source: rtems/c/src/lib/libcpu/powerpc/ppc403/timer/timer.c @ 5e77d129

4.104.114.84.95
Last change on this file since 5e77d129 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: 2.5 KB
Line 
1/*  timer.c
2 *
3 *  This file manages the interval timer on the PowerPC 403*.
4 *  We shall use the bottom 32 bits of the timebase register,
5 *
6 *  NOTE: It is important that the timer start/stop overhead be
7 *        determined when porting or modifying this code.
8 *
9 *  Author:     Andrew Bray <andy@i-cubed.co.uk>
10 *
11 *  COPYRIGHT (c) 1995 by i-cubed ltd.
12 *
13 *  To anyone who acknowledges that this file is provided "AS IS"
14 *  without any express or implied warranty:
15 *      permission to use, copy, modify, and distribute this file
16 *      for any purpose is hereby granted without fee, provided that
17 *      the above copyright notice and this notice appears in all
18 *      copies, and that the name of i-cubed limited not be used in
19 *      advertising or publicity pertaining to distribution of the
20 *      software without specific, written prior permission.
21 *      i-cubed limited makes no representations about the suitability
22 *      of this software for any purpose.
23 *
24 *  Derived from c/src/lib/libcpu/hppa1.1/timer/timer.c:
25 *
26 *  COPYRIGHT (c) 1989-1999.
27 *  On-Line Applications Research Corporation (OAR).
28 *
29 *  The license and distribution terms for this file may be
30 *  found in the file LICENSE in this distribution or at
31 *  http://www.OARcorp.com/rtems/license.html.
32 *
33 *  $Id$
34 */
35
36#include <rtems.h>
37
38static volatile rtems_unsigned32 Timer_starting;
39static rtems_boolean Timer_driver_Find_average_overhead;
40
41/*
42 *  This is so small that this code will be reproduced where needed.
43 */
44static inline rtems_unsigned32 get_itimer(void)
45{
46   rtems_unsigned32 ret;
47
48   asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); /* TBLO */
49
50   return ret;
51}
52
53void Timer_initialize()
54{
55  rtems_unsigned32 iocr;
56
57  asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); /* IOCR */
58  iocr &= ~4;
59  iocr |= 4;  /* Select external timer clock */
60  asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); /* IOCR */
61
62  Timer_starting = get_itimer();
63}
64
65int Read_timer()
66{
67  rtems_unsigned32 clicks;
68  rtems_unsigned32 total;
69
70  clicks = get_itimer();
71
72  total = clicks - Timer_starting;
73
74  if ( Timer_driver_Find_average_overhead == 1 )
75    return total;          /* in XXX microsecond units */
76
77  else {
78    if ( total < rtems_cpu_configuration_get_timer_least_valid() )
79      return 0;            /* below timer resolution */
80    return (total - rtems_cpu_configuration_get_timer_average_overhead());
81  }
82}
83
84rtems_status_code Empty_function( void )
85{
86  return RTEMS_SUCCESSFUL;
87}
88
89void Set_find_average_overhead(
90  rtems_boolean find_flag
91)
92{
93  Timer_driver_Find_average_overhead = find_flag;
94}
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