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 */ 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 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 60 int 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 } 71 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_update_odr, IIO_INV_SENSORS_TIMESTAMP); 72 73 static 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 86 static 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(&ts->chip_period, new_chip_period); 97 ts->period = ts->mult * ts->chip_period.val; 98 99 return true; 100 } 101 102 static 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 } 121 122 void 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 = ts->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(delta, fifo_nb); 143 valid = inv_update_chip_period(ts, 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 } 158 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_interrupt, IIO_INV_SENSORS_TIMESTAMP); 159 160 void 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 } 190 EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_apply_odr, IIO_INV_SENSORS_TIMESTAMP); 191 192 MODULE_AUTHOR("InvenSense, Inc."); 193 MODULE_DESCRIPTION("InvenSense sensors timestamp module"); 194 MODULE_LICENSE("GPL"); 195