                        return err;
        }
        return read_len;
}

int st_lsm6dsx_flush_fifo(struct st_lsm6dsx_hw *hw)
{
        int err;

        if (!hw->settings->fifo_ops.read_fifo)
                return -ENOTSUPP;

        mutex_lock(&hw->fifo_lock);

        hw->settings->fifo_ops.read_fifo(hw);
        err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_BYPASS);

        mutex_unlock(&hw->fifo_lock);

        return err;
}

int st_lsm6dsx_update_fifo(struct st_lsm6dsx_sensor *sensor, bool enable)
{
        struct st_lsm6dsx_hw *hw = sensor->hw;
        u8 fifo_mask;
        int err;

        mutex_lock(&hw->conf_lock);

        if (enable)
                fifo_mask = hw->fifo_mask | BIT(sensor->id);
        else
                fifo_mask = hw->fifo_mask & ~BIT(sensor->id);

        if (hw->fifo_mask) {
                err = st_lsm6dsx_flush_fifo(hw);
                if (err < 0)
                        goto out;
        }

        if (sensor->id == ST_LSM6DSX_ID_EXT0 ||
            sensor->id == ST_LSM6DSX_ID_EXT1 ||
            sensor->id == ST_LSM6DSX_ID_EXT2) {
                err = st_lsm6dsx_shub_set_enable(sensor, enable);
                if (err < 0)
                        goto out;
        } else {
                err = st_lsm6dsx_sensor_set_enable(sensor, enable);
                if (err < 0)
                        goto out;
        }

        err = st_lsm6dsx_set_fifo_odr(sensor, enable);
        if (err < 0)
                goto out;

        err = st_lsm6dsx_update_decimators(hw);
        if (err < 0)
                goto out;

        err = st_lsm6dsx_update_watermark(sensor, sensor->watermark);
        if (err < 0)
                goto out;

        if (fifo_mask) {
                err = st_lsm6dsx_resume_fifo(hw);
                if (err < 0)
                        goto out;
        }

        hw->fifo_mask = fifo_mask;

out:
        mutex_unlock(&hw->conf_lock);

        return err;
}

static int st_lsm6dsx_buffer_preenable(struct iio_dev *iio_dev)
{
        struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
        struct st_lsm6dsx_hw *hw = sensor->hw;

        if (!hw->settings->fifo_ops.update_fifo)
                return -ENOTSUPP;

        return hw->settings->fifo_ops.update_fifo(sensor, true);
}

static int st_lsm6dsx_buffer_postdisable(struct iio_dev *iio_dev)
{
        struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
        struct st_lsm6dsx_hw *hw = sensor->hw;

        if (!hw->settings->fifo_ops.update_fifo)
                return -ENOTSUPP;

        return hw->settings->fifo_ops.update_fifo(sensor, false);
}

static const struct iio_buffer_setup_ops st_lsm6dsx_buffer_ops = {
        .preenable = st_lsm6dsx_buffer_preenable,
        .postdisable = st_lsm6dsx_buffer_postdisable,
};

int st_lsm6dsx_fifo_setup(struct st_lsm6dsx_hw *hw)
{
        int i, ret;

        for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
                if (!hw->iio_devs[i])
                        continue;

                ret = devm_iio_kfifo_buffer_setup(hw->dev, hw->iio_devs[i],
                                                  INDIO_BUFFER_SOFTWARE,
                                                  &st_lsm6dsx_buffer_ops);
                if (ret)
                        return ret;
        }

        return 0;
}