1 | /* mbed Microcontroller Library
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2 | * Copyright (c) 2015 ARM Limited
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3 | *
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4 | * Licensed under the Apache License, Version 2.0 (the "License");
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5 | * you may not use this file except in compliance with the License.
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6 | * You may obtain a copy of the License at
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7 | *
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8 | * http://www.apache.org/licenses/LICENSE-2.0
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9 | *
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10 | * Unless required by applicable law or agreed to in writing, software
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11 | * distributed under the License is distributed on an "AS IS" BASIS,
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 | * See the License for the specific language governing permissions and
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14 | * limitations under the License.
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15 | */
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16 | #include <stdio.h>
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17 | #include <stddef.h>
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18 | #include "hal/ticker_api.h"
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19 | #include "platform/mbed_critical.h"
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20 | #include "platform/mbed_assert.h"
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21 |
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22 | static void schedule_interrupt(const ticker_data_t *const ticker);
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23 | static void update_present_time(const ticker_data_t *const ticker);
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24 |
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25 | /*
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26 | * Initialize a ticker instance.
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27 | */
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28 | static void initialize(const ticker_data_t *ticker)
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29 | {
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30 | // return if the queue has already been initialized, in that case the
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31 | // interface used by the queue is already initialized.
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32 | if (ticker->queue->initialized) {
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33 | return;
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34 | }
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35 | if (ticker->queue->suspended) {
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36 | return;
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37 | }
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38 |
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39 | ticker->interface->init();
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40 |
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41 | const ticker_info_t *info = ticker->interface->get_info();
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42 | uint32_t frequency = info->frequency;
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43 | if (info->frequency == 0) {
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44 | MBED_ASSERT(0);
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45 | frequency = 1000000;
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46 | }
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47 |
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48 | uint8_t frequency_shifts = 0;
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49 | for (uint8_t i = 31; i > 0; --i) {
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50 | if ((1 << i) == frequency) {
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51 | frequency_shifts = i;
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52 | break;
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53 | }
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54 | }
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55 |
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56 | uint32_t bits = info->bits;
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57 | if ((info->bits > 32) || (info->bits < 4)) {
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58 | MBED_ASSERT(0);
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59 | bits = 32;
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60 | }
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61 | uint32_t max_delta = 0x7 << (bits - 4); // 7/16th
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62 | uint64_t max_delta_us =
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63 | ((uint64_t)max_delta * 1000000 + frequency - 1) / frequency;
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64 |
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65 | ticker->queue->event_handler = NULL;
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66 | ticker->queue->head = NULL;
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67 | ticker->queue->tick_last_read = ticker->interface->read();
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68 | ticker->queue->tick_remainder = 0;
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69 | ticker->queue->frequency = frequency;
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70 | ticker->queue->frequency_shifts = frequency_shifts;
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71 | ticker->queue->bitmask = ((uint64_t)1 << bits) - 1;
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72 | ticker->queue->max_delta = max_delta;
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73 | ticker->queue->max_delta_us = max_delta_us;
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74 | ticker->queue->present_time = 0;
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75 | ticker->queue->dispatching = false;
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76 | ticker->queue->suspended = false;
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77 | ticker->queue->initialized = true;
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78 |
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79 | update_present_time(ticker);
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80 | schedule_interrupt(ticker);
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81 | }
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82 |
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83 | /**
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84 | * Set the event handler function of a ticker instance.
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85 | */
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86 | static void set_handler(const ticker_data_t *const ticker, ticker_event_handler handler)
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87 | {
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88 | ticker->queue->event_handler = handler;
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89 | }
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90 |
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91 | /*
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92 | * Convert a 32 bit timestamp into a 64 bit timestamp.
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93 | *
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94 | * A 64 bit timestamp is used as the point of time of reference while the
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95 | * timestamp to convert is relative to this point of time.
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96 | *
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97 | * The lower 32 bits of the timestamp returned will be equal to the timestamp to
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98 | * convert.
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99 | *
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100 | * If the timestamp to convert is less than the lower 32 bits of the time
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101 | * reference then the timestamp to convert is seen as an overflowed value and
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102 | * the upper 32 bit of the timestamp returned will be equal to the upper 32 bit
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103 | * of the reference point + 1.
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104 | * Otherwise, the upper 32 bit returned will be equal to the upper 32 bit of the
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105 | * reference point.
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106 | *
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107 | * @param ref: The 64 bit timestamp of reference.
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108 | * @param timestamp: The timestamp to convert.
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109 | */
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110 | static us_timestamp_t convert_timestamp(us_timestamp_t ref, timestamp_t timestamp)
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111 | {
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112 | bool overflow = timestamp < ((timestamp_t) ref) ? true : false;
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113 |
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114 | us_timestamp_t result = (ref & ~((us_timestamp_t)UINT32_MAX)) | timestamp;
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115 | if (overflow) {
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116 | result += (1ULL << 32);
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117 | }
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118 |
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119 | return result;
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120 | }
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121 |
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122 | /**
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123 | * Update the present timestamp value of a ticker.
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124 | */
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125 | static void update_present_time(const ticker_data_t *const ticker)
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126 | {
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127 | ticker_event_queue_t *queue = ticker->queue;
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128 | if (queue->suspended) {
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129 | return;
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130 | }
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131 | uint32_t ticker_time = ticker->interface->read();
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132 | if (ticker_time == ticker->queue->tick_last_read) {
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133 | // No work to do
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134 | return;
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135 | }
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136 |
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137 | uint64_t elapsed_ticks = (ticker_time - queue->tick_last_read) & queue->bitmask;
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138 | queue->tick_last_read = ticker_time;
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139 |
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140 | uint64_t elapsed_us;
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141 | if (1000000 == queue->frequency) {
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142 | // Optimized for 1MHz
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143 |
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144 | elapsed_us = elapsed_ticks;
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145 | } else if (0 != queue->frequency_shifts) {
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146 | // Optimized for frequencies divisible by 2
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147 | uint64_t us_x_ticks = elapsed_ticks * 1000000;
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148 | elapsed_us = us_x_ticks >> queue->frequency_shifts;
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149 |
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150 | // Update remainder
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151 | queue->tick_remainder += us_x_ticks - (elapsed_us << queue->frequency_shifts);
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152 | if (queue->tick_remainder >= queue->frequency) {
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153 | elapsed_us += 1;
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154 | queue->tick_remainder -= queue->frequency;
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155 | }
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156 | } else {
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157 | // General case
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158 |
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159 | uint64_t us_x_ticks = elapsed_ticks * 1000000;
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160 | elapsed_us = us_x_ticks / queue->frequency;
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161 |
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162 | // Update remainder
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163 | queue->tick_remainder += us_x_ticks - elapsed_us * queue->frequency;
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164 | if (queue->tick_remainder >= queue->frequency) {
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165 | elapsed_us += 1;
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166 | queue->tick_remainder -= queue->frequency;
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167 | }
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168 | }
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169 |
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170 | // Update current time
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171 | queue->present_time += elapsed_us;
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172 | }
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173 |
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174 | /**
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175 | * Given the absolute timestamp compute the hal tick timestamp rounded up.
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176 | */
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177 | static timestamp_t compute_tick_round_up(const ticker_data_t *const ticker, us_timestamp_t timestamp)
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178 | {
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179 | ticker_event_queue_t *queue = ticker->queue;
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180 | us_timestamp_t delta_us = timestamp - queue->present_time;
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181 |
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182 | timestamp_t delta = ticker->queue->max_delta;
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183 | if (delta_us <= ticker->queue->max_delta_us) {
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184 | // Checking max_delta_us ensures the operation will not overflow
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185 |
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186 | if (1000000 == queue->frequency) {
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187 | // Optimized for 1MHz
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188 |
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189 | delta = delta_us;
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190 | if (delta > ticker->queue->max_delta) {
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191 | delta = ticker->queue->max_delta;
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192 | }
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193 | } else if (0 != queue->frequency_shifts) {
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194 | // Optimized frequencies divisible by 2
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195 |
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196 | delta = ((delta_us << ticker->queue->frequency_shifts) + 1000000 - 1) / 1000000;
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197 | if (delta > ticker->queue->max_delta) {
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198 | delta = ticker->queue->max_delta;
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199 | }
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200 | } else {
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201 | // General case
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202 |
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203 | delta = (delta_us * queue->frequency + 1000000 - 1) / 1000000;
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204 | if (delta > ticker->queue->max_delta) {
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205 | delta = ticker->queue->max_delta;
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206 | }
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207 | }
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208 | }
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209 | return (queue->tick_last_read + delta) & queue->bitmask;
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210 | }
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211 |
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212 | /**
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213 | * Return 1 if the tick has incremented to or past match_tick, otherwise 0.
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214 | */
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215 | int _ticker_match_interval_passed(timestamp_t prev_tick, timestamp_t cur_tick, timestamp_t match_tick)
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216 | {
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217 | if (match_tick > prev_tick) {
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218 | return (cur_tick >= match_tick) || (cur_tick < prev_tick);
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219 | } else {
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220 | return (cur_tick < prev_tick) && (cur_tick >= match_tick);
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221 | }
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222 | }
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223 |
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224 | /**
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225 | * Compute the time when the interrupt has to be triggered and schedule it.
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226 | *
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227 | * If there is no event in the queue or the next event to execute is in more
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228 | * than ticker.queue.max_delta ticks from now then the ticker irq will be
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229 | * scheduled in ticker.queue.max_delta ticks. Otherwise the irq will be
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230 | * scheduled to happen when the running counter reach the timestamp of the
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231 | * first event in the queue.
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232 | *
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233 | * @note If there is no event in the queue then the interrupt is scheduled to
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234 | * in ticker.queue.max_delta. This is necessary to keep track
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235 | * of the timer overflow.
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236 | */
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237 | static void schedule_interrupt(const ticker_data_t *const ticker)
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238 | {
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239 | ticker_event_queue_t *queue = ticker->queue;
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240 | if (queue->suspended || ticker->queue->dispatching) {
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241 | // Don't schedule the next interrupt until dispatching is
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242 | // finished. This prevents repeated calls to interface->set_interrupt
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243 | return;
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244 | }
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245 |
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246 | update_present_time(ticker);
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247 |
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248 | if (ticker->queue->head) {
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249 | us_timestamp_t present = ticker->queue->present_time;
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250 | us_timestamp_t match_time = ticker->queue->head->timestamp;
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251 |
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252 | // if the event at the head of the queue is in the past then schedule
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253 | // it immediately.
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254 | if (match_time <= present) {
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255 | ticker->interface->fire_interrupt();
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256 | return;
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257 | }
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258 |
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259 | timestamp_t match_tick = compute_tick_round_up(ticker, match_time);
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260 |
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261 | // The same tick should never occur since match_tick is rounded up.
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262 | // If the same tick is returned scheduling will not work correctly.
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263 | MBED_ASSERT(match_tick != queue->tick_last_read);
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264 |
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265 | ticker->interface->set_interrupt(match_tick);
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266 | timestamp_t cur_tick = ticker->interface->read();
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267 |
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268 | if (_ticker_match_interval_passed(queue->tick_last_read, cur_tick, match_tick)) {
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269 | ticker->interface->fire_interrupt();
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270 | }
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271 | } else {
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272 | uint32_t match_tick =
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273 | (queue->tick_last_read + queue->max_delta) & queue->bitmask;
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274 | ticker->interface->set_interrupt(match_tick);
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275 | }
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276 | }
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277 |
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278 | void ticker_set_handler(const ticker_data_t *const ticker, ticker_event_handler handler)
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279 | {
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280 | initialize(ticker);
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281 |
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282 | core_util_critical_section_enter();
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283 | set_handler(ticker, handler);
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284 | core_util_critical_section_exit();
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285 | }
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286 |
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287 | void ticker_irq_handler(const ticker_data_t *const ticker)
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288 | {
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289 | core_util_critical_section_enter();
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290 |
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291 | ticker->interface->clear_interrupt();
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292 | if (ticker->queue->suspended) {
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293 | core_util_critical_section_exit();
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294 | return;
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295 | }
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296 |
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297 | /* Go through all the pending TimerEvents */
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298 | ticker->queue->dispatching = true;
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299 | while (1) {
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300 | if (ticker->queue->head == NULL) {
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301 | break;
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302 | }
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303 |
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304 | // update the current timestamp used by the queue
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305 | update_present_time(ticker);
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306 |
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307 | if (ticker->queue->head->timestamp <= ticker->queue->present_time) {
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308 | // This event was in the past:
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309 | // point to the following one and execute its handler
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310 | ticker_event_t *p = ticker->queue->head;
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311 | ticker->queue->head = ticker->queue->head->next;
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312 | if (ticker->queue->event_handler != NULL) {
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313 | (*ticker->queue->event_handler)(p->id); // NOTE: the handler can set new events
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314 | }
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315 | /* Note: We continue back to examining the head because calling the
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316 | * event handler may have altered the chain of pending events. */
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317 | } else {
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318 | break;
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319 | }
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320 | }
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321 | ticker->queue->dispatching = false;
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322 |
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323 | schedule_interrupt(ticker);
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324 |
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325 | core_util_critical_section_exit();
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326 | }
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327 |
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328 | void ticker_insert_event(const ticker_data_t *const ticker, ticker_event_t *obj, timestamp_t timestamp, uint32_t id)
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329 | {
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330 | core_util_critical_section_enter();
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331 |
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332 | // update the current timestamp
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333 | update_present_time(ticker);
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334 | us_timestamp_t absolute_timestamp = convert_timestamp(
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335 | ticker->queue->present_time,
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336 | timestamp
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337 | );
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338 |
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339 | // defer to ticker_insert_event_us
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340 | ticker_insert_event_us(
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341 | ticker,
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342 | obj, absolute_timestamp, id
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343 | );
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344 |
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345 | core_util_critical_section_exit();
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346 | }
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347 |
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348 | void ticker_insert_event_us(const ticker_data_t *const ticker, ticker_event_t *obj, us_timestamp_t timestamp, uint32_t id)
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349 | {
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350 | core_util_critical_section_enter();
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351 |
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352 | // update the current timestamp
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353 | update_present_time(ticker);
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354 |
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355 | // initialise our data
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356 | obj->timestamp = timestamp;
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357 | obj->id = id;
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358 |
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359 | /* Go through the list until we either reach the end, or find
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360 | an element this should come before (which is possibly the
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361 | head). */
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362 | ticker_event_t *prev = NULL, *p = ticker->queue->head;
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363 | while (p != NULL) {
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364 | /* check if we come before p */
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365 | if (timestamp < p->timestamp) {
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366 | break;
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367 | }
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368 | /* go to the next element */
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369 | prev = p;
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370 | p = p->next;
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371 | }
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372 |
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373 | /* if we're at the end p will be NULL, which is correct */
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374 | obj->next = p;
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375 |
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376 | /* if prev is NULL we're at the head */
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377 | if (prev == NULL) {
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378 | ticker->queue->head = obj;
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379 | schedule_interrupt(ticker);
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380 | } else {
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381 | prev->next = obj;
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382 | }
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383 |
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384 | core_util_critical_section_exit();
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385 | }
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386 |
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387 | void ticker_remove_event(const ticker_data_t *const ticker, ticker_event_t *obj)
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388 | {
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389 | core_util_critical_section_enter();
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390 |
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391 | // remove this object from the list
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392 | if (ticker->queue->head == obj) {
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393 | // first in the list, so just drop me
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394 | ticker->queue->head = obj->next;
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395 | schedule_interrupt(ticker);
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396 | } else {
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397 | // find the object before me, then drop me
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398 | ticker_event_t *p = ticker->queue->head;
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399 | while (p != NULL) {
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400 | if (p->next == obj) {
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401 | p->next = obj->next;
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402 | break;
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403 | }
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404 | p = p->next;
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405 | }
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406 | }
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407 |
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408 | core_util_critical_section_exit();
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409 | }
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410 |
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411 | timestamp_t ticker_read(const ticker_data_t *const ticker)
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412 | {
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413 | return ticker_read_us(ticker);
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414 | }
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415 |
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416 | us_timestamp_t ticker_read_us(const ticker_data_t *const ticker)
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417 | {
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418 | initialize(ticker);
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419 |
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420 | core_util_critical_section_enter();
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421 | update_present_time(ticker);
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422 | core_util_critical_section_exit();
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423 |
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424 | return ticker->queue->present_time;
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425 | }
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426 |
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427 | int ticker_get_next_timestamp(const ticker_data_t *const data, timestamp_t *timestamp)
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428 | {
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429 | int ret = 0;
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430 |
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431 | /* if head is NULL, there are no pending events */
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432 | core_util_critical_section_enter();
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433 | if (data->queue->head != NULL) {
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434 | *timestamp = data->queue->head->timestamp;
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435 | ret = 1;
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436 | }
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437 | core_util_critical_section_exit();
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438 |
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439 | return ret;
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440 | }
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441 |
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442 | void ticker_suspend(const ticker_data_t *const ticker)
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443 | {
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444 | core_util_critical_section_enter();
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445 |
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446 | ticker->queue->suspended = true;
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447 |
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448 | core_util_critical_section_exit();
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449 | }
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450 |
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451 | void ticker_resume(const ticker_data_t *const ticker)
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452 | {
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453 | core_util_critical_section_enter();
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454 |
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455 | ticker->queue->suspended = false;
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456 | if (ticker->queue->initialized) {
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457 | ticker->queue->tick_last_read = ticker->interface->read();
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458 |
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459 | update_present_time(ticker);
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460 | schedule_interrupt(ticker);
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461 | } else {
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462 | initialize(ticker);
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463 | }
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464 |
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465 | core_util_critical_section_exit();
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466 | }
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