los_sys.c

/*
 * Copyright (c) 2013-2019, Huawei Technologies Co., Ltd. All rights reserved.
 * Copyright (c) 2020, Huawei Device Co., Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
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 *    conditions and the following disclaimer.
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 * 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.
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 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without specific prior written
 *    permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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#include "los_sys_pri.h"
#include "los_sched_pri.h"

/******************************************************************************
基本概念
	时间管理以系统时钟为基础，给应用程序提供所有和时间有关的服务。

	系统时钟是由定时器/计数器产生的输出脉冲触发中断产生的，一般定义为整数或长整数。
	输出脉冲的周期叫做一个“时钟滴答”。系统时钟也称为时标或者Tick。

	用户以秒、毫秒为单位计时，而操作系统以Tick为单位计时，当用户需要对系统进行操作时，
	例如任务挂起、延时等，此时需要时间管理模块对Tick和秒/毫秒进行转换。
	时间管理模块提供时间转换、统计、延迟功能

相关概念
	Cycle
	系统最小的计时单位。Cycle的时长由系统主时钟频率决定，系统主时钟频率就是每秒钟的Cycle数。

	Tick
	Tick是操作系统的基本时间单位，由用户配置的每秒Tick数决定。

使用场景
	用户需要了解当前系统运行的时间以及Tick与秒、毫秒之间的转换关系等。 

时间管理的典型开发流程
	根据实际需求，在板级配置适配时确认是否使能LOSCFG_BASE_CORE_TICK_HW_TIME宏选择外部定时器，
	并配置系统主时钟频率OS_SYS_CLOCK（单位Hz）。OS_SYS_CLOCK的默认值基于硬件平台配置。
	通过make menuconfig配置LOSCFG_BASE_CORE_TICK_PER_SECOND。
	
注意事项
	时间管理不是单独的功能模块，依赖于OS_SYS_CLOCK和LOSCFG_BASE_CORE_TICK_PER_SECOND两个配置选项。
	系统的Tick数在关中断的情况下不进行计数，故系统Tick数不能作为准确时间使用。

参考
	https://gitee.com/LiteOS/LiteOS/blob/master/doc/Huawei_LiteOS_Kernel_Developer_Guide_zh.md#setup
******************************************************************************/
#define OS_MAX_VALUE    0xFFFFFFFFUL
//获取自系统启动以来的Tick数
LITE_OS_SEC_TEXT_MINOR UINT64 LOS_TickCountGet(VOID)
{
    return OsGerCurrSchedTimeCycle() / OS_CYCLE_PER_TICK;
}
//每个Tick多少Cycle数
LITE_OS_SEC_TEXT_MINOR UINT32 LOS_CyclePerTickGet(VOID)
{
    return g_sysClock / LOSCFG_BASE_CORE_TICK_PER_SECOND;
}
//毫秒转换成Tick
LITE_OS_SEC_TEXT_MINOR UINT32 LOS_MS2Tick(UINT32 millisec)
{
    if (millisec == OS_MAX_VALUE) {
        return OS_MAX_VALUE;
    }

    return ((UINT64)millisec * LOSCFG_BASE_CORE_TICK_PER_SECOND) / OS_SYS_MS_PER_SECOND;
}
//Tick转化为毫秒
LITE_OS_SEC_TEXT_MINOR UINT32 LOS_Tick2MS(UINT32 tick)
{
    return ((UINT64)tick * OS_SYS_MS_PER_SECOND) / LOSCFG_BASE_CORE_TICK_PER_SECOND;
}

LITE_OS_SEC_TEXT_MINOR UINT32 OsUS2Tick(UINT64 microsec)
{
    const UINT32 usPerTick = OS_SYS_US_PER_SECOND / LOSCFG_BASE_CORE_TICK_PER_SECOND;

    UINT64 ticks = (microsec + usPerTick - 1) / usPerTick;
    if (ticks > OS_MAX_VALUE) {
        ticks = OS_MAX_VALUE;
    }
    return (UINT32)ticks;
}