forked from Imagelibrary/rtems
58 lines
1.5 KiB
C
58 lines
1.5 KiB
C
/*
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* This file implements a benchmark timer using the count/compare
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* CP0 registers.
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*
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* Copyright (c) 2005 by Cogent Computer Systems
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* Written by Jay Monkman <jtm@lopingdog.com>
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.rtems.org/license/LICENSE.
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*/
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#include <assert.h>
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#include <bsp.h>
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#include <rtems/btimer.h>
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bool benchmark_timer_find_average_overhead;
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uint32_t tstart;
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void benchmark_timer_initialize(void)
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{
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__asm__ volatile ("mfc0 %0, $9\n" : "=r" (tstart));
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/* tick time in picooseconds */
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}
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#define AVG_OVERHEAD 0 /* It typically takes N instructions */
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/* to start/stop the timer. */
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#define LEAST_VALID 1 /* Don't trust a value lower than this */
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/* tx39 simulator can count instructions. :) */
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benchmark_timer_t benchmark_timer_read(void)
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{
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uint32_t total;
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uint32_t cnt;
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__asm__ volatile ("mfc0 %0, $9\n" : "=r" (cnt));
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total = cnt - tstart;
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total = (total * 1000) / 396; /* convert to nanoseconds */
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if ( benchmark_timer_find_average_overhead == true )
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return total; /* in one microsecond units */
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if ( total < LEAST_VALID )
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return 0; /* below timer resolution */
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return total - AVG_OVERHEAD;
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}
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void benchmark_timer_disable_subtracting_average_overhead(
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bool find_flag
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)
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{
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benchmark_timer_find_average_overhead = find_flag;
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}
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