source: rtems/c/src/lib/libcpu/mips/timer/timer.c @ df40cc9

4.11
Last change on this file since df40cc9 was c499856, checked in by Chris Johns <chrisj@…>, on Mar 20, 2014 at 9:10:47 PM

Change all references of rtems.com to rtems.org.

  • Property mode set to 100644
File size: 3.8 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 *  benchmark_timer_initialize() and benchmark_timer_read().  benchmark_timer_read() usually returns
25 *  the number of microseconds since benchmark_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.rtems.org/license/LICENSE.
36 */
37
38/*
39 *  Rather than deleting this, it is commented out to (hopefully) help
40 *  the submitter send updates.
41 *
42 *  static char _sccsid[] = "@(#)timer.c 08/20/96     1.5\n";
43 */
44
45
46#include <rtems.h>
47
48#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
49#define TIMER_MAX_VALUE 0xffffffff
50
51extern uint32_t   mips_read_timer( void );
52
53static bool benchmark_timer_find_average_overhead;
54static uint32_t   benchmark_timer_initial_value = 0;
55
56void benchmark_timer_initialize( void )
57{
58   benchmark_timer_initial_value = mips_read_timer();
59  /*
60   *  Somehow start the timer
61   */
62
63  /* Timer on 4650 is always running */
64}
65
66/*
67 *  The following controls the behavior of benchmark_timer_read().
68 *
69 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
70 *  is usually deducted from the number returned.
71 *
72 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
73 *  below this are "noise" and zero is returned.
74 */
75
76#define AVG_OVERHEAD      8  /* It typically takes X.X microseconds */
77                             /* (Y countdowns) to start/stop the timer. */
78                             /* This value is in cycles. */
79#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
80
81int benchmark_timer_read( void )
82{
83  uint64_t   clicks;
84  uint32_t   total;
85
86  /*
87   *  Read the timer and see how many clicks it has been since we started.
88   */
89
90  clicks = mips_read_timer();   /* XXX: read some HW here */
91  if (clicks < benchmark_timer_initial_value)
92  {
93      clicks += TIMER_MAX_VALUE;
94  }
95  clicks -= benchmark_timer_initial_value;
96
97  /*
98   *  Total is calculated by taking into account the number of timer overflow
99   *  interrupts since the timer was initialized and clicks since the last
100   *  interrupts.
101   */
102#if 0 /* leave total in number of cycles */
103   total = clicks / CLOCKS_PER_MICROSECOND;
104#else
105   total = clicks;
106#endif
107
108  if ( benchmark_timer_find_average_overhead == 1 )
109    return total;          /* in # cycles units */
110  else {
111    if ( total < LEAST_VALID )
112      return 0;            /* below timer resolution */
113  /*
114   *  leave total in cycles
115   */
116      return (total - AVG_OVERHEAD);
117    }
118}
119
120void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
121{
122  benchmark_timer_find_average_overhead = find_flag;
123}
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