S3C2440驱动篇—RTC驱动分析

RTC时钟驱动
Linux-2.6.32.2内核自带RTC驱动，但mach_smdk2440.c中没有添加该设备集，因此没有被激活，加入该平台设备，RTC平台设备定义在arch/arm/plat-s3c24xx/devs.c。

static struct platform_device *smdk2440_devices[] __initdata = {

&s3c_device_usb, /* arch/arm/mach-s3c2440/mach-smdk2440.c */

&s3c_device_lcd,

&s3c_device_wdt,

&s3c_device_i2c0,

&s3c_device_iis,

&s3c_device_rtc,

};

驱动实现：

#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 <mach/hardware.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <plat/regs-rtc.h>

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

static struct resource *s3c_rtc_mem;

static void __iomem *s3c_rtc_base;
static int s3c_rtc_alarmno = NO_IRQ;
static int s3c_rtc_tickno  = NO_IRQ;

static DEFINE_SPINLOCK(s3c_rtc_pie_lock);

/* IRQ Handlers */

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

/* 报警中断到来时，设定报警相关信息，函数实现位于drivers/rtc/interface.c */
rtc_update_irq(rdev, 1, RTC_AF | RTC_IRQF);
return IRQ_HANDLED;
}

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

rtc_update_irq(rdev, 1, RTC_PF | RTC_IRQF);
return IRQ_HANDLED;
}

/* Update control registers 设置RTCALM全局报警使能位*/
static void s3c_rtc_setaie(int to)
{
unsigned int tmp;

pr_debug("%s: aie=%d\n", __func__, to);

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

if (to)
tmp |= S3C2410_RTCALM_ALMEN;

writeb(tmp, s3c_rtc_base + S3C2410_RTCALM);
}

/* 节拍时间计数器使能 */
static int s3c_rtc_setpie(struct device *dev, int enabled)
{
unsigned int tmp;

pr_debug("%s: pie=%d\n", __func__, enabled);

spin_lock_irq(&s3c_rtc_pie_lock);
tmp = readb(s3c_rtc_base + S3C2410_TICNT) & ~S3C2410_TICNT_ENABLE;

if (enabled)
tmp |= S3C2410_TICNT_ENABLE;

writeb(tmp, s3c_rtc_base + S3C2410_TICNT);
spin_unlock_irq(&s3c_rtc_pie_lock);

return 0;
}

/* 节拍时间计数值设置*/
static int s3c_rtc_setfreq(struct device *dev, int freq)
{
unsigned int tmp;

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

spin_lock_irq(&s3c_rtc_pie_lock);

tmp = readb(s3c_rtc_base + S3C2410_TICNT) & S3C2410_TICNT_ENABLE;
tmp |= (128 / freq)-1;

writeb(tmp, s3c_rtc_base + S3C2410_TICNT);
spin_unlock_irq(&s3c_rtc_pie_lock);

return 0;
}

/* Time read/write */
/* 读取RTC中时间：分、时、日期、月、年、秒 */
static int s3c_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
{
unsigned int have_retried = 0;
void __iomem *base = s3c_rtc_base;

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 wether 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
*/
/* 如果读到秒为0，可能有进位，根据2440手册知道，要重新读一次 */
if (rtc_tm->tm_sec == 0 && !have_retried) {
have_retried = 1;
goto retry_get_time;
}

pr_debug("read time %02x.%02x.%02x %02x/%02x/%02x\n",
rtc_tm->tm_year, rtc_tm->tm_mon, rtc_tm->tm_mday,
rtc_tm->tm_hour, rtc_tm->tm_min, rtc_tm->tm_sec);

/* 将BCD码转换为二进制数 */
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);

/*这里为什么要加100年和减1月,查看数据手册得知区别1900年和2000年闰年的因素,1900年不是闰年而2000年是闰年*/
rtc_tm->tm_year += 100;
rtc_tm->tm_mon -= 1;

return 0;
}

/* 与s3c_rtc_gettime功能相反 */
static int s3c_rtc_settime(struct device *dev, struct rtc_time *tm)
{
void __iomem *base = s3c_rtc_base;
int year = tm->tm_year - 100;

pr_debug("set time %02d.%02d.%02d %02d/%02d/%02d\n",
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;
}

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);

return 0;
}

/* 读取RTC报警时间值 */
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;

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;

pr_debug("read alarm %02x %02x.%02x.%02x %02x/%02x/%02x\n",
alm_en,
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 = 0xff;

if (alm_en & S3C2410_RTCALM_MINEN)
alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
else
alm_tm->tm_min = 0xff;

if (alm_en & S3C2410_RTCALM_HOUREN)
alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
else
alm_tm->tm_hour = 0xff;

if (alm_en & S3C2410_RTCALM_DAYEN)
alm_tm->tm_mday = bcd2bin(alm_tm->tm_mday);
else
alm_tm->tm_mday = 0xff;

if (alm_en & S3C2410_RTCALM_MONEN) {
alm_tm->tm_mon = bcd2bin(alm_tm->tm_mon);
alm_tm->tm_mon -= 1;   //这里减1有待研究，为什么只有月没有年减1
} else {
alm_tm->tm_mon = 0xff;
}

if (alm_en & S3C2410_RTCALM_YEAREN)
alm_tm->tm_year = bcd2bin(alm_tm->tm_year);
else
alm_tm->tm_year = 0xffff;

return 0;
}
/* 与s3c_rtc_getalarm功能相反 */
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;

pr_debug("s3c_rtc_setalarm: %d, %02x/%02x/%02x %02x.%02x.%02x\n",
alrm->enabled,
tm->tm_mday & 0xff, tm->tm_mon & 0xff, tm->tm_year & 0xff,
tm->tm_hour & 0xff, tm->tm_min & 0xff, 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);
}

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

writeb(alrm_en, base + S3C2410_RTCALM);

s3c_rtc_setaie(alrm->enabled);

/*根据全局报警使能的状态来决定是唤醒RTC报警中断还是睡眠RTC报警中断*/
if (alrm->enabled)
enable_irq_wake(s3c_rtc_alarmno);
else
disable_irq_wake(s3c_rtc_alarmno);

return 0;
}

static int s3c_rtc_proc(struct device *dev, struct seq_file *seq)
{
unsigned int ticnt = readb(s3c_rtc_base + S3C2410_TICNT);

seq_printf(seq, "periodic_IRQ\t: %s\n",
(ticnt & S3C2410_TICNT_ENABLE) ? "yes" : "no" );
return 0;
}

/*RTC设备类打开接口函数*/
static int s3c_rtc_open(struct device *dev)
{
/*这里主要的目的是从系统平台设备中获取RTC设备类的数据，和RTC探测函数rtc_probe中
的platform_set_drvdata(pdev, rtc)的操作刚好相反。定义在platform_device.h中*/
struct platform_device *pdev = to_platform_device(dev);
struct rtc_device *rtc_dev = platform_get_drvdata(pdev);
int ret;

ret = request_irq(s3c_rtc_alarmno, s3c_rtc_alarmirq,
IRQF_DISABLED,  "s3c2410-rtc alarm", rtc_dev);

if (ret) {
dev_err(dev, "IRQ%d error %d\n", s3c_rtc_alarmno, ret);
return ret;
}

ret = request_irq(s3c_rtc_tickno, s3c_rtc_tickirq,
IRQF_DISABLED,  "s3c2410-rtc tick", rtc_dev);

if (ret) {
dev_err(dev, "IRQ%d error %d\n", s3c_rtc_tickno, ret);
goto tick_err;
}

return ret;

tick_err:
free_irq(s3c_rtc_alarmno, rtc_dev);
return ret;
}

static void s3c_rtc_release(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct rtc_device *rtc_dev = platform_get_drvdata(pdev);

/* do not clear AIE here, it may be needed for wake */

s3c_rtc_setpie(dev, 0);
free_irq(s3c_rtc_alarmno, rtc_dev);
free_irq(s3c_rtc_tickno, rtc_dev);
}

/*rtc_class_ops是RTC设备类在RTC驱动核心部分中定义的对RTC设备类进行操作的结构体，
类似字符设备在驱动中的file_operations对字符设备进行操作的意思。该结构体被定义
在include/linux/rtc.h中，对RTC的操作主要有打开、关闭、设置或获取时间、设置或
获取报警、设置节拍时间计数值等等，该结构体内接口函数的实现在前面*/
static const struct rtc_class_ops s3c_rtcops = {
.open		= s3c_rtc_open,
.release	= s3c_rtc_release,
.read_time	= s3c_rtc_gettime,
.set_time	= s3c_rtc_settime,
.read_alarm	= s3c_rtc_getalarm,
.set_alarm	= s3c_rtc_setalarm,
.irq_set_freq	= s3c_rtc_setfreq,
.irq_set_state	= s3c_rtc_setpie,
.proc	        = s3c_rtc_proc,
};

/* 控制RTCCON寄存器，rtc使能 */
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;

if (!en) {
tmp = readb(base + S3C2410_RTCCON);
writeb(tmp & ~S3C2410_RTCCON_RTCEN, base + S3C2410_RTCCON);

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

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

tmp = readb(base + S3C2410_RTCCON);
writeb(tmp|S3C2410_RTCCON_RTCEN, base+S3C2410_RTCCON);
}

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

tmp = readb(base + S3C2410_RTCCON);
writeb(tmp& ~S3C2410_RTCCON_CNTSEL, base+S3C2410_RTCCON);
}

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

tmp = readb(base + S3C2410_RTCCON);
writeb(tmp & ~S3C2410_RTCCON_CLKRST, base+S3C2410_RTCCON);
}
}
}

static int __devexit s3c_rtc_remove(struct platform_device *dev)
{
struct rtc_device *rtc = platform_get_drvdata(dev);

platform_set_drvdata(dev, NULL);
rtc_device_unregister(rtc);   /*注销RTC设备类*/

s3c_rtc_setpie(&dev->dev, 0);
s3c_rtc_setaie(0);

iounmap(s3c_rtc_base);
release_resource(s3c_rtc_mem);
kfree(s3c_rtc_mem);

return 0;
}

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

pr_debug("%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 -ENOENT;
}

s3c_rtc_alarmno = platform_get_irq(pdev, 0);
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);
if (res == NULL) {
dev_err(&pdev->dev, "failed to get memory region resource\n");
return -ENOENT;
}

s3c_rtc_mem = request_mem_region(res->start,
res->end-res->start+1,
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, res->end - res->start + 1);
if (s3c_rtc_base == NULL) {
dev_err(&pdev->dev, "failed ioremap()\n");
ret = -EINVAL;
goto err_nomap;
}

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

s3c_rtc_enable(pdev, 1);

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

s3c_rtc_setfreq(&pdev->dev, 1);

device_init_wakeup(&pdev->dev, 1);    //驱动支持电源管理

/* register RTC and exit */
/*将RTC注册为RTC设备类，RTC设备类在RTC驱动核心部分中由系统定义好的，注意rtcops这个参数是一个结构体，该结构体的作用和里面的接口函数前面实现。rtc_device_register函数在rtc.h中定义，在drivers/rtc/class.c中实现*/
rtc = rtc_device_register("s3c", &pdev->dev, &s3c_rtcops,THIS_MODULE);

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

rtc->max_user_freq = 128;

/*将RTC设备类的数据传递给系统平台设备。platform_set_drvdata是定义在platform_device.h的宏，如下：
#define platform_set_drvdata(_dev,data)    dev_set_drvdata(&(_dev)->dev, (data))
而dev_set_drvdata又被定义在include/linux/device.h中，如下：
static inline void dev_set_drvdata (struct device *dev, void *data)
{
dev->driver_data = data;
}*/
platform_set_drvdata(pdev, rtc);
return 0;

err_nortc:
s3c_rtc_enable(pdev, 0);
iounmap(s3c_rtc_base);

err_nomap:
release_resource(s3c_rtc_mem);

err_nores:
return ret;
}

#ifdef CONFIG_PM

/* RTC Power management control */

static int ticnt_save;

static int s3c_rtc_suspend(struct platform_device *pdev, pm_message_t state)
{
/* save TICNT for anyone using periodic interrupts */
ticnt_save = readb(s3c_rtc_base + S3C2410_TICNT);
s3c_rtc_enable(pdev, 0);
return 0;
}

static int s3c_rtc_resume(struct platform_device *pdev)
{
s3c_rtc_enable(pdev, 1);
writeb(ticnt_save, s3c_rtc_base + S3C2410_TICNT);
return 0;
}
#else
#define s3c_rtc_suspend NULL
#define s3c_rtc_resume  NULL
#endif

static struct platform_driver s3c2410_rtc_driver = {
.probe		= s3c_rtc_probe,
.remove		= __devexit_p(s3c_rtc_remove),
.suspend	= s3c_rtc_suspend,
.resume		= s3c_rtc_resume,
.driver		= {
.name	= "s3c2410-rtc",
.owner	= THIS_MODULE,
},
};

static char __initdata banner[] = "S3C24XX RTC, (c) 2004,2006 Simtec Electronics\n";

static int __init s3c_rtc_init(void)
{
printk(banner);
return platform_driver_register(&s3c2410_rtc_driver); //注册RTC平台驱动
}

static void __exit s3c_rtc_exit(void)
{
platform_driver_unregister(&s3c2410_rtc_driver);
}

module_init(s3c_rtc_init);
module_exit(s3c_rtc_exit);

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

配置内核，加入RTC驱动支持

Devide drivers --->

<*> Real Time Clock --->

<*> Samsung S3C series SoC RTC

测试：

# cat /proc/devices 查看rtc设备号

# ls –l /dev/rtc

crw-r--r-- 1 root root 254, 0 Jan 1 1970 /dev/rtc

lrwxr--r-- 1 root root 3Jan 1 1970 /dev/rtc0 -> rtc

date –s 072021352011 设置系统时间为2011-07-20 21:35

hwclock –w 把刚设置的系统时间存入RTC

开机时使用hwclock –s把RTC时间恢复到系统时间

hwclock参数说明：

Options:

-r Show hardware clock time

-s Set system time from hardware clock

-w Set hardware clock to system time

-u Hardware clock is in UTC

-l Hardware clock is in local time

-f FILE Use specified device (e.g. /dev/rtc2)