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