1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *	Acquire Single Board Computer Watchdog Timer driver
4  *
5  *	Based on wdt.c. Original copyright messages:
6  *
7  *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
8  *						All Rights Reserved.
9  *
10  *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
11  *	warranty for any of this software. This material is provided
12  *	"AS-IS" and at no charge.
13  *
14  *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
15  *
16  *	14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
17  *	    Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
18  *	    Can't add timeout - driver doesn't allow changing value
19  */
20 
21 /*
22  *	Theory of Operation:
23  *		The Watch-Dog Timer is provided to ensure that standalone
24  *		Systems can always recover from catastrophic conditions that
25  *		caused the CPU to crash. This condition may have occurred by
26  *		external EMI or a software bug. When the CPU stops working
27  *		correctly, hardware on the board will either perform a hardware
28  *		reset (cold boot) or a non-maskable interrupt (NMI) to bring the
29  *		system back to a known state.
30  *
31  *		The Watch-Dog Timer is controlled by two I/O Ports.
32  *		  443 hex	- Read	- Enable or refresh the Watch-Dog Timer
33  *		  043 hex	- Read	- Disable the Watch-Dog Timer
34  *
35  *		To enable the Watch-Dog Timer, a read from I/O port 443h must
36  *		be performed. This will enable and activate the countdown timer
37  *		which will eventually time out and either reset the CPU or cause
38  *		an NMI depending on the setting of a jumper. To ensure that this
39  *		reset condition does not occur, the Watch-Dog Timer must be
40  *		periodically refreshed by reading the same I/O port 443h.
41  *		The Watch-Dog Timer is disabled by reading I/O port 043h.
42  *
43  *		The Watch-Dog Timer Time-Out Period is set via jumpers.
44  *		It can be 1, 2, 10, 20, 110 or 220 seconds.
45  */
46 
47 /*
48  *	Includes, defines, variables, module parameters, ...
49  */
50 
51 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
52 
53 /* Includes */
54 #include <linux/module.h>		/* For module specific items */
55 #include <linux/moduleparam.h>		/* For new moduleparam's */
56 #include <linux/types.h>		/* For standard types (like size_t) */
57 #include <linux/errno.h>		/* For the -ENODEV/... values */
58 #include <linux/kernel.h>		/* For printk/panic/... */
59 #include <linux/miscdevice.h>		/* For struct miscdevice */
60 #include <linux/watchdog.h>		/* For the watchdog specific items */
61 #include <linux/fs.h>			/* For file operations */
62 #include <linux/ioport.h>		/* For io-port access */
63 #include <linux/platform_device.h>	/* For platform_driver framework */
64 #include <linux/init.h>			/* For __init/__exit/... */
65 #include <linux/uaccess.h>		/* For copy_to_user/put_user/... */
66 #include <linux/io.h>			/* For inb/outb/... */
67 
68 /* Module information */
69 #define DRV_NAME "acquirewdt"
70 #define WATCHDOG_NAME "Acquire WDT"
71 /* There is no way to see what the correct time-out period is */
72 #define WATCHDOG_HEARTBEAT 0
73 
74 /* internal variables */
75 /* the watchdog platform device */
76 static struct platform_device *acq_platform_device;
77 static unsigned long acq_is_open;
78 static char expect_close;
79 
80 /* module parameters */
81 /* You must set this - there is no sane way to probe for this board. */
82 static int wdt_stop = 0x43;
83 module_param(wdt_stop, int, 0);
84 MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
85 
86 /* You must set this - there is no sane way to probe for this board. */
87 static int wdt_start = 0x443;
88 module_param(wdt_start, int, 0);
89 MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
90 
91 static bool nowayout = WATCHDOG_NOWAYOUT;
92 module_param(nowayout, bool, 0);
93 MODULE_PARM_DESC(nowayout,
94 	"Watchdog cannot be stopped once started (default="
95 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
96 
97 /*
98  *	Watchdog Operations
99  */
100 
acq_keepalive(void)101 static void acq_keepalive(void)
102 {
103 	/* Write a watchdog value */
104 	inb_p(wdt_start);
105 }
106 
acq_stop(void)107 static void acq_stop(void)
108 {
109 	/* Turn the card off */
110 	inb_p(wdt_stop);
111 }
112 
113 /*
114  *	/dev/watchdog handling
115  */
116 
acq_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)117 static ssize_t acq_write(struct file *file, const char __user *buf,
118 						size_t count, loff_t *ppos)
119 {
120 	/* See if we got the magic character 'V' and reload the timer */
121 	if (count) {
122 		if (!nowayout) {
123 			size_t i;
124 			/* note: just in case someone wrote the magic character
125 			   five months ago... */
126 			expect_close = 0;
127 			/* scan to see whether or not we got the
128 			   magic character */
129 			for (i = 0; i != count; i++) {
130 				char c;
131 				if (get_user(c, buf + i))
132 					return -EFAULT;
133 				if (c == 'V')
134 					expect_close = 42;
135 			}
136 		}
137 		/* Well, anyhow someone wrote to us, we should
138 				return that favour */
139 		acq_keepalive();
140 	}
141 	return count;
142 }
143 
acq_ioctl(struct file * file,unsigned int cmd,unsigned long arg)144 static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
145 {
146 	int options, retval = -EINVAL;
147 	void __user *argp = (void __user *)arg;
148 	int __user *p = argp;
149 	static const struct watchdog_info ident = {
150 		.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
151 		.firmware_version = 1,
152 		.identity = WATCHDOG_NAME,
153 	};
154 
155 	switch (cmd) {
156 	case WDIOC_GETSUPPORT:
157 		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
158 
159 	case WDIOC_GETSTATUS:
160 	case WDIOC_GETBOOTSTATUS:
161 		return put_user(0, p);
162 
163 	case WDIOC_SETOPTIONS:
164 	{
165 		if (get_user(options, p))
166 			return -EFAULT;
167 		if (options & WDIOS_DISABLECARD) {
168 			acq_stop();
169 			retval = 0;
170 		}
171 		if (options & WDIOS_ENABLECARD) {
172 			acq_keepalive();
173 			retval = 0;
174 		}
175 		return retval;
176 	}
177 	case WDIOC_KEEPALIVE:
178 		acq_keepalive();
179 		return 0;
180 
181 	case WDIOC_GETTIMEOUT:
182 		return put_user(WATCHDOG_HEARTBEAT, p);
183 
184 	default:
185 		return -ENOTTY;
186 	}
187 }
188 
acq_open(struct inode * inode,struct file * file)189 static int acq_open(struct inode *inode, struct file *file)
190 {
191 	if (test_and_set_bit(0, &acq_is_open))
192 		return -EBUSY;
193 
194 	if (nowayout)
195 		__module_get(THIS_MODULE);
196 
197 	/* Activate */
198 	acq_keepalive();
199 	return stream_open(inode, file);
200 }
201 
acq_close(struct inode * inode,struct file * file)202 static int acq_close(struct inode *inode, struct file *file)
203 {
204 	if (expect_close == 42) {
205 		acq_stop();
206 	} else {
207 		pr_crit("Unexpected close, not stopping watchdog!\n");
208 		acq_keepalive();
209 	}
210 	clear_bit(0, &acq_is_open);
211 	expect_close = 0;
212 	return 0;
213 }
214 
215 /*
216  *	Kernel Interfaces
217  */
218 
219 static const struct file_operations acq_fops = {
220 	.owner		= THIS_MODULE,
221 	.llseek		= no_llseek,
222 	.write		= acq_write,
223 	.unlocked_ioctl	= acq_ioctl,
224 	.compat_ioctl	= compat_ptr_ioctl,
225 	.open		= acq_open,
226 	.release	= acq_close,
227 };
228 
229 static struct miscdevice acq_miscdev = {
230 	.minor	= WATCHDOG_MINOR,
231 	.name	= "watchdog",
232 	.fops	= &acq_fops,
233 };
234 
235 /*
236  *	Init & exit routines
237  */
238 
acq_probe(struct platform_device * dev)239 static int __init acq_probe(struct platform_device *dev)
240 {
241 	int ret;
242 
243 	if (wdt_stop != wdt_start) {
244 		if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
245 			pr_err("I/O address 0x%04x already in use\n", wdt_stop);
246 			ret = -EIO;
247 			goto out;
248 		}
249 	}
250 
251 	if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
252 		pr_err("I/O address 0x%04x already in use\n", wdt_start);
253 		ret = -EIO;
254 		goto unreg_stop;
255 	}
256 	ret = misc_register(&acq_miscdev);
257 	if (ret != 0) {
258 		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
259 		       WATCHDOG_MINOR, ret);
260 		goto unreg_regions;
261 	}
262 	pr_info("initialized. (nowayout=%d)\n", nowayout);
263 
264 	return 0;
265 unreg_regions:
266 	release_region(wdt_start, 1);
267 unreg_stop:
268 	if (wdt_stop != wdt_start)
269 		release_region(wdt_stop, 1);
270 out:
271 	return ret;
272 }
273 
acq_remove(struct platform_device * dev)274 static int acq_remove(struct platform_device *dev)
275 {
276 	misc_deregister(&acq_miscdev);
277 	release_region(wdt_start, 1);
278 	if (wdt_stop != wdt_start)
279 		release_region(wdt_stop, 1);
280 
281 	return 0;
282 }
283 
acq_shutdown(struct platform_device * dev)284 static void acq_shutdown(struct platform_device *dev)
285 {
286 	/* Turn the WDT off if we have a soft shutdown */
287 	acq_stop();
288 }
289 
290 static struct platform_driver acquirewdt_driver = {
291 	.remove		= acq_remove,
292 	.shutdown	= acq_shutdown,
293 	.driver		= {
294 		.name	= DRV_NAME,
295 	},
296 };
297 
acq_init(void)298 static int __init acq_init(void)
299 {
300 	int err;
301 
302 	pr_info("WDT driver for Acquire single board computer initialising\n");
303 
304 	acq_platform_device = platform_device_register_simple(DRV_NAME,
305 								-1, NULL, 0);
306 	if (IS_ERR(acq_platform_device))
307 		return PTR_ERR(acq_platform_device);
308 
309 	err = platform_driver_probe(&acquirewdt_driver, acq_probe);
310 	if (err)
311 		goto unreg_platform_device;
312 	return 0;
313 
314 unreg_platform_device:
315 	platform_device_unregister(acq_platform_device);
316 	return err;
317 }
318 
acq_exit(void)319 static void __exit acq_exit(void)
320 {
321 	platform_device_unregister(acq_platform_device);
322 	platform_driver_unregister(&acquirewdt_driver);
323 	pr_info("Watchdog Module Unloaded\n");
324 }
325 
326 module_init(acq_init);
327 module_exit(acq_exit);
328 
329 MODULE_AUTHOR("David Woodhouse");
330 MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
331 MODULE_LICENSE("GPL");
332