/* * drivers/char/watchdog/shwdt.c * * Watchdog driver for integrated watchdog in the SuperH processors. * * Copyright (C) 2001, 2002, 2003 Paul Mundt * * 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. * * 14-Dec-2001 Matt Domsch * Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT * * 19-Apr-2002 Rob Radez * Added expect close support, made emulated timeout runtime changeable * general cleanups, add some ioctls */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define PFX "shwdt: " /* * Default clock division ratio is 5.25 msecs. For an additional table of * values, consult the asm-sh/watchdog.h. Overload this at module load * time. * * In order for this to work reliably we need to have HZ set to 1000 or * something quite higher than 100 (or we need a proper high-res timer * implementation that will deal with this properly), otherwise the 10ms * resolution of a jiffy is enough to trigger the overflow. For things like * the SH-4 and SH-5, this isn't necessarily that big of a problem, though * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely * necssary. * * As a result of this timing problem, the only modes that are particularly * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms * overflow periods respectively. * * Also, since we can't really expect userspace to be responsive enough * before the overflow happens, we maintain two seperate timers .. One in * the kernel for clearing out WOVF every 2ms or so (again, this depends on * HZ == 1000), and another for monitoring userspace writes to the WDT device. * * As such, we currently use a configurable heartbeat interval which defaults * to 30s. In this case, the userspace daemon is only responsible for periodic * writes to the device before the next heartbeat is scheduled. If the daemon * misses its deadline, the kernel timer will allow the WDT to overflow. */ static int clock_division_ratio = WTCSR_CKS_4096; #define next_ping_period(cks) msecs_to_jiffies(cks - 4) static unsigned long shwdt_is_open; static struct watchdog_info sh_wdt_info; static char shwdt_expect_close; static struct timer_list timer; static unsigned long next_heartbeat; #define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */ static int heartbeat = WATCHDOG_HEARTBEAT; /* in seconds */ static int nowayout = WATCHDOG_NOWAYOUT; /** * sh_wdt_start - Start the Watchdog * * Starts the watchdog. */ static void sh_wdt_start(void) { __u8 csr; next_heartbeat = jiffies + (heartbeat * HZ); mod_timer(&timer, next_ping_period(clock_division_ratio)); csr = sh_wdt_read_csr(); csr |= WTCSR_WT | clock_division_ratio; sh_wdt_write_csr(csr); sh_wdt_write_cnt(0); /* * These processors have a bit of an inconsistent initialization * process.. starting with SH-3, RSTS was moved to WTCSR, and the * RSTCSR register was removed. * * On the SH-2 however, in addition with bits being in different * locations, we must deal with RSTCSR outright.. */ csr = sh_wdt_read_csr(); csr |= WTCSR_TME; csr &= ~WTCSR_RSTS; sh_wdt_write_csr(csr); #ifdef CONFIG_CPU_SH2 /* * Whoever came up with the RSTCSR semantics must've been smoking * some of the good stuff, since in addition to the WTCSR/WTCNT write * brain-damage, it's managed to fuck things up one step further.. * * If we need to clear the WOVF bit, the upper byte has to be 0xa5.. * but if we want to touch RSTE or RSTS, the upper byte has to be * 0x5a.. */ csr = sh_wdt_read_rstcsr(); csr &= ~RSTCSR_RSTS; sh_wdt_write_rstcsr(csr); #endif } /** * sh_wdt_stop - Stop the Watchdog * * Stops the watchdog. */ static void sh_wdt_stop(void) { __u8 csr; del_timer(&timer); csr = sh_wdt_read_csr(); csr &= ~WTCSR_TME; sh_wdt_write_csr(csr); } /** * sh_wdt_keepalive - Keep the Userspace Watchdog Alive * * The Userspace watchdog got a KeepAlive: schedule the next heartbeat. */ static void sh_wdt_keepalive(void) { next_heartbeat = jiffies + (heartbeat * HZ); } /** * sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat * * Set the Userspace Watchdog heartbeat */ static int sh_wdt_set_heartbeat(int t) { if ((t < 1) || (t > 3600)) /* arbitrary upper limit */ return -EINVAL; heartbeat = t; return 0; } /** * sh_wdt_ping - Ping the Watchdog * * @data: Unused * * Clears overflow bit, resets timer counter. */ static void sh_wdt_ping(unsigned long data) { if (time_before(jiffies, next_heartbeat)) { __u8 csr; csr = sh_wdt_read_csr(); csr &= ~WTCSR_IOVF; sh_wdt_write_csr(csr); sh_wdt_write_cnt(0); mod_timer(&timer, next_ping_period(clock_division_ratio)); } else { printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n"); } } /** * sh_wdt_open - Open the Device * * @inode: inode of device * @file: file handle of device * * Watchdog device is opened and started. */ static int sh_wdt_open(struct inode *inode, struct file *file) { if (test_and_set_bit(0, &shwdt_is_open)) return -EBUSY; if (nowayout) __module_get(THIS_MODULE); sh_wdt_start(); return nonseekable_open(inode, file); } /** * sh_wdt_close - Close the Device * * @inode: inode of device * @file: file handle of device * * Watchdog device is closed and stopped. */ static int sh_wdt_close(struct inode *inode, struct file *file) { if (shwdt_expect_close == 42) { sh_wdt_stop(); } else { printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n"); sh_wdt_keepalive(); } clear_bit(0, &shwdt_is_open); shwdt_expect_close = 0; return 0; } /** * sh_wdt_write - Write to Device * * @file: file handle of device * @buf: buffer to write * @count: length of buffer * @ppos: offset * * Pings the watchdog on write. */ static ssize_t sh_wdt_write(struct file *file, const char *buf, size_t count, loff_t *ppos) { if (count) { if (!nowayout) { size_t i; shwdt_expect_close = 0; for (i = 0; i != count; i++) { char c; if (get_user(c, buf + i)) return -EFAULT; if (c == 'V') shwdt_expect_close = 42; } } sh_wdt_keepalive(); } return count; } /** * sh_wdt_ioctl - Query Device * * @inode: inode of device * @file: file handle of device * @cmd: watchdog command * @arg: argument * * Query basic information from the device or ping it, as outlined by the * watchdog API. */ static int sh_wdt_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg) { int new_heartbeat; int options, retval = -EINVAL; switch (cmd) { case WDIOC_GETSUPPORT: return copy_to_user((struct watchdog_info *)arg, &sh_wdt_info, sizeof(sh_wdt_info)) ? -EFAULT : 0; case WDIOC_GETSTATUS: case WDIOC_GETBOOTSTATUS: return put_user(0, (int *)arg); case WDIOC_KEEPALIVE: sh_wdt_keepalive(); return 0; case WDIOC_SETTIMEOUT: if (get_user(new_heartbeat, (int *)arg)) return -EFAULT; if (sh_wdt_set_heartbeat(new_heartbeat)) return -EINVAL; sh_wdt_keepalive(); /* Fall */ case WDIOC_GETTIMEOUT: return put_user(heartbeat, (int *)arg); case WDIOC_SETOPTIONS: if (get_user(options, (int *)arg)) return -EFAULT; if (options & WDIOS_DISABLECARD) { sh_wdt_stop(); retval = 0; } if (options & WDIOS_ENABLECARD) { sh_wdt_start(); retval = 0; } return retval; default: return -ENOIOCTLCMD; } return 0; } /** * sh_wdt_notify_sys - Notifier Handler * * @this: notifier block * @code: notifier event * @unused: unused * * Handles specific events, such as turning off the watchdog during a * shutdown event. */ static int sh_wdt_notify_sys(struct notifier_block *this, unsigned long code, void *unused) { if (code == SYS_DOWN || code == SYS_HALT) { sh_wdt_stop(); } return NOTIFY_DONE; } static struct file_operations sh_wdt_fops = { .owner = THIS_MODULE, .llseek = no_llseek, .write = sh_wdt_write, .ioctl = sh_wdt_ioctl, .open = sh_wdt_open, .release = sh_wdt_close, }; static struct watchdog_info sh_wdt_info = { .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE, .firmware_version = 1, .identity = "SH WDT", }; static struct notifier_block sh_wdt_notifier = { .notifier_call = sh_wdt_notify_sys, }; static struct miscdevice sh_wdt_miscdev = { .minor = WATCHDOG_MINOR, .name = "watchdog", .fops = &sh_wdt_fops, }; /** * sh_wdt_init - Initialize module * * Registers the device and notifier handler. Actual device * initialization is handled by sh_wdt_open(). */ static int __init sh_wdt_init(void) { int rc; if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) { clock_division_ratio = WTCSR_CKS_4096; printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n", clock_division_ratio); } if (sh_wdt_set_heartbeat(heartbeat)) { heartbeat = WATCHDOG_HEARTBEAT; printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n", heartbeat); } init_timer(&timer); timer.function = sh_wdt_ping; timer.data = 0; rc = register_reboot_notifier(&sh_wdt_notifier); if (rc) { printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc); return rc; } rc = misc_register(&sh_wdt_miscdev); if (rc) { printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n", sh_wdt_miscdev.minor, rc); unregister_reboot_notifier(&sh_wdt_notifier); return rc; } printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n", heartbeat, nowayout); return 0; } /** * sh_wdt_exit - Deinitialize module * * Unregisters the device and notifier handler. Actual device * deinitialization is handled by sh_wdt_close(). */ static void __exit sh_wdt_exit(void) { misc_deregister(&sh_wdt_miscdev); unregister_reboot_notifier(&sh_wdt_notifier); } MODULE_AUTHOR("Paul Mundt "); MODULE_DESCRIPTION("SuperH watchdog driver"); MODULE_LICENSE("GPL"); MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); module_param(clock_division_ratio, int, 0); MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7."); module_param(heartbeat, int, 0); MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")"); module_param(nowayout, int, 0); MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)"); module_init(sh_wdt_init); module_exit(sh_wdt_exit);