diff options
Diffstat (limited to 'drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c')
| -rw-r--r-- | drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c new file mode 100644 index 000000000..7f2dc41f8 --- /dev/null +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2020 Invensense, Inc. + */ + +#include <linux/kernel.h> +#include <linux/regmap.h> +#include <linux/math64.h> + +#include "inv_icm42600.h" +#include "inv_icm42600_timestamp.h" + +/* internal chip period is 32kHz, 31250ns */ +#define INV_ICM42600_TIMESTAMP_PERIOD 31250 +/* allow a jitter of +/- 2% */ +#define INV_ICM42600_TIMESTAMP_JITTER 2 +/* compute min and max periods accepted */ +#define INV_ICM42600_TIMESTAMP_MIN_PERIOD(_p) \ + (((_p) * (100 - INV_ICM42600_TIMESTAMP_JITTER)) / 100) +#define INV_ICM42600_TIMESTAMP_MAX_PERIOD(_p) \ + (((_p) * (100 + INV_ICM42600_TIMESTAMP_JITTER)) / 100) + +/* Add a new value inside an accumulator and update the estimate value */ +static void inv_update_acc(struct inv_icm42600_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_icm42600_timestamp_init(struct inv_icm42600_timestamp *ts, + uint32_t period) +{ + /* initial odr for sensor after reset is 1kHz */ + const uint32_t default_period = 1000000; + + /* current multiplier and period values after reset */ + ts->mult = default_period / INV_ICM42600_TIMESTAMP_PERIOD; + ts->period = default_period; + /* new set multiplier is the one from chip initialization */ + ts->new_mult = period / INV_ICM42600_TIMESTAMP_PERIOD; + + /* use theoretical value for chip period */ + inv_update_acc(&ts->chip_period, INV_ICM42600_TIMESTAMP_PERIOD); +} + +int inv_icm42600_timestamp_setup(struct inv_icm42600_state *st) +{ + unsigned int val; + + /* enable timestamp register */ + val = INV_ICM42600_TMST_CONFIG_TMST_TO_REGS_EN | + INV_ICM42600_TMST_CONFIG_TMST_EN; + return regmap_update_bits(st->map, INV_ICM42600_REG_TMST_CONFIG, + INV_ICM42600_TMST_CONFIG_MASK, val); +} + +int inv_icm42600_timestamp_update_odr(struct inv_icm42600_timestamp *ts, + uint32_t period, bool fifo) +{ + /* when FIFO is on, prevent odr change if one is already pending */ + if (fifo && ts->new_mult != 0) + return -EAGAIN; + + ts->new_mult = period / INV_ICM42600_TIMESTAMP_PERIOD; + + return 0; +} + +static bool inv_validate_period(uint32_t period, uint32_t mult) +{ + const uint32_t chip_period = INV_ICM42600_TIMESTAMP_PERIOD; + uint32_t period_min, period_max; + + /* check that period is acceptable */ + period_min = INV_ICM42600_TIMESTAMP_MIN_PERIOD(chip_period) * mult; + period_max = INV_ICM42600_TIMESTAMP_MAX_PERIOD(chip_period) * mult; + if (period > period_min && period < period_max) + return true; + else + return false; +} + +static bool inv_compute_chip_period(struct inv_icm42600_timestamp *ts, + uint32_t mult, uint32_t period) +{ + uint32_t new_chip_period; + + if (!inv_validate_period(period, mult)) + return false; + + /* update chip internal period estimation */ + new_chip_period = period / mult; + inv_update_acc(&ts->chip_period, new_chip_period); + + return true; +} + +void inv_icm42600_timestamp_interrupt(struct inv_icm42600_timestamp *ts, + uint32_t fifo_period, size_t fifo_nb, + size_t sensor_nb, int64_t timestamp) +{ + struct inv_icm42600_timestamp_interval *it; + int64_t delta, interval; + const uint32_t fifo_mult = fifo_period / INV_ICM42600_TIMESTAMP_PERIOD; + uint32_t period = ts->period; + int32_t m; + bool valid = false; + + if (fifo_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, fifo_nb); + valid = inv_compute_chip_period(ts, fifo_mult, period); + /* update sensor period if chip internal period is updated */ + if (valid) + ts->period = ts->mult * ts->chip_period.val; + } + + /* 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)sensor_nb; + ts->timestamp = it->up - interval; + return; + } + + /* if interrupt interval is valid, sync with interrupt timestamp */ + if (valid) { + /* compute measured fifo_period */ + fifo_period = fifo_mult * ts->chip_period.val; + /* delta time between last sample and last interrupt */ + delta = it->lo - ts->timestamp; + /* if there are multiple samples, go back to first one */ + while (delta >= (fifo_period * 3 / 2)) + delta -= fifo_period; + /* compute maximal adjustment value */ + m = INV_ICM42600_TIMESTAMP_MAX_PERIOD(ts->period) - ts->period; + if (delta > m) + delta = m; + else if (delta < -m) + delta = -m; + ts->timestamp += delta; + } +} + +void inv_icm42600_timestamp_apply_odr(struct inv_icm42600_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 / INV_ICM42600_TIMESTAMP_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; + } +} |