source: rtems/c/src/lib/libcpu/mips64orion/timer/timer.c @ c8f3e82

Last change on this file since c8f3e82 was 08311cc3, checked in by Joel Sherrill <joel.sherrill@…>, on Nov 17, 1999 at 5:51:34 PM

Updated copyright notice.

  • Property mode set to 100644
File size: 3.9 KB
Line 
1/*  timer.c
2 *
3 *  This file contains the initialization code for the IDT 4650 timer driver.
4 *
5 *  Author:     Craig Lebakken <craigl@transition.com>
6 *
7 *  COPYRIGHT (c) 1996 by Transition Networks Inc.
8 *
9 *  To anyone who acknowledges that this file is provided "AS IS"
10 *  without any express or implied warranty:
11 *      permission to use, copy, modify, and distribute this file
12 *      for any purpose is hereby granted without fee, provided that
13 *      the above copyright notice and this notice appears in all
14 *      copies, and that the name of Transition Networks not be used in
15 *      advertising or publicity pertaining to distribution of the
16 *      software without specific, written prior permission.
17 *      Transition Networks makes no representations about the suitability
18 *      of this software for any purpose.
19 *
20 *  derived from src/lib/libbsp/no_cpu/no_bsp/timer/timer.c
21 *
22 *  This file manages the benchmark timer used by the RTEMS Timing Test
23 *  Suite.  Each measured time period is demarcated by calls to
24 *  Timer_initialize() and Read_timer().  Read_timer() usually returns
25 *  the number of microseconds since Timer_initialize() exitted.
26 *
27 *  NOTE: It is important that the timer start/stop overhead be
28 *        determined when porting or modifying this code.
29 *
30 *  COPYRIGHT (c) 1989-1999.
31 *  On-Line Applications Research Corporation (OAR).
32 *
33 *  The license and distribution terms for this file may be
34 *  found in the file LICENSE in this distribution or at
35 *  http://www.OARcorp.com/rtems/license.html.
36 *
37 *  $Id$
38 */
39
40/*
41 *  Rather than deleting this, it is commented out to (hopefully) help
42 *  the submitter send updates.
43 *
44 *  static char _sccsid[] = "@(#)timer.c 08/20/96     1.5\n";
45 */
46
47
48#include <rtems.h>
49
50#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
51#define TIMER_MAX_VALUE 0xffffffff
52
53extern unsigned32 mips_read_timer( void );
54
55static rtems_boolean Timer_driver_Find_average_overhead;
56static unsigned32 Timer_initial_value = 0;
57
58void Timer_initialize( void )
59{
60   Timer_initial_value = mips_read_timer();
61  /*
62   *  Somehow start the timer
63   */
64
65  /* Timer on 4650 is always running */
66}
67
68/*
69 *  The following controls the behavior of Read_timer().
70 *
71 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
72 *  is usually deducted from the number returned.
73 *
74 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
75 *  below this are "noise" and zero is returned.
76 */
77
78#define AVG_OVERHEAD      8  /* It typically takes X.X microseconds */
79                             /* (Y countdowns) to start/stop the timer. */
80                             /* This value is in cycles. */
81#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
82
83int Read_timer( void )
84{
85  unsigned64 clicks;
86  unsigned32 total;
87
88  /*
89   *  Read the timer and see how many clicks it has been since we started.
90   */
91
92  clicks = mips_read_timer();   /* XXX: read some HW here */
93  if (clicks < Timer_initial_value)
94  {
95      clicks += TIMER_MAX_VALUE;
96  }
97  clicks -= Timer_initial_value;
98
99  /*
100   *  Total is calculated by taking into account the number of timer overflow
101   *  interrupts since the timer was initialized and clicks since the last
102   *  interrupts.
103   */
104#if 0 /* leave total in number of cycles */
105   total = clicks / CLOCKS_PER_MICROSECOND;
106#else
107   total = clicks;
108#endif
109
110  if ( Timer_driver_Find_average_overhead == 1 )
111    return total;          /* in # cycles units */
112  else {
113    if ( total < LEAST_VALID )
114      return 0;            /* below timer resolution */
115  /*
116   *  leave total in cycles
117   */
118      return (total - AVG_OVERHEAD);
119    }
120}
121
122/*
123 *  Empty function call used in loops to measure basic cost of looping
124 *  in Timing Test Suite.
125 */
126
127rtems_status_code Empty_function( void )
128{
129  return RTEMS_SUCCESSFUL;
130}
131
132void Set_find_average_overhead(
133  rtems_boolean find_flag
134)
135{
136  Timer_driver_Find_average_overhead = find_flag;
137}
138
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