/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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#include "os/os_cputime.h"
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/**
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* This module implements cputime functionality for timers for which:
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* a. freq is a power of 2 Hz, and
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* b. 256 Hz <= freq < 1 MHz
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*/
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#if defined(OS_CPUTIME_FREQ_PWR2)
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/**
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* @addtogroup OSKernel Operating System Kernel
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* @{
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* @defgroup OSCPUTime High Resolution Timers
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* @{
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*/
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/**
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* os cputime usecs to ticks
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*
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* Converts the given number of microseconds into cputime ticks.
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*
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* @param usecs The number of microseconds to convert to ticks
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*
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* @return uint32_t The number of ticks corresponding to 'usecs'
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*/
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uint32_t
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os_cputime_usecs_to_ticks(uint32_t usecs)
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{
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uint64_t ticks;
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/*
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* Faster calculation but could be off 1 full tick since we do not
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* add residual back. Adding back the residual is commented out below, but
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* shown.
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*/
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ticks = (1ULL << 32) * MYNEWT_VAL(OS_CPUTIME_FREQ) / 1000000 * usecs;
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/* Residual for 32768 Hz. */
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//ticks += ((uint64_t)usecs * (1526122139+1)) >> 32;
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return ticks >> 32;
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}
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/**
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* cputime ticks to usecs
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*
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* Convert the given number of ticks into microseconds.
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*
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* @param ticks The number of ticks to convert to microseconds.
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*
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* @return uint32_t The number of microseconds corresponding to 'ticks'
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*
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* NOTE: This calculation will overflow if the value for ticks is greater
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* than 140737488. I am not going to check that here because that many ticks
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* is about 4222 seconds, way more than what this routine should be used for.
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*/
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uint32_t
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os_cputime_ticks_to_usecs(uint32_t ticks)
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{
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uint32_t usecs;
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uint32_t shift;
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shift = __builtin_popcount(MYNEWT_VAL(OS_CPUTIME_FREQ) - 1) - 6;
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usecs = ((ticks >> shift) * 15625) +
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(((ticks & ~(~0U << shift)) * 15625) >> shift);
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return usecs;
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}
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/**
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* @} OSCPUTime
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* @} OSKernel
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*/
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#endif
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