[21677c0e] | 1 | /* timer.c |
---|
| 2 | * |
---|
| 3 | * This file manages the benchmark timer used by the RTEMS Timing Test |
---|
| 4 | * Suite. Each measured time period is demarcated by calls to |
---|
| 5 | * Timer_initialize() and Read_timer(). Read_timer() usually returns |
---|
| 6 | * the number of microseconds since Timer_initialize() exitted. |
---|
| 7 | * |
---|
| 8 | * NOTE: It is important that the timer start/stop overhead be |
---|
| 9 | * determined when porting or modifying this code. |
---|
| 10 | * |
---|
| 11 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
---|
| 12 | * On-Line Applications Research Corporation (OAR). |
---|
| 13 | * All rights assigned to U.S. Government, 1994. |
---|
| 14 | * |
---|
| 15 | * This material may be reproduced by or for the U.S. Government pursuant |
---|
| 16 | * to the copyright license under the clause at DFARS 252.227-7013. This |
---|
| 17 | * notice must appear in all copies of this file and its derivatives. |
---|
| 18 | * |
---|
[4c46630] | 19 | * $Id$ |
---|
[21677c0e] | 20 | */ |
---|
| 21 | |
---|
| 22 | #ifndef lint |
---|
| 23 | static char _sccsid[] = "@(#)timer.c 05/07/96 1.4\n"; |
---|
| 24 | #endif |
---|
| 25 | |
---|
| 26 | #include <rtems.h> |
---|
[2a1ca73] | 27 | /* #include <bsp.h> */ |
---|
[21677c0e] | 28 | |
---|
| 29 | #define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ ) |
---|
| 30 | #define TIMER_MAX_VALUE 0xffffffff |
---|
| 31 | |
---|
[a1f89b4] | 32 | static unsigned32 read_timer( void ) |
---|
| 33 | { |
---|
| 34 | return 0; /* do something with real hardware here */ |
---|
| 35 | } |
---|
[21677c0e] | 36 | |
---|
| 37 | static rtems_boolean Timer_driver_Find_average_overhead; |
---|
| 38 | static unsigned32 Timer_initial_value = 0; |
---|
| 39 | |
---|
| 40 | void Timer_initialize( void ) |
---|
| 41 | { |
---|
[a1f89b4] | 42 | Timer_initial_value = read_timer(); |
---|
| 43 | |
---|
[21677c0e] | 44 | /* |
---|
| 45 | * Somehow start the timer |
---|
| 46 | */ |
---|
| 47 | |
---|
[2a1ca73] | 48 | /* Timer is always running */ |
---|
[21677c0e] | 49 | } |
---|
| 50 | |
---|
| 51 | /* |
---|
| 52 | * The following controls the behavior of Read_timer(). |
---|
| 53 | * |
---|
| 54 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
---|
| 55 | * is usually deducted from the number returned. |
---|
| 56 | * |
---|
| 57 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
---|
| 58 | * below this are "noise" and zero is returned. |
---|
| 59 | */ |
---|
| 60 | |
---|
| 61 | #define AVG_OVERHEAD 8 /* It typically takes X.X microseconds */ |
---|
| 62 | /* (Y countdowns) to start/stop the timer. */ |
---|
| 63 | /* This value is in cycles. */ |
---|
| 64 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
---|
| 65 | |
---|
| 66 | int Read_timer( void ) |
---|
| 67 | { |
---|
| 68 | unsigned64 clicks; |
---|
| 69 | unsigned32 total; |
---|
| 70 | |
---|
| 71 | /* |
---|
| 72 | * Read the timer and see how many clicks it has been since we started. |
---|
| 73 | */ |
---|
| 74 | |
---|
[a1f89b4] | 75 | clicks = read_timer(); /* XXX: read some HW here */ |
---|
[21677c0e] | 76 | if (clicks < Timer_initial_value) |
---|
| 77 | { |
---|
| 78 | clicks += TIMER_MAX_VALUE; |
---|
| 79 | } |
---|
| 80 | clicks -= Timer_initial_value; |
---|
| 81 | |
---|
| 82 | /* |
---|
| 83 | * Total is calculated by taking into account the number of timer overflow |
---|
| 84 | * interrupts since the timer was initialized and clicks since the last |
---|
| 85 | * interrupts. |
---|
| 86 | */ |
---|
| 87 | #if 0 /* leave total in number of cycles */ |
---|
| 88 | total = clicks / CLOCKS_PER_MICROSECOND; |
---|
| 89 | #else |
---|
| 90 | total = clicks; |
---|
| 91 | #endif |
---|
| 92 | |
---|
| 93 | if ( Timer_driver_Find_average_overhead == 1 ) |
---|
| 94 | return total; /* in # cycles units */ |
---|
| 95 | else { |
---|
| 96 | if ( total < LEAST_VALID ) |
---|
| 97 | return 0; /* below timer resolution */ |
---|
| 98 | /* |
---|
| 99 | * leave total in cycles |
---|
| 100 | */ |
---|
| 101 | return (total - AVG_OVERHEAD); |
---|
| 102 | } |
---|
| 103 | } |
---|
| 104 | |
---|
| 105 | /* |
---|
| 106 | * Empty function call used in loops to measure basic cost of looping |
---|
| 107 | * in Timing Test Suite. |
---|
| 108 | */ |
---|
| 109 | |
---|
| 110 | rtems_status_code Empty_function( void ) |
---|
| 111 | { |
---|
| 112 | return RTEMS_SUCCESSFUL; |
---|
| 113 | } |
---|
| 114 | |
---|
| 115 | void Set_find_average_overhead( |
---|
| 116 | rtems_boolean find_flag |
---|
| 117 | ) |
---|
| 118 | { |
---|
| 119 | Timer_driver_Find_average_overhead = find_flag; |
---|
| 120 | } |
---|
| 121 | |
---|