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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libcpu/] [powerpc/] [mpc821/] [timer/] [timer.c] - Blame information for rev 173

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1 30 unneback
/*  timer.c
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 *
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 *  This file manages the interval timer on the PowerPC MPC821.
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 *  NOTE: This is not the PIT, but rather the RTEMS interval
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 *        timer
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 *  We shall use the bottom 32 bits of the timebase register,
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 *
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 *  The following was in the 403 version of this file. I don't
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 *  know what it means. JTM 5/19/98
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 *  NOTE: It is important that the timer start/stop overhead be
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 *        determined when porting or modifying this code.
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 *
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 *  Author: Jay Monkman (jmonkman@frasca.com)
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 *  Copywright (C) 1998 by Frasca International, Inc.
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 *
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 *  Derived from c/src/lib/libcpu/ppc/ppc403/timer/timer.c:
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 *
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 *  Author:     Andrew Bray <andy@i-cubed.co.uk>
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 *
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 *  COPYRIGHT (c) 1995 by i-cubed ltd.
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 *
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 *  To anyone who acknowledges that this file is provided "AS IS"
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 *  without any express or implied warranty:
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 *      permission to use, copy, modify, and distribute this file
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 *      for any purpose is hereby granted without fee, provided that
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 *      the above copyright notice and this notice appears in all
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 *      copies, and that the name of i-cubed limited not be used in
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 *      advertising or publicity pertaining to distribution of the
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 *      software without specific, written prior permission.
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 *      i-cubed limited makes no representations about the suitability
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 *      of this software for any purpose.
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 *
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 *  Derived from c/src/lib/libcpu/hppa1_1/timer/timer.c:
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 *
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 *  COPYRIGHT (c) 1989-1999.
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 *  On-Line Applications Research Corporation (OAR).
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 *
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 *  The license and distribution terms for this file may be
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 *  found in the file LICENSE in this distribution or at
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 *  http://www.OARcorp.com/rtems/license.html.
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 *
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 *  $Id: timer.c,v 1.2 2001-09-27 12:01:28 chris Exp $
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 */
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#include <rtems.h>
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#include <mpc821.h>
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static volatile rtems_unsigned32 Timer_starting;
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static rtems_boolean Timer_driver_Find_average_overhead;
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/*
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 *  This is so small that this code will be reproduced where needed.
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 */
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static inline rtems_unsigned32 get_itimer(void)
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{
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   rtems_unsigned32 ret;
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   asm volatile ("mftb %0" : "=r" ((ret))); /* TBLO */
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   return ret;
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}
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void Timer_initialize(void)
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{
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  /* set interrupt level and enable timebase. This should never */
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  /*  generate an interrupt however. */
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  m821.tbscr |= M821_TBSCR_TBIRQ(4) | M821_TBSCR_TBE;
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  Timer_starting = get_itimer();
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}
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int Read_timer(void)
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{
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  rtems_unsigned32 clicks;
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  rtems_unsigned32 total;
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  clicks = get_itimer();
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  total = clicks - Timer_starting;
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  if ( Timer_driver_Find_average_overhead == 1 )
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    return total;          /* in XXX microsecond units */
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  else {
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    if ( total < rtems_cpu_configuration_get_timer_least_valid() ) {
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      return 0;            /* below timer resolution */
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    }
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    return (total - rtems_cpu_configuration_get_timer_average_overhead());
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  }
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}
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rtems_status_code Empty_function(void)
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{
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  return RTEMS_SUCCESSFUL;
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}
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void Set_find_average_overhead(rtems_boolean find_flag)
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{
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  Timer_driver_Find_average_overhead = find_flag;
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}

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