source: rtems/c/src/lib/libcpu/mips64orion/timer/timer.c @ 82478528

4.104.114.84.95
Last change on this file since 82478528 was 82478528, checked in by Joel Sherrill <joel.sherrill@…>, on Apr 7, 1997 at 9:30:16 PM

commented out sccs_id's to eliminate warnings.

  • Property mode set to 100644
File size: 4.0 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, 1990, 1991, 1992, 1993, 1994.
31 *  On-Line Applications Research Corporation (OAR).
32 *  All rights assigned to U.S. Government, 1994.
33 *
34 *  This material may be reproduced by or for the U.S. Government pursuant
35 *  to the copyright license under the clause at DFARS 252.227-7013.  This
36 *  notice must appear in all copies of this file and its derivatives.
37 *
38 *  $Id$
39 */
40
41/*
42 *  Rather than deleting this, it is commented out to (hopefully) help
43 *  the submitter send updates.
44 *
45 *  static char _sccsid[] = "@(#)timer.c 08/20/96     1.5\n";
46 */
47
48
49#include <rtems.h>
50#include <bsp.h>
51
52#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
53#define TIMER_MAX_VALUE 0xffffffff
54
55extern unsigned32 mips_read_timer( void );
56
57static rtems_boolean Timer_driver_Find_average_overhead;
58static unsigned32 Timer_initial_value = 0;
59
60void Timer_initialize( void )
61{
62   Timer_initial_value = mips_read_timer();
63  /*
64   *  Somehow start the timer
65   */
66
67  /* Timer on 4650 is always running */
68}
69
70/*
71 *  The following controls the behavior of Read_timer().
72 *
73 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
74 *  is usually deducted from the number returned.
75 *
76 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
77 *  below this are "noise" and zero is returned.
78 */
79
80#define AVG_OVERHEAD      8  /* It typically takes X.X microseconds */
81                             /* (Y countdowns) to start/stop the timer. */
82                             /* This value is in cycles. */
83#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
84
85int Read_timer( void )
86{
87  unsigned64 clicks;
88  unsigned32 total;
89
90  /*
91   *  Read the timer and see how many clicks it has been since we started.
92   */
93
94  clicks = mips_read_timer();   /* XXX: read some HW here */
95  if (clicks < Timer_initial_value)
96  {
97      clicks += TIMER_MAX_VALUE;
98  }
99  clicks -= Timer_initial_value;
100
101  /*
102   *  Total is calculated by taking into account the number of timer overflow
103   *  interrupts since the timer was initialized and clicks since the last
104   *  interrupts.
105   */
106#if 0 /* leave total in number of cycles */
107   total = clicks / CLOCKS_PER_MICROSECOND;
108#else
109   total = clicks;
110#endif
111
112  if ( Timer_driver_Find_average_overhead == 1 )
113    return total;          /* in # cycles units */
114  else {
115    if ( total < LEAST_VALID )
116      return 0;            /* below timer resolution */
117  /*
118   *  leave total in cycles
119   */
120      return (total - AVG_OVERHEAD);
121    }
122}
123
124/*
125 *  Empty function call used in loops to measure basic cost of looping
126 *  in Timing Test Suite.
127 */
128
129rtems_status_code Empty_function( void )
130{
131  return RTEMS_SUCCESSFUL;
132}
133
134void Set_find_average_overhead(
135  rtems_boolean find_flag
136)
137{
138  Timer_driver_Find_average_overhead = find_flag;
139}
140
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