1 | /* |
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2 | * Cogent CSB337 Timer driver |
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3 | * |
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4 | * This uses timer 0 for timing measurments. |
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5 | * |
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6 | * Copyright (c) 2004 by Jay Monkman <jtm@lopingdog.com> |
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7 | * |
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8 | * The license and distribution terms for this file may be |
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9 | * found in the file LICENSE in this distribution or at |
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10 | * |
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11 | * http://www.OARcorp.com/rtems/license.html. |
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12 | * |
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13 | * Notes: |
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14 | * This file manages the benchmark timer used by the RTEMS Timing Test |
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15 | * Suite. Each measured time period is demarcated by calls to |
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16 | * Timer_initialize() and Read_timer(). Read_timer() usually returns |
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17 | * the number of microseconds since Timer_initialize() exitted. |
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18 | * |
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19 | * It is important that the timer start/stop overhead be determined |
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20 | * when porting or modifying this code. |
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21 | * |
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22 | * $Id$ |
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23 | */ |
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24 | |
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25 | #include <rtems.h> |
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26 | #include <bsp.h> |
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27 | #include <at91rm9200.h> |
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28 | #include <at91rm9200_pmc.h> |
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29 | |
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30 | uint16_t tstart; |
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31 | rtems_boolean Timer_driver_Find_average_overhead; |
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32 | uint32_t tick_time; |
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33 | /* |
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34 | * Set up TC0 - |
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35 | * timer_clock2 (MCK/8) |
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36 | * capture mode - this shouldn't matter |
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37 | */ |
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38 | void Timer_initialize( void ) |
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39 | { |
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40 | uint32_t tmr_freq; |
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41 | |
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42 | /* since we are using timer_clock2, divide mck by 8 */ |
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43 | tmr_freq = at91rm9200_get_mck() / 8; |
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44 | |
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45 | TC_TC0_REG(TC_CMR) = TC_CMR_TCCLKS(1); /* timer_clock2 */ |
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46 | TC_TC0_REG(TC_CCR) = (TC_CCR_CLKEN /* enable the counter */ |
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47 | | TC_CCR_SWTRG); /* start it up */ |
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48 | |
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49 | /* tick time in nanoseconds */ |
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50 | tick_time = 1000000000/tmr_freq; |
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51 | |
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52 | } |
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53 | |
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54 | /* |
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55 | * The following controls the behavior of Read_timer(). |
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56 | * |
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57 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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58 | * is usually deducted from the number returned. |
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59 | * |
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60 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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61 | * below this are "noise" and zero is returned. |
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62 | */ |
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63 | |
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64 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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65 | /* (Y countdowns) to start/stop the timer. */ |
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66 | /* This value is in microseconds. */ |
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67 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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68 | |
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69 | int Read_timer( void ) |
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70 | { |
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71 | uint16_t t; |
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72 | uint32_t total; |
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73 | t = TC_TC0_REG(TC_CV); |
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74 | |
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75 | /* |
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76 | * Total is calculated by taking into account the number of timer overflow |
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77 | * interrupts since the timer was initialized and clicks since the last |
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78 | * interrupts. |
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79 | */ |
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80 | |
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81 | total = t * tick_time; |
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82 | |
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83 | if ( Timer_driver_Find_average_overhead == 1 ) |
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84 | return total; /* in nanosecond units */ |
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85 | else { |
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86 | if ( total < LEAST_VALID ) |
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87 | return 0; /* below timer resolution */ |
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88 | /* |
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89 | * Somehow convert total into microseconds |
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90 | */ |
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91 | return (total - AVG_OVERHEAD); |
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92 | } |
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93 | } |
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94 | |
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95 | /* |
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96 | * Empty function call used in loops to measure basic cost of looping |
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97 | * in Timing Test Suite. |
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98 | */ |
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99 | |
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100 | rtems_status_code Empty_function( void ) |
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101 | { |
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102 | return RTEMS_SUCCESSFUL; |
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103 | } |
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104 | |
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105 | void Set_find_average_overhead( |
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106 | rtems_boolean find_flag |
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107 | ) |
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108 | { |
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109 | Timer_driver_Find_average_overhead = find_flag; |
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110 | } |
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111 | |
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