1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
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;
}
}
|
