字符设备驱动实例（PWM和RTC）

目录

五、PWM

六、RTC

五、PWM

        PWM(Pulse Width Modulation，脉宽调制器)，顾名思义就是一个输出脉冲宽度可以调整的硬件器件，其实它不仅脉冲宽度可调，频率也可以调整。它的核心部件是一个硬件定时器，其工作原理可以用下图来说明。

        PWM 管脚默认输出高电平，在图中的时刻1将数值设为 109，比较值设为109，在时刻2启动定时器，PWM 立即输出低电平，在时钟的作用下，计数器开始做减法计数，当计数值减到和比较值一致时(时刻 3)，输出翻转，之后一直输出高电平。当计数到达0后(时刻4)，再完成一次计数，在时刻5 重新从 109 开始计数，输出再次变成低电平，如此周而复始就形成一个矩形波。波形的周期由计数值决定，占空比由比较值决定。在图中，占空比为 110/160，如果用于计数的时钟频率为 freq，那么波形的频率就为freg/160。
        FS4412使用了其中一路PWM 输出 (PWMO，对应管脚是GPD0.0)接蜂鸣器，其电路原理图如图所示。

PWM0的内部结构如图所示。


        PWM 的输入时钟是 PCLK，经过8位的预分频后再经过第二次分频的时钟最终给到PWMO所对应的计数器0。TCNTB0是计数值寄存器，用于控制PWM输出波形的频率TCMPB0是比较寄存器，用于控制 PWM 输出波形的占空比，其输出还可以选择是否反向，是否有死区控制等(关于死区暂时不做介绍，感兴趣的同学可以了解一下电机控制)。
        接下来以PWM0为例，来讨论 PWM 的各寄存器（重点关注相关位)

 TCON寄存器主要用timer0

        TCON寄存器的比特1比较特殊，当要手动更新TCNTBO或TCMPBO的值时，先将对应的值写入寄存器，然后将 TCON 寄存器的比特1先置1再清0，这样新的值才会生效。
        设备树节点的源码如下。

    beep@139D0000 {
        compatible = "fs4412,fspwm";
        reg=<0x139D0000 0x24>;
        clocks=<&clock 336>;
        clock-names="timers";
        pinctrl-0=<pwm0 out>;
        pinctrI-names ="default";
};

        因为 PWM 使用到了一个时钟，在这里的 clocks 属性指定了 PWM 所使用的时钟clock-names 属性则给该时钟取了一个名字叫 timers，方便在驱动中获取该时钟。时钟的编号可以查看Documentation/devicetree/bindings/clock/exynos4-clock.txt内核文档。pinctrl-0属性则描述了PWM使用的GPIO管脚，它指定管脚是pwm0_out，相应的设备树节点定义在arch/arm/boot/dts/exynos4x12-pinctrldtsi，内容如下。

    pwm0_out:pwm0-out {
        samsung,pins = "gpd0-0";
        samsung,pin-function = <2>;
        samsung,pin-drv = <0>;
        samsung,pin-drv=<0>;
    };

        有了这个节点的定义后，我们在驱动中可以利用 pinctrl 子系统的API接口函数快捷地将对应管脚设置为想要的配置方式(我们这里就不详细讨论 pinctrl 子系统，但最常用的一个API将会在后面说明)。上面的节点表示将 GPD0.0管脚配置为功能2，即PWM0 的输出不上拉，驱动强度为最低级别。pinctrl-names 属性是给管脚命名，方便在驱动中获取。

        下面就是时钟子系统和 pinctrl 子系统中最常用的函数。

struct cik *clk_get(struct device *dev, const char *id);
void clk_put (struct clk *clk);
unsigned long clk_get_rate(strut clk *clk);
int clk_set_rate(struct clk *clk, unsigned long rate);
int clk_prepare_enable(struct clk *clk);
void clk_disable_unprepare(struct clk *clk);
struct pinctrl * devm_pinctrl_get_select_default(struct device *dev);

        cik_get: 从dev 中的设备节点中获取名字为 id 的时钟，返回 structclk 结构对象地址，用ISERR宏判断是否错误，用PTR ERR返回错误代码。

        clkput:释放clk。
        clk_get_rate:获取时钟 clk 的频率.

        clk_set_rate:设置时钟clk 的频率。

        clk_prepare_enable:使能时钟。
        clk_disable_unprepare:禁止时钟。
        devm_pinctrl_get_select_default: 从 dev 中的设备节点中获取 pinctrl 管脚，并进行指定的配置。
        有了上面的基础之后，就可以编写相应的驱动代码了。下面的驱动用于驱动蜂鸣器发声，所以应用层应该能够启动 PWM、停止PWM、设置 PWM 输出波形的频率，占空比恒定为50%。关于频率的设置可以利用下面的公式:

out freg= PCIK /(Prescaler0 +1)/ Divider MUX0 / (TCNTBO+1)

主要的代码如下

 

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/cdev.h>

#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/uaccess.h>

#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>

#include <linux/of.h>
#include <linux/clk.h>
#include <linux/pinctrl/consumer.h>

#include "fspwm.h"

#define FSPWM_MAJOR	256
#define FSPWM_MINOR	7
#define FSPWM_DEV_NAME	"fspwm"

struct fspwm_dev {
	unsigned int __iomem *tcfg0;
	unsigned int __iomem *tcfg1;
	unsigned int __iomem *tcon;
	unsigned int __iomem *tcntb0;
	unsigned int __iomem *tcmpb0;
	unsigned int __iomem *tcnto0;
	struct clk *clk;
	unsigned long freq;
	struct pinctrl	*pctrl;
	atomic_t available;
	struct cdev cdev;
};

static int fspwm_open(struct inode *inode, struct file *filp)
{
	struct fspwm_dev *fspwm = container_of(inode->i_cdev, struct fspwm_dev, cdev);

	filp->private_data = fspwm;
	if (atomic_dec_and_test(&fspwm->available))
		return 0;
	else {
		atomic_inc(&fspwm->available);
		return -EBUSY;
	}
}

static int fspwm_release(struct inode *inode, struct file *filp)
{
	struct fspwm_dev *fspwm = filp->private_data;

	atomic_inc(&fspwm->available);
	return 0;
}

static long fspwm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	struct fspwm_dev *fspwm = filp->private_data;
	unsigned int div;

	if (_IOC_TYPE(cmd) != FSPWM_MAGIC)
		return -ENOTTY;

	switch (cmd) {
	case FSPWM_START:
		writel(readl(fspwm->tcon) | 0x1, fspwm->tcon);
		break;
	case FSPWM_STOP:
		writel(readl(fspwm->tcon) & ~0x1, fspwm->tcon);
		break;
	case FSPWM_SET_FREQ:
		if (arg > fspwm->freq || arg == 0)
			return -ENOTTY;
		div = fspwm->freq / arg - 1;
		writel(div, fspwm->tcntb0);
		writel(div / 2, fspwm->tcmpb0);
		writel(readl(fspwm->tcon) | 0x2, fspwm->tcon);
		writel(readl(fspwm->tcon) & ~0x2, fspwm->tcon);
		break;
	default:
		return -ENOTTY;
	}

	return 0;
}

static struct file_operations fspwm_ops = {
	.owner = THIS_MODULE,
	.open = fspwm_open,
	.release = fspwm_release,
	.unlocked_ioctl = fspwm_ioctl,
};

static int fspwm_probe(struct platform_device *pdev)
{
	int ret;
	dev_t dev;
	struct fspwm_dev *fspwm;
	struct resource *res;
	unsigned int prescaler0;

	dev = MKDEV(FSPWM_MAJOR, FSPWM_MINOR);
	ret = register_chrdev_region(dev, 1, FSPWM_DEV_NAME);
	if (ret)
		goto reg_err;

	fspwm = kzalloc(sizeof(struct fspwm_dev), GFP_KERNEL);
	if (!fspwm) {
		ret = -ENOMEM;
		goto mem_err;
	}
	platform_set_drvdata(pdev, fspwm);

	cdev_init(&fspwm->cdev, &fspwm_ops);
	fspwm->cdev.owner = THIS_MODULE;
	ret = cdev_add(&fspwm->cdev, dev, 1);
	if (ret)
		goto add_err;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		ret = -ENOENT;
		goto res_err;
	}

	fspwm->tcfg0 = ioremap(res->start, resource_size(res));
	if (!fspwm->tcfg0) {
		ret = -EBUSY;
		goto map_err;
	}
	fspwm->tcfg1  = fspwm->tcfg0 + 1;
	fspwm->tcon   = fspwm->tcfg0 + 2;
	fspwm->tcntb0 = fspwm->tcfg0 + 3;
	fspwm->tcmpb0 = fspwm->tcfg0 + 4;
	fspwm->tcnto0 = fspwm->tcfg0 + 5;

	fspwm->clk = clk_get(&pdev->dev, "timers");
	if (IS_ERR(fspwm->clk)) {
		ret =  PTR_ERR(fspwm->clk);
		goto get_clk_err;
	}

	ret = clk_prepare_enable(fspwm->clk);
	if (ret < 0)
		goto enable_clk_err;
	fspwm->freq = clk_get_rate(fspwm->clk);

	prescaler0 = readl(fspwm->tcfg0) & 0xFF;
	writel((readl(fspwm->tcfg1) & ~0xF) | 0x4, fspwm->tcfg1); 	/* 1/16 */
	fspwm->freq /= (prescaler0 + 1) * 16;				/* 3125000 */
	writel((readl(fspwm->tcon) & ~0xF) | 0x8, fspwm->tcon);		/* auto-reload */

	fspwm->pctrl = devm_pinctrl_get_select_default(&pdev->dev);

	atomic_set(&fspwm->available, 1);

	return 0;

enable_clk_err:
	clk_put(fspwm->clk);
get_clk_err:
	iounmap(fspwm->tcfg0);
map_err:
res_err:
	cdev_del(&fspwm->cdev);
add_err:
	kfree(fspwm);
mem_err:
	unregister_chrdev_region(dev, 1);
reg_err:
	return ret;
}

static int fspwm_remove(struct platform_device *pdev)
{
	dev_t dev;
	struct fspwm_dev *fspwm = platform_get_drvdata(pdev);

	dev = MKDEV(FSPWM_MAJOR, FSPWM_MINOR);

	clk_disable_unprepare(fspwm->clk);
	clk_put(fspwm->clk);
	iounmap(fspwm->tcfg0);
	cdev_del(&fspwm->cdev);
	kfree(fspwm);
	unregister_chrdev_region(dev, 1);
	return 0;
}

static const struct of_device_id fspwm_of_matches[] = {
	{ .compatible = "fs4412,fspwm", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, fspwm_of_matches);

struct platform_driver fspwm_drv = { 
	.driver = { 
		.name    = "fspwm",
		.owner   = THIS_MODULE,
		.of_match_table = of_match_ptr(fspwm_of_matches),
	},  
	.probe   = fspwm_probe,
	.remove  = fspwm_remove,
};

module_platform_driver(fspwm_drv);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("name <e-mail>");
MODULE_DESCRIPTION("PWM driver");

#ifndef _FSPWM_H
#define _FSPWM_H

#define FSPWM_MAGIC	'f'

#define FSPWM_START	_IO(FSPWM_MAGIC, 0)
#define FSPWM_STOP	_IO(FSPWM_MAGIC, 1)
#define FSPWM_SET_FREQ	_IOW(FSPWM_MAGIC, 2, unsigned int)

#endif

        代码第 27 行至第 32 行是对应的寄存器虚拟地址成员变量。代码第 33 行是获得的PCLK时钟对象指针。代码第 34 行是计算后得到的送入定时器0的时钟频率。代码第35行是PWM输出管脚所对应的pinctrl对象指针。
        在 fspwm_probe 函数中，和前面一样也是注册字符设备、获取IO资源并进行映射等操作。代码第 142行至第 151 行是获取 PCLK 时钟，然后使能和获取频率的代码。代码第 153 行获得了预分频值。代码第 154 行将二级分频设置为 16，代码第 155 行则计算得到了输入到定时器0的时钟频率。代码第 156 行将定时器设置为自动重装模式，用于持续输出PWM 波形。代码第158 行将 GPDO.0管脚设置为 PWMO的输出。
        在fspwm_ioctl 函数中，FSPWM_START 是启动 PWM 的命令，将TCON 的比特0置1即可。FSPWM_STOP 是停止 PWM 的命令，将 TCON 的比特0清0即可FSPWM_SET_FREQ 是设置频率的命令，首先判断了要设置的频率是否超过了范围和是否合法，接下来根据前面的公式计算出了计数值，然后设置了 TCNTBO和TCMPBO，最后根据前面的描述操作 TCON 的比特 1更新新的计数值和比较值。
测试的应用层头文件代码如下。 

#ifndef _MUSIC_H
#define _MUSIC_H

typedef struct
{
	int pitch; 
	int dimation;
} note;

// 1		2		3		4		5		6       7
// C		D		E		F		G		A	B
// 261.6256	293.6648	329.6276	349.2282	391.9954	440	493.8833

// C调
#define DO	262
#define RE	294
#define MI	330
#define FA	349
#define SOL	392
#define LA	440
#define SI	494

#define BEAT	(60000000 / 120)

const note HappyNewYear[] = {
	{DO,   BEAT/2}, {DO,   BEAT/2}, {DO,   BEAT}, {SOL/2, BEAT},
	{MI,   BEAT/2}, {MI,   BEAT/2}, {MI,   BEAT}, {DO,    BEAT},
	{DO,   BEAT/2}, {MI,   BEAT/2}, {SOL,  BEAT}, {SOL,    BEAT},
	{FA,   BEAT/2}, {MI,   BEAT/2}, {RE,   BEAT}, {RE,    BEAT},
	{RE,   BEAT/2}, {MI,   BEAT/2}, {FA,   BEAT}, {FA,    BEAT},
	{MI,   BEAT/2}, {RE,   BEAT/2}, {MI,   BEAT}, {DO,    BEAT},
	{DO,   BEAT/2}, {MI,   BEAT/2}, {RE,   BEAT}, {SOL/2, BEAT},
	{SI/2, BEAT/2}, {RE,   BEAT/2}, {DO,   BEAT}, {DO,    BEAT},
};

#endif

        note 表示的是一个音符，pitch 表示音高，dimation 表示音符演奏的时间HappyNewYear是《新年好》歌曲的各音符表示。测试的应用层代码如下

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>

#include "fspwm.h"
#include "music.h"

#define ARRAY_SIZE(a)	(sizeof(a) / sizeof(a[0]))

int main(int argc, char *argv[])
{
	int i;
	int fd;
	int ret;
	unsigned int freq;

	fd = open("/dev/pwm", O_RDWR);
	if (fd == -1)
		goto fail;

	ret = ioctl(fd, FSPWM_START);
	if (ret == -1)
		goto fail;

	for (i = 0; i < ARRAY_SIZE(HappyNewYear); i++) {
		ret = ioctl(fd, FSPWM_SET_FREQ, HappyNewYear[i].pitch);
		if (ret == -1)
			goto fail;
		usleep(HappyNewYear[i].dimation);
	}

	ret = ioctl(fd, FSPWM_STOP);
	if (ret == -1)
		goto fail;

	exit(EXIT_SUCCESS);
fail:
	perror("pwm test");
	exit(EXIT_FAILURE);
}

        代码中首先打开了设备，然后启动了 PWM 输出，在 for 循环中依次取出乐曲中的各个音符，然后设置频率，再延时指定的时间，这就完成了乐曲的演奏，最后停止了 PWM。

        编译和测试的命令如下，如果工作正常会听到《新年好》的音乐声。

 效果我发了个视频还没审核过感兴趣的可以后面看我在csdn上的视频

六、RTC

        RTC(Real Time Clock，实时时钟) 用于产生年、月、日、时、分、秒的硬件器件。现在的计算机系统上几乎都包含了这个器件，有的 RTC 还带闹钟功能。它的工作原理也非常简单，就是将 1Hz 的时钟用于计数，按照不同的进制产生进位，从而生成上面的时间。
        Exynos4412 上自带一个RTC，带闹钟的功能，为了简单，我们省略对这部分内容的讨论，只关心和时间相关的寄存器，见下表。

        上面只列出了秒时间的寄存器，类似的还有分、天、月等。上面涉及一个BCD 码,所谓的BCD码就是用十六进制来表示十进制，比如0x59就是十进制的59。Linux内核提供了两者之间相互转换的宏，bcd2bin 是将 BCD码转换成一般的整形数，bin2bcd 则相反。
        下面是RTC的设备树节点。

    rtc@100700000 {
        compatible = "fs4412,fsrtc"；
        reg = <0x10070000 0x100>;
        clocks = <&clock 346>;
        clock-names ="rtc";
        status = "okay";
    };

        时钟属性请参照 Documentation/devicetree/bindings/clock/exynos4-clock.txt 内核文档status属性设定为okay，是因为该节点在arch/arm/boot/dts/exynos4.dtsi中已经定义过了在那里status 的值为 disabled，表示禁止，要使能该节点就需要将 status 属性改为 okay。

        驱动的实现比较简单，在时间的设置方面，首先将 RTCCON 寄存器的比特0置1然后将时间值转换成 BCD 码再写入到相应的寄存器，最后将 RTCCON 寄存器的比特0清0即可。时间获取则读出寄存器的值，然后将 BCD码转成一般的整数即可。关于时间定义了一个结构 struct rtc_time，请参见源码的头文件。关键的驱动代码如下
 

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/cdev.h>

#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/uaccess.h>

#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>

#include <linux/of.h>
#include <linux/clk.h>
#include <linux/pinctrl/consumer.h>
#include <linux/bcd.h>

#include "fsrtc.h"

#define FSRTC_MAJOR	256
#define FSRTC_MINOR	8
#define FSRTC_DEV_NAME	"fsrtc"

struct fsrtc_dev {
	unsigned int __iomem *rtccon;
	unsigned int __iomem *bcdsec;
	unsigned int __iomem *bcdmin;
	unsigned int __iomem *bcdhour;
	unsigned int __iomem *bcdday;
	unsigned int __iomem *bcdmon;
	unsigned int __iomem *bcdyear;
	struct clk *clk;
	atomic_t available;
	struct cdev cdev;
};

static int fsrtc_open(struct inode *inode, struct file *filp)
{
	struct fsrtc_dev *fsrtc = container_of(inode->i_cdev, struct fsrtc_dev, cdev);

	filp->private_data = fsrtc;
	if (atomic_dec_and_test(&fsrtc->available))
		return 0;
	else {
		atomic_inc(&fsrtc->available);
		return -EBUSY;
	}
}

static int fsrtc_release(struct inode *inode, struct file *filp)
{
	struct fsrtc_dev *fsrtc = filp->private_data;

	atomic_inc(&fsrtc->available);
	return 0;
}

static long fsrtc_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	struct fsrtc_dev *fsrtc = filp->private_data;
	struct rtc_time time;

	if (_IOC_TYPE(cmd) != FSRTC_MAGIC)
		return -ENOTTY;

	switch (cmd) {
	case FSRTC_SET:
		if (copy_from_user(&time, (struct rtc_time __user *)arg, sizeof(struct rtc_time)))
			return -ENOTTY;
		writel(readl(fsrtc->rtccon) | 0x1, fsrtc->rtccon);

		writel(bin2bcd(time.tm_sec ),  fsrtc->bcdsec);
		writel(bin2bcd(time.tm_min ),  fsrtc->bcdmin);
		writel(bin2bcd(time.tm_hour),  fsrtc->bcdhour);
		writel(bin2bcd(time.tm_mday),  fsrtc->bcdday);
		writel(bin2bcd(time.tm_mon ),  fsrtc->bcdmon);
		writel(bin2bcd(time.tm_year - 2000),  fsrtc->bcdyear);

		writel(readl(fsrtc->rtccon) & ~0x1, fsrtc->rtccon);
		break;
	case FSRTC_GET:
		time.tm_sec  = bcd2bin(readl(fsrtc->bcdsec));
		time.tm_min  = bcd2bin(readl(fsrtc->bcdmin));
		time.tm_hour = bcd2bin(readl(fsrtc->bcdhour));
		time.tm_mday = bcd2bin(readl(fsrtc->bcdday));
		time.tm_mon  = bcd2bin(readl(fsrtc->bcdmon));
		time.tm_year = bcd2bin(readl(fsrtc->bcdyear)) + 2000;

		if (copy_to_user((struct rtc_time __user *)arg, &time, sizeof(struct rtc_time)))
			return -ENOTTY;
		break;
	default:
		return -ENOTTY;
	}

	return 0;
}

static struct file_operations fsrtc_ops = {
	.owner = THIS_MODULE,
	.open = fsrtc_open,
	.release = fsrtc_release,
	.unlocked_ioctl = fsrtc_ioctl,
};

static int fsrtc_probe(struct platform_device *pdev)
{
	int ret;
	dev_t dev;
	struct fsrtc_dev *fsrtc;
	struct resource *res;
	unsigned int __iomem *regbase;

	dev = MKDEV(FSRTC_MAJOR, FSRTC_MINOR);
	ret = register_chrdev_region(dev, 1, FSRTC_DEV_NAME);
	if (ret)
		goto reg_err;

	fsrtc = kzalloc(sizeof(struct fsrtc_dev), GFP_KERNEL);
	if (!fsrtc) {
		ret = -ENOMEM;
		goto mem_err;
	}
	platform_set_drvdata(pdev, fsrtc);

	cdev_init(&fsrtc->cdev, &fsrtc_ops);
	fsrtc->cdev.owner = THIS_MODULE;
	ret = cdev_add(&fsrtc->cdev, dev, 1);
	if (ret)
		goto add_err;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		ret = -ENOENT;
		goto res_err;
	}

	regbase = ioremap(res->start, resource_size(res));
	if (!regbase) {
		ret = -EBUSY;
		goto map_err;
	}
	fsrtc->rtccon     = regbase + 16;
	fsrtc->bcdsec     = regbase + 28;
	fsrtc->bcdmin     = regbase + 29;
	fsrtc->bcdhour    = regbase + 30;
	fsrtc->bcdday     = regbase + 31;
	fsrtc->bcdmon     = regbase + 33;
	fsrtc->bcdyear    = regbase + 34;

	fsrtc->clk = clk_get(&pdev->dev, "rtc");
	if (IS_ERR(fsrtc->clk)) {
		ret =  PTR_ERR(fsrtc->clk);
		goto get_clk_err;
	}

	ret = clk_prepare_enable(fsrtc->clk);
	if (ret < 0)
		goto enable_clk_err;

	writel(0, fsrtc->rtccon);

	atomic_set(&fsrtc->available, 1);

	return 0;

enable_clk_err:
	clk_put(fsrtc->clk);
get_clk_err:
	iounmap(fsrtc->rtccon - 16);
map_err:
res_err:
	cdev_del(&fsrtc->cdev);
add_err:
	kfree(fsrtc);
mem_err:
	unregister_chrdev_region(dev, 1);
reg_err:
	return ret;
}

static int fsrtc_remove(struct platform_device *pdev)
{
	dev_t dev;
	struct fsrtc_dev *fsrtc = platform_get_drvdata(pdev);

	dev = MKDEV(FSRTC_MAJOR, FSRTC_MINOR);

	clk_disable_unprepare(fsrtc->clk);
	clk_put(fsrtc->clk);
	iounmap(fsrtc->rtccon - 16);
	cdev_del(&fsrtc->cdev);
	kfree(fsrtc);
	unregister_chrdev_region(dev, 1);
	return 0;
}

static const struct of_device_id fsrtc_of_matches[] = {
	{ .compatible = "fs4412,fsrtc", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, fsrtc_of_matches);

struct platform_driver fsrtc_drv = { 
	.driver = { 
		.name    = "fsrtc",
		.owner   = THIS_MODULE,
		.of_match_table = of_match_ptr(fsrtc_of_matches),
	},  
	.probe   = fsrtc_probe,
	.remove  = fsrtc_remove,
};

module_platform_driver(fsrtc_drv);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("name <e-mail>");
MODULE_DESCRIPTION("RTC driver");

#ifndef _FSRTC_H
#define _FSRTC_H

struct rtc_time {
	int tm_sec;
	int tm_min;
	int tm_hour;
	int tm_mday;
	int tm_mon;
	int tm_year;
	int tm_wday;
	int tm_yday;
};

#define FSRTC_MAGIC	'f'

#define FSRTC_SET	_IOW(FSRTC_MAGIC, 0, struct rtc_time)
#define FSRTC_GET	_IOR(FSRTC_MAGIC, 1, struct rtc_time)

#endif

        上面的代码比较简单，在此不再多解释。需要注意的是，手册给出的 BCDDAYWEEK和BCDDAY 两个寄存器的地址交换了，需要交换过来。另外，寄存器存放的年份只有3位，所以固定添加了 2000 的偏移。应用层的测试代码也请参见下载资源里面的源码。
        测试的结果如下。

        其实 Linux 内核针对 RTC有一个现成的框架，类似于输入子系统一样，我们只需要使用相应的API，然后再实现要求的接口函数即可。Exynos4412的 RTC 驱动在内核中也已经实现好了，请参见内核源码 drivers/rtc/rtc-s3c.c，这个源码留给大家自己去分析。那么我们要如何使用这个驱动呢?首先将设备树节点改为下面的样子。


        没错，确实这么简单，因为在arch/arm/boot/dts/exynos4.dtsi中已经定义过该节点了现在只需要使能该节点即可。另外就是要确认内核中驱动已经被选配，参见下面的面置项。

        重新编译设备树和内核后，复制文件到 TFTP 服务器指定的目录，启动开发板，使用下面的命令可以确认驱动工作正常。

/* drivers/rtc/rtc-s3c.c
 *
 * Copyright (c) 2010 Samsung Electronics Co., Ltd.
 *		http://www.samsung.com/
 *
 * Copyright (c) 2004,2006 Simtec Electronics
 *	Ben Dooks, <ben@simtec.co.uk>
 *	http://armlinux.simtec.co.uk/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * S3C2410/S3C2440/S3C24XX Internal RTC Driver
*/

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/clk.h>
#include <linux/log2.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#include <asm/irq.h>
#include "rtc-s3c.h"

enum s3c_cpu_type {
	TYPE_S3C2410,
	TYPE_S3C2416,
	TYPE_S3C2443,
	TYPE_S3C64XX,
};

struct s3c_rtc_drv_data {
	int cpu_type;
};

/* I have yet to find an S3C implementation with more than one
 * of these rtc blocks in */

static struct clk *rtc_clk;
static void __iomem *s3c_rtc_base;
static int s3c_rtc_alarmno = NO_IRQ;
static int s3c_rtc_tickno  = NO_IRQ;
static enum s3c_cpu_type s3c_rtc_cpu_type;

static DEFINE_SPINLOCK(s3c_rtc_pie_lock);

static void s3c_rtc_alarm_clk_enable(bool enable)
{
	static DEFINE_SPINLOCK(s3c_rtc_alarm_clk_lock);
	static bool alarm_clk_enabled;
	unsigned long irq_flags;

	spin_lock_irqsave(&s3c_rtc_alarm_clk_lock, irq_flags);
	if (enable) {
		if (!alarm_clk_enabled) {
			clk_enable(rtc_clk);
			alarm_clk_enabled = true;
		}
	} else {
		if (alarm_clk_enabled) {
			clk_disable(rtc_clk);
			alarm_clk_enabled = false;
		}
	}
	spin_unlock_irqrestore(&s3c_rtc_alarm_clk_lock, irq_flags);
}

/* IRQ Handlers */

static irqreturn_t s3c_rtc_alarmirq(int irq, void *id)
{
	struct rtc_device *rdev = id;

	clk_enable(rtc_clk);
	rtc_update_irq(rdev, 1, RTC_AF | RTC_IRQF);

	if (s3c_rtc_cpu_type == TYPE_S3C64XX)
		writeb(S3C2410_INTP_ALM, s3c_rtc_base + S3C2410_INTP);

	clk_disable(rtc_clk);

	s3c_rtc_alarm_clk_enable(false);

	return IRQ_HANDLED;
}

static irqreturn_t s3c_rtc_tickirq(int irq, void *id)
{
	struct rtc_device *rdev = id;

	clk_enable(rtc_clk);
	rtc_update_irq(rdev, 1, RTC_PF | RTC_IRQF);

	if (s3c_rtc_cpu_type == TYPE_S3C64XX)
		writeb(S3C2410_INTP_TIC, s3c_rtc_base + S3C2410_INTP);

	clk_disable(rtc_clk);
	return IRQ_HANDLED;
}

/* Update control registers */
static int s3c_rtc_setaie(struct device *dev, unsigned int enabled)
{
	unsigned int tmp;

	dev_dbg(dev, "%s: aie=%d\n", __func__, enabled);

	clk_enable(rtc_clk);
	tmp = readb(s3c_rtc_base + S3C2410_RTCALM) & ~S3C2410_RTCALM_ALMEN;

	if (enabled)
		tmp |= S3C2410_RTCALM_ALMEN;

	writeb(tmp, s3c_rtc_base + S3C2410_RTCALM);
	clk_disable(rtc_clk);

	s3c_rtc_alarm_clk_enable(enabled);

	return 0;
}

static int s3c_rtc_setfreq(struct device *dev, int freq)
{
	struct platform_device *pdev = to_platform_device(dev);
	struct rtc_device *rtc_dev = platform_get_drvdata(pdev);
	unsigned int tmp = 0;
	int val;

	if (!is_power_of_2(freq))
		return -EINVAL;

	clk_enable(rtc_clk);
	spin_lock_irq(&s3c_rtc_pie_lock);

	if (s3c_rtc_cpu_type != TYPE_S3C64XX) {
		tmp = readb(s3c_rtc_base + S3C2410_TICNT);
		tmp &= S3C2410_TICNT_ENABLE;
	}

	val = (rtc_dev->max_user_freq / freq) - 1;

	if (s3c_rtc_cpu_type == TYPE_S3C2416 || s3c_rtc_cpu_type == TYPE_S3C2443) {
		tmp |= S3C2443_TICNT_PART(val);
		writel(S3C2443_TICNT1_PART(val), s3c_rtc_base + S3C2443_TICNT1);

		if (s3c_rtc_cpu_type == TYPE_S3C2416)
			writel(S3C2416_TICNT2_PART(val), s3c_rtc_base + S3C2416_TICNT2);
	} else {
		tmp |= val;
	}

	writel(tmp, s3c_rtc_base + S3C2410_TICNT);
	spin_unlock_irq(&s3c_rtc_pie_lock);
	clk_disable(rtc_clk);

	return 0;
}

/* Time read/write */

static int s3c_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
{
	unsigned int have_retried = 0;
	void __iomem *base = s3c_rtc_base;

	clk_enable(rtc_clk);
 retry_get_time:
	rtc_tm->tm_min  = readb(base + S3C2410_RTCMIN);
	rtc_tm->tm_hour = readb(base + S3C2410_RTCHOUR);
	rtc_tm->tm_mday = readb(base + S3C2410_RTCDATE);
	rtc_tm->tm_mon  = readb(base + S3C2410_RTCMON);
	rtc_tm->tm_year = readb(base + S3C2410_RTCYEAR);
	rtc_tm->tm_sec  = readb(base + S3C2410_RTCSEC);

	/* the only way to work out whether the system was mid-update
	 * when we read it is to check the second counter, and if it
	 * is zero, then we re-try the entire read
	 */

	if (rtc_tm->tm_sec == 0 && !have_retried) {
		have_retried = 1;
		goto retry_get_time;
	}

	rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
	rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
	rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
	rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
	rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
	rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);

	rtc_tm->tm_year += 100;

	dev_dbg(dev, "read time %04d.%02d.%02d %02d:%02d:%02d\n",
		 1900 + rtc_tm->tm_year, rtc_tm->tm_mon, rtc_tm->tm_mday,
		 rtc_tm->tm_hour, rtc_tm->tm_min, rtc_tm->tm_sec);

	rtc_tm->tm_mon -= 1;

	clk_disable(rtc_clk);
	return rtc_valid_tm(rtc_tm);
}

static int s3c_rtc_settime(struct device *dev, struct rtc_time *tm)
{
	void __iomem *base = s3c_rtc_base;
	int year = tm->tm_year - 100;

	dev_dbg(dev, "set time %04d.%02d.%02d %02d:%02d:%02d\n",
		 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
		 tm->tm_hour, tm->tm_min, tm->tm_sec);

	/* we get around y2k by simply not supporting it */

	if (year < 0 || year >= 100) {
		dev_err(dev, "rtc only supports 100 years\n");
		return -EINVAL;
	}

	clk_enable(rtc_clk);
	writeb(bin2bcd(tm->tm_sec),  base + S3C2410_RTCSEC);
	writeb(bin2bcd(tm->tm_min),  base + S3C2410_RTCMIN);
	writeb(bin2bcd(tm->tm_hour), base + S3C2410_RTCHOUR);
	writeb(bin2bcd(tm->tm_mday), base + S3C2410_RTCDATE);
	writeb(bin2bcd(tm->tm_mon + 1), base + S3C2410_RTCMON);
	writeb(bin2bcd(year), base + S3C2410_RTCYEAR);
	clk_disable(rtc_clk);

	return 0;
}

static int s3c_rtc_getalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct rtc_time *alm_tm = &alrm->time;
	void __iomem *base = s3c_rtc_base;
	unsigned int alm_en;

	clk_enable(rtc_clk);
	alm_tm->tm_sec  = readb(base + S3C2410_ALMSEC);
	alm_tm->tm_min  = readb(base + S3C2410_ALMMIN);
	alm_tm->tm_hour = readb(base + S3C2410_ALMHOUR);
	alm_tm->tm_mon  = readb(base + S3C2410_ALMMON);
	alm_tm->tm_mday = readb(base + S3C2410_ALMDATE);
	alm_tm->tm_year = readb(base + S3C2410_ALMYEAR);

	alm_en = readb(base + S3C2410_RTCALM);

	alrm->enabled = (alm_en & S3C2410_RTCALM_ALMEN) ? 1 : 0;

	dev_dbg(dev, "read alarm %d, %04d.%02d.%02d %02d:%02d:%02d\n",
		 alm_en,
		 1900 + alm_tm->tm_year, alm_tm->tm_mon, alm_tm->tm_mday,
		 alm_tm->tm_hour, alm_tm->tm_min, alm_tm->tm_sec);


	/* decode the alarm enable field */

	if (alm_en & S3C2410_RTCALM_SECEN)
		alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
	else
		alm_tm->tm_sec = -1;

	if (alm_en & S3C2410_RTCALM_MINEN)
		alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
	else
		alm_tm->tm_min = -1;

	if (alm_en & S3C2410_RTCALM_HOUREN)
		alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
	else
		alm_tm->tm_hour = -1;

	if (alm_en & S3C2410_RTCALM_DAYEN)
		alm_tm->tm_mday = bcd2bin(alm_tm->tm_mday);
	else
		alm_tm->tm_mday = -1;

	if (alm_en & S3C2410_RTCALM_MONEN) {
		alm_tm->tm_mon = bcd2bin(alm_tm->tm_mon);
		alm_tm->tm_mon -= 1;
	} else {
		alm_tm->tm_mon = -1;
	}

	if (alm_en & S3C2410_RTCALM_YEAREN)
		alm_tm->tm_year = bcd2bin(alm_tm->tm_year);
	else
		alm_tm->tm_year = -1;

	clk_disable(rtc_clk);
	return 0;
}

static int s3c_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct rtc_time *tm = &alrm->time;
	void __iomem *base = s3c_rtc_base;
	unsigned int alrm_en;

	clk_enable(rtc_clk);
	dev_dbg(dev, "s3c_rtc_setalarm: %d, %04d.%02d.%02d %02d:%02d:%02d\n",
		 alrm->enabled,
		 1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
		 tm->tm_hour, tm->tm_min, tm->tm_sec);

	alrm_en = readb(base + S3C2410_RTCALM) & S3C2410_RTCALM_ALMEN;
	writeb(0x00, base + S3C2410_RTCALM);

	if (tm->tm_sec < 60 && tm->tm_sec >= 0) {
		alrm_en |= S3C2410_RTCALM_SECEN;
		writeb(bin2bcd(tm->tm_sec), base + S3C2410_ALMSEC);
	}

	if (tm->tm_min < 60 && tm->tm_min >= 0) {
		alrm_en |= S3C2410_RTCALM_MINEN;
		writeb(bin2bcd(tm->tm_min), base + S3C2410_ALMMIN);
	}

	if (tm->tm_hour < 24 && tm->tm_hour >= 0) {
		alrm_en |= S3C2410_RTCALM_HOUREN;
		writeb(bin2bcd(tm->tm_hour), base + S3C2410_ALMHOUR);
	}

	dev_dbg(dev, "setting S3C2410_RTCALM to %08x\n", alrm_en);

	writeb(alrm_en, base + S3C2410_RTCALM);

	s3c_rtc_setaie(dev, alrm->enabled);

	clk_disable(rtc_clk);
	return 0;
}

static int s3c_rtc_proc(struct device *dev, struct seq_file *seq)
{
	unsigned int ticnt;

	clk_enable(rtc_clk);
	if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
		ticnt = readw(s3c_rtc_base + S3C2410_RTCCON);
		ticnt &= S3C64XX_RTCCON_TICEN;
	} else {
		ticnt = readb(s3c_rtc_base + S3C2410_TICNT);
		ticnt &= S3C2410_TICNT_ENABLE;
	}

	seq_printf(seq, "periodic_IRQ\t: %s\n", ticnt  ? "yes" : "no");
	clk_disable(rtc_clk);
	return 0;
}

static const struct rtc_class_ops s3c_rtcops = {
	.read_time	= s3c_rtc_gettime,
	.set_time	= s3c_rtc_settime,
	.read_alarm	= s3c_rtc_getalarm,
	.set_alarm	= s3c_rtc_setalarm,
	.proc		= s3c_rtc_proc,
	.alarm_irq_enable = s3c_rtc_setaie,
};

static void s3c_rtc_enable(struct platform_device *pdev, int en)
{
	void __iomem *base = s3c_rtc_base;
	unsigned int tmp;

	if (s3c_rtc_base == NULL)
		return;

	clk_enable(rtc_clk);
	if (!en) {
		tmp = readw(base + S3C2410_RTCCON);
		if (s3c_rtc_cpu_type == TYPE_S3C64XX)
			tmp &= ~S3C64XX_RTCCON_TICEN;
		tmp &= ~S3C2410_RTCCON_RTCEN;
		writew(tmp, base + S3C2410_RTCCON);

		if (s3c_rtc_cpu_type != TYPE_S3C64XX) {
			tmp = readb(base + S3C2410_TICNT);
			tmp &= ~S3C2410_TICNT_ENABLE;
			writeb(tmp, base + S3C2410_TICNT);
		}
	} else {
		/* re-enable the device, and check it is ok */

		if ((readw(base+S3C2410_RTCCON) & S3C2410_RTCCON_RTCEN) == 0) {
			dev_info(&pdev->dev, "rtc disabled, re-enabling\n");

			tmp = readw(base + S3C2410_RTCCON);
			writew(tmp | S3C2410_RTCCON_RTCEN,
				base + S3C2410_RTCCON);
		}

		if ((readw(base + S3C2410_RTCCON) & S3C2410_RTCCON_CNTSEL)) {
			dev_info(&pdev->dev, "removing RTCCON_CNTSEL\n");

			tmp = readw(base + S3C2410_RTCCON);
			writew(tmp & ~S3C2410_RTCCON_CNTSEL,
				base + S3C2410_RTCCON);
		}

		if ((readw(base + S3C2410_RTCCON) & S3C2410_RTCCON_CLKRST)) {
			dev_info(&pdev->dev, "removing RTCCON_CLKRST\n");

			tmp = readw(base + S3C2410_RTCCON);
			writew(tmp & ~S3C2410_RTCCON_CLKRST,
				base + S3C2410_RTCCON);
		}
	}
	clk_disable(rtc_clk);
}

static int s3c_rtc_remove(struct platform_device *dev)
{
	s3c_rtc_setaie(&dev->dev, 0);

	clk_unprepare(rtc_clk);
	rtc_clk = NULL;

	return 0;
}

static const struct of_device_id s3c_rtc_dt_match[];

static inline int s3c_rtc_get_driver_data(struct platform_device *pdev)
{
#ifdef CONFIG_OF
	struct s3c_rtc_drv_data *data;
	if (pdev->dev.of_node) {
		const struct of_device_id *match;
		match = of_match_node(s3c_rtc_dt_match, pdev->dev.of_node);
		data = (struct s3c_rtc_drv_data *) match->data;
		return data->cpu_type;
	}
#endif
	return platform_get_device_id(pdev)->driver_data;
}

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

	dev_dbg(&pdev->dev, "%s: probe=%p\n", __func__, pdev);

	/* find the IRQs */

	s3c_rtc_tickno = platform_get_irq(pdev, 1);
	if (s3c_rtc_tickno < 0) {
		dev_err(&pdev->dev, "no irq for rtc tick\n");
		return s3c_rtc_tickno;
	}

	s3c_rtc_alarmno = platform_get_irq(pdev, 0);
	if (s3c_rtc_alarmno < 0) {
		dev_err(&pdev->dev, "no irq for alarm\n");
		return s3c_rtc_alarmno;
	}

	dev_dbg(&pdev->dev, "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);
	s3c_rtc_base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(s3c_rtc_base))
		return PTR_ERR(s3c_rtc_base);

	rtc_clk = devm_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;
		return ret;
	}

	clk_prepare_enable(rtc_clk);

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

	s3c_rtc_enable(pdev, 1);

	dev_dbg(&pdev->dev, "s3c2410_rtc: RTCCON=%02x\n",
		 readw(s3c_rtc_base + S3C2410_RTCCON));

	device_init_wakeup(&pdev->dev, 1);

	/* register RTC and exit */

	rtc = devm_rtc_device_register(&pdev->dev, "s3c", &s3c_rtcops,
				  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 = s3c_rtc_get_driver_data(pdev);

	/* 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_S3C2410)
		rtc->max_user_freq = 32768;
	else
		rtc->max_user_freq = 128;

	if (s3c_rtc_cpu_type == TYPE_S3C2416 || s3c_rtc_cpu_type == TYPE_S3C2443) {
		tmp = readw(s3c_rtc_base + S3C2410_RTCCON);
		tmp |= S3C2443_RTCCON_TICSEL;
		writew(tmp, s3c_rtc_base + S3C2410_RTCCON);
	}

	platform_set_drvdata(pdev, rtc);

	s3c_rtc_setfreq(&pdev->dev, 1);

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

	ret = devm_request_irq(&pdev->dev, s3c_rtc_tickno, s3c_rtc_tickirq,
			  0,  "s3c2410-rtc tick", rtc);
	if (ret) {
		dev_err(&pdev->dev, "IRQ%d error %d\n", s3c_rtc_tickno, ret);
		goto err_nortc;
	}

	clk_disable(rtc_clk);

	return 0;

 err_nortc:
	s3c_rtc_enable(pdev, 0);
	clk_disable_unprepare(rtc_clk);

	return ret;
}

#ifdef CONFIG_PM_SLEEP
/* RTC Power management control */

static int ticnt_save, ticnt_en_save;
static bool wake_en;

static int s3c_rtc_suspend(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);

	clk_enable(rtc_clk);
	/* save TICNT for anyone using periodic interrupts */
	if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
		ticnt_en_save = readw(s3c_rtc_base + S3C2410_RTCCON);
		ticnt_en_save &= S3C64XX_RTCCON_TICEN;
		ticnt_save = readl(s3c_rtc_base + S3C2410_TICNT);
	} else {
		ticnt_save = readb(s3c_rtc_base + S3C2410_TICNT);
	}
	s3c_rtc_enable(pdev, 0);

	if (device_may_wakeup(dev) && !wake_en) {
		if (enable_irq_wake(s3c_rtc_alarmno) == 0)
			wake_en = true;
		else
			dev_err(dev, "enable_irq_wake failed\n");
	}
	clk_disable(rtc_clk);

	return 0;
}

static int s3c_rtc_resume(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);
	unsigned int tmp;

	clk_enable(rtc_clk);
	s3c_rtc_enable(pdev, 1);
	if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
		writel(ticnt_save, s3c_rtc_base + S3C2410_TICNT);
		if (ticnt_en_save) {
			tmp = readw(s3c_rtc_base + S3C2410_RTCCON);
			writew(tmp | ticnt_en_save,
					s3c_rtc_base + S3C2410_RTCCON);
		}
	} else {
		writeb(ticnt_save, s3c_rtc_base + S3C2410_TICNT);
	}

	if (device_may_wakeup(dev) && wake_en) {
		disable_irq_wake(s3c_rtc_alarmno);
		wake_en = false;
	}
	clk_disable(rtc_clk);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(s3c_rtc_pm_ops, s3c_rtc_suspend, s3c_rtc_resume);

#ifdef CONFIG_OF
static struct s3c_rtc_drv_data s3c_rtc_drv_data_array[] = {
	[TYPE_S3C2410] = { TYPE_S3C2410 },
	[TYPE_S3C2416] = { TYPE_S3C2416 },
	[TYPE_S3C2443] = { TYPE_S3C2443 },
	[TYPE_S3C64XX] = { TYPE_S3C64XX },
};

static const struct of_device_id s3c_rtc_dt_match[] = {
	{
		.compatible = "samsung,s3c2410-rtc",
		.data = &s3c_rtc_drv_data_array[TYPE_S3C2410],
	}, {
		.compatible = "samsung,s3c2416-rtc",
		.data = &s3c_rtc_drv_data_array[TYPE_S3C2416],
	}, {
		.compatible = "samsung,s3c2443-rtc",
		.data = &s3c_rtc_drv_data_array[TYPE_S3C2443],
	}, {
		.compatible = "samsung,s3c6410-rtc",
		.data = &s3c_rtc_drv_data_array[TYPE_S3C64XX],
	},
	{},
};
MODULE_DEVICE_TABLE(of, s3c_rtc_dt_match);
#endif

static struct platform_device_id s3c_rtc_driver_ids[] = {
	{
		.name		= "s3c2410-rtc",
		.driver_data	= TYPE_S3C2410,
	}, {
		.name		= "s3c2416-rtc",
		.driver_data	= TYPE_S3C2416,
	}, {
		.name		= "s3c2443-rtc",
		.driver_data	= TYPE_S3C2443,
	}, {
		.name		= "s3c64xx-rtc",
		.driver_data	= TYPE_S3C64XX,
	},
	{ }
};

MODULE_DEVICE_TABLE(platform, s3c_rtc_driver_ids);

static struct platform_driver s3c_rtc_driver = {
	.probe		= s3c_rtc_probe,
	.remove		= s3c_rtc_remove,
	.id_table	= s3c_rtc_driver_ids,
	.driver		= {
		.name	= "s3c-rtc",
		.owner	= THIS_MODULE,
		.pm	= &s3c_rtc_pm_ops,
		.of_match_table	= of_match_ptr(s3c_rtc_dt_match),
	},
};

module_platform_driver(s3c_rtc_driver);

MODULE_DESCRIPTION("Samsung S3C RTC Driver");
MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:s3c2410-rtc");

 文章来源地址https://www.toymoban.com/news/detail-660958.html

/*
 * Copyright (c) 2003 Simtec Electronics <linux@simtec.co.uk>
 *		      http://www.simtec.co.uk/products/SWLINUX/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * S3C2410 Internal RTC register definition
*/

#ifndef __ASM_ARCH_REGS_RTC_H
#define __ASM_ARCH_REGS_RTC_H __FILE__

#define S3C2410_RTCREG(x) (x)
#define S3C2410_INTP		S3C2410_RTCREG(0x30)
#define S3C2410_INTP_ALM	(1 << 1)
#define S3C2410_INTP_TIC	(1 << 0)

#define S3C2410_RTCCON		S3C2410_RTCREG(0x40)
#define S3C2410_RTCCON_RTCEN	(1 << 0)
#define S3C2410_RTCCON_CNTSEL	(1 << 2)
#define S3C2410_RTCCON_CLKRST	(1 << 3)
#define S3C2443_RTCCON_TICSEL	(1 << 4)
#define S3C64XX_RTCCON_TICEN	(1 << 8)

#define S3C2410_TICNT		S3C2410_RTCREG(0x44)
#define S3C2410_TICNT_ENABLE	(1 << 7)

/* S3C2443: tick count is 15 bit wide
 * TICNT[6:0] contains upper 7 bits
 * TICNT1[7:0] contains lower 8 bits
 */
#define S3C2443_TICNT_PART(x)	((x & 0x7f00) >> 8)
#define S3C2443_TICNT1		S3C2410_RTCREG(0x4C)
#define S3C2443_TICNT1_PART(x)	(x & 0xff)

/* S3C2416: tick count is 32 bit wide
 * TICNT[6:0] contains bits [14:8]
 * TICNT1[7:0] contains lower 8 bits
 * TICNT2[16:0] contains upper 17 bits
 */
#define S3C2416_TICNT2		S3C2410_RTCREG(0x48)
#define S3C2416_TICNT2_PART(x)	((x & 0xffff8000) >> 15)

#define S3C2410_RTCALM		S3C2410_RTCREG(0x50)
#define S3C2410_RTCALM_ALMEN	(1 << 6)
#define S3C2410_RTCALM_YEAREN	(1 << 5)
#define S3C2410_RTCALM_MONEN	(1 << 4)
#define S3C2410_RTCALM_DAYEN	(1 << 3)
#define S3C2410_RTCALM_HOUREN	(1 << 2)
#define S3C2410_RTCALM_MINEN	(1 << 1)
#define S3C2410_RTCALM_SECEN	(1 << 0)

#define S3C2410_ALMSEC		S3C2410_RTCREG(0x54)
#define S3C2410_ALMMIN		S3C2410_RTCREG(0x58)
#define S3C2410_ALMHOUR		S3C2410_RTCREG(0x5c)

#define S3C2410_ALMDATE		S3C2410_RTCREG(0x60)
#define S3C2410_ALMMON		S3C2410_RTCREG(0x64)
#define S3C2410_ALMYEAR		S3C2410_RTCREG(0x68)

#define S3C2410_RTCSEC		S3C2410_RTCREG(0x70)
#define S3C2410_RTCMIN		S3C2410_RTCREG(0x74)
#define S3C2410_RTCHOUR		S3C2410_RTCREG(0x78)
#define S3C2410_RTCDATE		S3C2410_RTCREG(0x7c)
#define S3C2410_RTCMON		S3C2410_RTCREG(0x84)
#define S3C2410_RTCYEAR		S3C2410_RTCREG(0x88)

#endif /* __ASM_ARCH_REGS_RTC_H */

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