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Diffstat (limited to 'drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c')
-rw-r--r--drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c195
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;
+ }
+}