Function cpu_loops_per_tick_init

libcpu/aarch64/common/setup.c:86–121

}

static void cpu_loops_per_tick_init(void)
{
    rt_ubase_t offset;
    volatile rt_ubase_t freq, step, cycles_end1, cycles_end2;
    volatile rt_uint32_t cycles_count1 = 0, cycles_count2 = 0;

    rt_hw_sysreg_read(cntfrq_el0, freq);
    step = freq / RT_TICK_PER_SECOND;

    cycles_end1 = cpu_get_cycles() + step;

    while (cpu_get_cycles() < cycles_end1)
    {
        __asm__ volatile ("nop");
        __asm__ volatile ("add %0, %0, #1":"=r"(cycles_count1));
    }

    cycles_end2 = cpu_get_cycles() + step;

    while (cpu_get_cycles() < cycles_end2)
    {
        __asm__ volatile ("add %0, %0, #1":"=r"(cycles_count2));
    }

    if ((rt_int32_t)(cycles_count2 - cycles_count1) > 0)
    {
        offset = cycles_count2 - cycles_count1;
    }
    else
    {
        /* Impossible, but prepared for any eventualities */
        offset = cycles_count2 / 4;
    }

    loops_per_tick[rt_hw_cpu_id()] = offset;
}

static void cpu_us_delay(rt_uint32_t us)
{