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 }
OK,上面加了些注释,基本上的流程是这样:先获取device的资源,mem或irq,然后映射内存空间,对硬件进行初始化。注册irq,设置irq服务函数。
接着注册rtc设备,将rtc_class_ops注册到设备里。将rtc设备赋值给rtc驱动。
remove函数
1 static int __exit snvs_rtc_remove(struct platform_device *pdev) 2 { 3 struct rtc_drv_data *pdata = platform_get_drvdata(pdev); 4 rtc_device_unregister(pdata->rtc); 5 if (pdata->irq >= 0) 6 free_irq(pdata->irq, pdev); 7 8 kfree(pdata); 9 return 0; 10 }
获取设备里面驱动数据,然后将驱动里面rtc注销。注销irq。释放驱动数据空间。
驱动里面的init函数和exit函数就很简单了,针对platform_driver进行注册和注销。
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", 7 }, 8 .probe = snvs_rtc_probe, 9 .remove = __exit_p(snvs_rtc_remove), 10 .suspend = snvs_rtc_suspend, 11 .resume = snvs_rtc_resume, 12 }; 13 14 /*! 15 * This function creates the /proc/driver/rtc file and registers the device RTC 16 * in the /dev/misc directory. It also reads the RTC value from external source 17 * and setup the internal RTC properly. 18 * 19 * @return -1 if RTC is failed to initialize; 0 is successful. 20 */ 21 static int __init snvs_rtc_init(void) 22 { 23 return platform_driver_register(&snvs_rtc_driver); 24 } 25 26 /*! 27 * This function removes the /proc/driver/rtc file and un-registers the 28 * device RTC from the /dev/misc directory. 29 */ 30 static void __exit snvs_rtc_exit(void) 31 { 32 platform_driver_unregister(&snvs_rtc_driver); 33 34 }
好吧,这是IMX6Q自带的rtc,它有缺点就是耗电流较大!!!所以freescale的工程师也不建议使用!!!纽扣电池扛不了多久!
我们选用了一个intersil公司的isl1208作为RTC芯片。它的驱动,在发行的linux版本上都有,在config文件中添加就行。如何实现rtc的功能呢???
还是先看device端,因为isl1208是isl1208是I2C接口,所以我们只需在板级端,注册其I2C的信息即可,这个信息包括isl1208的地址,以及驱动名。这两个信息都要注意!
其地址:1101111X,当x为0时是写操作,为1是读操作。在i2c_board_info的注册时是不要后面的x位的,高位右移一位。其地址为0x6f;
驱动名:device的驱动名要和i2c_device_id里面的name一致,而不是i2c_driver里面driver的name一致。
好吧,看device端的设置吧:
1 static struct imxi2c_platform_data mx6q_sabresd_i2c_data = { 2 .bitrate = 100000, 3 }; 4 5 static struct i2c_board_info mxc_i2c0_board_info[] __initdata = { 6 { 7 I2C_BOARD_INFO("wm89**", 0x1a), 8 }, 9 { 10 I2C_BOARD_INFO("ov564x", 0x3c), 11 .platform_data = (void *)&camera_data, 12 }, 13 { 14 I2C_BOARD_INFO("mma8451", 0x1c), 15 .platform_data = (void *)&mma8451_position, 16 }, 17 { 18 I2C_BOARD_INFO("isl1208", 0x6f), 19 }, 20 21 };
在board_init函数里面,加入:
1 imx6q_add_imx_i2c(0, &mx6q_sabresd_i2c_data);
2 i2c_register_board_info(0, mxc_i2c0_board_info, ARRAY_SIZE(mxc_i2c0_board_info));
这样device端就完成了注册工作。
driver端呢?
跟上面的差不多,要完成一个rtc_device_register将isl1208_rtc_ops这些操作硬件的函数注册进去。
代码发行的版本都有,就不贴了。
罗里吧嗦那么多,其实就是提了些代码的流程。对代码的理解还不够!要努力啊!