// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2020 Invensense, Inc.
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/module.h>

#include <linux/iio/common/inv_sensors_timestamp.h>

/* compute jitter, min and max following jitter in per mille */
#define INV_SENSORS_TIMESTAMP_JITTER(_val, _jitter)             \
        (div_s64((_val) * (_jitter), 1000))
#define INV_SENSORS_TIMESTAMP_MIN(_val, _jitter)                \
        (((_val) * (1000 - (_jitter))) / 1000)
#define INV_SENSORS_TIMESTAMP_MAX(_val, _jitter)                \
        (((_val) * (1000 + (_jitter))) / 1000)

/* Add a new value inside an accumulator and update the estimate value */
static void inv_update_acc(struct inv_sensors_timestamp_acc *acc, uint32_t val)
{
        uint64_t sum = 0;
        size_t i;

        acc->values[acc->idx++] = val;
        if (acc->idx >= ARRAY_SIZE(acc->values))
                acc->idx = 0;

        /* compute the mean of all stored values, use 0 as empty slot */
        for (i = 0; i < ARRAY_SIZE(acc->values); ++i) {
                if (acc->values[i] == 0)
                        break;
                sum += acc->values[i];
        }

        acc->val = div_u64(sum, i);
}

void inv_sensors_timestamp_init(struct inv_sensors_timestamp *ts,
                                const struct inv_sensors_timestamp_chip *chip)
{
        memset(ts, 0, sizeof(*ts));

        /* save chip parameters and compute min and max clock period */
        ts->chip = *chip;
        ts->min_period = INV_SENSORS_TIMESTAMP_MIN(chip->clock_period, chip->jitter);
        ts->max_period = INV_SENSORS_TIMESTAMP_MAX(chip->clock_period, chip->jitter);

        /* current multiplier and period values after reset */
        ts->mult = chip->init_period / chip->clock_period;
        ts->period = chip->init_period;

        /* use theoretical value for chip period */
        inv_update_acc(&ts->chip_period, chip->clock_period);
}
EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_init, "IIO_INV_SENSORS_TIMESTAMP");

int inv_sensors_timestamp_update_odr(struct inv_sensors_timestamp *ts,
                                     uint32_t period, bool fifo)
{
        uint32_t mult;

        /* when FIFO is on, prevent odr change if one is already pending */
        if (fifo && ts->new_mult != 0)
                return -EAGAIN;

        mult = period / ts->chip.clock_period;
        if (mult != ts->mult)
                ts->new_mult = mult;

        /* When FIFO is off, directly apply the new ODR */
        if (!fifo)
                inv_sensors_timestamp_apply_odr(ts, 0, 0, 0);

        return 0;
}
EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_update_odr, "IIO_INV_SENSORS_TIMESTAMP");

static bool inv_validate_period(struct inv_sensors_timestamp *ts, uint32_t period)
{
        uint32_t period_min, period_max;

        /* check that period is acceptable */
        period_min = ts->min_period * ts->mult;
        period_max = ts->max_period * ts->mult;
        if (period > period_min && period < period_max)
                return true;
        else
                return false;
}

static bool inv_update_chip_period(struct inv_sensors_timestamp *ts,
                                   uint32_t period)
{
        uint32_t new_chip_period;

        if (!inv_validate_period(ts, period))
                return false;

        /* update chip internal period estimation */
        new_chip_period = period / ts->mult;
        inv_update_acc(&ts->chip_period, new_chip_period);
        ts->period = ts->mult * ts->chip_period.val;

        return true;
}

static void inv_align_timestamp_it(struct inv_sensors_timestamp *ts)
{
        const int64_t period_min = (int64_t)ts->min_period * ts->mult;
        const int64_t period_max = (int64_t)ts->max_period * ts->mult;
        int64_t add_max, sub_max;
        int64_t delta, jitter;
        int64_t adjust;

        /* delta time between last sample and last interrupt */
        delta = ts->it.lo - ts->timestamp;

        /* adjust timestamp while respecting jitter */
        add_max = period_max - (int64_t)ts->period;
        sub_max = period_min - (int64_t)ts->period;
        jitter = INV_SENSORS_TIMESTAMP_JITTER((int64_t)ts->period, ts->chip.jitter);
        if (delta > jitter)
                adjust = add_max;
        else if (delta < -jitter)
                adjust = sub_max;
        else
                adjust = 0;

        ts->timestamp += adjust;
}

void inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp *ts,
                                     size_t sample_nb, int64_t timestamp)
{
        struct inv_sensors_timestamp_interval *it;
        int64_t delta, interval;
        uint32_t period;
        bool valid = false;

        if (sample_nb == 0)
                return;

        /* update interrupt timestamp and compute chip and sensor periods */
        it = &ts->it;
        it->lo = it->up;
        it->up = timestamp;
        delta = it->up - it->lo;
        if (it->lo != 0) {
                /* compute period: delta time divided by number of samples */
                period = div_s64(delta, sample_nb);
                valid = inv_update_chip_period(ts, period);
        }

        /* no previous data, compute theoritical value from interrupt */
        if (ts->timestamp == 0) {
                /* elapsed time: sensor period * sensor samples number */
                interval = (int64_t)ts->period * (int64_t)sample_nb;
                ts->timestamp = it->up - interval;
                return;
        }

        /* if interrupt interval is valid, sync with interrupt timestamp */
        if (valid)
                inv_align_timestamp_it(ts);
}
EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_interrupt, "IIO_INV_SENSORS_TIMESTAMP");

void inv_sensors_timestamp_apply_odr(struct inv_sensors_timestamp *ts,
                                     uint32_t fifo_period, size_t fifo_nb,
                                     unsigned int fifo_no)
{
        int64_t interval;
        uint32_t fifo_mult;

        if (ts->new_mult == 0)
                return;

        /* update to new multiplier and update period */
        ts->mult = ts->new_mult;
        ts->new_mult = 0;
        ts->period = ts->mult * ts->chip_period.val;

        /*
         * After ODR change the time interval with the previous sample is
         * undertermined (depends when the change occures). So we compute the
         * timestamp from the current interrupt using the new FIFO period, the
         * total number of samples and the current sample numero.
         */
        if (ts->timestamp != 0) {
                /* compute measured fifo period */
                fifo_mult = fifo_period / ts->chip.clock_period;
                fifo_period = fifo_mult * ts->chip_period.val;
                /* computes time interval between interrupt and this sample */
                interval = (int64_t)(fifo_nb - fifo_no) * (int64_t)fifo_period;
                ts->timestamp = ts->it.up - interval;
        }
}
EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_apply_odr, "IIO_INV_SENSORS_TIMESTAMP");

MODULE_AUTHOR("InvenSense, Inc.");
MODULE_DESCRIPTION("InvenSense sensors timestamp module");
MODULE_LICENSE("GPL");