1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Watchdog driver for Atmel AT91RM9200 (Thunder)
4  *
5  *  Copyright (C) 2003 SAN People (Pty) Ltd
6  *
7  */
8 
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10 
11 #include <linux/bitops.h>
12 #include <linux/delay.h>
13 #include <linux/errno.h>
14 #include <linux/fs.h>
15 #include <linux/init.h>
16 #include <linux/io.h>
17 #include <linux/kernel.h>
18 #include <linux/mfd/syscon.h>
19 #include <linux/mfd/syscon/atmel-st.h>
20 #include <linux/miscdevice.h>
21 #include <linux/module.h>
22 #include <linux/moduleparam.h>
23 #include <linux/platform_device.h>
24 #include <linux/reboot.h>
25 #include <linux/regmap.h>
26 #include <linux/types.h>
27 #include <linux/watchdog.h>
28 #include <linux/uaccess.h>
29 #include <linux/of.h>
30 #include <linux/of_device.h>
31 
32 #define WDT_DEFAULT_TIME	5	/* seconds */
33 #define WDT_MAX_TIME		256	/* seconds */
34 
35 static int wdt_time = WDT_DEFAULT_TIME;
36 static bool nowayout = WATCHDOG_NOWAYOUT;
37 static struct regmap *regmap_st;
38 
39 module_param(wdt_time, int, 0);
40 MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="
41 				__MODULE_STRING(WDT_DEFAULT_TIME) ")");
42 
43 #ifdef CONFIG_WATCHDOG_NOWAYOUT
44 module_param(nowayout, bool, 0);
45 MODULE_PARM_DESC(nowayout,
46 		"Watchdog cannot be stopped once started (default="
47 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
48 #endif
49 
50 
51 static unsigned long at91wdt_busy;
52 
53 /* ......................................................................... */
54 
55 static int at91rm9200_restart(struct notifier_block *this,
56 					unsigned long mode, void *cmd)
57 {
58 	/*
59 	 * Perform a hardware reset with the use of the Watchdog timer.
60 	 */
61 	regmap_write(regmap_st, AT91_ST_WDMR,
62 		     AT91_ST_RSTEN | AT91_ST_EXTEN | 1);
63 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
64 
65 	mdelay(2000);
66 
67 	pr_emerg("Unable to restart system\n");
68 	return NOTIFY_DONE;
69 }
70 
71 static struct notifier_block at91rm9200_restart_nb = {
72 	.notifier_call = at91rm9200_restart,
73 	.priority = 192,
74 };
75 
76 /*
77  * Disable the watchdog.
78  */
79 static inline void at91_wdt_stop(void)
80 {
81 	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN);
82 }
83 
84 /*
85  * Enable and reset the watchdog.
86  */
87 static inline void at91_wdt_start(void)
88 {
89 	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN |
90 				(((65536 * wdt_time) >> 8) & AT91_ST_WDV));
91 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
92 }
93 
94 /*
95  * Reload the watchdog timer.  (ie, pat the watchdog)
96  */
97 static inline void at91_wdt_reload(void)
98 {
99 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
100 }
101 
102 /* ......................................................................... */
103 
104 /*
105  * Watchdog device is opened, and watchdog starts running.
106  */
107 static int at91_wdt_open(struct inode *inode, struct file *file)
108 {
109 	if (test_and_set_bit(0, &at91wdt_busy))
110 		return -EBUSY;
111 
112 	at91_wdt_start();
113 	return nonseekable_open(inode, file);
114 }
115 
116 /*
117  * Close the watchdog device.
118  * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
119  *  disabled.
120  */
121 static int at91_wdt_close(struct inode *inode, struct file *file)
122 {
123 	/* Disable the watchdog when file is closed */
124 	if (!nowayout)
125 		at91_wdt_stop();
126 
127 	clear_bit(0, &at91wdt_busy);
128 	return 0;
129 }
130 
131 /*
132  * Change the watchdog time interval.
133  */
134 static int at91_wdt_settimeout(int new_time)
135 {
136 	/*
137 	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
138 	 *
139 	 * Since WDV is a 16-bit counter, the maximum period is
140 	 * 65536 / 256 = 256 seconds.
141 	 */
142 	if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
143 		return -EINVAL;
144 
145 	/* Set new watchdog time. It will be used when
146 	   at91_wdt_start() is called. */
147 	wdt_time = new_time;
148 	return 0;
149 }
150 
151 static const struct watchdog_info at91_wdt_info = {
152 	.identity	= "at91 watchdog",
153 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
154 };
155 
156 /*
157  * Handle commands from user-space.
158  */
159 static long at91_wdt_ioctl(struct file *file,
160 					unsigned int cmd, unsigned long arg)
161 {
162 	void __user *argp = (void __user *)arg;
163 	int __user *p = argp;
164 	int new_value;
165 
166 	switch (cmd) {
167 	case WDIOC_GETSUPPORT:
168 		return copy_to_user(argp, &at91_wdt_info,
169 				sizeof(at91_wdt_info)) ? -EFAULT : 0;
170 	case WDIOC_GETSTATUS:
171 	case WDIOC_GETBOOTSTATUS:
172 		return put_user(0, p);
173 	case WDIOC_SETOPTIONS:
174 		if (get_user(new_value, p))
175 			return -EFAULT;
176 		if (new_value & WDIOS_DISABLECARD)
177 			at91_wdt_stop();
178 		if (new_value & WDIOS_ENABLECARD)
179 			at91_wdt_start();
180 		return 0;
181 	case WDIOC_KEEPALIVE:
182 		at91_wdt_reload();	/* pat the watchdog */
183 		return 0;
184 	case WDIOC_SETTIMEOUT:
185 		if (get_user(new_value, p))
186 			return -EFAULT;
187 		if (at91_wdt_settimeout(new_value))
188 			return -EINVAL;
189 		/* Enable new time value */
190 		at91_wdt_start();
191 		/* Return current value */
192 		return put_user(wdt_time, p);
193 	case WDIOC_GETTIMEOUT:
194 		return put_user(wdt_time, p);
195 	default:
196 		return -ENOTTY;
197 	}
198 }
199 
200 /*
201  * Pat the watchdog whenever device is written to.
202  */
203 static ssize_t at91_wdt_write(struct file *file, const char *data,
204 						size_t len, loff_t *ppos)
205 {
206 	at91_wdt_reload();		/* pat the watchdog */
207 	return len;
208 }
209 
210 /* ......................................................................... */
211 
212 static const struct file_operations at91wdt_fops = {
213 	.owner		= THIS_MODULE,
214 	.llseek		= no_llseek,
215 	.unlocked_ioctl	= at91_wdt_ioctl,
216 	.open		= at91_wdt_open,
217 	.release	= at91_wdt_close,
218 	.write		= at91_wdt_write,
219 };
220 
221 static struct miscdevice at91wdt_miscdev = {
222 	.minor		= WATCHDOG_MINOR,
223 	.name		= "watchdog",
224 	.fops		= &at91wdt_fops,
225 };
226 
227 static int at91wdt_probe(struct platform_device *pdev)
228 {
229 	struct device *dev = &pdev->dev;
230 	struct device *parent;
231 	int res;
232 
233 	if (at91wdt_miscdev.parent)
234 		return -EBUSY;
235 	at91wdt_miscdev.parent = &pdev->dev;
236 
237 	parent = dev->parent;
238 	if (!parent) {
239 		dev_err(dev, "no parent\n");
240 		return -ENODEV;
241 	}
242 
243 	regmap_st = syscon_node_to_regmap(parent->of_node);
244 	if (IS_ERR(regmap_st))
245 		return -ENODEV;
246 
247 	res = misc_register(&at91wdt_miscdev);
248 	if (res)
249 		return res;
250 
251 	res = register_restart_handler(&at91rm9200_restart_nb);
252 	if (res)
253 		dev_warn(dev, "failed to register restart handler\n");
254 
255 	pr_info("AT91 Watchdog Timer enabled (%d seconds%s)\n",
256 		wdt_time, nowayout ? ", nowayout" : "");
257 	return 0;
258 }
259 
260 static int at91wdt_remove(struct platform_device *pdev)
261 {
262 	struct device *dev = &pdev->dev;
263 	int res;
264 
265 	res = unregister_restart_handler(&at91rm9200_restart_nb);
266 	if (res)
267 		dev_warn(dev, "failed to unregister restart handler\n");
268 
269 	misc_deregister(&at91wdt_miscdev);
270 	at91wdt_miscdev.parent = NULL;
271 
272 	return res;
273 }
274 
275 static void at91wdt_shutdown(struct platform_device *pdev)
276 {
277 	at91_wdt_stop();
278 }
279 
280 #ifdef CONFIG_PM
281 
282 static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
283 {
284 	at91_wdt_stop();
285 	return 0;
286 }
287 
288 static int at91wdt_resume(struct platform_device *pdev)
289 {
290 	if (at91wdt_busy)
291 		at91_wdt_start();
292 	return 0;
293 }
294 
295 #else
296 #define at91wdt_suspend NULL
297 #define at91wdt_resume	NULL
298 #endif
299 
300 static const struct of_device_id at91_wdt_dt_ids[] = {
301 	{ .compatible = "atmel,at91rm9200-wdt" },
302 	{ /* sentinel */ }
303 };
304 MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids);
305 
306 static struct platform_driver at91wdt_driver = {
307 	.probe		= at91wdt_probe,
308 	.remove		= at91wdt_remove,
309 	.shutdown	= at91wdt_shutdown,
310 	.suspend	= at91wdt_suspend,
311 	.resume		= at91wdt_resume,
312 	.driver		= {
313 		.name	= "atmel_st_watchdog",
314 		.of_match_table = at91_wdt_dt_ids,
315 	},
316 };
317 
318 static int __init at91_wdt_init(void)
319 {
320 	/* Check that the heartbeat value is within range;
321 	   if not reset to the default */
322 	if (at91_wdt_settimeout(wdt_time)) {
323 		at91_wdt_settimeout(WDT_DEFAULT_TIME);
324 		pr_info("wdt_time value must be 1 <= wdt_time <= 256, using %d\n",
325 			wdt_time);
326 	}
327 
328 	return platform_driver_register(&at91wdt_driver);
329 }
330 
331 static void __exit at91_wdt_exit(void)
332 {
333 	platform_driver_unregister(&at91wdt_driver);
334 }
335 
336 module_init(at91_wdt_init);
337 module_exit(at91_wdt_exit);
338 
339 MODULE_AUTHOR("Andrew Victor");
340 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
341 MODULE_LICENSE("GPL");
342 MODULE_ALIAS("platform:atmel_st_watchdog");
343