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/*  timer.c

 *

 *  This file manages the interval timer on the PowerPC 403*.

 *  We shall use the bottom 32 bits of the timebase register,

 *

 *  NOTE: It is important that the timer start/stop overhead be

 *        determined when porting or modifying this code.

 *

 *  Author:     Andrew Bray <andy@i-cubed.co.uk>

 *

 *  COPYRIGHT (c) 1995 by i-cubed ltd.

 *

 *  To anyone who acknowledges that this file is provided "AS IS"

 *  without any express or implied warranty:

 *      permission to use, copy, modify, and distribute this file

 *      for any purpose is hereby granted without fee, provided that

 *      the above copyright notice and this notice appears in all

 *      copies, and that the name of i-cubed limited not be used in

 *      advertising or publicity pertaining to distribution of the

 *      software without specific, written prior permission.

 *      i-cubed limited makes no representations about the suitability

 *      of this software for any purpose.

 *

 *  Derived from c/src/lib/libcpu/hppa1.1/timer/timer.c:

 *

 *  COPYRIGHT (c) 1989-1999.

 *  On-Line Applications Research Corporation (OAR).

 *

 *  The license and distribution terms for this file may be

 *  found in the file LICENSE in this distribution or at

 *  http://www.OARcorp.com/rtems/license.html.

 *

 *  $Id: timer.c,v 1.2 2001-09-27 12:01:30 chris Exp $

 */

#include <rtems.h>

static volatile rtems_unsigned32 Timer_starting;

static rtems_boolean Timer_driver_Find_average_overhead;

/*

 *  This is so small that this code will be reproduced where needed.

 */

static inline rtems_unsigned32 get_itimer(void)

{

   rtems_unsigned32 ret;

   asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); /* TBLO */

   return ret;

}

void Timer_initialize()

{

  rtems_unsigned32 iocr;

  asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); /* IOCR */

  iocr &= ~4;

  iocr |= 4;  /* Select external timer clock */

  asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); /* IOCR */

  Timer_starting = get_itimer();

}

int Read_timer()

{

  rtems_unsigned32 clicks;

  rtems_unsigned32 total;

  clicks = get_itimer();

  total = clicks - Timer_starting;

  if ( Timer_driver_Find_average_overhead == 1 )

    return total;          /* in XXX microsecond units */

  else {

    if ( total < rtems_cpu_configuration_get_timer_least_valid() )

      return 0;            /* below timer resolution */

    return (total - rtems_cpu_configuration_get_timer_average_overhead());

  }

}

rtems_status_code Empty_function( void )

{

  return RTEMS_SUCCESSFUL;

}

void Set_find_average_overhead(

  rtems_boolean find_flag

)

{

  Timer_driver_Find_average_overhead = find_flag;

}