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/*
* This file implements a benchmark timer using the count/compare
* CP0 registers.
*
* Copyright (c) 2005 by Cogent Computer Systems
* Written by Jay Monkman <jtm@lopingdog.com>
*
* The license and distribution terms for this file may be
* found in found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#include <assert.h>
#include <bsp.h>
rtems_boolean benchmark_timer_find_average_overhead;
uint32_t tstart;
void benchmark_timer_initialize(void)
{
asm volatile ("mfc0 %0, $9\n" : "=r" (tstart));
/* tick time in picooseconds */
}
#define AVG_OVERHEAD 0 /* It typically takes N instructions */
/* to start/stop the timer. */
#define LEAST_VALID 1 /* Don't trust a value lower than this */
/* tx39 simulator can count instructions. :) */
int benchmark_timer_read(void)
{
uint32_t total;
uint32_t cnt;
asm volatile ("mfc0 %0, $9\n" : "=r" (cnt));
total = cnt - tstart;
total = (total * 1000) / 396; /* convert to nanoseconds */
if ( benchmark_timer_find_average_overhead == 1 )
return total; /* in one microsecond units */
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
return total - AVG_OVERHEAD;
}
void benchmark_timer_disable_subtracting_average_overhead(
rtems_boolean find_flag
)
{
benchmark_timer_find_average_overhead = find_flag;
}
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