1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2020 Invensense, Inc.
4 */
5
6#include <linux/errno.h>
7#include <linux/kernel.h>
8#include <linux/math64.h>
9#include <linux/module.h>
10
11#include <linux/iio/common/inv_sensors_timestamp.h>
12
13/* compute jitter, min and max following jitter in per mille */
14#define INV_SENSORS_TIMESTAMP_JITTER(_val, _jitter) \
15 (div_s64((_val) * (_jitter), 1000))
16#define INV_SENSORS_TIMESTAMP_MIN(_val, _jitter) \
17 (((_val) * (1000 - (_jitter))) / 1000)
18#define INV_SENSORS_TIMESTAMP_MAX(_val, _jitter) \
19 (((_val) * (1000 + (_jitter))) / 1000)
20
21/* Add a new value inside an accumulator and update the estimate value */
22static void inv_update_acc(struct inv_sensors_timestamp_acc *acc, uint32_t val)
23{
24 uint64_t sum = 0;
25 size_t i;
26
27 acc->values[acc->idx++] = val;
28 if (acc->idx >= ARRAY_SIZE(acc->values))
29 acc->idx = 0;
30
31 /* compute the mean of all stored values, use 0 as empty slot */
32 for (i = 0; i < ARRAY_SIZE(acc->values); ++i) {
33 if (acc->values[i] == 0)
34 break;
35 sum += acc->values[i];
36 }
37
38 acc->val = div_u64(dividend: sum, divisor: i);
39}
40
41void inv_sensors_timestamp_init(struct inv_sensors_timestamp *ts,
42 const struct inv_sensors_timestamp_chip *chip)
43{
44 memset(ts, 0, sizeof(*ts));
45
46 /* save chip parameters and compute min and max clock period */
47 ts->chip = *chip;
48 ts->min_period = INV_SENSORS_TIMESTAMP_MIN(chip->clock_period, chip->jitter);
49 ts->max_period = INV_SENSORS_TIMESTAMP_MAX(chip->clock_period, chip->jitter);
50
51 /* current multiplier and period values after reset */
52 ts->mult = chip->init_period / chip->clock_period;
53 ts->period = chip->init_period;
54
55 /* use theoretical value for chip period */
56 inv_update_acc(acc: &ts->chip_period, val: chip->clock_period);
57}
58EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_init, IIO_INV_SENSORS_TIMESTAMP);
59
60int inv_sensors_timestamp_update_odr(struct inv_sensors_timestamp *ts,
61 uint32_t period, bool fifo)
62{
63 /* when FIFO is on, prevent odr change if one is already pending */
64 if (fifo && ts->new_mult != 0)
65 return -EAGAIN;
66
67 ts->new_mult = period / ts->chip.clock_period;
68
69 return 0;
70}
71EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_update_odr, IIO_INV_SENSORS_TIMESTAMP);
72
73static bool inv_validate_period(struct inv_sensors_timestamp *ts, uint32_t period, uint32_t mult)
74{
75 uint32_t period_min, period_max;
76
77 /* check that period is acceptable */
78 period_min = ts->min_period * mult;
79 period_max = ts->max_period * mult;
80 if (period > period_min && period < period_max)
81 return true;
82 else
83 return false;
84}
85
86static bool inv_update_chip_period(struct inv_sensors_timestamp *ts,
87 uint32_t mult, uint32_t period)
88{
89 uint32_t new_chip_period;
90
91 if (!inv_validate_period(ts, period, mult))
92 return false;
93
94 /* update chip internal period estimation */
95 new_chip_period = period / mult;
96 inv_update_acc(acc: &ts->chip_period, val: new_chip_period);
97 ts->period = ts->mult * ts->chip_period.val;
98
99 return true;
100}
101
102static void inv_align_timestamp_it(struct inv_sensors_timestamp *ts)
103{
104 int64_t delta, jitter;
105 int64_t adjust;
106
107 /* delta time between last sample and last interrupt */
108 delta = ts->it.lo - ts->timestamp;
109
110 /* adjust timestamp while respecting jitter */
111 jitter = INV_SENSORS_TIMESTAMP_JITTER((int64_t)ts->period, ts->chip.jitter);
112 if (delta > jitter)
113 adjust = jitter;
114 else if (delta < -jitter)
115 adjust = -jitter;
116 else
117 adjust = 0;
118
119 ts->timestamp += adjust;
120}
121
122void inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp *ts,
123 uint32_t fifo_period, size_t fifo_nb,
124 size_t sensor_nb, int64_t timestamp)
125{
126 struct inv_sensors_timestamp_interval *it;
127 int64_t delta, interval;
128 const uint32_t fifo_mult = fifo_period / ts->chip.clock_period;
129 uint32_t period;
130 bool valid = false;
131
132 if (fifo_nb == 0)
133 return;
134
135 /* update interrupt timestamp and compute chip and sensor periods */
136 it = &ts->it;
137 it->lo = it->up;
138 it->up = timestamp;
139 delta = it->up - it->lo;
140 if (it->lo != 0) {
141 /* compute period: delta time divided by number of samples */
142 period = div_s64(dividend: delta, divisor: fifo_nb);
143 valid = inv_update_chip_period(ts, mult: fifo_mult, period);
144 }
145
146 /* no previous data, compute theoritical value from interrupt */
147 if (ts->timestamp == 0) {
148 /* elapsed time: sensor period * sensor samples number */
149 interval = (int64_t)ts->period * (int64_t)sensor_nb;
150 ts->timestamp = it->up - interval;
151 return;
152 }
153
154 /* if interrupt interval is valid, sync with interrupt timestamp */
155 if (valid)
156 inv_align_timestamp_it(ts);
157}
158EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_interrupt, IIO_INV_SENSORS_TIMESTAMP);
159
160void inv_sensors_timestamp_apply_odr(struct inv_sensors_timestamp *ts,
161 uint32_t fifo_period, size_t fifo_nb,
162 unsigned int fifo_no)
163{
164 int64_t interval;
165 uint32_t fifo_mult;
166
167 if (ts->new_mult == 0)
168 return;
169
170 /* update to new multiplier and update period */
171 ts->mult = ts->new_mult;
172 ts->new_mult = 0;
173 ts->period = ts->mult * ts->chip_period.val;
174
175 /*
176 * After ODR change the time interval with the previous sample is
177 * undertermined (depends when the change occures). So we compute the
178 * timestamp from the current interrupt using the new FIFO period, the
179 * total number of samples and the current sample numero.
180 */
181 if (ts->timestamp != 0) {
182 /* compute measured fifo period */
183 fifo_mult = fifo_period / ts->chip.clock_period;
184 fifo_period = fifo_mult * ts->chip_period.val;
185 /* computes time interval between interrupt and this sample */
186 interval = (int64_t)(fifo_nb - fifo_no) * (int64_t)fifo_period;
187 ts->timestamp = ts->it.up - interval;
188 }
189}
190EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_apply_odr, IIO_INV_SENSORS_TIMESTAMP);
191
192MODULE_AUTHOR("InvenSense, Inc.");
193MODULE_DESCRIPTION("InvenSense sensors timestamp module");
194MODULE_LICENSE("GPL");
195

source code of linux/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c