forked from Imagelibrary/rtems
92 lines
2.4 KiB
C
92 lines
2.4 KiB
C
/**
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* @file
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* @brief Cogent CSB337 Timer driver
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*
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* This uses timer 0 for timing measurments.
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*/
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/*
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* Copyright (c) 2004 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 <bsp.h>
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#include <rtems.h>
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#include <rtems/btimer.h>
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#include <at91rm9200.h>
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#include <at91rm9200_pmc.h>
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uint16_t tstart;
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bool benchmark_timer_find_average_overhead;
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uint32_t tick_time;
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/*
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* Set up TC0 -
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* timer_clock2 (MCK/8)
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* capture mode - this shouldn't matter
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*/
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void benchmark_timer_initialize( void )
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{
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uint32_t tmr_freq;
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/* since we are using timer_clock2, divide mck by 8 */
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tmr_freq = at91rm9200_get_mck() / 8;
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TC_TC0_REG(TC_CMR) = TC_CMR_TCCLKS(1); /* timer_clock2 */
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TC_TC0_REG(TC_CCR) = (TC_CCR_CLKEN /* enable the counter */
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| TC_CCR_SWTRG); /* start it up */
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/* tick time in nanoseconds */
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tick_time = 1000000000/tmr_freq;
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}
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/*
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* The following controls the behavior of benchmark_timer_read().
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*
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* AVG_OVEREHAD is the overhead for starting and stopping the timer. It
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* is usually deducted from the number returned.
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*
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* LEAST_VALID is the lowest number this routine should trust. Numbers
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* below this are "noise" and zero is returned.
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*/
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#define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */
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/* (Y countdowns) to start/stop the timer. */
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/* This value is in microseconds. */
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#define LEAST_VALID 1 /* Don't trust a clicks value lower than this */
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benchmark_timer_t benchmark_timer_read( void )
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{
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uint16_t t;
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uint32_t total;
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t = TC_TC0_REG(TC_CV);
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/*
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* Total is calculated by taking into account the number of timer overflow
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* interrupts since the timer was initialized and clicks since the last
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* interrupts.
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*/
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total = t * tick_time;
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if ( benchmark_timer_find_average_overhead == 1 )
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return total; /* in nanosecond units */
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else {
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if ( total < LEAST_VALID )
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return 0; /* below timer resolution */
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/*
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* Somehow convert total into microseconds
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*/
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return (total - AVG_OVERHEAD);
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}
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}
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void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
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{
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benchmark_timer_find_average_overhead = find_flag;
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}
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