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[/] [or1k/] [trunk/] [rtems-20020807/] [c/] [src/] [lib/] [libbsp/] [c4x/] [c4xsim/] [timer/] [timer.c] - Blame information for rev 1026

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1 1026 ivang 
/*  timer.c
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 *
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 *  This file manages the benchmark timer used by the RTEMS Timing Test
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 *  Suite.  Each measured time period is demarcated by calls to
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 *  Timer_initialize() and Read_timer().  Read_timer() usually returns
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 *  the number of microseconds since Timer_initialize() exitted.
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 *
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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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 *  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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 *  timer.c,v 1.1 2000/02/22 18:39:52 joel Exp
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 */
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#include <rtems.h>
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#include <bsp.h>
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#include <c4xio.h>
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rtems_unsigned32 Timer_interrupts;
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rtems_boolean Timer_driver_Find_average_overhead;
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static unsigned32 start;
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void Timer_initialize( void )
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{
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  /*
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   *  Timer has never overflowed.  This may not be necessary on some
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   *  implemenations of timer but ....
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   */
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  c4x_timer_stop(C4X_TIMER_0);
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  c4x_timer_set_period(C4X_TIMER_0, 0xffffffff); /* so no interupts */
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  c4x_timer_start(C4X_TIMER_0);
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  start = c4x_timer_get_counter(C4X_TIMER_0);
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  Timer_interrupts = 0;
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  /*
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   *  Somehow start the timer
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   */
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}
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/*
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 *  The following controls the behavior of Read_timer().
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 *
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 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
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 *  is usually deducted from the number returned.
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 *
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 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
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 *  below this are "noise" and zero is returned.
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 */
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#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
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                             /* (Y countdowns) to start/stop the timer. */
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                             /* This value is in microseconds. */
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#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
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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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  int            tmp;
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  /*
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   *  Read the timer and see how many clicks it has been since we started.
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   */
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  clicks = c4x_timer_get_counter(C4X_TIMER_0);
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  clicks -= start;
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  /*
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   *  Total is calculated by taking into account the number of timer overflow
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   *  interrupts since the timer was initialized and clicks since the last
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   *  interrupts.
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   */
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  total = clicks * 1;
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  if ( Timer_driver_Find_average_overhead == 1 ) {
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    return total;          /* in count units where each count is */
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                           /* 1 / (clock frequency/2) */
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  } else {
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    if ( total < LEAST_VALID )
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      return 0;            /* below timer resolution */
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  /*
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   *  Somehow convert total into microseconds
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   */
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      tmp = (int) ((float) total * ((1.0 / 25.0)));
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      return (tmp - AVG_OVERHEAD);
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    }
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}
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/*
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 *  Empty function call used in loops to measure basic cost of looping
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 *  in Timing Test Suite.
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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(
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  rtems_boolean find_flag
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)
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{
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  Timer_driver_Find_average_overhead = find_flag;
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}
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