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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libcpu/] [a29k/] [timer/] [timer.c] - Blame information for rev 30

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1 30 unneback
/*  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, 1990, 1991, 1992, 1993, 1994.
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 *  On-Line Applications Research Corporation (OAR).
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 *  All rights assigned to U.S. Government, 1994.
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 *
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 *  This material may be reproduced by or for the U.S. Government pursuant
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 *  to the copyright license under the clause at DFARS 252.227-7013.  This
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 *  notice must appear in all copies of this file and its derivatives.
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 *
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 *  $Id: timer.c,v 1.2 2001-09-27 12:01:20 chris Exp $
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 */
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#ifndef lint
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static char _sccsid[] = "@(#)timer.c 05/07/96     1.4\n";
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#endif
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#include <rtems.h>
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#include <bsp.h>
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#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
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#define TIMER_MAX_VALUE 0xffffffff
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static unsigned32 read_timer( void )
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{
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  return 0; /* do something with real hardware here */
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}
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static rtems_boolean Timer_driver_Find_average_overhead;
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static unsigned32 Timer_initial_value = 0;
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void Timer_initialize( void )
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{
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   Timer_initial_value = read_timer();
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  /*
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   *  Somehow start the timer
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   */
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  /* Timer on 4650 is always running */
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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      8  /* 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 cycles. */
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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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  unsigned64 clicks;
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  unsigned32 total;
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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 = read_timer();   /* XXX: read some HW here */
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  if (clicks < Timer_initial_value)
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  {
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      clicks += TIMER_MAX_VALUE;
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  }
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  clicks -= Timer_initial_value;
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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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#if 0 /* leave total in number of cycles */
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   total = clicks / CLOCKS_PER_MICROSECOND;
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#else
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   total = clicks;
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#endif
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  if ( Timer_driver_Find_average_overhead == 1 )
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    return total;          /* in # cycles units */
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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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   *  leave total in cycles
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   */
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      return (total - 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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