1 | /** |
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2 | * @file |
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3 | * |
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4 | * @ingroup ClassicCounter |
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5 | * |
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6 | * @brief Free-Running Counter and Busy Wait Delay API |
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7 | */ |
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8 | |
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9 | /* |
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10 | * Copyright (c) 2014 embedded brains GmbH. All rights reserved. |
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11 | * |
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12 | * embedded brains GmbH |
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13 | * Dornierstr. 4 |
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14 | * 82178 Puchheim |
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15 | * Germany |
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16 | * <rtems@embedded-brains.de> |
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17 | * |
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18 | * The license and distribution terms for this file may be |
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19 | * found in the file LICENSE in this distribution or at |
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20 | * http://www.rtems.com/license/LICENSE. |
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21 | */ |
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22 | |
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23 | #ifndef _RTEMS_SAPI_COUNTER_H |
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24 | #define _RTEMS_SAPI_COUNTER_H |
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25 | |
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26 | #include <rtems/score/cpu.h> |
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27 | |
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28 | #ifdef __cplusplus |
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29 | extern "C" { |
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30 | #endif /* __cplusplus */ |
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31 | |
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32 | /** |
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33 | * @defgroup ClassicCounter Free-Running Counter and Busy Wait Delay |
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34 | * |
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35 | * @ingroup ClassicRTEMS |
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36 | * |
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37 | * @brief Free-running counter and busy wait delay functions. |
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38 | * |
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39 | * The RTEMS counter is some free-running counter. It ticks usually with a |
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40 | * frequency close to the CPU or system bus clock. |
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41 | * |
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42 | * The counter can be used in case the overhead of the |
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43 | * rtems_clock_get_uptime_nanoseconds() is too high. The step from counter |
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44 | * ticks to/from nanoseconds is explicit in this API unlike to |
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45 | * rtems_clock_get_uptime_nanoseconds() which performs the conversion on each |
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46 | * invocation. |
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47 | * |
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48 | * This counter works without a clock driver and during system initialization. |
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49 | * |
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50 | * The counter can be used to profile low-level operations like SMP locks or |
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51 | * interrupt disabled critical sections. The counter can act also as an |
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52 | * entropy source for a random number generator. |
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53 | * |
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54 | * The period of the counter depends on the actual hardware. |
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55 | * |
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56 | * @{ |
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57 | */ |
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58 | |
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59 | /** |
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60 | * @brief Unsigned integer type for counter values. |
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61 | */ |
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62 | typedef CPU_Counter_ticks rtems_counter_ticks; |
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63 | |
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64 | /** |
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65 | * @brief Reads the current counter values. |
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66 | * |
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67 | * @return The current counter values. |
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68 | */ |
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69 | static inline rtems_counter_ticks rtems_counter_read( void ) |
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70 | { |
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71 | return _CPU_Counter_read(); |
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72 | } |
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73 | |
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74 | /** |
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75 | * @brief Returns the difference between the second and first CPU counter |
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76 | * value. |
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77 | * |
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78 | * This operation may be carried out as a modulo operation depending on the |
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79 | * range of the CPU counter device. |
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80 | * |
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81 | * @param[in] second The second CPU counter value. |
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82 | * @param[in] first The first CPU counter value. |
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83 | * |
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84 | * @return Returns second minus first modulo counter period. |
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85 | */ |
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86 | static inline rtems_counter_ticks rtems_counter_difference( |
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87 | rtems_counter_ticks second, |
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88 | rtems_counter_ticks first |
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89 | ) |
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90 | { |
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91 | return _CPU_Counter_difference( second, first ); |
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92 | } |
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93 | |
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94 | /** |
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95 | * @brief Converts counter ticks into nanoseconds. |
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96 | * |
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97 | * @param[in] ticks Some counter ticks. |
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98 | * |
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99 | * @return The nanoseconds corresponding to the counter ticks. The value is |
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100 | * rounded up. |
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101 | */ |
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102 | uint64_t rtems_counter_ticks_to_nanoseconds( |
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103 | rtems_counter_ticks ticks |
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104 | ); |
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105 | |
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106 | /** |
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107 | * @brief Converts nanoseconds into counter ticks. |
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108 | * |
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109 | * @param[in] nanoseconds Some nanoseconds. |
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110 | * |
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111 | * @return The counter ticks corresponding to the nanoseconds. The value is |
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112 | * rounded up. |
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113 | */ |
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114 | rtems_counter_ticks rtems_counter_nanoseconds_to_ticks( |
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115 | uint32_t nanoseconds |
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116 | ); |
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117 | |
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118 | /** |
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119 | * @brief Initializes the counter ticks to/from nanoseconds converter functions. |
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120 | * |
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121 | * This function must be used to initialize the |
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122 | * rtems_counter_ticks_to_nanoseconds() and |
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123 | * rtems_counter_nanoseconds_to_ticks() functions. It should be called during |
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124 | * system initialization by the board support package. |
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125 | * |
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126 | * @param[in] uint32_t frequency The current counter frequency in Hz. |
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127 | */ |
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128 | void rtems_counter_initialize_converter( uint32_t frequency ); |
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129 | |
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130 | /** |
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131 | * @brief Busy wait for some counter ticks. |
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132 | * |
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133 | * This function does not disable interrupts. Thus task switches and |
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134 | * interrupts can interfere with this busy wait may prolong the delay. This |
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135 | * function busy waits at least the specified time. Due to some overhead the |
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136 | * actual delay may be longer. |
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137 | * |
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138 | * @param[in] ticks The minimum busy wait time in counter ticks. |
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139 | */ |
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140 | void rtems_counter_delay_ticks( rtems_counter_ticks ticks ); |
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141 | |
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142 | /** |
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143 | * @brief Busy wait for some nanoseconds. |
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144 | * |
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145 | * This function does not disable interrupts. Thus task switches and |
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146 | * interrupts can interfere with this busy wait may prolong the delay. This |
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147 | * function busy waits at least the specified time. Due to some overhead the |
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148 | * actual delay may be longer. |
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149 | * |
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150 | * @param[in] nanoseconds The minimum busy wait time in nanoseconds. |
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151 | */ |
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152 | void rtems_counter_delay_nanoseconds( uint32_t nanoseconds ); |
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153 | |
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154 | /** @} */ |
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155 | |
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156 | #ifdef __cplusplus |
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157 | } |
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158 | #endif /* __cplusplus */ |
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159 | |
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160 | #endif /* _RTEMS_SAPI_COUNTER_H */ |
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