linux挂起/唤醒如何用于mach-omap2 2？

Question

我试图弄清楚mach-omap2是如何实现挂起/唤醒的，特别是在针对TI out 3530/‘m 3730的Linux2.6.37中。

下面是一些相关代码：

http://lxr.free-electrons.com/source/arch/arm/mach-omap2/pm34xx.c?v=2.6.37

static int omap3_pm_suspend(void)
{
    struct power_state *pwrst;
    int state, ret = 0;

    if (wakeup_timer_seconds || wakeup_timer_milliseconds)
        omap2_pm_wakeup_on_timer(wakeup_timer_seconds,
                     wakeup_timer_milliseconds);

    /* Read current next_pwrsts */
    list_for_each_entry(pwrst, &pwrst_list, node)
        pwrst->saved_state = pwrdm_read_next_pwrst(pwrst->pwrdm);
    /* Set ones wanted by suspend */
    list_for_each_entry(pwrst, &pwrst_list, node) {
        if (omap_set_pwrdm_state(pwrst->pwrdm, pwrst->next_state))
            goto restore;
        if (pwrdm_clear_all_prev_pwrst(pwrst->pwrdm))
            goto restore;
    }

    omap_uart_prepare_suspend();
    omap3_intc_suspend();

    omap_sram_idle();

restore:
    /* Restore next_pwrsts */
    list_for_each_entry(pwrst, &pwrst_list, node) {
        state = pwrdm_read_prev_pwrst(pwrst->pwrdm);
        if (state > pwrst->next_state) {
            printk(KERN_INFO "Powerdomain (%s) didn't enter "
                   "target state %d\n",
                   pwrst->pwrdm->name, pwrst->next_state);
            ret = -1;
        }
        omap_set_pwrdm_state(pwrst->pwrdm, pwrst->saved_state);
    }
    if (ret)
        printk(KERN_ERR "Could not enter target state in pm_suspend\n");
    else
        printk(KERN_INFO "Successfully put all powerdomains "
               "to target state\n");

    return ret;
}

我真的很难理解它是怎么工作的。

看起来，当挂起过程在omap_sram_idle();之后运行时，系统已经处于挂起模式，在这个函数的上下文中，所有东西都会冻结在那里。当它醒来时，它只是继续从restore:中恢复一切。这是正确的吗？

Answer 1

系统挂起发生在的中间 of omap_sram_idle()。omap_sram_idle()的第二部分实际上是还原代码。更准确地说，实际睡眠是通过wfi ARM指令在omap34xx_cpu_suspend()汇编程序函数中完成的。详情请进一步阅读。

挂起路径

• 看看闲置()函数的实现
• 您可以看到(从注释中判断)，系统进入休眠状态之前的最后一行是_omap_sram_idle()调用(这里)。
• _omap_sram_idle()指向以前复制到SRAM的暂停()汇编程序函数(因此它不会在关闭内存时丢失)；请看下面的代码行：

1. [\_omap\_sram\_idle() assignment](http://lxr.linux.no/#linux+v2.6.37/arch/arm/mach-omap2/pm34xx.c#L998) (notice that first parameter that is passed to it is `omap34xx_cpu_suspend` function address)
2. [omap\_sram\_push()](http://lxr.linux.no/#linux+v2.6.37/arch/arm/plat-omap/sram.c#L247) implementation; pay attention to [memcpy() call](http://lxr.linux.no/#linux+v2.6.37/arch/arm/plat-omap/sram.c#L256): `omap_sram_ceil` is start address of SRAM memory, `start` is address of `omap34xx_cpu_suspend() function`
3. [omap34xx\_cpu\_suspend()](http://lxr.linux.no/#linux+v2.6.37/arch/arm/mach-omap2/sleep34xx.S#L187) implementation; it's the actual function being executed at [this line](http://lxr.linux.no/#linux+v2.6.37/arch/arm/mach-omap2/pm34xx.c#L446) (instead of `_omap_sram_idle()`). Take a look at comment above this function:

/* *强制OMAP进入空闲状态** omap34xx_suspend() -这段代码只对普通的idles执行WFI *。**注意:此代码在启动时被复制到内部SRAM中。当OMAP *醒来的时候，它会在睡觉的时候继续执行。*/

​

• 实际睡眠发生在wfi (等待中断) ARM指令中(在omap34xx_cpu_suspend()函数中)；处理器将休眠，只有当某些IRQ发生时它才会醒来。
• 在omap34xx_cpu_suspend()中有两个地方可以执行wfi：
  • 如果不需要上下文保存：这里
  • 如果需要上下文保存：这里

​

恢复路径

一旦出现了一些唤醒信号，CPU将在wfi指令之后继续执行指令(这首先使它进入睡眠状态)。因此，您的系统在omap34xx_cpu_suspend()汇编程序函数(从wait_sdrk_ok:标签开始)中醒来，然后返回到omap_sram_idle() (到这行)，然后返回到omap3_pm_suspend()，返回到restore:标签。