USB发送过程中USB_DeviceEhciTransfer死循环可能会是什么情况呢

大量数据发送过程中，程序死循环在 USB_DeviceEhciTransfer 中的下面这段代码里。可能会是什么情况呢？

/* If QH is empty or the endpoint is not primed, need to link current dtd head to the QH. */
/* When the endpoint is not primed if qhIdle is zero, it means the QH is empty. */
if ((qhIdle) || (!(epStatus & primeBit)))
{
    ehciState->qh[index].nextDtdPointer = (uint32_t)dtdHard;
    ehciState->qh[index].dtdTokenUnion.dtdToken = 0U;
    ehciState->registerBase->EPPRIME = primeBit;
    while (!(ehciState->registerBase->EPSR & primeBit))
    {
        if (ehciState->registerBase->EPCOMPLETE & primeBit)
        {
            break;
        }
        else
        {
            ehciState->registerBase->EPPRIME = primeBit;
        }
    }
}