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68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/*
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* Copyright (C) 2018 Eistec AB
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup sys_spin_random
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*
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* @{
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* @file
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* @brief spin_random implementation
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*
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* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
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*
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* @}
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*/
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#include <stdint.h>
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#include <inttypes.h>
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#include <limits.h>
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#include "spin_random.h"
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#include "random.h"
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#define ENABLE_DEBUG 0
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#include "debug.h"
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/* Default is whatever, just some small delay if the user forgets to initialize */
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static uint32_t spin_max = 64;
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/**
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* @brief Busy wait (spin) for the given number of loop iterations
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*/
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static void spin(uint32_t limit)
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{
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/* Platform independent busy wait loop, should never be optimized out
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* because of the volatile asm statement */
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while (limit--) {
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__asm__ volatile ("");
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}
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}
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void spin_random_delay(void)
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{
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uint32_t limit = random_uint32_range(0, spin_max);
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spin(limit);
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}
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uint32_t spin_random_calibrate(tim_t timer_dev, uint32_t spin_max_target)
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{
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spin_max = 16;
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uint32_t t1;
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uint32_t t2;
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DEBUG("spin_random_calibrate: Begin calibration with timer %u against "
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"target %" PRIu32 "\n", (unsigned) timer_dev, spin_max_target);
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do {
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spin_max = (spin_max * 5) / 4;
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t1 = timer_read(timer_dev);
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spin(spin_max);
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t2 = timer_read(timer_dev);
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} while ((t2 - t1) < spin_max_target && (spin_max < (UINT32_MAX / 5)));
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DEBUG("spin_max = %" PRIu32 "\n", spin_max);
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return spin_max;
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}
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