linuxdebug/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c

196 lines
5.7 KiB
C

// 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;
}
}