// SPDX-License-Identifier: GPL-2.0+ /* * Acquire Single Board Computer Watchdog Timer driver * * Based on wdt.c. Original copyright messages: * * (c) Copyright 1996 Alan Cox , * All Rights Reserved. * * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide * warranty for any of this software. This material is provided * "AS-IS" and at no charge. * * (c) Copyright 1995 Alan Cox * * 14-Dec-2001 Matt Domsch * Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT * Can't add timeout - driver doesn't allow changing value */ /* * Theory of Operation: * The Watch-Dog Timer is provided to ensure that standalone * Systems can always recover from catastrophic conditions that * caused the CPU to crash. This condition may have occurred by * external EMI or a software bug. When the CPU stops working * correctly, hardware on the board will either perform a hardware * reset (cold boot) or a non-maskable interrupt (NMI) to bring the * system back to a known state. * * The Watch-Dog Timer is controlled by two I/O Ports. * 443 hex - Read - Enable or refresh the Watch-Dog Timer * 043 hex - Read - Disable the Watch-Dog Timer * * To enable the Watch-Dog Timer, a read from I/O port 443h must * be performed. This will enable and activate the countdown timer * which will eventually time out and either reset the CPU or cause * an NMI depending on the setting of a jumper. To ensure that this * reset condition does not occur, the Watch-Dog Timer must be * periodically refreshed by reading the same I/O port 443h. * The Watch-Dog Timer is disabled by reading I/O port 043h. * * The Watch-Dog Timer Time-Out Period is set via jumpers. * It can be 1, 2, 10, 20, 110 or 220 seconds. */ /* * Includes, defines, variables, module parameters, ... */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt /* Includes */ #include /* For module specific items */ #include /* For new moduleparam's */ #include /* For standard types (like size_t) */ #include /* For the -ENODEV/... values */ #include /* For printk/panic/... */ #include /* For struct miscdevice */ #include /* For the watchdog specific items */ #include /* For file operations */ #include /* For io-port access */ #include /* For platform_driver framework */ #include /* For __init/__exit/... */ #include /* For copy_to_user/put_user/... */ #include /* For inb/outb/... */ /* Module information */ #define DRV_NAME "acquirewdt" #define WATCHDOG_NAME "Acquire WDT" /* There is no way to see what the correct time-out period is */ #define WATCHDOG_HEARTBEAT 0 /* internal variables */ /* the watchdog platform device */ static struct platform_device *acq_platform_device; static unsigned long acq_is_open; static char expect_close; /* module parameters */ /* You must set this - there is no sane way to probe for this board. */ static int wdt_stop = 0x43; module_param(wdt_stop, int, 0); MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)"); /* You must set this - there is no sane way to probe for this board. */ static int wdt_start = 0x443; module_param(wdt_start, int, 0); MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)"); static bool nowayout = WATCHDOG_NOWAYOUT; module_param(nowayout, bool, 0); MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); /* * Watchdog Operations */ static void acq_keepalive(void) { /* Write a watchdog value */ inb_p(wdt_start); } static void acq_stop(void) { /* Turn the card off */ inb_p(wdt_stop); } /* * /dev/watchdog handling */ static ssize_t acq_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { /* See if we got the magic character 'V' and reload the timer */ if (count) { if (!nowayout) { size_t i; /* note: just in case someone wrote the magic character five months ago... */ expect_close = 0; /* scan to see whether or not we got the magic character */ for (i = 0; i != count; i++) { char c; if (get_user(c, buf + i)) return -EFAULT; if (c == 'V') expect_close = 42; } } /* Well, anyhow someone wrote to us, we should return that favour */ acq_keepalive(); } return count; } static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { int options, retval = -EINVAL; void __user *argp = (void __user *)arg; int __user *p = argp; static const struct watchdog_info ident = { .options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE, .firmware_version = 1, .identity = WATCHDOG_NAME, }; switch (cmd) { case WDIOC_GETSUPPORT: return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; case WDIOC_GETSTATUS: case WDIOC_GETBOOTSTATUS: return put_user(0, p); case WDIOC_SETOPTIONS: { if (get_user(options, p)) return -EFAULT; if (options & WDIOS_DISABLECARD) { acq_stop(); retval = 0; } if (options & WDIOS_ENABLECARD) { acq_keepalive(); retval = 0; } return retval; } case WDIOC_KEEPALIVE: acq_keepalive(); return 0; case WDIOC_GETTIMEOUT: return put_user(WATCHDOG_HEARTBEAT, p); default: return -ENOTTY; } } static int acq_open(struct inode *inode, struct file *file) { if (test_and_set_bit(0, &acq_is_open)) return -EBUSY; if (nowayout) __module_get(THIS_MODULE); /* Activate */ acq_keepalive(); return stream_open(inode, file); } static int acq_close(struct inode *inode, struct file *file) { if (expect_close == 42) { acq_stop(); } else { pr_crit("Unexpected close, not stopping watchdog!\n"); acq_keepalive(); } clear_bit(0, &acq_is_open); expect_close = 0; return 0; } /* * Kernel Interfaces */ static const struct file_operations acq_fops = { .owner = THIS_MODULE, .write = acq_write, .unlocked_ioctl = acq_ioctl, .compat_ioctl = compat_ptr_ioctl, .open = acq_open, .release = acq_close, }; static struct miscdevice acq_miscdev = { .minor = WATCHDOG_MINOR, .name = "watchdog", .fops = &acq_fops, }; /* * Init & exit routines */ static int __init acq_probe(struct platform_device *dev) { int ret; if (wdt_stop != wdt_start) { if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) { pr_err("I/O address 0x%04x already in use\n", wdt_stop); ret = -EIO; goto out; } } if (!request_region(wdt_start, 1, WATCHDOG_NAME)) { pr_err("I/O address 0x%04x already in use\n", wdt_start); ret = -EIO; goto unreg_stop; } ret = misc_register(&acq_miscdev); if (ret != 0) { pr_err("cannot register miscdev on minor=%d (err=%d)\n", WATCHDOG_MINOR, ret); goto unreg_regions; } pr_info("initialized. (nowayout=%d)\n", nowayout); return 0; unreg_regions: release_region(wdt_start, 1); unreg_stop: if (wdt_stop != wdt_start) release_region(wdt_stop, 1); out: return ret; } static void acq_remove(struct platform_device *dev) { misc_deregister(&acq_miscdev); release_region(wdt_start, 1); if (wdt_stop != wdt_start) release_region(wdt_stop, 1); } static void acq_shutdown(struct platform_device *dev) { /* Turn the WDT off if we have a soft shutdown */ acq_stop(); } static struct platform_driver acquirewdt_driver = { .remove = acq_remove, .shutdown = acq_shutdown, .driver = { .name = DRV_NAME, }, }; static int __init acq_init(void) { int err; pr_info("WDT driver for Acquire single board computer initialising\n"); acq_platform_device = platform_device_register_simple(DRV_NAME, -1, NULL, 0); if (IS_ERR(acq_platform_device)) return PTR_ERR(acq_platform_device); err = platform_driver_probe(&acquirewdt_driver, acq_probe); if (err) goto unreg_platform_device; return 0; unreg_platform_device: platform_device_unregister(acq_platform_device); return err; } static void __exit acq_exit(void) { platform_device_unregister(acq_platform_device); platform_driver_unregister(&acquirewdt_driver); pr_info("Watchdog Module Unloaded\n"); } module_init(acq_init); module_exit(acq_exit); MODULE_AUTHOR("David Woodhouse"); MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver"); MODULE_LICENSE("GPL");