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 int wdt_start(struct watchdog_device *dev)
110 {
111 	char *ebc_cmd;
112 	size_t len;
113 	int ret;
114 	unsigned int func;
115 
116 	ret = -ENODEV;
117 
118 	if (MACHINE_IS_VM) {
119 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
120 		if (!ebc_cmd)
121 			return -ENOMEM;
122 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
123 		ASCEBC(ebc_cmd, MAX_CMDLEN);
124 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
125 
126 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
127 			: WDT_FUNC_INIT;
128 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
129 		WARN_ON(ret != 0);
130 		kfree(ebc_cmd);
131 	} else {
132 		ret = __diag288_lpar(WDT_FUNC_INIT,
133 				     dev->timeout, LPARWDT_RESTART);
134 	}
135 
136 	if (ret) {
137 		pr_err("The watchdog cannot be activated\n");
138 		return ret;
139 	}
140 	return 0;
141 }
142 
143 static int wdt_stop(struct watchdog_device *dev)
144 {
145 	int ret;
146 
147 	diag_stat_inc(DIAG_STAT_X288);
148 	ret = __diag288(WDT_FUNC_CANCEL, 0, 0, 0);
149 	return ret;
150 }
151 
152 static int wdt_ping(struct watchdog_device *dev)
153 {
154 	char *ebc_cmd;
155 	size_t len;
156 	int ret;
157 	unsigned int func;
158 
159 	ret = -ENODEV;
160 
161 	if (MACHINE_IS_VM) {
162 		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
163 		if (!ebc_cmd)
164 			return -ENOMEM;
165 		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
166 		ASCEBC(ebc_cmd, MAX_CMDLEN);
167 		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
168 
169 		/*
170 		 * It seems to be ok to z/VM to use the init function to
171 		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
172 		 * be used when the watchdog is running.
173 		 */
174 		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
175 			: WDT_FUNC_INIT;
176 
177 		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
178 		WARN_ON(ret != 0);
179 		kfree(ebc_cmd);
180 	} else {
181 		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
182 	}
183 
184 	if (ret)
185 		pr_err("The watchdog timer cannot be started or reset\n");
186 	return ret;
187 }
188 
189 static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
190 {
191 	dev->timeout = new_to;
192 	return wdt_ping(dev);
193 }
194 
195 static struct watchdog_ops wdt_ops = {
196 	.owner = THIS_MODULE,
197 	.start = wdt_start,
198 	.stop = wdt_stop,
199 	.ping = wdt_ping,
200 	.set_timeout = wdt_set_timeout,
201 };
202 
203 static struct watchdog_info wdt_info = {
204 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
205 	.firmware_version = 0,
206 	.identity = "z Watchdog",
207 };
208 
209 static struct watchdog_device wdt_dev = {
210 	.parent = NULL,
211 	.info = &wdt_info,
212 	.ops = &wdt_ops,
213 	.bootstatus = 0,
214 	.timeout = WDT_DEFAULT_TIMEOUT,
215 	.min_timeout = MIN_INTERVAL,
216 	.max_timeout = MAX_INTERVAL,
217 };
218 
219 /*
220  * It makes no sense to go into suspend while the watchdog is running.
221  * Depending on the memory size, the watchdog might trigger, while we
222  * are still saving the memory.
223  * We reuse the open flag to ensure that suspend and watchdog open are
224  * exclusive operations
225  */
226 static int wdt_suspend(void)
227 {
228 	if (test_and_set_bit(WDOG_DEV_OPEN, &wdt_dev.status)) {
229 		pr_err("Linux cannot be suspended while the watchdog is in use\n");
230 		return notifier_from_errno(-EBUSY);
231 	}
232 	if (test_bit(WDOG_ACTIVE, &wdt_dev.status)) {
233 		clear_bit(WDOG_DEV_OPEN, &wdt_dev.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(WDOG_DEV_OPEN, &wdt_dev.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 
272 	watchdog_set_nowayout(&wdt_dev, nowayout_info);
273 
274 	if (MACHINE_IS_VM) {
275 		if (__diag288_vm(WDT_FUNC_INIT, 15,
276 				 ebc_begin, sizeof(ebc_begin)) != 0) {
277 			pr_err("The watchdog cannot be initialized\n");
278 			return -EINVAL;
279 		}
280 	} else {
281 		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
282 			pr_err("The watchdog cannot be initialized\n");
283 			return -EINVAL;
284 		}
285 	}
286 
287 	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {
288 		pr_err("The watchdog cannot be deactivated\n");
289 		return -EINVAL;
290 	}
291 
292 	ret = register_pm_notifier(&wdt_power_notifier);
293 	if (ret)
294 		return ret;
295 
296 	ret = watchdog_register_device(&wdt_dev);
297 	if (ret)
298 		unregister_pm_notifier(&wdt_power_notifier);
299 
300 	return ret;
301 }
302 
303 static void __exit diag288_exit(void)
304 {
305 	watchdog_unregister_device(&wdt_dev);
306 	unregister_pm_notifier(&wdt_power_notifier);
307 }
308 
309 module_init(diag288_init);
310 module_exit(diag288_exit);
311