forked from Imagelibrary/rtems
94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
/**
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* @file
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* @brief Cogent CSB336 Timer driver
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*
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* This uses timer 2 for timing measurments.
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*/
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/*
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* Copyright (c) 2004 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 <rtems.h>
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#include <bsp.h>
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#include <rtems/btimer.h>
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#include <mc9328mxl.h>
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uint32_t g_start;
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uint32_t g_freq;
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bool benchmark_timer_find_average_overhead;
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/*
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* Set up Timer 1
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*/
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void benchmark_timer_initialize( void )
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{
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MC9328MXL_TMR2_TCTL = (MC9328MXL_TMR_TCTL_CLKSRC_PCLK1 |
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MC9328MXL_TMR_TCTL_FRR |
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MC9328MXL_TMR_TCTL_TEN);
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/* set prescaler to 1 (register value + 1) */ \
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MC9328MXL_TMR2_TPRER = 0;
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/* get freq of counter in KHz */
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g_freq = get_perclk1_freq() / 1000;
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g_start = MC9328MXL_TMR2_TCN;
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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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uint32_t t;
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unsigned long long total;
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t = MC9328MXL_TMR2_TCN;
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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 - g_start);
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/* convert to nanoseconds */
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total = (total * 1000)/ g_freq;
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if ( benchmark_timer_find_average_overhead == 1 ) {
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return (int) total;
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} else if ( total < LEAST_VALID ) {
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return 0;
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}
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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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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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