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mini6410 看門狗源碼分析

看門狗代碼放在linux/drivers/char/watchdog/s3c2410_wdt.c中分析如下：

/* linux/drivers/char/watchdog/s3c2410_wdt.c
*
* Copyright (c) 2004 Simtec Electronics
* Ben Dooks <[email protected]>
*
* S3C2410 Watchdog Timer Support
*
* Based on, softdog.c by Alan Cox,
* (c) Copyright 1996 Alan Cox <[email protected]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/clk.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <mach/map.h>
#undef S3C_VA_WATCHDOG
#define S3C_VA_WATCHDOG (0)
#include <plat/regs-watchdog.h>
#define PFX "s3c2410-wdt: "
#define CONFIG_S3C2410_WATCHDOG_ATBOOT (0)
#define CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME (15)
/*
*nowayout表示決不允許看門狗關閉，為1表示不允許關閉，為0表示允許關閉；
*tmr_margin表示默認的看門狗喂狗時間為15s；
*tmr_atboot表示系統啟動時就使能看門狗，為1表示使能，為0表示關閉；
*soft_noboot表示看門狗工作的方式，看門狗可以作為定時器使用也可作為復位硬件使用，
*soft_noboot為1表示看門狗作為定時器使用，不發送復位信號；
*debug表示是否使用調試模式來調試代碼，該模式中，會打印調試信息。
*/
static int nowayout = WATCHDOG_NOWAYOUT;
static int tmr_margin = CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME;
static int tmr_atboot = CONFIG_S3C2410_WATCHDOG_ATBOOT;
static int soft_noboot;
static int debug;
module_param(tmr_margin, int, 0);
module_param(tmr_atboot, int, 0);
module_param(nowayout, int, 0);
module_param(soft_noboot, int, 0);
module_param(debug, int, 0);
MODULE_PARM_DESC(tmr_margin, "Watchdog tmr_margin in seconds. (default="
__MODULE_STRING(CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME) ")");
MODULE_PARM_DESC(tmr_atboot,
"Watchdog is started at boot time if set to 1, default="
__MODULE_STRING(CONFIG_S3C2410_WATCHDOG_ATBOOT));
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
MODULE_PARM_DESC(soft_noboot, "Watchdog action, set to 1 to ignore reboots, "
"0 to reboot (default 0)");
MODULE_PARM_DESC(debug, "Watchdog debug, set to >1 for debug (default 0)");
static unsigned long open_lock;
static struct device *wdt_dev; /* platform device attached to */
static struct resource *wdt_mem;
static struct resource *wdt_irq;
static struct clk *wdt_clock;
static void __iomem *wdt_base;
static unsigned int wdt_count;
static char expect_close;
static DEFINE_SPINLOCK(wdt_lock);
/* watchdog control routines */
#define DBG(msg...) do { \
if (debug) \
printk(KERN_INFO msg); \
} while (0)
/* functions */
static void s3c2410wdt_keepalive(void)
{
spin_lock(&wdt_lock);
writel(wdt_count, wdt_base + S3C2410_WTCNT);
spin_unlock(&wdt_lock);
}
static void __s3c2410wdt_stop(void)
{
unsigned long wtcon;
wtcon = readl(wdt_base + S3C2410_WTCON);
wtcon &= ~(S3C2410_WTCON_ENABLE | S3C2410_WTCON_RSTEN);
writel(wtcon, wdt_base + S3C2410_WTCON);
}
static void s3c2410wdt_stop(void)
{
spin_lock(&wdt_lock);
__s3c2410wdt_stop();
spin_unlock(&wdt_lock);
}
static void s3c2410wdt_start(void)
{
unsigned long wtcon;
spin_lock(&wdt_lock);
/*首先停止看門狗*/
__s3c2410wdt_stop();
/*讀看門狗的控制寄存器*/
wtcon = readl(wdt_base + S3C2410_WTCON);
/*使能看門狗，設置時鐘分頻值為128*/
wtcon |= S3C2410_WTCON_ENABLE | S3C2410_WTCON_DIV128;
/*上邊說過看門狗一個作為一個正常的16位內部定時器也可作為復位硬件*/
if (soft_noboot) {//如果作為內部定時器
wtcon |= S3C2410_WTCON_INTEN;//開中斷使能
wtcon &= ~S3C2410_WTCON_RSTEN;//關閉復位使能
} else {//如果作為復位硬件
wtcon &= ~S3C2410_WTCON_INTEN;//關閉中斷使能
wtcon |= S3C2410_WTCON_RSTEN;//開復位使能
}
DBG("%s: wdt_count=0x%08x, wtcon=%08lx\n",
__func__, wdt_count, wtcon);
/*這裡為什麼要設置WTCNT的值，不是WTDAT中的值自動載入WTCNT嗎？看看datasheet就知道了，看門狗定時器最初
*使能的時候，WTDAT寄存器的值不會自動載入時間計數器，所以WTCNT寄存器必須在使能它之前設置一個初始值
*/
writel(wdt_count, wdt_base + S3C2410_WTDAT);
writel(wdt_count, wdt_base + S3C2410_WTCNT);
writel(wtcon, wdt_base + S3C2410_WTCON);
spin_unlock(&wdt_lock);
}
static inline int s3c2410wdt_is_running(void)
{
return readl(wdt_base + S3C2410_WTCON) & S3C2410_WTCON_ENABLE;
}
static int s3c2410wdt_set_heartbeat(int timeout)
{
/*首先獲得看門狗的時鐘*/
unsigned long freq = clk_get_rate(wdt_clock);
unsigned int count;
unsigned int divisor = 1;
unsigned long wtcon;
if (timeout < 1)
return -EINVAL;
freq /= 128;
/*秒數乘以每秒的時間滴答等於計數值*/
count = timeout * freq;
DBG("%s: count=%d, timeout=%d, freq=%lu\n",
__func__, count, timeout, freq);
/* if the count is bigger than the watchdog register,
then work out what we need to do (and if) we can
actually make this value
*/
/*計數值不能大於WTCNT的最大范圍，WTCNT是一個16位的計數器，最大值是0x10000*/
if (count >= 0x10000) {
for (divisor = 1; divisor <= 0x100; divisor++) {
if ((count / divisor) < 0x10000)
break;
}
/*未找到返回錯誤*/
if ((count / divisor) >= 0x10000) {
dev_err(wdt_dev, "timeout %d too big\n", timeout);
return -EINVAL;
}
}
/*看門狗的喂狗時間*/
tmr_margin = timeout;
DBG("%s: timeout=%d, divisor=%d, count=%d (%08x)\n",
__func__, timeout, divisor, count, count/divisor);
count /= divisor;
wdt_count = count;
/* update the pre-scaler */
//讀看門狗的控制寄存器
wtcon = readl(wdt_base + S3C2410_WTCON);
//看門狗控制器高8位清零，也就是預分頻部分清零
wtcon &= ~S3C2410_WTCON_PRESCALE_MASK;
//填入預分頻系數
wtcon |= S3C2410_WTCON_PRESCALE(divisor-1);
//填入計數值
writel(count, wdt_base + S3C2410_WTDAT);
//填入控制寄存器的值
writel(wtcon, wdt_base + S3C2410_WTCON);
return 0;
}
/*
* /dev/watchdog handling
*/
static int s3c2410wdt_open(struct inode *inode, struct file *file)
{
/*檢查open_lock的第0位，如果open_lock的第0位為0，則表示test_and_set_bit的返回值為0，
表示wdt設備沒有被其他進程打開，如果為1，表示被其他進程打開，返回EBUSY*/
if (test_and_set_bit(0, &open_lock))
return -EBUSY;
/*如果決不允許關閉看門狗，增加引用計數*/
if (nowayout)
__module_get(THIS_MODULE);
/*設為不允許關閉*/
expect_close = 0;
/* start the timer */
/*開啟看門狗*/
s3c2410wdt_start();
/*這些寄存器不需要像文件一樣對位置進行尋址*/
return nonseekable_open(inode, file);
}
static int s3c2410wdt_release(struct inode *inode, struct file *file)
{
/*
* Shut off the timer.
* Lock it in if it's a module and we set nowayout
*/
if (expect_close == 42)//看門狗為允許關閉狀態
s3c2410wdt_stop();//關閉看門狗
else {
dev_err(wdt_dev, "Unexpected close, not stopping watchdog\n");
s3c2410wdt_keepalive();//否則喂狗
}
expect_close = 0; //設為不允許關閉
clear_bit(0, &open_lock);//將open_lock的第0位設為0，是原子操作
return 0;
}
static ssize_t s3c2410wdt_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
/*
* Refresh the timer.
*/
if (len) {//有數據寫入len不為0
if (!nowayout) {//允許關閉
size_t i;
/* In case it was set long ago */
expect_close = 0; //關閉允許關閉狀態
for (i = 0; i != len; i++) {
char c;
if (get_user(c, data + i))
return -EFAULT;
if (c == 'V')//如果向設備寫入'V'，就允許關閉設
expect_close = 42;
}
}
s3c2410wdt_keepalive();
}
return len;
}
#define OPTIONS (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE)
static const struct watchdog_info s3c2410_wdt_ident = {
.options = OPTIONS,
.firmware_version = 0,
.identity = "S3C2410 Watchdog",
};
static long s3c2410wdt_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
void __user *argp = (void __user *)arg;
int __user *p = argp;
int new_margin;
switch (cmd) {
case WDIOC_GETSUPPORT://獲得看門狗設備的信息
return copy_to_user(argp, &s3c2410_wdt_ident,
sizeof(s3c2410_wdt_ident)) ? -EFAULT : 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
return put_user(0, p);
case WDIOC_KEEPALIVE://對看門狗進行喂狗
s3c2410wdt_keepalive();
return 0;
case WDIOC_SETTIMEOUT://設置看門狗的超時時間
if (get_user(new_margin, p))
return -EFAULT;
if (s3c2410wdt_set_heartbeat(new_margin))
return -EINVAL;
s3c2410wdt_keepalive();
return put_user(tmr_margin, p);
case WDIOC_GETTIMEOUT:
return put_user(tmr_margin, p);
default:
return -ENOTTY;
}
}
/* kernel interface */
/*
*看門狗驅動作為字符驅動的file_operations結構
*/
static const struct file_operations s3c2410wdt_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.write = s3c2410wdt_write,
.unlocked_ioctl = s3c2410wdt_ioctl,
.open = s3c2410wdt_open,
.release = s3c2410wdt_release,
};
static struct miscdevice s3c2410wdt_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &s3c2410wdt_fops,
};
/* interrupt handler code */
/*
*如果選擇了看門狗作為內部定時器，則當計數值為0時調用中斷處理函數，中斷處理函數的主要功能就是喂狗
*/
static irqreturn_t s3c2410wdt_irq(int irqno, void *param)
{
dev_info(wdt_dev, "watchdog timer expired (irq)\n");
/*中斷處理中調用喂狗*/
s3c2410wdt_keepalive();
return IRQ_HANDLED;
}
#ifdef CONFIG_CPU_FREQ
static int s3c2410wdt_cpufreq_transition(struct notifier_block *nb,
unsigned long val, void *data)
{
int ret;
if (!s3c2410wdt_is_running())
goto done;
if (val == CPUFREQ_PRECHANGE) {
/* To ensure that over the change we don't cause the
* watchdog to trigger, we perform an keep-alive if
* the watchdog is running.
*/
s3c2410wdt_keepalive();
} else if (val == CPUFREQ_POSTCHANGE) {
s3c2410wdt_stop();
ret = s3c2410wdt_set_heartbeat(tmr_margin);
if (ret >= 0)
s3c2410wdt_start();
else
goto err;
}
done:
return 0;
err:
dev_err(wdt_dev, "cannot set new value for timeout %d\n", tmr_margin);
return ret;
}
static struct notifier_block s3c2410wdt_cpufreq_transition_nb = {
.notifier_call = s3c2410wdt_cpufreq_transition,
};
static inline int s3c2410wdt_cpufreq_register(void)
{
return cpufreq_register_notifier(&s3c2410wdt_cpufreq_transition_nb,
CPUFREQ_TRANSITION_NOTIFIER);
}
static inline void s3c2410wdt_cpufreq_deregister(void)
{
cpufreq_unregister_notifier(&s3c2410wdt_cpufreq_transition_nb,
CPUFREQ_TRANSITION_NOTIFIER);
}
#else
static inline int s3c2410wdt_cpufreq_register(void)
{
return 0;
}
static inline void s3c2410wdt_cpufreq_deregister(void)
{
}
#endif
/* device interface */
static int __devinit s3c2410wdt_probe(struct platform_device *pdev)
{
struct resource *res;
struct device *dev;
unsigned int wtcon;
int started = 0;
int ret;
int size;
DBG("%s: probe=%p\n", __func__, pdev);
/*平台設備中的設備結構體device*/
dev = &pdev->dev;
wdt_dev = &pdev->dev;
/* get the memory region for the watchdog timer */
/*獲得看門狗的內存資源*/
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
/*獲取失敗則推出*/
if (res == NULL) {
dev_err(dev, "no memory resource specified\n");
return -ENOENT;
}
/*內存資源所占的字節數*/
size = resource_size(res);
/*申請一塊IO內存，對應看門狗的3個寄存器*/
wdt_mem = request_mem_region(res->start, size, pdev->name);
if (wdt_mem == NULL) {
dev_err(dev, "failed to get memory region\n");
return -EBUSY;
}
/*獲得虛擬地址*/
wdt_base = ioremap(res->start, size);
if (wdt_base == NULL) {
dev_err(dev, "failed to ioremap() region\n");
ret = -EINVAL;
goto err_req;
}
DBG("probe: mapped wdt_base=%p\n", wdt_base);
/*申請中斷*/
wdt_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (wdt_irq == NULL) {
dev_err(dev, "no irq resource specified\n");
ret = -ENOENT;
goto err_map;
}
/*並注冊中斷處理函數*/
ret = request_irq(wdt_irq->start, s3c2410wdt_irq, 0, pdev->name, pdev);
if (ret != 0) {
dev_err(dev, "failed to install irq (%d)\n", ret);
goto err_map;
}
/*獲得看門狗時鐘*/
wdt_clock = clk_get(&pdev->dev, "watchdog");
if (IS_ERR(wdt_clock)) {
dev_err(dev, "failed to find watchdog clock source\n");
ret = PTR_ERR(wdt_clock);
goto err_irq;
}
/*時鐘使能*/
clk_enable(wdt_clock);
if (s3c2410wdt_cpufreq_register() < 0) {
printk(KERN_ERR PFX "failed to register cpufreq\n");
goto err_clk;
}
/* see if we can actually set the requested timer margin, and if
* not, try the default value */
/*設置看門狗復位時間，如果成功返回0*/
if (s3c2410wdt_set_heartbeat(tmr_margin)) {
/*如果不成功，看門狗的復位時間設置成默認值*/
started = s3c2410wdt_set_heartbeat(
CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
if (started == 0)
dev_info(dev,
"tmr_margin value out of range, default %d used\n",
CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
else
dev_info(dev, "default timer value is out of range, "
"cannot start\n");
}
/*注冊混雜設備*/
ret = misc_register(&s3c2410wdt_miscdev);
if (ret) {
dev_err(dev, "cannot register miscdev on minor=%d (%d)\n",
WATCHDOG_MINOR, ret);
goto err_cpufreq;
}
/*如果開機的時候就啟動看門狗*/
if (tmr_atboot && started == 0) {
dev_info(dev, "starting watchdog timer\n");
s3c2410wdt_start();//啟動看門狗
} else if (!tmr_atboot) {
/* if we're not enabling the watchdog, then ensure it is
* disabled if it has been left running from the bootloader
* or other source */
s3c2410wdt_stop();//關閉看門狗
}
/* print out a statement of readiness */
/*讀出看門狗控制寄存器的值*/
wtcon = readl(wdt_base + S3C2410_WTCON);
/*打印看門狗是否使能，是否允許發出復位信號，是否允許發出中斷信號*/
dev_info(dev, "watchdog %sactive, reset %sabled, irq %sabled\n",
(wtcon & S3C2410_WTCON_ENABLE) ? "" : "in",
(wtcon & S3C2410_WTCON_RSTEN) ? "" : "dis",
(wtcon & S3C2410_WTCON_INTEN) ? "" : "en");
return 0;
err_cpufreq:
s3c2410wdt_cpufreq_deregister();
err_clk:
clk_disable(wdt_clock);
clk_put(wdt_clock);
err_irq:
free_irq(wdt_irq->start, pdev);
err_map:
iounmap(wdt_base);
err_req:
release_resource(wdt_mem);
kfree(wdt_mem);
return ret;
}
static int __devexit s3c2410wdt_remove(struct platform_device *dev)
{
misc_deregister(&s3c2410wdt_miscdev);//注銷混雜設備
s3c2410wdt_cpufreq_deregister();
clk_disable(wdt_clock);//關閉時鐘
clk_put(wdt_clock);//減少時鐘引用計數
wdt_clock = NULL;
free_irq(wdt_irq->start, dev);//釋放中斷號
wdt_irq = NULL;
iounmap(wdt_base);//關閉內存映射
release_resource(wdt_mem);//釋放平台資源
kfree(wdt_mem);//釋放I/O內存
wdt_mem = NULL;
return 0;
}
static void s3c2410wdt_shutdown(struct platform_device *dev)
{
s3c2410wdt_stop();
}
#ifdef CONFIG_PM
static unsigned long wtcon_save;
static unsigned long wtdat_save;
/*
*平台驅動中的電源管理部分
*/
static int s3c2410wdt_suspend(struct platform_device *dev, pm_message_t state)
{
/* Save watchdog state, and turn it off. */
/*只要保存S3C2410_WTDAT就可以了，不需要保存S3C2410_WTCNT，
*S3C2410_WTCNT的值會在系統還原的時候直接賦為S3C2410_WTDAT中的值
*/
wtcon_save = readl(wdt_base + S3C2410_WTCON);
wtdat_save = readl(wdt_base + S3C2410_WTDAT);
/* Note that WTCNT doesn't need to be saved. */
s3c2410wdt_stop();
return 0;
}
static int s3c2410wdt_resume(struct platform_device *dev)
{
/* Restore watchdog state. */
writel(wtdat_save, wdt_base + S3C2410_WTDAT);
writel(wtdat_save, wdt_base + S3C2410_WTCNT); /* Reset count */
writel(wtcon_save, wdt_base + S3C2410_WTCON);
printk(KERN_INFO PFX "watchdog %sabled\n",
(wtcon_save & S3C2410_WTCON_ENABLE) ? "en" : "dis");
return 0;
}
#else
#define s3c2410wdt_suspend NULL
#define s3c2410wdt_resume NULL
#endif /* CONFIG_PM */
/*
*S3C2410的看門狗同時具有多重身份：字符設備，混雜設備，平台設備。
*下面是看門狗驅動作為平台驅動的描述：
*/
static struct platform_driver s3c2410wdt_driver = {
.probe = s3c2410wdt_probe,
.remove = __devexit_p(s3c2410wdt_remove),
.shutdown = s3c2410wdt_shutdown,
.suspend = s3c2410wdt_suspend,
.resume = s3c2410wdt_resume,
.driver = {
.owner = THIS_MODULE,
.name = "s3c2410-wdt",
},
};
static char banner[] __initdata =
KERN_INFO "S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics\n";
/*
*看門狗驅動作為平台驅動的注冊
*/
static int __init watchdog_init(void)
{
printk(banner);
return platform_driver_register(&s3c2410wdt_driver);
}
static void __exit watchdog_exit(void)
{
platform_driver_unregister(&s3c2410wdt_driver);
}
module_init(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Ben Dooks <[email protected]>, "
"Dimitry Andric <[email protected]>");
MODULE_DESCRIPTION("S3C2410 Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:s3c2410-wdt");

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