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116 lines
3.3 KiB
C
116 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0+-with-RTEMS-exception */
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/**
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* @file
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* @brief IDT 4650 Timer Driver.
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*
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* This file manages the benchmark timer used by the RTEMS Timing Test
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* Suite.
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*/
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/*
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* Author: Craig Lebakken <craigl@transition.com>
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*
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* COPYRIGHT (c) 1996 by Transition Networks Inc.
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*
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* To anyone who acknowledges that this file is provided "AS IS"
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* without any express or implied warranty:
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* permission to use, copy, modify, and distribute this file
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* for any purpose is hereby granted without fee, provided that
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* the above copyright notice and this notice appears in all
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* copies, and that the name of Transition Networks not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* Transition Networks makes no representations about the suitability
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* of this software for any purpose.
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*
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* derived from src/lib/libbsp/no_cpu/no_bsp/timer/timer.c
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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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 <rtems/btimer.h>
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#define CLOCKS_PER_MICROSECOND ( CPU_CLOCK_RATE_MHZ )
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#define TIMER_MAX_VALUE 0xffffffff
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extern uint32_t mips_read_timer( void );
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static bool benchmark_timer_find_average_overhead;
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static uint32_t benchmark_timer_initial_value = 0;
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void benchmark_timer_initialize( void )
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{
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benchmark_timer_initial_value = mips_read_timer();
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/*
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* Somehow start the timer
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*/
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/* Timer on 4650 is always running */
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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 8 /* 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 cycles. */
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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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uint64_t clicks;
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uint32_t total;
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/*
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* Read the timer and see how many clicks it has been since we started.
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*/
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clicks = mips_read_timer(); /* XXX: read some HW here */
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if (clicks < benchmark_timer_initial_value)
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{
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clicks += TIMER_MAX_VALUE;
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}
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clicks -= benchmark_timer_initial_value;
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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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#if 0 /* leave total in number of cycles */
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total = clicks / CLOCKS_PER_MICROSECOND;
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#else
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total = clicks;
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#endif
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if ( benchmark_timer_find_average_overhead == 1 )
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return total; /* in # cycles 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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* leave total in cycles
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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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