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