[96284fd8] | 1 | /* timer.c |
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| 2 | * |
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| 3 | * This file manages the benchmark timer used by the RTEMS Timing Test |
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| 4 | * Suite. Each measured time period is demarcated by calls to |
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| 5 | * Timer_initialize() and Read_timer(). Read_timer() usually returns |
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| 6 | * the number of microseconds since Timer_initialize() exitted. |
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| 7 | * |
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| 8 | * NOTE: It is important that the timer start/stop overhead be |
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| 9 | * determined when porting or modifying this code. |
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| 10 | * |
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| 11 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
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| 12 | * On-Line Applications Research Corporation (OAR). |
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| 13 | * |
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[8f6a68e8] | 14 | * $Id$ |
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[96284fd8] | 15 | */ |
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| 16 | |
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[a982e0c6] | 17 | #include <rtems.h> |
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[96284fd8] | 18 | |
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| 19 | rtems_boolean Timer_driver_Find_average_overhead; |
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| 20 | |
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| 21 | static unsigned int volatile lastInitValue; |
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| 22 | |
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| 23 | void Timer_initialize( void ) |
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| 24 | { |
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| 25 | asm volatile( " mftb %0": "=r" (lastInitValue) ); |
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| 26 | } |
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| 27 | |
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| 28 | /* |
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| 29 | * The following controls the behavior of Read_timer(). |
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| 30 | * |
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| 31 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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| 32 | * is usually deducted from the number returned. |
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| 33 | * |
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| 34 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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| 35 | * below this are "noise" and zero is returned. |
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| 36 | */ |
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| 37 | |
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| 38 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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| 39 | /* (Y countdowns) to start/stop the timer. */ |
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| 40 | /* This value is in microseconds. */ |
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| 41 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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| 42 | |
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| 43 | int Read_timer( void ) |
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| 44 | { |
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| 45 | rtems_unsigned32 value; |
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| 46 | asm volatile ( " mftb %0": "=r" (value) ); |
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| 47 | return value - lastInitValue; |
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| 48 | } |
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| 49 | |
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| 50 | /* |
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| 51 | * Empty function call used in loops to measure basic cost of looping |
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| 52 | * in Timing Test Suite. |
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| 53 | */ |
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| 54 | |
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| 55 | rtems_status_code Empty_function( void ) |
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| 56 | { |
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| 57 | return RTEMS_SUCCESSFUL; |
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| 58 | } |
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| 59 | |
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| 60 | void Set_find_average_overhead( |
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| 61 | rtems_boolean find_flag |
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| 62 | ) |
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| 63 | { |
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| 64 | Timer_driver_Find_average_overhead = find_flag; |
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| 65 | } |
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