[HarmonyOS] 踩准时钟节拍、玩转时间转换，鸿蒙轻内核时间管理有妙招

  

摘要：本文带领大家一起剖析了鸿蒙轻内核的时间管理模块的源代码。时间管理模块为任务调度提供必要的时钟节拍，会向应用程序提供所有和时间有关的服务，如时间转换、统计、延迟功能。

#define OS_SYS_CLOCK                    96000000
#define LOSCFG_BASE_CORE_TICK_PER_SECOND          (1000UL)
#define LOSCFG_BASE_CORE_TICK_HW_TIME             0

LITE_OS_SEC_TEXT_INIT UINT32 LOS_Start(VOID)
{
  return HalStartSchedule(OsTickHandler);
}

LITE_OS_SEC_TEXT_INIT UINT32 HalStartSchedule(OS_TICK_HANDLER handler)
{
  UINT32 ret;
⑴  ret = HalTickStart(handler);
  if (ret != LOS_OK) {
    return ret;
  }
⑵  HalStartToRun();
  return LOS_OK; /* never return */
}

WEAK UINT32 HalTickStart(OS_TICK_HANDLER *handler)
{
  UINT32 ret;
⑴  if ((OS_SYS_CLOCK == 0) ||
    (LOSCFG_BASE_CORE_TICK_PER_SECOND == 0) ||
    (LOSCFG_BASE_CORE_TICK_PER_SECOND > OS_SYS_CLOCK)) {
    return LOS_ERRNO_TICK_CFG_INVALID;
  }
#if (LOSCFG_USE_SYSTEM_DEFINED_INTERRUPT == 1)
#if (OS_HWI_WITH_ARG == 1)
  OsSetVector(SysTick_IRQn, (HWI_PROC_FUNC)handler, NULL);
#else
⑵  OsSetVector(SysTick_IRQn, (HWI_PROC_FUNC)handler);
#endif
#endif
⑶  g_sysClock = OS_SYS_CLOCK;
  g_cyclesPerTick = OS_SYS_CLOCK / LOSCFG_BASE_CORE_TICK_PER_SECOND;
  g_ullTickCount = 0;
⑷  ret = SysTick_Config(g_cyclesPerTick);
  if (ret == 1) {
    return LOS_ERRNO_TICK_PER_SEC_TOO_SMALL;
  }
  return LOS_OK;
}

LITE_OS_SEC_TEXT VOID OsTickHandler(VOID)
{
#if (LOSCFG_BASE_CORE_TICK_HW_TIME == 1)
⑴  platform_tick_handler();
#endif
⑵  g_ullTickCount++;
#if (LOSCFG_BASE_CORE_TIMESLICE == 1)
⑶  OsTimesliceCheck();
#endif
⑷   OsTaskScan();  // task timeout scan
#if (LOSCFG_BASE_CORE_SWTMR == 1)
⑸  (VOID)OsSwtmrScan();
#endif
}

LITE_OS_SEC_TEXT_MINOR UINT32 LOS_MS2Tick(UINT32 millisec)
{
  if (millisec == OS_NULL_INT) {
    return OS_NULL_INT;
  }
  return ((UINT64)millisec * LOSCFG_BASE_CORE_TICK_PER_SECOND) / OS_SYS_MS_PER_SECOND;
}

LITE_OS_SEC_TEXT_MINOR UINT32 LOS_Tick2MS(UINT32 ticks)
{
  return ((UINT64)ticks * OS_SYS_MS_PER_SECOND) / LOSCFG_BASE_CORE_TICK_PER_SECOND;
}

typedef struct tagCpuTick {
  UINT32 cntHi; /* < 一个64位数值的高32位 */
  UINT32 cntLo; /* < 一个64位数值的低32位 */
} CpuTick;

LITE_OS_SEC_TEXT_INIT UINT32 OsCpuTick2MS(CpuTick *cpuTick, UINT32 *msHi, UINT32 *msLo)
{
  UINT64 tmpCpuTick;
  DOUBLE temp;
⑴  if ((cpuTick == NULL) || (msHi == NULL) || (msLo == NULL)) {
    return LOS_ERRNO_SYS_PTR_NULL;
  }
⑵  if (g_sysClock == 0) {
    return LOS_ERRNO_SYS_CLOCK_INVALID;
  }
⑶  tmpCpuTick = ((UINT64)cpuTick->cntHi << OS_SYS_MV_32_BIT) | cpuTick->cntLo;
⑷  temp = tmpCpuTick / ((DOUBLE)g_sysClock / OS_SYS_MS_PER_SECOND);
  tmpCpuTick = (UINT64)temp;
  *msLo = (UINT32)tmpCpuTick;
  *msHi = (UINT32)(tmpCpuTick >> OS_SYS_MV_32_BIT);
  return LOS_OK;
}

LITE_OS_SEC_TEXT_INIT UINT32 OsCpuTick2US(CpuTick *cpuTick, UINT32 *usHi, UINT32 *usLo)
{
  UINT64 tmpCpuTick;
  DOUBLE temp;
  if ((cpuTick == NULL) || (usHi == NULL) || (usLo == NULL)) {
    return LOS_ERRNO_SYS_PTR_NULL;
  }
  if (g_sysClock == 0) {
    return LOS_ERRNO_SYS_CLOCK_INVALID;
  }
  tmpCpuTick = ((UINT64)cpuTick->cntHi << OS_SYS_MV_32_BIT) | cpuTick->cntLo;
  temp = tmpCpuTick / ((DOUBLE)g_sysClock / OS_SYS_US_PER_SECOND);
  tmpCpuTick = (UINT64)temp;
  *usLo = (UINT32)tmpCpuTick;
  *usHi = (UINT32)(tmpCpuTick >> OS_SYS_MV_32_BIT);
  return LOS_OK;
}

LITE_OS_SEC_TEXT_MINOR UINT32 LOS_CyclePerTickGet(VOID)
{
  return g_cyclesPerTick;
}

LITE_OS_SEC_TEXT_MINOR UINT64 LOS_TickCountGet(VOID)
{
  return g_ullTickCount;
}

UINT32 LOS_SysClockGet(VOID)
{
  return g_sysClock;
}

LITE_OS_SEC_TEXT_MINOR VOID HalGetCpuCycle(UINT32 *cntHi, UINT32 *cntLo)
{
  UINT64 swTick;
  UINT64 cycle;
  UINT32 hwCycle;
  UINTPTR intSave;
  intSave = LOS_IntLock();
⑴  swTick = g_ullTickCount;
⑵  hwCycle = SysTick->VAL;
⑶  if ((SCB->ICSR & TICK_CHECK) != 0) {
    hwCycle = SysTick->VAL;
    swTick++;
  }
⑷  cycle = (((swTick) * g_cyclesPerTick) + (g_cyclesPerTick - hwCycle));
⑸  *cntHi = cycle >> SHIFT_32_BIT;
  *cntLo = cycle & CYCLE_CHECK;
  LOS_IntRestore(intSave);
  return;
}