source: rtems/c/src/lib/libcpu/powerpc/ppc403/timer/timer.c @ 0b50855

4.104.114.84.95
Last change on this file since 0b50855 was 93bea77, checked in by Joel Sherrill <joel.sherrill@…>, on Sep 30, 1996 at 8:16:05 PM

changed INLINE to inline since INLINE is no longer defined by RTEMS

  • Property mode set to 100644
File size: 2.7 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, 1990, 1991, 1992, 1993, 1994.
27 *  On-Line Applications Research Corporation (OAR).
28 *  All rights assigned to U.S. Government, 1994.
29 *
30 *  This material may be reproduced by or for the U.S. Government pursuant
31 *  to the copyright license under the clause at DFARS 252.227-7013.  This
32 *  notice must appear in all copies of this file and its derivatives.
33 *
34 *  $Id$
35 */
36
37#include <bsp.h>
38#include <rtems.h>
39
40extern rtems_cpu_table           Cpu_table;             /* owned by BSP */
41
42static volatile rtems_unsigned32 Timer_starting;
43static rtems_boolean Timer_driver_Find_average_overhead;
44
45/*
46 *  This is so small that this code will be reproduced where needed.
47 */
48static inline rtems_unsigned32 get_itimer(void)
49{
50   rtems_unsigned32 ret;
51
52   asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); /* TBLO */
53
54   return ret;
55}
56
57void Timer_initialize()
58{
59  rtems_unsigned32 iocr;
60
61  asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); /* IOCR */
62  iocr &= ~4;
63  iocr |= 4;  /* Select external timer clock */
64  asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); /* IOCR */
65
66  Timer_starting = get_itimer();
67}
68
69int Read_timer()
70{
71  rtems_unsigned32 clicks;
72  rtems_unsigned32 total;
73
74  clicks = get_itimer();
75
76  total = clicks - Timer_starting;
77
78  if ( Timer_driver_Find_average_overhead == 1 )
79    return total;          /* in XXX microsecond units */
80
81  else {
82    if ( total < Cpu_table.timer_least_valid )
83      return 0;            /* below timer resolution */
84    return (total - Cpu_table.timer_average_overhead);
85  }
86}
87
88rtems_status_code Empty_function( void )
89{
90  return RTEMS_SUCCESSFUL;
91}
92
93void Set_find_average_overhead(
94  rtems_boolean find_flag
95)
96{
97  Timer_driver_Find_average_overhead = find_flag;
98}
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