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");
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 	ret = -ENODEV;
122 
123 	if (MACHINE_IS_VM) {
124 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
125 		if (!ebc_cmd) {
126 			clear_bit(DIAG_WDOG_BUSY, &wdt_status);
127 			return -ENOMEM;
128 		}
129 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
130 		ASCEBC(ebc_cmd, MAX_CMDLEN);
131 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
132 
133 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
134 			: WDT_FUNC_INIT;
135 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
136 		WARN_ON(ret != 0);
137 		kfree(ebc_cmd);
138 	} else {
139 		ret = __diag288_lpar(WDT_FUNC_INIT,
140 				     dev->timeout, LPARWDT_RESTART);
141 	}
142 
143 	if (ret) {
144 		pr_err("The watchdog cannot be activated\n");
145 		clear_bit(DIAG_WDOG_BUSY, &wdt_status);
146 		return ret;
147 	}
148 	return 0;
149 }
150 
151 static int wdt_stop(struct watchdog_device *dev)
152 {
153 	int ret;
154 
155 	diag_stat_inc(DIAG_STAT_X288);
156 	ret = __diag288(WDT_FUNC_CANCEL, 0, 0, 0);
157 
158 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
159 
160 	return ret;
161 }
162 
163 static int wdt_ping(struct watchdog_device *dev)
164 {
165 	char *ebc_cmd;
166 	size_t len;
167 	int ret;
168 	unsigned int func;
169 
170 	ret = -ENODEV;
171 
172 	if (MACHINE_IS_VM) {
173 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
174 		if (!ebc_cmd)
175 			return -ENOMEM;
176 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
177 		ASCEBC(ebc_cmd, MAX_CMDLEN);
178 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
179 
180 		/*
181 		 * It seems to be ok to z/VM to use the init function to
182 		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
183 		 * be used when the watchdog is running.
184 		 */
185 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
186 			: WDT_FUNC_INIT;
187 
188 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
189 		WARN_ON(ret != 0);
190 		kfree(ebc_cmd);
191 	} else {
192 		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
193 	}
194 
195 	if (ret)
196 		pr_err("The watchdog timer cannot be started or reset\n");
197 	return ret;
198 }
199 
200 static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
201 {
202 	dev->timeout = new_to;
203 	return wdt_ping(dev);
204 }
205 
206 static const struct watchdog_ops wdt_ops = {
207 	.owner = THIS_MODULE,
208 	.start = wdt_start,
209 	.stop = wdt_stop,
210 	.ping = wdt_ping,
211 	.set_timeout = wdt_set_timeout,
212 };
213 
214 static const struct watchdog_info wdt_info = {
215 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
216 	.firmware_version = 0,
217 	.identity = "z Watchdog",
218 };
219 
220 static struct watchdog_device wdt_dev = {
221 	.parent = NULL,
222 	.info = &wdt_info,
223 	.ops = &wdt_ops,
224 	.bootstatus = 0,
225 	.timeout = WDT_DEFAULT_TIMEOUT,
226 	.min_timeout = MIN_INTERVAL,
227 	.max_timeout = MAX_INTERVAL,
228 };
229 
230 /*
231  * It makes no sense to go into suspend while the watchdog is running.
232  * Depending on the memory size, the watchdog might trigger, while we
233  * are still saving the memory.
234  */
235 static int wdt_suspend(void)
236 {
237 	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status)) {
238 		pr_err("Linux cannot be suspended while the watchdog is in use\n");
239 		return notifier_from_errno(-EBUSY);
240 	}
241 	return NOTIFY_DONE;
242 }
243 
244 static int wdt_resume(void)
245 {
246 	clear_bit(DIAG_WDOG_BUSY, &wdt_status);
247 	return NOTIFY_DONE;
248 }
249 
250 static int wdt_power_event(struct notifier_block *this, unsigned long event,
251 			   void *ptr)
252 {
253 	switch (event) {
254 	case PM_POST_HIBERNATION:
255 	case PM_POST_SUSPEND:
256 		return wdt_resume();
257 	case PM_HIBERNATION_PREPARE:
258 	case PM_SUSPEND_PREPARE:
259 		return wdt_suspend();
260 	default:
261 		return NOTIFY_DONE;
262 	}
263 }
264 
265 static struct notifier_block wdt_power_notifier = {
266 	.notifier_call = wdt_power_event,
267 };
268 
269 static int __init diag288_init(void)
270 {
271 	int ret;
272 	char ebc_begin[] = {
273 		194, 197, 199, 201, 213
274 	};
275 
276 	watchdog_set_nowayout(&wdt_dev, nowayout_info);
277 
278 	if (MACHINE_IS_VM) {
279 		if (__diag288_vm(WDT_FUNC_INIT, 15,
280 				 ebc_begin, sizeof(ebc_begin)) != 0) {
281 			pr_err("The watchdog cannot be initialized\n");
282 			return -EINVAL;
283 		}
284 	} else {
285 		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
286 			pr_err("The watchdog cannot be initialized\n");
287 			return -EINVAL;
288 		}
289 	}
290 
291 	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {
292 		pr_err("The watchdog cannot be deactivated\n");
293 		return -EINVAL;
294 	}
295 
296 	ret = register_pm_notifier(&wdt_power_notifier);
297 	if (ret)
298 		return ret;
299 
300 	ret = watchdog_register_device(&wdt_dev);
301 	if (ret)
302 		unregister_pm_notifier(&wdt_power_notifier);
303 
304 	return ret;
305 }
306 
307 static void __exit diag288_exit(void)
308 {
309 	watchdog_unregister_device(&wdt_dev);
310 	unregister_pm_notifier(&wdt_power_notifier);
311 }
312 
313 module_init(diag288_init);
314 module_exit(diag288_exit);
315