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/watchdog.h>
30 #include <linux/suspend.h>
31 #include <asm/ebcdic.h>
32 #include <asm/diag.h>
33 #include <linux/io.h>
34 
35 #define MAX_CMDLEN 240
36 #define DEFAULT_CMD "SYSTEM RESTART"
37 
38 #define MIN_INTERVAL 15     /* Minimal time supported by diag88 */
39 #define MAX_INTERVAL 3600   /* One hour should be enough - pure estimation */
40 
41 #define WDT_DEFAULT_TIMEOUT 30
42 
43 /* Function codes - init, change, cancel */
44 #define WDT_FUNC_INIT 0
45 #define WDT_FUNC_CHANGE 1
46 #define WDT_FUNC_CANCEL 2
47 #define WDT_FUNC_CONCEAL 0x80000000
48 
49 /* Action codes for LPAR watchdog */
50 #define LPARWDT_RESTART 0
51 
52 static char wdt_cmd[MAX_CMDLEN] = DEFAULT_CMD;
53 static bool conceal_on;
54 static bool nowayout_info = WATCHDOG_NOWAYOUT;
55 
56 MODULE_LICENSE("GPL");
57 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
58 MODULE_AUTHOR("Philipp Hachtmann <phacht@de.ibm.com>");
59 
60 MODULE_DESCRIPTION("System z diag288  Watchdog Timer");
61 
62 module_param_string(cmd, wdt_cmd, MAX_CMDLEN, 0644);
63 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers (z/VM only)");
64 
65 module_param_named(conceal, conceal_on, bool, 0644);
66 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog is active (z/VM only)");
67 
68 module_param_named(nowayout, nowayout_info, bool, 0444);
69 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default = CONFIG_WATCHDOG_NOWAYOUT)");
70 
71 MODULE_ALIAS("vmwatchdog");
72 
73 static int __diag288(unsigned int func, unsigned int timeout,
74 		     unsigned long action, unsigned int len)
75 {
76 	register unsigned long __func asm("2") = func;
77 	register unsigned long __timeout asm("3") = timeout;
78 	register unsigned long __action asm("4") = action;
79 	register unsigned long __len asm("5") = len;
80 	int err;
81 
82 	err = -EINVAL;
83 	asm volatile(
84 		"	diag	%1, %3, 0x288\n"
85 		"0:	la	%0, 0\n"
86 		"1:\n"
87 		EX_TABLE(0b, 1b)
88 		: "+d" (err) : "d"(__func), "d"(__timeout),
89 		  "d"(__action), "d"(__len) : "1", "cc", "memory");
90 	return err;
91 }
92 
93 static int __diag288_vm(unsigned int  func, unsigned int timeout,
94 			char *cmd, size_t len)
95 {
96 	diag_stat_inc(DIAG_STAT_X288);
97 	return __diag288(func, timeout, virt_to_phys(cmd), len);
98 }
99 
100 static int __diag288_lpar(unsigned int func, unsigned int timeout,
101 			  unsigned long action)
102 {
103 	diag_stat_inc(DIAG_STAT_X288);
104 	return __diag288(func, timeout, action, 0);
105 }
106 
107 static unsigned long wdt_status;
108 
109 #define DIAG_WDOG_BUSY	0
110 
111 static int wdt_start(struct watchdog_device *dev)
112 {
113 	char *ebc_cmd;
114 	size_t len;
115 	int ret;
116 	unsigned int func;
117 
118 	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status))
119 		return -EBUSY;
120 
121 	if (MACHINE_IS_VM) {
122 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
123 		if (!ebc_cmd) {
124 			clear_bit(DIAG_WDOG_BUSY, &wdt_status);
125 			return -ENOMEM;
126 		}
127 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
128 		ASCEBC(ebc_cmd, MAX_CMDLEN);
129 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
130 
131 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
132 			: WDT_FUNC_INIT;
133 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
134 		WARN_ON(ret != 0);
135 		kfree(ebc_cmd);
136 	} else {
137 		ret = __diag288_lpar(WDT_FUNC_INIT,
138 				     dev->timeout, LPARWDT_RESTART);
139 	}
140 
141 	if (ret) {
142 		pr_err("The watchdog cannot be activated\n");
143 		clear_bit(DIAG_WDOG_BUSY, &wdt_status);
144 		return ret;
145 	}
146 	return 0;
147 }
148 
149 static int wdt_stop(struct watchdog_device *dev)
150 {
151 	int ret;
152 
153 	diag_stat_inc(DIAG_STAT_X288);
154 	ret = __diag288(WDT_FUNC_CANCEL, 0, 0, 0);
155 
156 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
157 
158 	return ret;
159 }
160 
161 static int wdt_ping(struct watchdog_device *dev)
162 {
163 	char *ebc_cmd;
164 	size_t len;
165 	int ret;
166 	unsigned int func;
167 
168 	if (MACHINE_IS_VM) {
169 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
170 		if (!ebc_cmd)
171 			return -ENOMEM;
172 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
173 		ASCEBC(ebc_cmd, MAX_CMDLEN);
174 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
175 
176 		/*
177 		 * It seems to be ok to z/VM to use the init function to
178 		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
179 		 * be used when the watchdog is running.
180 		 */
181 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
182 			: WDT_FUNC_INIT;
183 
184 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
185 		WARN_ON(ret != 0);
186 		kfree(ebc_cmd);
187 	} else {
188 		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
189 	}
190 
191 	if (ret)
192 		pr_err("The watchdog timer cannot be started or reset\n");
193 	return ret;
194 }
195 
196 static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
197 {
198 	dev->timeout = new_to;
199 	return wdt_ping(dev);
200 }
201 
202 static const struct watchdog_ops wdt_ops = {
203 	.owner = THIS_MODULE,
204 	.start = wdt_start,
205 	.stop = wdt_stop,
206 	.ping = wdt_ping,
207 	.set_timeout = wdt_set_timeout,
208 };
209 
210 static const struct watchdog_info wdt_info = {
211 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
212 	.firmware_version = 0,
213 	.identity = "z Watchdog",
214 };
215 
216 static struct watchdog_device wdt_dev = {
217 	.parent = NULL,
218 	.info = &wdt_info,
219 	.ops = &wdt_ops,
220 	.bootstatus = 0,
221 	.timeout = WDT_DEFAULT_TIMEOUT,
222 	.min_timeout = MIN_INTERVAL,
223 	.max_timeout = MAX_INTERVAL,
224 };
225 
226 /*
227  * It makes no sense to go into suspend while the watchdog is running.
228  * Depending on the memory size, the watchdog might trigger, while we
229  * are still saving the memory.
230  */
231 static int wdt_suspend(void)
232 {
233 	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status)) {
234 		pr_err("Linux cannot be suspended while the watchdog is in use\n");
235 		return notifier_from_errno(-EBUSY);
236 	}
237 	return NOTIFY_DONE;
238 }
239 
240 static int wdt_resume(void)
241 {
242 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
243 	return NOTIFY_DONE;
244 }
245 
246 static int wdt_power_event(struct notifier_block *this, unsigned long event,
247 			   void *ptr)
248 {
249 	switch (event) {
250 	case PM_POST_HIBERNATION:
251 	case PM_POST_SUSPEND:
252 		return wdt_resume();
253 	case PM_HIBERNATION_PREPARE:
254 	case PM_SUSPEND_PREPARE:
255 		return wdt_suspend();
256 	default:
257 		return NOTIFY_DONE;
258 	}
259 }
260 
261 static struct notifier_block wdt_power_notifier = {
262 	.notifier_call = wdt_power_event,
263 };
264 
265 static int __init diag288_init(void)
266 {
267 	int ret;
268 	char ebc_begin[] = {
269 		194, 197, 199, 201, 213
270 	};
271 	char *ebc_cmd;
272 
273 	watchdog_set_nowayout(&wdt_dev, nowayout_info);
274 
275 	if (MACHINE_IS_VM) {
276 		ebc_cmd = kmalloc(sizeof(ebc_begin), GFP_KERNEL);
277 		if (!ebc_cmd) {
278 			pr_err("The watchdog cannot be initialized\n");
279 			return -ENOMEM;
280 		}
281 		memcpy(ebc_cmd, ebc_begin, sizeof(ebc_begin));
282 		ret = __diag288_vm(WDT_FUNC_INIT, 15,
283 				   ebc_cmd, sizeof(ebc_begin));
284 		kfree(ebc_cmd);
285 		if (ret != 0) {
286 			pr_err("The watchdog cannot be initialized\n");
287 			return -EINVAL;
288 		}
289 	} else {
290 		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
291 			pr_err("The watchdog cannot be initialized\n");
292 			return -EINVAL;
293 		}
294 	}
295 
296 	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {
297 		pr_err("The watchdog cannot be deactivated\n");
298 		return -EINVAL;
299 	}
300 
301 	ret = register_pm_notifier(&wdt_power_notifier);
302 	if (ret)
303 		return ret;
304 
305 	ret = watchdog_register_device(&wdt_dev);
306 	if (ret)
307 		unregister_pm_notifier(&wdt_power_notifier);
308 
309 	return ret;
310 }
311 
312 static void __exit diag288_exit(void)
313 {
314 	watchdog_unregister_device(&wdt_dev);
315 	unregister_pm_notifier(&wdt_power_notifier);
316 }
317 
318 module_init(diag288_init);
319 module_exit(diag288_exit);
320