Merge remote-tracking branch 'stable/linux-5.15.y' into rpi-5.15.y
[platform/kernel/linux-rpi.git] / drivers / watchdog / softdog.c
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *      SoftDog:        A Software Watchdog Device
4  *
5  *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
6  *                                                      All Rights Reserved.
7  *
8  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
9  *      warranty for any of this software. This material is provided
10  *      "AS-IS" and at no charge.
11  *
12  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
13  *
14  *      Software only watchdog driver. Unlike its big brother the WDT501P
15  *      driver this won't always recover a failed machine.
16  */
17
18 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20 #include <linux/hrtimer.h>
21 #include <linux/init.h>
22 #include <linux/kernel.h>
23 #include <linux/kthread.h>
24 #include <linux/module.h>
25 #include <linux/moduleparam.h>
26 #include <linux/reboot.h>
27 #include <linux/types.h>
28 #include <linux/watchdog.h>
29 #include <linux/workqueue.h>
30
31 #define TIMER_MARGIN    60              /* Default is 60 seconds */
32 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
33 module_param(soft_margin, uint, 0);
34 MODULE_PARM_DESC(soft_margin,
35         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
36                                         __MODULE_STRING(TIMER_MARGIN) ")");
37
38 static bool nowayout = WATCHDOG_NOWAYOUT;
39 module_param(nowayout, bool, 0);
40 MODULE_PARM_DESC(nowayout,
41                 "Watchdog cannot be stopped once started (default="
42                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
43
44 static int soft_noboot;
45 module_param(soft_noboot, int, 0);
46 MODULE_PARM_DESC(soft_noboot,
47         "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
48
49 static int soft_panic;
50 module_param(soft_panic, int, 0);
51 MODULE_PARM_DESC(soft_panic,
52         "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
53
54 static char *soft_reboot_cmd;
55 module_param(soft_reboot_cmd, charp, 0000);
56 MODULE_PARM_DESC(soft_reboot_cmd,
57         "Set reboot command. Emergency reboot takes place if unset");
58
59 static bool soft_active_on_boot;
60 module_param(soft_active_on_boot, bool, 0000);
61 MODULE_PARM_DESC(soft_active_on_boot,
62         "Set to true to active Softdog on boot (default=false)");
63
64 static struct hrtimer softdog_ticktock;
65 static struct hrtimer softdog_preticktock;
66
67 static int reboot_kthread_fn(void *data)
68 {
69         kernel_restart(soft_reboot_cmd);
70         return -EPERM; /* Should not reach here */
71 }
72
73 static void reboot_work_fn(struct work_struct *unused)
74 {
75         kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");
76 }
77
78 static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
79 {
80         static bool soft_reboot_fired;
81
82         module_put(THIS_MODULE);
83         if (soft_noboot) {
84                 pr_crit("Triggered - Reboot ignored\n");
85         } else if (soft_panic) {
86                 pr_crit("Initiating panic\n");
87                 panic("Software Watchdog Timer expired");
88         } else {
89                 pr_crit("Initiating system reboot\n");
90                 if (!soft_reboot_fired && soft_reboot_cmd != NULL) {
91                         static DECLARE_WORK(reboot_work, reboot_work_fn);
92                         /*
93                          * The 'kernel_restart' is a 'might-sleep' operation.
94                          * Also, executing it in system-wide workqueues blocks
95                          * any driver from using the same workqueue in its
96                          * shutdown callback function. Thus, we should execute
97                          * the 'kernel_restart' in a standalone kernel thread.
98                          * But since starting a kernel thread is also a
99                          * 'might-sleep' operation, so the 'reboot_work' is
100                          * required as a launcher of the kernel thread.
101                          *
102                          * After request the reboot, restart the timer to
103                          * schedule an 'emergency_restart' reboot after
104                          * 'TIMER_MARGIN' seconds. It's because if the softdog
105                          * hangs, it might be because of scheduling issues. And
106                          * if that is the case, both 'schedule_work' and
107                          * 'kernel_restart' may possibly be malfunctional at the
108                          * same time.
109                          */
110                         soft_reboot_fired = true;
111                         schedule_work(&reboot_work);
112                         hrtimer_add_expires_ns(timer,
113                                         (u64)TIMER_MARGIN * NSEC_PER_SEC);
114
115                         return HRTIMER_RESTART;
116                 }
117                 emergency_restart();
118                 pr_crit("Reboot didn't ?????\n");
119         }
120
121         return HRTIMER_NORESTART;
122 }
123
124 static struct watchdog_device softdog_dev;
125
126 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
127 {
128         watchdog_notify_pretimeout(&softdog_dev);
129
130         return HRTIMER_NORESTART;
131 }
132
133 static int softdog_ping(struct watchdog_device *w)
134 {
135         if (!hrtimer_active(&softdog_ticktock))
136                 __module_get(THIS_MODULE);
137         hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
138                       HRTIMER_MODE_REL);
139
140         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
141                 if (w->pretimeout)
142                         hrtimer_start(&softdog_preticktock,
143                                       ktime_set(w->timeout - w->pretimeout, 0),
144                                       HRTIMER_MODE_REL);
145                 else
146                         hrtimer_cancel(&softdog_preticktock);
147         }
148
149         return 0;
150 }
151
152 static int softdog_stop(struct watchdog_device *w)
153 {
154         if (hrtimer_cancel(&softdog_ticktock))
155                 module_put(THIS_MODULE);
156
157         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
158                 hrtimer_cancel(&softdog_preticktock);
159
160         return 0;
161 }
162
163 static struct watchdog_info softdog_info = {
164         .identity = "Software Watchdog",
165         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
166 };
167
168 static const struct watchdog_ops softdog_ops = {
169         .owner = THIS_MODULE,
170         .start = softdog_ping,
171         .stop = softdog_stop,
172 };
173
174 static struct watchdog_device softdog_dev = {
175         .info = &softdog_info,
176         .ops = &softdog_ops,
177         .min_timeout = 1,
178         .max_timeout = 65535,
179         .timeout = TIMER_MARGIN,
180 };
181
182 static int __init softdog_init(void)
183 {
184         int ret;
185
186         watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
187         watchdog_set_nowayout(&softdog_dev, nowayout);
188         watchdog_stop_on_reboot(&softdog_dev);
189
190         hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
191         softdog_ticktock.function = softdog_fire;
192
193         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
194                 softdog_info.options |= WDIOF_PRETIMEOUT;
195                 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
196                              HRTIMER_MODE_REL);
197                 softdog_preticktock.function = softdog_pretimeout;
198         }
199
200         if (soft_active_on_boot)
201                 softdog_ping(&softdog_dev);
202
203         ret = watchdog_register_device(&softdog_dev);
204         if (ret)
205                 return ret;
206
207         pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
208                 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
209         pr_info("             soft_reboot_cmd=%s soft_active_on_boot=%d\n",
210                 soft_reboot_cmd ?: "<not set>", soft_active_on_boot);
211
212         return 0;
213 }
214 module_init(softdog_init);
215
216 static void __exit softdog_exit(void)
217 {
218         watchdog_unregister_device(&softdog_dev);
219 }
220 module_exit(softdog_exit);
221
222 MODULE_AUTHOR("Alan Cox");
223 MODULE_DESCRIPTION("Software Watchdog Device Driver");
224 MODULE_LICENSE("GPL");