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/* Timer for Blackfin
*
* 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.
*
* Copyright (c) 2006 by Atos Automacao Industrial Ltda.
* written by Alain Schaefer <alain.schaefer@easc.ch>
* and Antonio Giovanini <antonio@atos.com.br>
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#include <rtems.h>
#include <bsp.h>
uint32_t Timer_interrupts;
bool benchmark_timer_find_average_overhead;
/*
* benchmark_timer_initialize
*
* Blackfin processor has a counter for clock cycles.
*/
void benchmark_timer_initialize( void )
{
/*reset counters*/
__asm__ ("R2 = 0;");
__asm__ ("CYCLES = R2;");
__asm__ ("CYCLES2 = R2;");
/*start counters*/
__asm__ ("R2 = SYSCFG;");
__asm__ ("BITSET(R2,1);");
__asm__ ("SYSCFG = R2");
}
/*
* 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 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 clicks;
uint32_t total;
register uint32_t cycles __asm__ ("R2");
/* stop counter */
__asm__ ("R2 = SYSCFG;");
__asm__ ("BITCLR(R2,1);");
__asm__ ("SYSCFG = R2;");
__asm__ ("R2 = CYCLES;");
clicks = cycles; /* Clock cycles */
/* converting to microseconds */
total = clicks / (CCLK/1000000);
if ( benchmark_timer_find_average_overhead == 1 )
return total; /* in XXX microsecond units */
else {
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
/*
* Somehow convert total into microseconds
*/
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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