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/* timer.c
*
* This file implements a benchmark timer using the General Purpose Timer.
*
* Notes:
*
* BSP_TIMER_AVG_OVERHEAD and BSP_TIMER_LEAST_VALID are required to be
* provided in bsp.h
*
* COPYRIGHT (c) 1989-2009.
* 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.
*/
#include <assert.h>
#include <bsp.h>
#include <rtems/btimer.h>
uint64_t Timer_driver_Start_time;
bool benchmark_timer_find_average_overhead;
/*
* benchmark_timer_initialize
*/
void benchmark_timer_initialize()
{
/*
* Timer runs long and accurate enough not to require an interrupt.
*/
Timer_driver_Start_time = PPC_Get_timebase_register();
}
/*
* benchmark_timer_read
*/
benchmark_timer_t benchmark_timer_read()
{
uint64_t clicks;
uint64_t total64;
uint32_t total;
/* approximately CLOCK_SPEED clicks per microsecond */
clicks = PPC_Get_timebase_register();
assert( clicks > Timer_driver_Start_time );
total64 = clicks - Timer_driver_Start_time;
assert( total64 <= 0xffffffff ); /* fits into a uint32_t */
total = (uint32_t) total64;
if ( benchmark_timer_find_average_overhead == true )
return total; /* in "clicks" of the decrementer units */
if ( total < BSP_TIMER_LEAST_VALID )
return 0; /* below timer resolution */
return BSP_Convert_decrementer(total - BSP_TIMER_AVG_OVERHEAD);
}
void benchmark_timer_disable_subtracting_average_overhead(
bool find_flag
)
{
benchmark_timer_find_average_overhead = find_flag;
}
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