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/*  timer.c

 *

 *  This file manages the benchmark timer used by the RTEMS Timing Test

 *  Suite.  Each measured time period is demarcated by calls to

 *  Timer_initialize() and Read_timer().  Read_timer() usually returns

 *  the number of microseconds since Timer_initialize() exitted.

 *

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

 *        determined when porting or modifying this code.

 *

 *  COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.

 *  On-Line Applications Research Corporation (OAR).

 *  All rights assigned to U.S. Government, 1994.

 *

 *  This material may be reproduced by or for the U.S. Government pursuant

 *  to the copyright license under the clause at DFARS 252.227-7013.  This

 *  notice must appear in all copies of this file and its derivatives.

 *

 *  timer.c,v 1.2 1995/05/31 16:56:39 joel Exp

 */

#include "rtems.h"

rtems_boolean Timer_driver_Find_average_overhead;

static unsigned int volatile lastInitValue;

void Timer_initialize( void )

{

  asm volatile( " mftb %0": "=r" (lastInitValue) );

}

/*

 *  The following controls the behavior of Read_timer().

 *

 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It

 *  is usually deducted from the number returned.

 *

 *  LEAST_VALID is the lowest number this routine should trust.  Numbers

 *  below this are "noise" and zero is returned.

 */

#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */

                             /* (Y countdowns) to start/stop the timer. */

                             /* This value is in microseconds. */

#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */

int Read_timer( void )

{

  rtems_unsigned32 value;

  asm volatile ( " mftb %0": "=r" (value) );

  return value - lastInitValue;

}

/*

 *  Empty function call used in loops to measure basic cost of looping

 *  in Timing Test Suite.

 */

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;

}