mini6410 看门狗源码分析

看门狗代码放在linux/drivers/char/watchdog/s3c2410_wdt.c中分析如下： 仅供技术参考，转载请注明出处：http://write.blog.youkuaiyun.com/postedit/7067072 /* linux/drivers/char/watchdog/s3c2410_wdt.c * * Copyright (c) 2004 Simtec Electronics * Ben Dooks <ben@simtec.co.uk> * * S3C2410 Watchdog Timer Support * * Based on, softdog.c by Alan Cox, * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk> * * 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表示决不允许看门狗关闭，为1表示不允许关闭，为0表示允许关闭； *tmr_margin表示默认的看门狗喂狗时间为15s； *tmr_atboot表示系统启动时就使能看门狗，为1表示使能，为0表示关闭； *soft_noboot表示看门狗工作的方式，看门狗可以作为定时器使用也可作为复位硬件使用， *soft_noboot为1表示看门狗作为定时器使用，不发送复位信号； *debug表示是否使用调试模式来调试代码，该模式中，会打印调试信息。 */ 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); /*首先停止看门狗*/ __s3c2410wdt_stop(); /*读看门狗的控制寄存器*/ wtcon = readl(wdt_base + S3C2410_WTCON); /*使能看门狗，设置时钟分频值为128*/ wtcon |= S3C2410_WTCON_ENABLE | S3C2410_WTCON_DIV128; /*上边说过看门狗一个作为一个正常的16位内部定时器也可作为复位硬件*/ if (soft_noboot) {//如果作为内部定时器 wtcon |= S3C2410_WTCON_INTEN;//开中断使能 wtcon &= ~S3C2410_WTCON_RSTEN;//关闭复位使能 } else {//如果作为复位硬件 wtcon &= ~S3C2410_WTCON_INTEN;//关闭中断使能 wtcon |= S3C2410_WTCON_RSTEN;//开复位使能 } DBG("%s: wdt_count=0x%08x, wtcon=%08lx\n", __func__, wdt_count, wtcon); /*这里为什么要设置WTCNT的值，不是WTDAT中的值自动载入WTCNT吗？看看datasheet就知道了，看门狗定时器最初 *使能的时候，WTDAT寄存器的值不会自动载入时 间计数器，所以WTCNT寄存器必须在使能它之前设置一个初始值 */ 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) { /*首先获得看门狗的时钟*/ 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; /*秒数乘以每秒的时间滴答等于计数值*/ 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 */ /*计数值不能大于WTCNT的最大范围，WTCNT是一个16位的计数器，最大值是0x10000*/ if (count >= 0x10000) { for (divisor = 1; divisor <= 0x100; divisor++) { if ((count / divisor) < 0x10000) break; } /*未找到返回错误*/ if ((count / divisor) >= 0x10000) { dev_err(wdt_dev, "timeout %d too big\n", timeout); return -EINVAL; } } /*看门狗的喂狗时间*/ 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 */ //读看门狗的控制寄存器 wtcon = readl(wdt_base + S3C2410_WTCON); //看门狗控制器高8位清零，也就是预分频部分清零 wtcon &= ~S3C2410_WTCON_PRESCALE_MASK; //填入预分频系数 wtcon |= S3C2410_WTCON_PRESCALE(divisor-1); //填入计数值 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) { /*检查open_lock的第0位，如果open_lock的第0位为0，则表示test_and_set_bit的返回值为0， 表示wdt设备没有被其他进程打开，如果为1，表示被其他进程打开，返回EBUSY*/ if (test_and_set_bit(0, &open_lock)) return -EBUSY; /*如果决不允许关闭看门狗，增加引用计数*/ if (nowayout) __module_get(THIS_MODULE); /*设为不允许关闭*/ expect_close = 0; /* start the timer */ /*开启看门狗*/ s3c2410wdt_start(); /*这些寄存器不需要像文件一样对位置进行寻址*/ 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)//看门狗为允许关闭状态 s3c2410wdt_stop();//关闭看门狗 else { dev_err(wdt_dev, "Unexpected close, not stopping watchdog\n"); s3c2410wdt_keepalive();//否则喂狗 } expect_close = 0; //设为不允许关闭 clear_bit(0, &open_lock);//将open_lock的第0位设为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) {//有数据写入len不为0 if (!nowayout) {//允许关闭 size_t i; /* In case it was set long ago */ expect_close = 0; //关闭允许关闭状态 for (i = 0; i != len; i++) { char c; if (get_user(c, data + i)) return -EFAULT; if (c == 'V')//如果向设备写入'V'，就允许关闭设 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://获得看门狗设备的信息 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://对看门狗进行喂狗 s3c2410wdt_keepalive(); return 0; case WDIOC_SETTIMEOUT://设置看门狗的超时时间 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 */ /* *看门狗驱动作为字符驱动的file_operations结构 */ 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 */ /* *如果选择了看门狗作为内部定时器，则当计数值为0时调用中断处理函数，中断处理函数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"); /*中断处理中调用喂狗*/ 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); /*平台设备中的设备结构体device*/ dev = &pdev->dev; wdt_dev = &pdev->dev; /* get the memory region for the watchdog timer */ /*获得看门狗的内存资源*/ res = platform_get_resource(pdev, IORESOURCE_MEM, 0); /*获取失败则推出*/ if (res == NULL) { dev_err(dev, "no memory resource specified\n"); return -ENOENT; } /*内存资源所占的字节数*/ size = resource_size(res); /*申请一块IO内存，对应看门狗的3个寄存器*/ 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; } /*获得虚拟地址*/ 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); /*申请中断*/ 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; } /*并注册中断处理函数*/ 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; } /*获得看门狗时钟*/ 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; } /*时钟使能*/ 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 */ /*设置看门狗复位时间，如果成功返回0*/ if (s3c2410wdt_set_heartbeat(tmr_margin)) { /*如果不成功，看门狗的复位时间设置成默认值*/ 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"); } /*注册混杂设备*/ ret = misc_register(&s3c2410wdt_miscdev); if (ret) { dev_err(dev, "cannot register miscdev on minor=%d (%d)\n", WATCHDOG_MINOR, ret); goto err_cpufreq; } /*如果开机的时候就启动看门狗*/ if (tmr_atboot && started == 0) { dev_info(dev, "starting watchdog timer\n"); s3c2410wdt_start();//启动看门狗 } 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();//关闭看门狗 } /* print out a statement of readiness */ /*读出看门狗控制寄存器的值*/ wtcon = readl(wdt_base + S3C2410_WTCON); /*打印看门狗是否使能，是否允许发出复位信号，是否允许发出中断信号*/ 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);//注销混杂设备 s3c2410wdt_cpufreq_deregister(); clk_disable(wdt_clock);//关闭时钟 clk_put(wdt_clock);//减少时钟引用计数 wdt_clock = NULL; free_irq(wdt_irq->start, dev);//释放中断号 wdt_irq = NULL; iounmap(wdt_base);//关闭内存映射 release_resource(wdt_mem);//释放平台资源 kfree(wdt_mem);//释放I/O内存 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; /* *平台驱动中的电源管理部分 */ 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的值会在系统还原的时候直接赋为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的看门狗同时具有多重身份：字符设备，混杂设备，平台设备。 *下面是看门狗驱动作为平台驱动的描述： */ 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"; /* *看门狗驱动作为平台驱动的注册 */ 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 <ben@simtec.co.uk>, " "Dimitry Andric <dimitry.andric@tomtom.com>"); MODULE_DESCRIPTION("S3C2410 Watchdog Device Driver"); MODULE_LICENSE("GPL"); MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); MODULE_ALIAS("platform:s3c2410-wdt");