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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
* benchmark_timer_initialize() and benchmark_timer_read().
* benchmark_timer_read() usually returns the number of microseconds
* since benchmark_timer_initialize() exitted.
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* COPYRIGHT (c) Yann Sionneau <yann.sionneau@telecom-sudparis.eu> (GSoC 2010)
* Telecom SudParis
*/
#include <rtems.h>
#include <bsp.h>
#include <rtems/btimer.h>
#include "../include/system_conf.h"
#include "../../shared/clock/clock.h"
bool benchmark_timer_find_average_overhead;
void benchmark_timer_initialize(void)
{
MM_WRITE(MM_TIMER1_COMPARE, 0xffffffff);
MM_WRITE(MM_TIMER1_COUNTER, 0);
MM_WRITE(MM_TIMER1_CONTROL, TIMER_ENABLE);
}
/*
* The following controls the behavior of benchmark_timer_read().
*
* 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 4 /* It typically takes X.X microseconds */
/* (Y countdowns) to start/stop the timer. */
/* This value is in microseconds. */
#define LEAST_VALID 4 /* Don't trust a clicks value lower than this */
uint32_t benchmark_timer_read(void)
{
uint32_t ticks;
uint32_t total;
ticks = MM_READ(MM_TIMER1_COUNTER);
if (ticks == 0xffffffff)
printk("Timer overflow!\n");
total = ticks / (MM_READ(MM_FREQUENCY) / 1000000);
if (benchmark_timer_find_average_overhead)
return total;
else
{
if (total < LEAST_VALID)
return 0;
return (total - AVG_OVERHEAD);
}
}
void benchmark_timer_disable_subtracting_average_overhead(
bool find_flag
)
{
benchmark_timer_find_average_overhead = find_flag;
}
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