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/* SPDX-License-Identifier: BSD-2-Clause */
/**
* @file
*
* @ingroup RTEMSTestFrameworkImpl
*
* @brief Implementation of T_get_one_clock_tick_busy().
*/
/*
* Copyright (C) 2014, 2020 embedded brains GmbH (http://www.embedded-brains.de)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/test.h>
#include <rtems.h>
static uint_fast32_t
T_estimate_busy_loop_maximum(void)
{
uint_fast32_t initial;
uint_fast32_t units;
initial = rtems_clock_get_ticks_since_boot();
units = 0;
while (initial == rtems_clock_get_ticks_since_boot()) {
++units;
}
return units;
}
static uint_fast32_t
T_wait_for_tick_change(void)
{
uint_fast32_t initial;
uint_fast32_t now;
initial = rtems_clock_get_ticks_since_boot();
do {
now = rtems_clock_get_ticks_since_boot();
} while (now == initial);
return now;
}
uint_fast32_t
T_get_one_clock_tick_busy(void)
{
uint_fast32_t last;
uint_fast32_t now;
uint_fast32_t a;
uint_fast32_t b;
uint_fast32_t m;
/* Choose a lower bound */
a = 1;
/* Estimate an upper bound */
T_wait_for_tick_change();
b = 2 * T_estimate_busy_loop_maximum();
while (true) {
last = T_wait_for_tick_change();
T_busy(b);
now = rtems_clock_get_ticks_since_boot();
if (now != last) {
break;
}
b *= 2;
last = now;
}
/* Find a good value */
do {
m = (a + b) / 2;
last = T_wait_for_tick_change();
T_busy(m);
now = rtems_clock_get_ticks_since_boot();
if (now != last) {
b = m;
} else {
a = m;
}
} while (b - a > 1);
return m;
}
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