forked from Imagelibrary/rtems
83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
/*
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* Cirrus EP7312 Timer driver
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*
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* Copyright (c) 2002 by Jay Monkman <jtm@smoothsmoothie.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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*
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* http://www.rtems.com/license/LICENSE.
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*
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* Notes:
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* This file manages the benchmark timer used by the RTEMS Timing Test
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* Suite. Each measured time period is demarcated by calls to
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* benchmark_timer_initialize() and benchmark_timer_read(). benchmark_timer_read() usually returns
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* the number of microseconds since benchmark_timer_initialize() exitted.
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*
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* It is important that the timer start/stop overhead be determined
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* when porting or modifying this code.
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*
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* $Id$
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*/
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#include <rtems.h>
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#include <bsp.h>
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#include <ep7312.h>
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uint16_t tstart;
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bool benchmark_timer_find_average_overhead;
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void benchmark_timer_initialize( void )
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{
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*EP7312_SYSCON1 |= EP7312_SYSCON1_TC2_512KHZ;
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*EP7312_TC2D = 0xffff;
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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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int 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 = *EP7312_TC2D;
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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 = (uint32_t)0x0000ffff - t; /* result is 1/512000 = ~2 uS */
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total = (total * 1953) / 1000; /* convert to uS */
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if ( benchmark_timer_find_average_overhead == true )
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return total; /* in XXX microsecond 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(
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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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