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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.
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* 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.
*
* Jukka Pietarinen <jukka.pietarinen@mrf.fi>, 2008,
* Micro-Research Finland Oy
*/
#include <rtems.h>
#include <bsp.h>
#include <rtems/btimer.h>
#include "../include/system_conf.h"
#include "../../shared/clock/clock.h"
static inline int timerread(unsigned int reg)
{
#if ON_SIMULATOR && defined(TIMER0_BASE_ADDRESS)
return *((int*)(TIMER0_BASE_ADDRESS + reg));
#elif defined(TIMER1_BASE_ADDRESS)
return *((int*)(TIMER1_BASE_ADDRESS + reg));
#else
#warning "Benchmarking timer not available!"
return 0;
#endif
}
static inline void timerwrite(unsigned int reg, int value)
{
#if ON_SIMULATOR && defined(TIMER0_BASE_ADDRESS)
*((int*)(TIMER0_BASE_ADDRESS + reg)) = value;
#elif defined(TIMER1_BASE_ADDRESS)
*((int*)(TIMER1_BASE_ADDRESS + reg)) = value;
#endif
}
bool benchmark_timer_find_average_overhead;
void benchmark_timer_initialize( void )
{
/* Set timer period */
timerwrite(LM32_CLOCK_PERIOD, 0xffffffff);
/* Stop timer */
timerwrite(LM32_CLOCK_CR, LM32_CLOCK_CR_STOP);
/* Clear status register */
timerwrite(LM32_CLOCK_SR, 0);
/* Start timer */
timerwrite(LM32_CLOCK_CR, LM32_CLOCK_CR_START);
}
/*
* 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;
uint32_t status;
ticks = 0xffffffff - timerread(LM32_CLOCK_SNAPSHOT);
status = timerread(LM32_CLOCK_SR);
if (status & LM32_CLOCK_SR_TO)
printk("Timer overflow!\n");
total = ticks / (CPU_FREQUENCY / 1000000);
if ( benchmark_timer_find_average_overhead == true )
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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