IMX6Q RTC驱动分析

对于在工作中学习驱动的，讲究的是先使用，再理解。好吧，我们来看看板子里是如何注册的？

在板文件里，它的注册函数是这样的：

imx6q_add_imx_snvs_rtc()

好吧，让我们追踪下去：

 1 extern const struct imx_snvs_rtc_data imx6q_imx_snvs_rtc_data __initconst;
 2 #define imx6q_add_imx_snvs_rtc() \
 3  imx_add_snvs_rtc(&imx6q_imx_snvs_rtc_data)
 4 
 5 #define imx_snvs_rtc_data_entry_single(soc)    \
 6  {        \
 7   .iobase = soc ## _SNVS_BASE_ADDR,   \
 8   .irq = soc ## _INT_SNVS,    \
 9  }
10 
11 #ifdef CONFIG_SOC_IMX6Q
12 const struct imx_snvs_rtc_data imx6q_imx_snvs_rtc_data __initconst =
13  imx_snvs_rtc_data_entry_single(MX6Q);
14 #endif /* ifdef CONFIG_SOC_IMX6Q */
15 
16 struct platform_device *__init imx_add_snvs_rtc(
17   const struct imx_snvs_rtc_data *data)
18 {
19  struct resource res[] = {
20   {
21    .start = data->iobase,
22    .end = data->iobase + SZ_4K - 1,
23    .flags = IORESOURCE_MEM,
24   }, {
25    .start = data->irq,
26    .end = data->irq,
27    .flags = IORESOURCE_IRQ,
28   },
29  };
30 
31  return imx_add_platform_device("snvs_rtc", 0,
32    res, ARRAY_SIZE(res), NULL, 0);
33 }

最终调用imx_add_platform_device将rtc注册进去。

那么在驱动端，其代码是如何的呢？分析下主要的部分：

 1 /*!
 2  * The RTC driver structure
 3  */
 4 static struct rtc_class_ops snvs_rtc_ops = {
 5     .open = snvs_rtc_open,
 6     .release = snvs_rtc_release,
 7     .read_time = snvs_rtc_read_time,
 8     .set_time = snvs_rtc_set_time,
 9     .read_alarm = snvs_rtc_read_alarm,
10     .set_alarm = snvs_rtc_set_alarm,
11     .proc = snvs_rtc_proc,
12     .ioctl = snvs_rtc_ioctl,
13     .alarm_irq_enable = snvs_rtc_alarm_irq_enable,
14 };

rtc_class_ops里面的函数实例需要我们去完成。

定义一个platform_driver结构体：

 1 /*!
 2  * Contains pointers to the power management callback functions.
 3  */
 4 static struct platform_driver snvs_rtc_driver = {
 5     .driver = {
 6            .name = "snvs_rtc",     //注意这个要和device端名字一样
 7            },
 8     .probe = snvs_rtc_probe,
 9     .remove = __exit_p(snvs_rtc_remove),
10     .suspend = snvs_rtc_suspend,
11     .resume = snvs_rtc_resume,
12 };

在probe函数中完成rtc_class_ops的注册。好吧，详细的分析下probe：

 1 /*! SNVS RTC Power management control */
 2 static int snvs_rtc_probe(struct platform_device *pdev)
 3 {
 4     struct timespec tv;
 5     struct resource *res;
 6     struct rtc_device *rtc;
 7     struct rtc_drv_data *pdata = NULL;
 8     void __iomem *ioaddr;
 9     u32 lp_cr;
10     int ret = 0;
11 
12     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);     //获取资源，即注册在device里面的内存首末地址
13     if (!res)
14         return -ENODEV;
15 
16     pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
17     if (!pdata)
18         return -ENOMEM;
19 
20     pdata->baseaddr = res->start;
21     pdata->ioaddr = ioremap(pdata->baseaddr, 0xC00);    //分配IO内存空间
22     ioaddr = pdata->ioaddr;
23     pdata->irq = platform_get_irq(pdev, 0);            //获取中断号
24     platform_set_drvdata(pdev, pdata);                //将rtc_drv_data 赋给platform_device的私有数据
25 
26 
27     /* Added to support sysfs wakealarm attribute */
28     pdev->dev.power.can_wakeup = 1;                //
29 
30     /* initialize glitch detect */                //在分配IO内存后，就可以对其寄存器进行硬件的一些初始化工作。
31     __raw_writel(SNVS_LPPGDR_INIT, ioaddr + SNVS_LPPGDR);
32     udelay(100);
33 
34     /* clear lp interrupt status */
35     __raw_writel(0xFFFFFFFF, ioaddr + SNVS_LPSR);
36 
37     /* Enable RTC */
38     lp_cr = __raw_readl(ioaddr + SNVS_LPCR);
39     if ((lp_cr & SNVS_LPCR_SRTC_ENV) == 0)
40         __raw_writel(lp_cr | SNVS_LPCR_SRTC_ENV, ioaddr + SNVS_LPCR);
41 
42     udelay(100);
43 
44     __raw_writel(0xFFFFFFFF, ioaddr + SNVS_LPSR);
45     udelay(100);
46 
47     if (pdata->irq >= 0) {                    //设置中断函数
48         if (request_irq(pdata->irq, snvs_rtc_interrupt, IRQF_SHARED,
49                 pdev->name, pdev) < 0) {
50             dev_warn(&pdev->dev, "interrupt not available.\n");
51             pdata->irq = -1;
52         } else {
53             disable_irq(pdata->irq);
54             pdata->irq_enable = false;
55         }
56     }
57 
58     rtc = rtc_device_register(pdev->name, &pdev->dev,        //重要！！！RTC设备注册！！！
59                   &snvs_rtc_ops, THIS_MODULE);
60     if (IS_ERR(rtc)) {
61         ret = PTR_ERR(rtc);
62         goto err_out;
63     }
64 
65     pdata->rtc = rtc;                            //将注册上的rtc，赋给驱动！
66 
67     tv.tv_nsec = 0;
68     tv.tv_sec = rtc_read_lp_counter(ioaddr + SNVS_LPSRTCMR);
69 
70     /* Remove can_wakeup flag to add common power wakeup interface */
71     pdev->dev.power.can_wakeup = 0;
72 
73     /* By default, devices should wakeup if they can */
74     /* So snvs is set as "should wakeup" as it can */
75     device_init_wakeup(&pdev->dev, 1);
76 
77     return ret;
78 
79 err_out:
80     iounmap(ioaddr);
81     if (pdata->irq >= 0)
82         free_irq(pdata->irq, pdev);
83     kfree(pdata);
84     return ret;
85 }

probe function