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 */
inv_update_acc(struct inv_sensors_timestamp_acc * acc,uint32_t val)22 static 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(sum, i);
39 }
40
inv_sensors_timestamp_init(struct inv_sensors_timestamp * ts,const struct inv_sensors_timestamp_chip * chip)41 void 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(&ts->chip_period, chip->clock_period);
57 }
58 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_init, IIO_INV_SENSORS_TIMESTAMP);
59
inv_sensors_timestamp_update_odr(struct inv_sensors_timestamp * ts,uint32_t period,bool fifo)60 int inv_sensors_timestamp_update_odr(struct inv_sensors_timestamp *ts,
61 uint32_t period, bool fifo)
62 {
63 uint32_t mult;
64
65 /* when FIFO is on, prevent odr change if one is already pending */
66 if (fifo && ts->new_mult != 0)
67 return -EAGAIN;
68
69 mult = period / ts->chip.clock_period;
70 if (mult != ts->mult)
71 ts->new_mult = mult;
72
73 return 0;
74 }
75 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_update_odr, IIO_INV_SENSORS_TIMESTAMP);
76
inv_validate_period(struct inv_sensors_timestamp * ts,uint32_t period,uint32_t mult)77 static bool inv_validate_period(struct inv_sensors_timestamp *ts, uint32_t period, uint32_t mult)
78 {
79 uint32_t period_min, period_max;
80
81 /* check that period is acceptable */
82 period_min = ts->min_period * mult;
83 period_max = ts->max_period * mult;
84 if (period > period_min && period < period_max)
85 return true;
86 else
87 return false;
88 }
89
inv_update_chip_period(struct inv_sensors_timestamp * ts,uint32_t mult,uint32_t period)90 static bool inv_update_chip_period(struct inv_sensors_timestamp *ts,
91 uint32_t mult, uint32_t period)
92 {
93 uint32_t new_chip_period;
94
95 if (!inv_validate_period(ts, period, mult))
96 return false;
97
98 /* update chip internal period estimation */
99 new_chip_period = period / mult;
100 inv_update_acc(&ts->chip_period, new_chip_period);
101 ts->period = ts->mult * ts->chip_period.val;
102
103 return true;
104 }
105
inv_align_timestamp_it(struct inv_sensors_timestamp * ts)106 static void inv_align_timestamp_it(struct inv_sensors_timestamp *ts)
107 {
108 const int64_t period_min = ts->min_period * ts->mult;
109 const int64_t period_max = ts->max_period * ts->mult;
110 int64_t add_max, sub_max;
111 int64_t delta, jitter;
112 int64_t adjust;
113
114 /* delta time between last sample and last interrupt */
115 delta = ts->it.lo - ts->timestamp;
116
117 /* adjust timestamp while respecting jitter */
118 add_max = period_max - (int64_t)ts->period;
119 sub_max = period_min - (int64_t)ts->period;
120 jitter = INV_SENSORS_TIMESTAMP_JITTER((int64_t)ts->period, ts->chip.jitter);
121 if (delta > jitter)
122 adjust = add_max;
123 else if (delta < -jitter)
124 adjust = sub_max;
125 else
126 adjust = 0;
127
128 ts->timestamp += adjust;
129 }
130
inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp * ts,uint32_t fifo_period,size_t fifo_nb,size_t sensor_nb,int64_t timestamp)131 void inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp *ts,
132 uint32_t fifo_period, size_t fifo_nb,
133 size_t sensor_nb, int64_t timestamp)
134 {
135 struct inv_sensors_timestamp_interval *it;
136 int64_t delta, interval;
137 const uint32_t fifo_mult = fifo_period / ts->chip.clock_period;
138 uint32_t period = ts->period;
139 bool valid = false;
140
141 if (fifo_nb == 0)
142 return;
143
144 /* update interrupt timestamp and compute chip and sensor periods */
145 it = &ts->it;
146 it->lo = it->up;
147 it->up = timestamp;
148 delta = it->up - it->lo;
149 if (it->lo != 0) {
150 /* compute period: delta time divided by number of samples */
151 period = div_s64(delta, fifo_nb);
152 valid = inv_update_chip_period(ts, fifo_mult, period);
153 }
154
155 /* no previous data, compute theoritical value from interrupt */
156 if (ts->timestamp == 0) {
157 /* elapsed time: sensor period * sensor samples number */
158 interval = (int64_t)ts->period * (int64_t)sensor_nb;
159 ts->timestamp = it->up - interval;
160 return;
161 }
162
163 /* if interrupt interval is valid, sync with interrupt timestamp */
164 if (valid)
165 inv_align_timestamp_it(ts);
166 }
167 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_interrupt, IIO_INV_SENSORS_TIMESTAMP);
168
inv_sensors_timestamp_apply_odr(struct inv_sensors_timestamp * ts,uint32_t fifo_period,size_t fifo_nb,unsigned int fifo_no)169 void inv_sensors_timestamp_apply_odr(struct inv_sensors_timestamp *ts,
170 uint32_t fifo_period, size_t fifo_nb,
171 unsigned int fifo_no)
172 {
173 int64_t interval;
174 uint32_t fifo_mult;
175
176 if (ts->new_mult == 0)
177 return;
178
179 /* update to new multiplier and update period */
180 ts->mult = ts->new_mult;
181 ts->new_mult = 0;
182 ts->period = ts->mult * ts->chip_period.val;
183
184 /*
185 * After ODR change the time interval with the previous sample is
186 * undertermined (depends when the change occures). So we compute the
187 * timestamp from the current interrupt using the new FIFO period, the
188 * total number of samples and the current sample numero.
189 */
190 if (ts->timestamp != 0) {
191 /* compute measured fifo period */
192 fifo_mult = fifo_period / ts->chip.clock_period;
193 fifo_period = fifo_mult * ts->chip_period.val;
194 /* computes time interval between interrupt and this sample */
195 interval = (int64_t)(fifo_nb - fifo_no) * (int64_t)fifo_period;
196 ts->timestamp = ts->it.up - interval;
197 }
198 }
199 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_apply_odr, IIO_INV_SENSORS_TIMESTAMP);
200
201 MODULE_AUTHOR("InvenSense, Inc.");
202 MODULE_DESCRIPTION("InvenSense sensors timestamp module");
203 MODULE_LICENSE("GPL");
204