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/*
* PXA255 timer by Yang Xi <hiyangxi@gmail.com>
* Copyright (c) 2004 by Jay Monkman <jtm@lopingdog.com>
*
* Notes:
* 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.
*
* 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.
*/
#include <rtems.h>
#include <bsp.h>
#include <pxa255.h>
uint32_t tstart;
static uint32_t tick_time;
bool benchmark_timer_find_average_overhead;
bool benchmark_timer_is_initialized = false;
/*
* Use the timer count register to measure.
* The frequency of it is 3.4864MHZ
* The longest period we are able to capture is 4G/3.4864MHZ
*/
void benchmark_timer_initialize(void)
{
tick_time = XSCALE_OS_TIMER_TCR;
}
/*
* 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 benchmark_timer_read(void)
{
uint32_t total;
total = XSCALE_OS_TIMER_TCR;
if(total>=tick_time)
total -= tick_time;
else
total += 0xffffffff - tick_time; /*Round up but not overflow*/
if ( benchmark_timer_find_average_overhead == true )
return total; /*Counter cycles*/
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
return total;
}
void benchmark_timer_disable_subtracting_average_overhead(
bool find_flag
)
{
benchmark_timer_find_average_overhead = find_flag;
}
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