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/*
* Cirrus EP7312 Timer driver
*
* Copyright (c) 2002 by Jay Monkman <jtm@smoothsmoothie.com>
*
* 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.
*
* Notes:
* 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.
*
* It is important that the timer start/stop overhead be determined
* when porting or modifying this code.
*/
#include <rtems.h>
#include <bsp.h>
#include <rtems/btimer.h>
#include <ep7312.h>
uint16_t tstart;
bool benchmark_timer_find_average_overhead;
void benchmark_timer_initialize( void )
{
*EP7312_SYSCON1 |= EP7312_SYSCON1_TC2_512KHZ;
*EP7312_TC2D = 0xffff;
}
/*
* 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 */
uint32_t benchmark_timer_read( void )
{
uint16_t t;
uint32_t total;
t = *EP7312_TC2D;
/*
* Total is calculated by taking into account the number of timer overflow
* interrupts since the timer was initialized and clicks since the last
* interrupts.
*/
total = (uint32_t)0x0000ffff - t; /* result is 1/512000 = ~2 uS */
total = (total * 1953) / 1000; /* convert to uS */
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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