[f198c63] | 1 | /* timer.c |
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| 2 | * |
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| 3 | * This file contains the initialization code for the IDT 4650 timer driver. |
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| 4 | * |
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| 5 | * Author: Craig Lebakken <craigl@transition.com> |
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| 6 | * |
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| 7 | * COPYRIGHT (c) 1996 by Transition Networks Inc. |
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| 8 | * |
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| 9 | * To anyone who acknowledges that this file is provided "AS IS" |
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| 10 | * without any express or implied warranty: |
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| 11 | * permission to use, copy, modify, and distribute this file |
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| 12 | * for any purpose is hereby granted without fee, provided that |
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| 13 | * the above copyright notice and this notice appears in all |
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| 14 | * copies, and that the name of Transition Networks not be used in |
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| 15 | * advertising or publicity pertaining to distribution of the |
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| 16 | * software without specific, written prior permission. |
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| 17 | * Transition Networks makes no representations about the suitability |
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| 18 | * of this software for any purpose. |
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| 19 | * |
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| 20 | * derived from src/lib/libbsp/no_cpu/no_bsp/timer/timer.c |
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| 21 | * |
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| 22 | * This file manages the benchmark timer used by the RTEMS Timing Test |
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| 23 | * Suite. Each measured time period is demarcated by calls to |
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| 24 | * Timer_initialize() and Read_timer(). Read_timer() usually returns |
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| 25 | * the number of microseconds since Timer_initialize() exitted. |
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| 26 | * |
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| 27 | * NOTE: It is important that the timer start/stop overhead be |
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| 28 | * determined when porting or modifying this code. |
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| 29 | * |
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| 30 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
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| 31 | * On-Line Applications Research Corporation (OAR). |
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| 32 | * All rights assigned to U.S. Government, 1994. |
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| 33 | * |
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| 34 | * This material may be reproduced by or for the U.S. Government pursuant |
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| 35 | * to the copyright license under the clause at DFARS 252.227-7013. This |
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| 36 | * notice must appear in all copies of this file and its derivatives. |
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| 37 | * |
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[0971cd5] | 38 | * $Id$ |
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[f198c63] | 39 | */ |
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| 40 | |
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[82478528] | 41 | /* |
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| 42 | * Rather than deleting this, it is commented out to (hopefully) help |
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| 43 | * the submitter send updates. |
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| 44 | * |
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| 45 | * static char _sccsid[] = "@(#)timer.c 08/20/96 1.5\n"; |
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| 46 | */ |
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| 47 | |
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[f198c63] | 48 | |
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| 49 | #include <rtems.h> |
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| 50 | #include <bsp.h> |
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| 51 | |
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| 52 | #define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ ) |
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| 53 | #define TIMER_MAX_VALUE 0xffffffff |
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| 54 | |
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| 55 | extern unsigned32 mips_read_timer( void ); |
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| 56 | |
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| 57 | static rtems_boolean Timer_driver_Find_average_overhead; |
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| 58 | static unsigned32 Timer_initial_value = 0; |
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| 59 | |
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| 60 | void Timer_initialize( void ) |
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| 61 | { |
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| 62 | Timer_initial_value = mips_read_timer(); |
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| 63 | /* |
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| 64 | * Somehow start the timer |
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| 65 | */ |
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| 66 | |
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| 67 | /* Timer on 4650 is always running */ |
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| 68 | } |
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| 69 | |
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| 70 | /* |
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| 71 | * The following controls the behavior of Read_timer(). |
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| 72 | * |
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| 73 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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| 74 | * is usually deducted from the number returned. |
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| 75 | * |
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| 76 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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| 77 | * below this are "noise" and zero is returned. |
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| 78 | */ |
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| 79 | |
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| 80 | #define AVG_OVERHEAD 8 /* It typically takes X.X microseconds */ |
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| 81 | /* (Y countdowns) to start/stop the timer. */ |
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| 82 | /* This value is in cycles. */ |
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| 83 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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| 84 | |
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| 85 | int Read_timer( void ) |
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| 86 | { |
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| 87 | unsigned64 clicks; |
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| 88 | unsigned32 total; |
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| 89 | |
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| 90 | /* |
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| 91 | * Read the timer and see how many clicks it has been since we started. |
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| 92 | */ |
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| 93 | |
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| 94 | clicks = mips_read_timer(); /* XXX: read some HW here */ |
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| 95 | if (clicks < Timer_initial_value) |
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| 96 | { |
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| 97 | clicks += TIMER_MAX_VALUE; |
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| 98 | } |
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| 99 | clicks -= Timer_initial_value; |
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| 100 | |
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| 101 | /* |
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| 102 | * Total is calculated by taking into account the number of timer overflow |
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| 103 | * interrupts since the timer was initialized and clicks since the last |
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| 104 | * interrupts. |
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| 105 | */ |
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| 106 | #if 0 /* leave total in number of cycles */ |
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| 107 | total = clicks / CLOCKS_PER_MICROSECOND; |
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| 108 | #else |
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| 109 | total = clicks; |
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| 110 | #endif |
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| 111 | |
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| 112 | if ( Timer_driver_Find_average_overhead == 1 ) |
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| 113 | return total; /* in # cycles units */ |
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| 114 | else { |
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| 115 | if ( total < LEAST_VALID ) |
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| 116 | return 0; /* below timer resolution */ |
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| 117 | /* |
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| 118 | * leave total in cycles |
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| 119 | */ |
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| 120 | return (total - AVG_OVERHEAD); |
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| 121 | } |
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| 122 | } |
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| 123 | |
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| 124 | /* |
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| 125 | * Empty function call used in loops to measure basic cost of looping |
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| 126 | * in Timing Test Suite. |
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| 127 | */ |
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| 128 | |
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| 129 | rtems_status_code Empty_function( void ) |
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| 130 | { |
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| 131 | return RTEMS_SUCCESSFUL; |
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| 132 | } |
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| 133 | |
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| 134 | void Set_find_average_overhead( |
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| 135 | rtems_boolean find_flag |
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| 136 | ) |
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| 137 | { |
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| 138 | Timer_driver_Find_average_overhead = find_flag; |
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| 139 | } |
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| 140 | |
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