source: rtems/c/src/lib/libbsp/m68k/ods68302/timer/timer.c @ 8fbe2e6

4.11
Last change on this file since 8fbe2e6 was 8fbe2e6, checked in by Joel Sherrill <joel.sherrill@…>, on Sep 4, 2014 at 1:59:49 PM

Use correct prototype of benchmark_timer_read()

This change starts with removing the effectively empty file
timerdrv.h. The prototypes for benchmark_timer_XXX() were in
btimer.h which was not universally used. Thus every use of
timerdrv.h had to be changed to btimer.h. Then the prototypes
for benchmark_timer_read() had to be adjusted to return
benchmark_timer_t rather than int or uint32_t.

I took this opportunity to also correct the file headers to
separate the copyright from the file description comments which
is needed to ensure the copyright isn't propagated into Doxygen
output.

  • Property mode set to 100644
File size: 3.0 KB
Line 
1/*
2 *
3 *  This routine initializes TIMER 2 for an MC68302.
4 *
5 *  COPYRIGHT (c) 1989-1999.
6 *  On-Line Applications Research Corporation (OAR).
7 *
8 *  The license and distribution terms for this file may be
9 *  found in the file LICENSE in this distribution or at
10 *  http://www.rtems.org/license/LICENSE.
11 */
12
13#include <rtems.h>
14#include <bsp.h>
15#include <rtems/btimer.h>
16#include <rtems/m68k/m68302.h>
17
18#define TMR2_VAL 0x071b /* Timer mode register
19                         * (section 3.5.2.1 in 68302 manual)
20                         * 15-8: "7"    prescaler divide by 8 (x+1)
21                         *  7-6: 00     dis. intr. on capture event
22                         *    5:  0     active-low pulse
23                         *    4:  1     intr. on reaching reference
24                         *    3:  1     restart counter on reference
25                         *  2-1: 01     master clock input source
26                         *    0:  1     enable timer
27                         */
28#define TRR2_VAL 2000   /* Timer reference register
29                         * (section 3.5.2.2 in 68302 manual)
30                         * 2000 ticks @ (16MHz/1)/8 = 1-ms count
31                         */
32
33uint32_t         Timer_interrupts;
34
35bool benchmark_timer_find_average_overhead;
36
37rtems_isr timerisr(void);
38
39void benchmark_timer_initialize( void )
40{
41    m302.reg.tmr2 = 0;                  /* disable timer */
42
43    Timer_interrupts = 0;               /* clear timer ISR count */
44
45    m302.reg.trr2 = TRR2_VAL;           /* set timer reference register */
46    m302.reg.tmr2 = TMR2_VAL;           /* set timer mode register */
47    m302.reg.imr |= RBIT_IMR_TIMER2;    /* set 68302 int-mask to allow ints */
48}
49
50/*
51 *  The following controls the behavior of benchmark_timer_read().
52 *
53 *  FIND_AVG_OVERHEAD *  instructs the routine to return the "raw" count.
54 *
55 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
56 *  is usually deducted from the number returned.
57 *
58 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
59 *  below this are "noise" and zero is returned.
60 */
61
62#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
63                             /* (Y countdowns) to start/stop the timer. */
64                             /* This value is in microseconds. */
65#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
66
67/*
68 * Return timer value in 1/2-microsecond units
69 */
70benchmark_timer_t benchmark_timer_read( void )
71{
72  uint16_t         clicks;
73  uint32_t         total;
74
75  /*
76   *  Read the timer and see how many clicks it has been since counter
77   *  rolled over.
78   */
79
80  clicks = m302.reg.tcn2;
81
82  /*
83   *  Total is calculated by taking into account the number of timer overflow
84   *  interrupts since the timer was initialized and clicks since the last
85   *  interrupts.
86   */
87
88  total = (Timer_interrupts * TRR2_VAL) + clicks;
89
90  if ( benchmark_timer_find_average_overhead == true )
91    return total;          /* in XXX microsecond units */
92
93  if ( total < LEAST_VALID )
94    return 0;            /* below timer resolution */
95
96  /*
97   *  Convert 1/2-microsecond count into microseconds
98   */
99
100  return (total - AVG_OVERHEAD) >> 1;
101}
102
103void benchmark_timer_disable_subtracting_average_overhead(
104  bool find_flag
105)
106{
107  benchmark_timer_find_average_overhead = find_flag;
108}
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