s3c2410电源管理

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 linux中，电源管理，分为apm,acpi两种电源管理方式，两者不建议同时使用。而对于S3c2410来说，
    电源管理是采用apm.  
  我们就先看下apm:
  apm提供了一种用户可控制的通信方式，注册设备：
  apm注册了一个apm_bios设备，通过对这个设备的操作即达到获取apm的相关事件和操作。
  下面就来看下代码是如何实现的：
  static int __init apm_init(void)
{
	int ret;

	if (apm_disabled) {
		printk(KERN_NOTICE "apm: disabled on user request.\n");
		return -ENODEV;
	}

	if (PM_IS_ACTIVE()) {
		printk(KERN_NOTICE "apm: overridden by ACPI.\n");
		return -EINVAL;
	}

	pm_active = 1;

	ret = kernel_thread(kapmd, NULL, CLONE_KERNEL);
	if (ret < 0) {
		pm_active = 0;
		return ret;
	}

#ifdef CONFIG_PROC_FS
	create_proc_info_entry("apm", 0, NULL, apm_get_info);
#endif

	ret = misc_register(&apm_device);
//这个地方就注册了apm_bios设备.
	if (ret != 0) {
		remove_proc_entry("apm", NULL);

		pm_active = 0;
		wake_up(&kapmd_wait);
		wait_for_completion(&kapmd_exit);
	}

	return ret;
}
static struct file_operations apm_bios_fops = {
	.owner		= THIS_MODULE,
	.read		= apm_read,
	.poll		= apm_poll,
	.ioctl		= apm_ioctl,
	.open		= apm_open,
	.release	= apm_release,
};

static struct miscdevice apm_device = {
	.minor		= APM_MINOR_DEV,
	.name		= "apm_bios",
	.fops		= &apm_bios_fops
};
这样就我们就可以像对一般的设备文件一样，读取apm_bios的相关信息了。
首先是open

static int apm_open(struct inode * inode, struct file * filp)
{
	struct apm_user *as;

	as = (struct apm_user *)kmalloc(sizeof(*as), GFP_KERNEL);
	if (as) {
		memset(as, 0, sizeof(*as));

		/*
		 * XXX - this is a tiny bit broken, when we consider BSD
		 * process accounting. If the device is opened by root, we
		 * instantly flag that we used superuser privs. Who knows,
		 * we might close the device immediately without doing a
		 * privileged operation -- cevans
		 */
		as->suser = capable(CAP_SYS_ADMIN);
		as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
		as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;

		down_write(&user_list_lock);
		list_add(&as->list, &apm_user_list);
		up_write(&user_list_lock);

		filp->private_data = as;
	}

	return as ? 0 : -ENOMEM;
}
struct apm_user {
	struct list_head	list;

	unsigned int		suser: 1;
	unsigned int		writer: 1;
	unsigned int		reader: 1;

	int			suspend_result;
	unsigned int		suspend_state;
#define SUSPEND_NONE	0		/* no suspend pending */
#define SUSPEND_PENDING	1		/* suspend pending read */
#define SUSPEND_READ	2		/* suspend read, pending ack */
#define SUSPEND_ACKED	3		/* suspend acked */
#define SUSPEND_DONE	4		/* suspend completed */

	struct apm_queue	queue;
};

/
这个关键是apm_user结构变量as，它是用户和apm内核部分沟通的桥梁，当有apm事件发生时，
就把event挂到apm_user的queue上，这样当用户读时就会读到相关事件然后处理。
static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
{
	struct apm_user *as = fp->private_data;
	apm_event_t event;
	int i = count, ret = 0;

	if (count < sizeof(apm_event_t))
		return -EINVAL;

	if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
		return -EAGAIN;

	wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
//这个就等待queue非空，即等待apm事件的来临：

	while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
		event = queue_get_event(&as->queue);

		ret = -EFAULT;
		if (copy_to_user(buf, &event, sizeof(event)))
			break;

		if (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND)
			as->suspend_state = SUSPEND_READ;

		buf += sizeof(event);
		i -= sizeof(event);
	}

	if (i < count)
		ret = count - i;

	return ret;
}
再来看ioctl函数：
static int
apm_ioctl(struct inode * inode, struct file *filp, u_int cmd, u_long arg)
{
	struct apm_user *as = filp->private_data;
	unsigned long flags;
	int err = -EINVAL;

	if (!as->suser || !as->writer)
		return -EPERM;
／／只有超级用户才能执行回复。
	switch (cmd) {
	case APM_IOC_SUSPEND:
		as->suspend_result = -EINTR;

		if (as->suspend_state == SUSPEND_READ) {
         ／／这个就是当user读取到event时的状态，这是发送这个事件意味这是回应ack。
			/*
			 * If we read a suspend command from /dev/apm_bios,
			 * then the corresponding APM_IOC_SUSPEND ioctl is
			 * interpreted as an acknowledge.
			 */
			as->suspend_state = SUSPEND_ACKED;
			suspends_pending--;
		} else {
			/*
			 * Otherwise it is a request to suspend the system.
			 * Queue an event for all readers, and expect an
			 * acknowledge from all writers who haven't already
			 * acknowledged.
			 */
			queue_event(APM_USER_SUSPEND, as);
		}

		/*
		 * If there are no further acknowledges required, suspend
		 * the system.
		 */
		if (suspends_pending == 0)
			apm_suspend();

		/*
		 * Wait for the suspend/resume to complete.  If there are
		 * pending acknowledges, we wait here for them.
		 *
		 * Note that we need to ensure that the PM subsystem does
		 * not kick us out of the wait when it suspends the threads.
		 */
		flags = current->flags;
		current->flags |= PF_NOFREEZE;

		/*
		 * Note: do not allow a thread which is acking the suspend
		 * to escape until the resume is complete.
		 */
		if (as->suspend_state == SUSPEND_ACKED)
			wait_event(apm_suspend_waitqueue,
					 as->suspend_state == SUSPEND_DONE);
		else
			wait_event_interruptible(apm_suspend_waitqueue,
					 as->suspend_state == SUSPEND_DONE);
//等待所有用户回应了事件，这个在apm_suspend函数中将所有apm_user赋值为suspend_state == SUSPEND_DONE。
		current->flags = flags;
		err = as->suspend_result;
		as->suspend_state = SUSPEND_NONE;
		break;
	}

	return err;
}


static void queue_event(apm_event_t event, struct apm_user *sender)
{
	struct apm_user *as;

	down_read(&user_list_lock);
	list_for_each_entry(as, &apm_user_list, list) {
		if (as != sender && as->reader)
			queue_event_one_user(as, event);
／／这个是将这个事件发给每个需要知道事件的apm_user
	}
	up_read(&user_list_lock);
	wake_up_interruptible(&apm_waitqueue);
}

static void queue_event_one_user(struct apm_user *as, apm_event_t event)
{
	if (as->suser && as->writer) {
		switch (event) {
		case APM_SYS_SUSPEND:
		case APM_USER_SUSPEND:
			/*
			 * If this user already has a suspend pending,
			 * don't queue another one.
			 */
			if (as->suspend_state != SUSPEND_NONE)
				return;

			as->suspend_state = SUSPEND_PENDING;
			suspends_pending++;
			break;
		}
	}
	queue_add_event(&as->queue, event);
}
上面要注意的一点是 suspends_pending，这个是全局变量，且只有suer即超级用户才执行suspends_pending++,
也就是只有超级用户，内核才等待其回复。

所有用户回复了，可以执行了suspend了。
static void apm_suspend(void)
{
	struct apm_user *as;
	int err = pm_suspend(PM_SUSPEND_MEM);
／／为啥只是 PM_SUSPEND_MEM，这个就是本身就是suspend的一种，在s3c2410里，只支持这一种。
       这个在下面的s3c2410_pm_enter可以看到。
	/*
	 * Anyone on the APM queues will think we're still suspended.
	 * Send a message so everyone knows we're now awake again.
	 */
	queue_event(APM_NORMAL_RESUME, NULL);

	/*
	 * Finally, wake up anyone who is sleeping on the suspend.
	 */
	down_read(&user_list_lock);
	list_for_each_entry(as, &apm_user_list, list) {
		as->suspend_result = err;
		as->suspend_state = SUSPEND_DONE;
	}
	up_read(&user_list_lock);

	wake_up(&apm_suspend_waitqueue);
}

int pm_suspend(suspend_state_t state)
{
	if (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX)
		return enter_state(state);
	return -EINVAL;
}

static int enter_state(suspend_state_t state)
{
	int error;

	if (!valid_state(state))
		return -ENODEV;
	if (!mutex_trylock(&pm_mutex))
		return -EBUSY;

	if (state == PM_SUSPEND_DISK) {
		error = pm_suspend_disk();
		goto Unlock;
	}

	pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
	if ((error = suspend_prepare(state)))
		goto Unlock;

	pr_debug("PM: Entering %s sleep\n", pm_states[state]);
	error = suspend_enter(state);

	pr_debug("PM: Finishing wakeup.\n");
	suspend_finish(state);
 Unlock:
	mutex_unlock(&pm_mutex);
	return error;
}

int suspend_enter(suspend_state_t state)
{
	int error = 0;
	unsigned long flags;

	local_irq_save(flags);

	if ((error = device_power_down(PMSG_SUSPEND))) {
		printk(KERN_ERR "Some devices failed to power down\n");
		goto Done;
	}
	error = pm_ops->enter(state);
	device_power_up();
 Done:
	local_irq_restore(flags);
	return error;
}
而这个pm_ops就是用set_pm_ops赋值的。
void pm_set_ops(struct pm_ops * ops)
{
	mutex_lock(&pm_mutex);
	pm_ops = ops;
	mutex_unlock(&pm_mutex);
}

可想而知s3c2410的电源管理要想起作用，也必须通过这个函数注册。

然后看下s3c2410的电源管理如何和这个关联的。

int __init s3c2410_pm_init(void)
{
	printk("S3C2410 Power Management, (c) 2004 Simtec Electronics\n");

	pm_set_ops(&s3c2410_pm_ops);
	return 0;
}
这样执行上面的pm_enter时就会执行 s3c2410_pm_enter。

static int s3c2410_pm_enter(suspend_state_t state)
{
	unsigned long regs_save[16];
	unsigned long tmp;

	/* ensure the debug is initialised (if enabled) */

	s3c2410_pm_debug_init();

	DBG("s3c2410_pm_enter(%d)\n", state);

	if (state != PM_SUSPEND_MEM) {
		printk(KERN_ERR PFX "error: only PM_SUSPEND_MEM supported\n");
		return -EINVAL;
	}

	/* check if we have anything to wake-up with... bad things seem
	 * to happen if you suspend with no wakeup (system will often
	 * require a full power-cycle)
	*/

	if (!any_allowed(s3c_irqwake_intmask, s3c_irqwake_intallow) &&
	    !any_allowed(s3c_irqwake_eintmask, s3c_irqwake_eintallow)) {
		printk(KERN_ERR PFX "No sources enabled for wake-up!\n");
		printk(KERN_ERR PFX "Aborting sleep\n");
		return -EINVAL;
	}

	/* prepare check area if configured */

	s3c2410_pm_check_prepare();

	/* store the physical address of the register recovery block */

	s3c2410_sleep_save_phys = virt_to_phys(regs_save);

	DBG("s3c2410_sleep_save_phys=0x%08lx\n", s3c2410_sleep_save_phys);

	/* ensure at least GESTATUS3 has the resume address */

	__raw_writel(virt_to_phys(s3c2410_cpu_resume), S3C2410_GSTATUS3);

	DBG("GSTATUS3 0x%08x\n", __raw_readl(S3C2410_GSTATUS3));
	DBG("GSTATUS4 0x%08x\n", __raw_readl(S3C2410_GSTATUS4));

	/* save all necessary core registers not covered by the drivers */

	s3c2410_pm_do_save(gpio_save, ARRAY_SIZE(gpio_save));
	s3c2410_pm_do_save(irq_save, ARRAY_SIZE(irq_save));
	s3c2410_pm_do_save(core_save, ARRAY_SIZE(core_save));
	s3c2410_pm_do_save(uart_save, ARRAY_SIZE(uart_save));

	/* set the irq configuration for wake */

	s3c2410_pm_configure_extint();

	DBG("sleep: irq wakeup masks: %08lx,%08lx\n",
	    s3c_irqwake_intmask, s3c_irqwake_eintmask);

	__raw_writel(s3c_irqwake_intmask, S3C2410_INTMSK);
	__raw_writel(s3c_irqwake_eintmask, S3C2410_EINTMASK);

	/* ack any outstanding external interrupts before we go to sleep */

	__raw_writel(__raw_readl(S3C2410_EINTPEND), S3C2410_EINTPEND);

	/* flush cache back to ram */

	arm920_flush_kern_cache_all();

	s3c2410_pm_check_store();

	// need to make some form of time-delta

	/* send the cpu to sleep... */

	__raw_writel(0x00, S3C2410_CLKCON);  /* turn off clocks over sleep */

	s3c2410_cpu_suspend(regs_save);
   //这个是汇编级的进入sleep状态的代码。

	/* unset the return-from-sleep flag, to ensure reset */

	tmp = __raw_readl(S3C2410_GSTATUS2);
	tmp &= S3C2410_GSTATUS2_OFFRESET;
	__raw_writel(tmp, S3C2410_GSTATUS2);

	/* restore the system state */

	s3c2410_pm_do_restore_core(core_save, ARRAY_SIZE(core_save));
	s3c2410_pm_do_restore(gpio_save, ARRAY_SIZE(gpio_save));
	s3c2410_pm_do_restore(irq_save, ARRAY_SIZE(irq_save));
	s3c2410_pm_do_restore(uart_save, ARRAY_SIZE(uart_save));

	s3c2410_pm_debug_init();

	/* check what irq (if any) restored the system */

	DBG("post sleep: IRQs 0x%08x, 0x%08x\n",
	    __raw_readl(S3C2410_SRCPND),
	    __raw_readl(S3C2410_EINTPEND));

	s3c2410_pm_show_resume_irqs(IRQ_EINT0, __raw_readl(S3C2410_SRCPND),
				    s3c_irqwake_intmask);

	s3c2410_pm_show_resume_irqs(IRQ_EINT4-4, __raw_readl(S3C2410_EINTPEND),
				    s3c_irqwake_eintmask);

	DBG("post sleep, preparing to return\n");

	s3c2410_pm_check_restore();

	/* ok, let's return from sleep */

	DBG("S3C2410 PM Resume (post-restore)\n");
	return 0;
}


ENTRY(s3c2410_cpu_suspend)
	stmfd	sp!, { r4 - r12, lr }

	@@ store co-processor registers

	mrc	p15, 0, r4, c15, c1, 0	@ CP access register
	mrc	p15, 0, r5, c13, c0, 0	@ PID
	mrc	p15, 0, r6, c3, c0, 0	@ Domain ID
	mrc	p15, 0, r7, c2, c0, 0	@ translation table base address
	mrc	p15, 0, r8, c2, c0, 0	@ auxiliary control register
	mrc	p15, 0, r9, c1, c0, 0	@ control register

	stmia	r0, { r4 - r13 }
	//这个就是将r4-r13保存到 regs_save
	
	@@ flush the caches to ensure everything is back out to
	@@ SDRAM before the core powers down

	bl	arm920_flush_kern_cache_all

	@@ prepare cpu to sleep

	ldr	r4, =S3C2410_REFRESH
	ldr	r5, =S3C2410_MISCCR
	ldr	r6, =S3C2410_CLKCON
	ldr	r7, [ r4 ]		@ get REFRESH (and ensure in TLB)
	ldr	r8, [ r5 ]		@ get MISCCR (and ensure in TLB)
	ldr	r9, [ r6 ]		@ get CLKCON (and ensure in TLB)

	orr	r7, r7, #S3C2410_REFRESH_SELF	@ SDRAM sleep command
	orr	r8, r8, #S3C2410_MISCCR_SDSLEEP @ SDRAM power-down signals
	orr	r9, r9, #S3C2410_CLKCON_POWER	@ power down command

	teq	pc, #0			@ first as a trial-run to load cache
	bl	s3c2410_do_sleep
	teq	r0, r0			@ now do it for real
	b	s3c2410_do_sleep	@

	@@ align next bit of code to cache line
	.align	8
s3c2410_do_sleep:
	streq	r7, [ r4 ]			@ SDRAM sleep command
	streq	r8, [ r5 ]			@ SDRAM power-down config
	streq	r9, [ r6 ]			@ CPU sleep
//进入sleep
1:	beq	1b
//因为第一次是pc,#进行比较，所以上面不会执行，因为不eq
	mov	pc, r14


电源管理机制讲完，但是在应用层如何实现控制呢：
#include
#include
#include 
#include 
#define APM_IOC_STANDBY		_IO('A', 1)
#define APM_IOC_SUSPEND		_IO('A', 2)
//#define _IO(x,y)	(((x)<<8)|y)
int main(){
    int file=open("/dev/misc/apm_bios",O_WRONLY);
//打开电源管理设备文件。
    if(file>0){
	printf("open amp_bios\n");
   	ioctl(file,APM_IOC_SUSPEND);
    	close(file);
    }
}
通过如上的方式即管理电源。