drivers/iio/common/inv_sensors/inv_sensors_timestamp.c

Source file repositories/reference/linux-study-clean/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c

File Facts

System
Linux kernel
Corpus path
drivers/iio/common/inv_sensors/inv_sensors_timestamp.c
Extension
.c
Size
5996 bytes
Lines
206
Domain
Driver Families
Bucket
drivers/iio
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// 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

Annotation

Implementation Notes