rtc驱动框架分析

本驱动框架的代码以linux 3.1.0为主

1. rtc的启动代码分析

subsys_initcall(rtc_init)，说明rtc框架的初始化是在initcall4来调用的。

static int __init rtc_init(void)
{
	rtc_class = class_create(THIS_MODULE, "rtc");		//创建rtc类
	if (IS_ERR(rtc_class)) {
		printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
		return PTR_ERR(rtc_class);
	}
	rtc_class->suspend = rtc_suspend;
	rtc_class->resume = rtc_resume;
	rtc_dev_init();		//创建rtc字符设备
	rtc_sysfs_init(rtc_class);		//创建sysfs相关的文件。
	return 0;
}

module_init(s3c_rtc_init)，说明s3c-rtc平台设备驱动的初始化是在initcall6来调用的，大部分驱动都是在initcall6调用的。

static struct platform_driver s3c_rtc_driver = {
	.probe		= s3c_rtc_probe,
	.remove		= __devexit_p(s3c_rtc_remove),
	.suspend	= s3c_rtc_suspend,
	.resume		= s3c_rtc_resume,
	.id_table	= s3c_rtc_driver_ids,
	.driver		= {
		.name	= "s3c-rtc",
		.owner	= THIS_MODULE,
	},
};
static int __init s3c_rtc_init(void)
{
	printk(banner);
	return platform_driver_register(&s3c_rtc_driver);      //注册s3c_rtc_driver
}

platform_driver_register，向platform这个虚拟总线上注册s3c-rtc驱动，在setup_arch这个函数里面会调用platform_add_device，所以在platform总线上有s3c-rtc设备，它们之间在”bus，device，device_driver“这个框架的设计下相遇，然后进行probe，分配相应的数据结构（struct rtc_device)，向内核注册此数据结构。

static int __devinit s3c_rtc_probe(struct platform_device *pdev)
{
	struct rtc_device *rtc;
	struct rtc_time rtc_tm;
	struct resource *res;
	int ret;

	pr_debug("%s: probe=%p\n", __func__, pdev);

	/* find the IRQs */

	s3c_rtc_tickno = platform_get_irq(pdev, 1);                             //获取滴答中断号
	if (s3c_rtc_tickno < 0) {
		dev_err(&pdev->dev, "no irq for rtc tick\n");
		return -ENOENT;
	}

	s3c_rtc_alarmno = platform_get_irq(pdev, 0);                           //获取报警中断号
	if (s3c_rtc_alarmno < 0) {
		dev_err(&pdev->dev, "no irq for alarm\n");
		return -ENOENT;
	}

	pr_debug("s3c2410_rtc: tick irq %d, alarm irq %d\n",
		 s3c_rtc_tickno, s3c_rtc_alarmno);

	/* get the memory region */

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);                  //得到IO内存资源信息
	if (res == NULL) {
		dev_err(&pdev->dev, "failed to get memory region resource\n");
		return -ENOENT;
	}

	s3c_rtc_mem = request_mem_region(res->start, resource_size(res),       //申请IO内存资源
					 pdev->name);

	if (s3c_rtc_mem == NULL) {
		dev_err(&pdev->dev, "failed to reserve memory region\n");
		ret = -ENOENT;
		goto err_nores;
	}

	s3c_rtc_base = ioremap(res->start, resource_size(res));              //完成IO内存资源的映射
	if (s3c_rtc_base == NULL) {
		dev_err(&pdev->dev, "failed ioremap()\n");
		ret = -EINVAL;
		goto err_nomap;
	}

	rtc_clk = clk_get(&pdev->dev, "rtc");
	if (IS_ERR(rtc_clk)) {
		dev_err(&pdev->dev, "failed to find rtc clock source\n");
		ret = PTR_ERR(rtc_clk);
		rtc_clk = NULL;
		goto err_clk;
	}

	clk_enable(rtc_clk);

	/* check to see if everything is setup correctly */

	s3c_rtc_enable(pdev, 1);                                   //打开RTC实时时钟

	pr_debug("s3c2410_rtc: RTCCON=%02x\n",
		 readw(s3c_rtc_base + S3C2410_RTCCON));

	device_init_wakeup(&pdev->dev, 1);

	/* register RTC and exit */

	rtc = rtc_device_register("s3c", &pdev->dev, &s3c_rtcops,           //分配struct rtc_device结构并且初始化
				  THIS_MODULE);

	if (IS_ERR(rtc)) {
		dev_err(&pdev->dev, "cannot attach rtc\n");
		ret = PTR_ERR(rtc);
		goto err_nortc;
	}

	s3c_rtc_cpu_type = platform_get_device_id(pdev)->driver_data;

	/* Check RTC Time */

	s3c_rtc_gettime(NULL, &rtc_tm);

	if (rtc_valid_tm(&rtc_tm)) {
		rtc_tm.tm_year	= 100;
		rtc_tm.tm_mon	= 0;
		rtc_tm.tm_mday	= 1;
		rtc_tm.tm_hour	= 0;
		rtc_tm.tm_min	= 0;
		rtc_tm.tm_sec	= 0;

		s3c_rtc_settime(NULL, &rtc_tm);

		dev_warn(&pdev->dev, "warning: invalid RTC value so initializing it\n");
	}

	if (s3c_rtc_cpu_type == TYPE_S3C64XX)
		rtc->max_user_freq = 32768;
	else
		rtc->max_user_freq = 128;

	platform_set_drvdata(pdev, rtc);        //设置平台设备的驱动数据是struct rtc_device指针

	s3c_rtc_setfreq(&pdev->dev, 1);

	ret = request_irq(s3c_rtc_alarmno, s3c_rtc_alarmirq,
			  IRQF_DISABLED,  "s3c2410-rtc alarm", rtc);
	if (ret) {
		dev_err(&pdev->dev, "IRQ%d error %d\n", s3c_rtc_alarmno, ret);
		goto err_alarm_irq;
	}

	ret = request_irq(s3c_rtc_tickno, s3c_rtc_tickirq,
			  IRQF_DISABLED,  "s3c2410-rtc tick", rtc);
	if (ret) {
		dev_err(&pdev->dev, "IRQ%d error %d\n", s3c_rtc_tickno, ret);
		free_irq(s3c_rtc_alarmno, rtc);
		goto err_tick_irq;
	}

	clk_disable(rtc_clk);

	return 0;

 err_tick_irq:
	free_irq(s3c_rtc_alarmno, rtc);

 err_alarm_irq:
	platform_set_drvdata(pdev, NULL);
	rtc_device_unregister(rtc);

 err_nortc:
	s3c_rtc_enable(pdev, 0);
	clk_disable(rtc_clk);
	clk_put(rtc_clk);

 err_clk:
	iounmap(s3c_rtc_base);

 err_nomap:
	release_resource(s3c_rtc_mem);

 err_nores:
	return ret;
}

struct rtc_device
{
	struct device dev;                        //内嵌的设备结构体
	struct module *owner;

	int id;                                   //设备的ID号
	char name[RTC_DEVICE_NAME_SIZE];

	const struct rtc_class_ops *ops;          //类操作函数集
	struct mutex ops_lock;

	struct cdev char_dev;                    //内嵌的字符设备
	unsigned long flags;

	unsigned long irq_data;
	spinlock_t irq_lock;
	wait_queue_head_t irq_queue;             //中断等待队列
	struct fasync_struct *async_queue;       //异步队列

	struct rtc_task *irq_task;               //rtc的任务结构体
	spinlock_t irq_task_lock;
	int irq_freq;                            //中断频率
	int max_user_freq;

	struct timerqueue_head timerqueue;
	struct rtc_timer aie_timer;
	struct rtc_timer uie_rtctimer;
	struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
	int pie_enabled;
	struct work_struct irqwork;


#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
	struct work_struct uie_task;
	struct timer_list uie_timer;
	/* Those fields are protected by rtc->irq_lock */
	unsigned int oldsecs;
	unsigned int uie_irq_active:1;
	unsigned int stop_uie_polling:1;
	unsigned int uie_task_active:1;
	unsigned int uie_timer_active:1;
#endif
};

struct rtc_device *rtc_device_register(const char *name, struct device *dev,
					const struct rtc_class_ops *ops,
					struct module *owner)
{
	struct rtc_device *rtc;
	struct rtc_wkalrm alrm;
	int id, err;

	if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) {
		err = -ENOMEM;
		goto exit;
	}


	mutex_lock(&idr_lock);
	err = idr_get_new(&rtc_idr, NULL, &id);
	mutex_unlock(&idr_lock);

	if (err < 0)
		goto exit;

	id = id & MAX_ID_MASK;

	rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
	if (rtc == NULL) {
		err = -ENOMEM;
		goto exit_idr;
	}

	rtc->id = id;
	rtc->ops = ops;
	rtc->owner = owner;
	rtc->irq_freq = 1;
	rtc->max_user_freq = 64;
	rtc->dev.parent = dev;
	rtc->dev.class = rtc_class;
	rtc->dev.release = rtc_device_release;

	mutex_init(&rtc->ops_lock);
	spin_lock_init(&rtc->irq_lock);
	spin_lock_init(&rtc->irq_task_lock);
	init_waitqueue_head(&rtc->irq_queue);

	/* Init timerqueue */
	timerqueue_init_head(&rtc->timerqueue);
	INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
	/* Init aie timer */
	rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);
	/* Init uie timer */
	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);
	/* Init pie timer */
	hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	rtc->pie_timer.function = rtc_pie_update_irq;
	rtc->pie_enabled = 0;

	/* Check to see if there is an ALARM already set in hw */
	err = __rtc_read_alarm(rtc, &alrm);

	if (!err && !rtc_valid_tm(&alrm.time))
		rtc_initialize_alarm(rtc, &alrm);

	strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
	dev_set_name(&rtc->dev, "rtc%d", id);

	rtc_dev_prepare(rtc);

	err = device_register(&rtc->dev);                //向内核注册此设备
	if (err) {
		put_device(&rtc->dev);
		goto exit_kfree;
	}

	rtc_dev_add_device(rtc);                      //向dev文件系统注册设备
	rtc_sysfs_add_device(rtc);                    //向sys文件系统注册设备
	rtc_proc_add_device(rtc);                     //向proc文件系统注册设备

	dev_info(dev, "rtc core: registered %s as %s\n",
			rtc->name, dev_name(&rtc->dev));

	return rtc;

exit_kfree:
	kfree(rtc);

exit_idr:
	mutex_lock(&idr_lock);
	idr_remove(&rtc_idr, id);
	mutex_unlock(&idr_lock);

exit:
	dev_err(dev, "rtc core: unable to register %s, err = %d\n",
			name, err);
	return ERR_PTR(err);
}

所以初始化主要是分配了一个struct  rtc_device结构，并且设置了类操作函数集指针struct rtc_class_ops

2. rtc设备的接口函数

RTC实时时钟获得时间函数s3c_rtc_gettime

RTC实时时钟设置时间函数s3c_rtc_settime

在正常模式和掉电模式下，RTC在指定的时刻会产生一个报警信号。在掉电模式还会产生一个唤醒信号

RTC报警获取函数s3c_rtc_getalarm

RTC设置报警时间函数s3c_rtc_setalarm