source: rtems/c/src/lib/libcpu/a29k/timer/timer.c @ 946178d

4.104.114.84.95
Last change on this file since 946178d was 946178d, checked in by Joel Sherrill <joel.sherrill@…>, on Oct 18, 2000 at 1:09:03 PM

2000-10-18 Joel Sherrill <joel@…>

  • clock/ckinit.c: Removed commented out include of bsp.h.
  • Property mode set to 100644
File size: 3.1 KB
Line 
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 *
19 *  $Id$
20 */
21
22#ifndef lint
23static char _sccsid[] = "@(#)timer.c 05/07/96     1.4\n";
24#endif
25
26#include <rtems.h>
27
28#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
29#define TIMER_MAX_VALUE 0xffffffff
30
31static unsigned32 read_timer( void )
32{
33  return 0; /* do something with real hardware here */
34}
35
36static rtems_boolean Timer_driver_Find_average_overhead;
37static unsigned32 Timer_initial_value = 0;
38
39void Timer_initialize( void )
40{
41   Timer_initial_value = read_timer();
42
43  /*
44   *  Somehow start the timer
45   */
46
47  /* Timer is always running */
48}
49
50/*
51 *  The following controls the behavior of Read_timer().
52 *
53 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
54 *  is usually deducted from the number returned.
55 *
56 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
57 *  below this are "noise" and zero is returned.
58 */
59
60#define AVG_OVERHEAD      8  /* It typically takes X.X microseconds */
61                             /* (Y countdowns) to start/stop the timer. */
62                             /* This value is in cycles. */
63#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
64
65int Read_timer( void )
66{
67  unsigned64 clicks;
68  unsigned32 total;
69
70  /*
71   *  Read the timer and see how many clicks it has been since we started.
72   */
73
74  clicks = read_timer();   /* XXX: read some HW here */
75  if (clicks < Timer_initial_value)
76  {
77      clicks += TIMER_MAX_VALUE;
78  }
79  clicks -= Timer_initial_value;
80
81  /*
82   *  Total is calculated by taking into account the number of timer overflow
83   *  interrupts since the timer was initialized and clicks since the last
84   *  interrupts.
85   */
86#if 0 /* leave total in number of cycles */
87   total = clicks / CLOCKS_PER_MICROSECOND;
88#else
89   total = clicks;
90#endif
91
92  if ( Timer_driver_Find_average_overhead == 1 )
93    return total;          /* in # cycles units */
94  else {
95    if ( total < LEAST_VALID )
96      return 0;            /* below timer resolution */
97  /*
98   *  leave total in cycles
99   */
100      return (total - AVG_OVERHEAD);
101    }
102}
103
104/*
105 *  Empty function call used in loops to measure basic cost of looping
106 *  in Timing Test Suite.
107 */
108
109rtems_status_code Empty_function( void )
110{
111  return RTEMS_SUCCESSFUL;
112}
113
114void Set_find_average_overhead(
115  rtems_boolean find_flag
116)
117{
118  Timer_driver_Find_average_overhead = find_flag;
119}
120
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