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2012-05-29 12:56:57
原文地址：s3c2410 RTC驱动框架linux内核源码分析 作者：yaoqigui
* 理解如果编写驱动的硬件，它包括了最基本的硬中断，软中断的底层机制；* s3c2410的RTC驱动的实现个人认为更是对linux设备驱动一个很好的例子，他是通过二层结构来* 实现的一个驱动，上层是一个arm common的公共层，对上提供标准的通用的RTC操作接口，下层由* 我们来实现针对自己的chip和自己要提供的功能来实现的一层驱动；** @FileTree:**********************************************************************************************************linux-2.6.14.6||--arch| || |--arm| | |--mach-s3c2410| | | |-devs.c //包含了对各个部件的resource的分配和定义，在这看rtc的资源；| | |--common| | | |-rtctime.c //一个arm平台的通用rtc函数层，它对上隐藏了各种soc的rtc driver的区别；| | |--kernel| | | |-time.c //内核的初始化例程time_init()会调用的xxx_cmos_xxx函数的实现；定义了全局自旋锁rtc_lock用来串行化所有CPU对RTC的操作||--drivers| |--char| | |-s3c2410-rtc.c //具体的s3c2410上的rtc chip的驱动实现,如果需要在arm平台的| | 板子上实现一个驱动，改写它就ok了。||--include| |--asm-arm| | |--arch-s3c2410| | | |-regs-rtc.h //S3C2410 Internal RTC register definition refer to datasheet;| | |-rtc.h //arm平台rtc操作抽象层rtctime.c对应的.h| |--linux| | |-time.h //mktime的实现；| | |-rtc.h //公用RTC .h**[小结]*1)提供给user的接口，在arch/arm/common/rtctime.c,include/asm-arm/rtc.h中实现，调用操作硬件驱动在drivers/char/s3c2410-rtc.c,include/asm-arm/arch-s3c2410/regs-rtc.h实现;*2)提供给kernel的接口，在arch/arm/kernel/time.c,include/linux/time.h中实现，调用操作硬件驱动在drivers/char/s3c2410-rtc.c,include/asm-arm/arch-s3c2410/regs-rtc.h实现;************************************************************************************************************ @Author: liyangth@gmail.com * * @Function List: ** ** * @Changelog:* 2007-06-24 LiYang First version** @FQA:* [50%]Q1.在驱动中要将设备注册到总线，必须将设备封装成struct device_driver；调查这个结构体中的每个成员.* [0%]Q2.在板子（什么类型）上什么样的设备要用总线（什么类型）注册？* [90%]Q3.* struct device --总线设备* struct device_driver --总线设备驱动* struct platform_device --平台设备* struct resource --平台资源* * [！0%]Q4.初始化rtc register的函数的后面的flag具体控制什么? (在s2s65a里是否可以用它控制是softReset or hardwareReset)** [0%]Q5.什么时候调用suspend, resume?
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/**//***************************************************************************** * Structures & Unions & Enums (#typedef) *//**//*[include/linux/device.h] *总线设备驱动结构体，将它注册到板子的总线上 */static struct device_driver s3c2410_rtcdrv = ...{ .name = "s3c2410-rtc", .owner = THIS_MODULE, .bus = &platform_bus_type, //总线类型，貌似不用管 .probe = s3c2410_rtc_probe, //自检->初始化REG->注册到上一层 .remove = s3c2410_rtc_remove, //注销 .suspend = s3c2410_rtc_suspend, //[挂起？？？] .resume = s3c2410_rtc_resume, //[重起？？？]};/**//*[/include/asm-arm/rtc.h] *底层特别操作集，将他注册到上层的arm common操作层 */static struct rtc_ops s3c2410_rtcops = ...{ .owner = THIS_MODULE, .open = s3c2410_rtc_open, .release = s3c2410_rtc_release, .ioctl = s3c2410_rtc_ioctl, .read_time = s3c2410_rtc_gettime, .set_time = s3c2410_rtc_settime, .read_alarm = s3c2410_rtc_getalarm, .set_alarm = s3c2410_rtc_setalarm, .proc = s3c2410_rtc_proc,};/**//***************************************************************************** * Global Variables */ s3c2410-rtc.c||/**//* IRQ Handlers */|-s3c2410_rtc_alarmirq(int irq, void *id, struct pt_regs *r)| || |-rtc_update(1, RTC_AF | RTC_IRQF); //获得中断标志，和唤醒read阻塞，异步通知；||-s3c2410_rtc_tickirq(int irq, void *id, struct pt_regs *r)||/**//* Update control registers,与硬件实现有关，refer to datasheet */|-s3c2410_rtc_setaie(int to)|-s3c2410_rtc_setpie(int to)|-s3c2410_rtc_setfreq(int freq)||/**//* 实现了要插到上层arm common层的具体的硬件操作,来填充struct rtc_ops，这个具体与硬件相关的操作集会用| register_rtc注册到上层的 */||-s3c2410_rtc_gettime(struct rtc_time *rtc_tm)||-s3c2410_rtc_settime(struct rtc_time *tm)||-s3c2410_rtc_getalarm(struct rtc_wkalrm *alrm)||-s3c2410_rtc_setalarm(struct rtc_wkalrm *alrm)||/**//*| * 插入到上层ioctl中的ioctl,上层中已经通过这个driver中的gettime,settime在其ioctl中实现了取得和设置时间| *，和一些共同的ioctl操作了| * 所以我们在这只要实现与硬件不同部分的ioctl操作 */|-s3c2410_rtc_ioctl(unsigned int cmd, unsigned long arg)||-s3c2410_rtc_proc(char *buf)|-s3c2410_rtc_open(void)| || |1.注册申请闹钟中断ISQ --s3c2410_rtc_alarmirq| |2.周期中断ISQ --s3c2410_rtc_tickirq| |-s3c2410_rtc_release(void)||/**//* Initialize RTC Regs */|-s3c2410_rtc_enable(struct device *dev, int en)| || |-if(!en)| |/**//*before power off, the RTCEN bit should be cleared to| | 0 to prevent inadvertent writing into RTC registers.*/| |1.将控制R的RTCEN位清0;| || |2.disable interrupt.| || |-else /**//* re-enable the device, and check it is ok */| || |1.将控制R的RTCEN位致1。| || |2.BCD count select.--0=Merge BCD counters| || |3.RTC clock count reset.--0=noreset| |||||-s3c2410_rtc_probe(struct device *dev)| |[??]struct platform_device *pdev = to_platform_device(dev); //通过这个设备找到它宿主平台的大设备；| | struct resource *res;| || |/**//* find the IRQs,RTC有2中中断，周期中断和闹钟中断 */| |-s3c2410_rtc_tickno = platform_get_irq(pdev, 1); //从平台上取得一个IRQ号给这个设备；| || |/**//* get the memory region */| |-res = platform_get_resource(pdev, IORESOURCE_MEM, 0);| || |/**//* 向内核申请资源空间 */| |-s3c2410_rtc_mem = request_mem_region(res->start, res->end-res->start+1, pdev->name); //res->start这些资源的分配和在哪个段下，可以看../mach-s3c2410/devs.c | || |/**//* 然后将物理地址映射到虚拟地址，这样驱动和内核就可以看到设备的I/O regs了 */| |-s3c2410_rtc_base = ioremap(res->start, res->end - res->start + 1);| || |/**//* 初始化设备regs */| |-s3c2410_rtc_enable(dev, 1); //可以用后面这个1(这个flag在s2s65a中可以用ram0-7来保存，掉电不清的)来控制是softreset还是hardwarereset.| || |-s3c2410_rtc_setfreq(s3c2410_rtc_freq); //设定RTC周期频率；| || |/**//* 最关键的一步，将与具体不同的底层硬件相关的设备驱动注册给arm通用操作层common/rtctime.c */| |-register_rtc(&s3c2410_rtcops);||-s3c2410_rtc_remove(struct device *dev)| |-unregister_rtc(&s3c2410_rtcops); //从上一层将s3c2410的rtc的device dirver operation set拔下来。| || |-s3c2410_rtc_setpie(0); //disable 周期中断| || |-s3c2410_rtc_setaie(0); //disable alarm interrupt| || |-iounmap(s3c2410_rtc_base);| || |-release_resource(s3c2410_rtc_mem);| || |-kfree(s3c2410_rtc_mem); //[MQA]哪块kmalloc了呢，为什么这要free?|||#ifdef CONFIG_PM //如果电源控制开关打开||-s3c2410_rtc_suspend(struct device *dev, pm_message_t state, u32 level)| || |if (level == SUSPEND_POWER_DOWN) //SUSPEND_POWER_DOWN在include/linux/device.h（generic, centralized driver model）中定义，这个里面是否是对设备的一些公用的行为的操作宏的定义呢？| | |1.保存周期中断寄存器的值；| | || | |2.从RTC中读出时间| | |-s3c2410_rtc_gettime(&tm); //[local variable]struct rtc_time tm;| | || | |3.将从RTC取出的时间Convert Gregorian date to seconds since 01-01-1970 00:00:00.| | |-rtc_tm_to_time(&tm, &time.tv_sec); //[arch/arm/common/rtctime.c]| | || | |4.将系统时间和RTC时间的差值保存到s3c2410_rtc_delta里;| | |-save_time_delta(&s3c2410_rtc_delta, &time); | | || | |5.启动RTC，注意这次启动后面的falg为0了；| | |-s3c2410_rtc_enable(dev, 0);|||-s3c2410_rtc_resume(struct device *dev, u32 level)| || |1.启动RTC，注意这次启动后面的falg为1了；| |-s3c2410_rtc_enable(dev, 1);| || |2.从RTC中读出时间| |-s3c2410_rtc_gettime(&tm);| || |3.转换| |-rtc_tm_to_time(&tm, &time.tv_sec);| || |4.利用在suspend中保存的delta来恢复系统时间| |-restore_time_delta(&s3c2410_rtc_delta, &time);| | | |5.恢复周期中断寄存器的值；| |[LiY]|suspend(暂停，挂起)和resume(恢复，再开始)有点象关机前保存现场和开机后再恢复现场一样；||#else|#define s3c2410_rtc_suspend NULL|#define s3c2410_rtc_resume NULL|#endif|||module_init(s3c2410_rtc_init)|-s3c2410_rtc_init| |-driver_register(&s3c2410_rtcdrv);| | |[purpose]register driver with bus;||module_exit(s3c2410_rtc_exit)|-s3c2410_rtc_exit(void)| |-driver_unregister(&s3c2410_rtcdrv)/**//***************************************************************************** * Extern Function Details *//**//**[drivers/base/driver.c] * driver_register - register driver with bus * @drv: driver to register * * We pass off most of the work to the bus_add_driver() call, * since most of the things we have to do deal with the bus * structures. * * The one interesting aspect is that we setup @drv->unloaded * as a completion that gets complete when the driver reference * count reaches 0. */int driver_register(struct device_driver * drv)...{ klist_init(&drv->klist_devices, klist_devices_get, klist_devices_put); init_completion(&drv->unloaded); return bus_add_driver(drv);}/**//**[drivers/base/platform.c] * platform_get_irq - get an IRQ for a device * @dev: platform device * @num: IRQ number index */int platform_get_irq(struct platform_device *dev, unsigned int num)...{ struct resource *r = platform_get_resource(dev, IORESOURCE_IRQ, num); return r ? r->start : 0;}/**//**[drivers/base/platform.c] * platform_get_resource - get a resource for a device * @dev: platform device * @type: resource type * @num: resource index */struct resource *platform_get_resource(struct platform_device *dev, unsigned int type, unsigned int num)...{ int i;
for (i = 0; i < dev->num_resources; i++) ...{ struct resource *r = &dev->resource[i]; if ((r->flags & (IORESOURCE_IO|IORESOURCE_MEM| IORESOURCE_IRQ|IORESOURCE_DMA)) == type) if (num-- == 0) return r;
} return NULL;}/**//*[../include/linux/ioport.h] * Resources are tree-like, allowing * nesting etc.. */struct resource ...{ const char *name; unsigned long start, end; unsigned long flags; struct resource *parent, *sibling, *child;};/**//**[arch/arm/kernel/time.c] * save_time_delta - Save the offset between system time and RTC time * @delta: pointer to timespec to store delta * @rtc: pointer to timespec for current RTC time * * Return a delta between the system time and the RTC time, such * that system time can be restored later with restore_time_delta() * *[LiY]返回一个系统时间和RTC时间的差值，在重起或系统去读RTC后，可以再用这个差值(delta)来恢复系统时间(系统时间不一定非要和RTC时间相同的); */void save_time_delta(struct timespec *delta, struct timespec *rtc)...{ set_normalized_timespec(delta, xtime.tv_sec - rtc->tv_sec, xtime.tv_nsec - rtc->tv_nsec);}/**//***[arch/arm/kernel/time.c] * restore_time_delta - Restore the current system time * @delta: delta returned by save_time_delta() * @rtc: pointer to timespec for current RTC time */void restore_time_delta(struct timespec *delta, struct timespec *rtc)...{ struct timespec ts; set_normalized_timespec(&ts, delta->tv_sec + rtc->tv_sec, delta->tv_nsec + rtc->tv_nsec); do_settimeofday(&ts);}/**//* *[arch/arm/common/rtctime.c]*/void rtc_update(unsigned long num, unsigned long events)...{ spin_lock(&rtc_lock); rtc_irq_data = (rtc_irq_data + (num << 8)) | events; spin_unlock(&rtc_lock); wake_up_interruptible(&rtc_wait); kill_fasync(&rtc_async_queue, SIGIO, POLL_IN);}