1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Watchdog driver for z/VM and LPAR using the diag 288 interface.
4  *
5  * Under z/VM, expiration of the watchdog will send a "system restart" command
6  * to CP.
7  *
8  * The command can be altered using the module parameter "cmd". This is
9  * not recommended because it's only supported on z/VM but not whith LPAR.
10  *
11  * On LPAR, the watchdog will always trigger a system restart. the module
12  * paramter cmd is meaningless here.
13  *
14  *
15  * Copyright IBM Corp. 2004, 2013
16  * Author(s): Arnd Bergmann (arndb@de.ibm.com)
17  *	      Philipp Hachtmann (phacht@de.ibm.com)
18  *
19  */
20 
21 #define KMSG_COMPONENT "diag288_wdt"
22 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
23 
24 #include <linux/init.h>
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/moduleparam.h>
28 #include <linux/slab.h>
29 #include <linux/miscdevice.h>
30 #include <linux/watchdog.h>
31 #include <linux/suspend.h>
32 #include <asm/ebcdic.h>
33 #include <asm/diag.h>
34 #include <linux/io.h>
35 #include <linux/uaccess.h>
36 
37 #define MAX_CMDLEN 240
38 #define DEFAULT_CMD "SYSTEM RESTART"
39 
40 #define MIN_INTERVAL 15     /* Minimal time supported by diag88 */
41 #define MAX_INTERVAL 3600   /* One hour should be enough - pure estimation */
42 
43 #define WDT_DEFAULT_TIMEOUT 30
44 
45 /* Function codes - init, change, cancel */
46 #define WDT_FUNC_INIT 0
47 #define WDT_FUNC_CHANGE 1
48 #define WDT_FUNC_CANCEL 2
49 #define WDT_FUNC_CONCEAL 0x80000000
50 
51 /* Action codes for LPAR watchdog */
52 #define LPARWDT_RESTART 0
53 
54 static char wdt_cmd[MAX_CMDLEN] = DEFAULT_CMD;
55 static bool conceal_on;
56 static bool nowayout_info = WATCHDOG_NOWAYOUT;
57 
58 MODULE_LICENSE("GPL");
59 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
60 MODULE_AUTHOR("Philipp Hachtmann <phacht@de.ibm.com>");
61 
62 MODULE_DESCRIPTION("System z diag288  Watchdog Timer");
63 
64 module_param_string(cmd, wdt_cmd, MAX_CMDLEN, 0644);
65 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers (z/VM only)");
66 
67 module_param_named(conceal, conceal_on, bool, 0644);
68 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog is active (z/VM only)");
69 
70 module_param_named(nowayout, nowayout_info, bool, 0444);
71 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default = CONFIG_WATCHDOG_NOWAYOUT)");
72 
73 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
74 MODULE_ALIAS("vmwatchdog");
75 
76 static int __diag288(unsigned int func, unsigned int timeout,
77 		     unsigned long action, unsigned int len)
78 {
79 	register unsigned long __func asm("2") = func;
80 	register unsigned long __timeout asm("3") = timeout;
81 	register unsigned long __action asm("4") = action;
82 	register unsigned long __len asm("5") = len;
83 	int err;
84 
85 	err = -EINVAL;
86 	asm volatile(
87 		"	diag	%1, %3, 0x288\n"
88 		"0:	la	%0, 0\n"
89 		"1:\n"
90 		EX_TABLE(0b, 1b)
91 		: "+d" (err) : "d"(__func), "d"(__timeout),
92 		  "d"(__action), "d"(__len) : "1", "cc");
93 	return err;
94 }
95 
96 static int __diag288_vm(unsigned int  func, unsigned int timeout,
97 			char *cmd, size_t len)
98 {
99 	diag_stat_inc(DIAG_STAT_X288);
100 	return __diag288(func, timeout, virt_to_phys(cmd), len);
101 }
102 
103 static int __diag288_lpar(unsigned int func, unsigned int timeout,
104 			  unsigned long action)
105 {
106 	diag_stat_inc(DIAG_STAT_X288);
107 	return __diag288(func, timeout, action, 0);
108 }
109 
110 static unsigned long wdt_status;
111 
112 #define DIAG_WDOG_BUSY	0
113 
114 static int wdt_start(struct watchdog_device *dev)
115 {
116 	char *ebc_cmd;
117 	size_t len;
118 	int ret;
119 	unsigned int func;
120 
121 	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status))
122 		return -EBUSY;
123 
124 	ret = -ENODEV;
125 
126 	if (MACHINE_IS_VM) {
127 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
128 		if (!ebc_cmd) {
129 			clear_bit(DIAG_WDOG_BUSY, &wdt_status);
130 			return -ENOMEM;
131 		}
132 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
133 		ASCEBC(ebc_cmd, MAX_CMDLEN);
134 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
135 
136 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
137 			: WDT_FUNC_INIT;
138 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
139 		WARN_ON(ret != 0);
140 		kfree(ebc_cmd);
141 	} else {
142 		ret = __diag288_lpar(WDT_FUNC_INIT,
143 				     dev->timeout, LPARWDT_RESTART);
144 	}
145 
146 	if (ret) {
147 		pr_err("The watchdog cannot be activated\n");
148 		clear_bit(DIAG_WDOG_BUSY, &wdt_status);
149 		return ret;
150 	}
151 	return 0;
152 }
153 
154 static int wdt_stop(struct watchdog_device *dev)
155 {
156 	int ret;
157 
158 	diag_stat_inc(DIAG_STAT_X288);
159 	ret = __diag288(WDT_FUNC_CANCEL, 0, 0, 0);
160 
161 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
162 
163 	return ret;
164 }
165 
166 static int wdt_ping(struct watchdog_device *dev)
167 {
168 	char *ebc_cmd;
169 	size_t len;
170 	int ret;
171 	unsigned int func;
172 
173 	ret = -ENODEV;
174 
175 	if (MACHINE_IS_VM) {
176 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
177 		if (!ebc_cmd)
178 			return -ENOMEM;
179 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
180 		ASCEBC(ebc_cmd, MAX_CMDLEN);
181 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
182 
183 		/*
184 		 * It seems to be ok to z/VM to use the init function to
185 		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
186 		 * be used when the watchdog is running.
187 		 */
188 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
189 			: WDT_FUNC_INIT;
190 
191 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
192 		WARN_ON(ret != 0);
193 		kfree(ebc_cmd);
194 	} else {
195 		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
196 	}
197 
198 	if (ret)
199 		pr_err("The watchdog timer cannot be started or reset\n");
200 	return ret;
201 }
202 
203 static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
204 {
205 	dev->timeout = new_to;
206 	return wdt_ping(dev);
207 }
208 
209 static const struct watchdog_ops wdt_ops = {
210 	.owner = THIS_MODULE,
211 	.start = wdt_start,
212 	.stop = wdt_stop,
213 	.ping = wdt_ping,
214 	.set_timeout = wdt_set_timeout,
215 };
216 
217 static const struct watchdog_info wdt_info = {
218 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
219 	.firmware_version = 0,
220 	.identity = "z Watchdog",
221 };
222 
223 static struct watchdog_device wdt_dev = {
224 	.parent = NULL,
225 	.info = &wdt_info,
226 	.ops = &wdt_ops,
227 	.bootstatus = 0,
228 	.timeout = WDT_DEFAULT_TIMEOUT,
229 	.min_timeout = MIN_INTERVAL,
230 	.max_timeout = MAX_INTERVAL,
231 };
232 
233 /*
234  * It makes no sense to go into suspend while the watchdog is running.
235  * Depending on the memory size, the watchdog might trigger, while we
236  * are still saving the memory.
237  */
238 static int wdt_suspend(void)
239 {
240 	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status)) {
241 		pr_err("Linux cannot be suspended while the watchdog is in use\n");
242 		return notifier_from_errno(-EBUSY);
243 	}
244 	return NOTIFY_DONE;
245 }
246 
247 static int wdt_resume(void)
248 {
249 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
250 	return NOTIFY_DONE;
251 }
252 
253 static int wdt_power_event(struct notifier_block *this, unsigned long event,
254 			   void *ptr)
255 {
256 	switch (event) {
257 	case PM_POST_HIBERNATION:
258 	case PM_POST_SUSPEND:
259 		return wdt_resume();
260 	case PM_HIBERNATION_PREPARE:
261 	case PM_SUSPEND_PREPARE:
262 		return wdt_suspend();
263 	default:
264 		return NOTIFY_DONE;
265 	}
266 }
267 
268 static struct notifier_block wdt_power_notifier = {
269 	.notifier_call = wdt_power_event,
270 };
271 
272 static int __init diag288_init(void)
273 {
274 	int ret;
275 	char ebc_begin[] = {
276 		194, 197, 199, 201, 213
277 	};
278 
279 	watchdog_set_nowayout(&wdt_dev, nowayout_info);
280 
281 	if (MACHINE_IS_VM) {
282 		if (__diag288_vm(WDT_FUNC_INIT, 15,
283 				 ebc_begin, sizeof(ebc_begin)) != 0) {
284 			pr_err("The watchdog cannot be initialized\n");
285 			return -EINVAL;
286 		}
287 	} else {
288 		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
289 			pr_err("The watchdog cannot be initialized\n");
290 			return -EINVAL;
291 		}
292 	}
293 
294 	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {
295 		pr_err("The watchdog cannot be deactivated\n");
296 		return -EINVAL;
297 	}
298 
299 	ret = register_pm_notifier(&wdt_power_notifier);
300 	if (ret)
301 		return ret;
302 
303 	ret = watchdog_register_device(&wdt_dev);
304 	if (ret)
305 		unregister_pm_notifier(&wdt_power_notifier);
306 
307 	return ret;
308 }
309 
310 static void __exit diag288_exit(void)
311 {
312 	watchdog_unregister_device(&wdt_dev);
313 	unregister_pm_notifier(&wdt_power_notifier);
314 }
315 
316 module_init(diag288_init);
317 module_exit(diag288_exit);
318