1// SPDX-License-Identifier: GPL-2.0
2/*
3 * SVC Greybus "watchdog" driver.
4 *
5 * Copyright 2016 Google Inc.
6 */
7
8#include <linux/delay.h>
9#include <linux/suspend.h>
10#include <linux/workqueue.h>
11#include <linux/greybus.h>
12
13#define SVC_WATCHDOG_PERIOD	(2 * HZ)
14
15struct gb_svc_watchdog {
16	struct delayed_work	work;
17	struct gb_svc		*svc;
18	bool			enabled;
19	struct notifier_block pm_notifier;
20};
21
22static struct delayed_work reset_work;
23
24static int svc_watchdog_pm_notifier(struct notifier_block *notifier,
25				    unsigned long pm_event, void *unused)
26{
27	struct gb_svc_watchdog *watchdog =
28		container_of(notifier, struct gb_svc_watchdog, pm_notifier);
29
30	switch (pm_event) {
31	case PM_SUSPEND_PREPARE:
32		gb_svc_watchdog_disable(watchdog->svc);
33		break;
34	case PM_POST_SUSPEND:
35		gb_svc_watchdog_enable(watchdog->svc);
36		break;
37	default:
38		break;
39	}
40
41	return NOTIFY_DONE;
42}
43
44static void greybus_reset(struct work_struct *work)
45{
46	static char const start_path[] = "/system/bin/start";
47	static char *envp[] = {
48		"HOME=/",
49		"PATH=/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin",
50		NULL,
51	};
52	static char *argv[] = {
53		(char *)start_path,
54		"unipro_reset",
55		NULL,
56	};
57
58	pr_err("svc_watchdog: calling \"%s %s\" to reset greybus network!\n",
59	       argv[0], argv[1]);
60	call_usermodehelper(start_path, argv, envp, UMH_WAIT_EXEC);
61}
62
63static void do_work(struct work_struct *work)
64{
65	struct gb_svc_watchdog *watchdog;
66	struct gb_svc *svc;
67	int retval;
68
69	watchdog = container_of(work, struct gb_svc_watchdog, work.work);
70	svc = watchdog->svc;
71
72	dev_dbg(&svc->dev, "%s: ping.\n", __func__);
73	retval = gb_svc_ping(svc);
74	if (retval) {
75		/*
76		 * Something went really wrong, let's warn userspace and then
77		 * pull the plug and reset the whole greybus network.
78		 * We need to do this outside of this workqueue as we will be
79		 * tearing down the svc device itself.  So queue up
80		 * yet-another-callback to do that.
81		 */
82		dev_err(&svc->dev,
83			"SVC ping has returned %d, something is wrong!!!\n",
84			retval);
85
86		if (svc->action == GB_SVC_WATCHDOG_BITE_PANIC_KERNEL) {
87			panic("SVC is not responding\n");
88		} else if (svc->action == GB_SVC_WATCHDOG_BITE_RESET_UNIPRO) {
89			dev_err(&svc->dev, "Resetting the greybus network, watch out!!!\n");
90
91			INIT_DELAYED_WORK(&reset_work, greybus_reset);
92			schedule_delayed_work(&reset_work, HZ / 2);
93
94			/*
95			 * Disable ourselves, we don't want to trip again unless
96			 * userspace wants us to.
97			 */
98			watchdog->enabled = false;
99		}
100	}
101
102	/* resubmit our work to happen again, if we are still "alive" */
103	if (watchdog->enabled)
104		schedule_delayed_work(&watchdog->work, SVC_WATCHDOG_PERIOD);
105}
106
107int gb_svc_watchdog_create(struct gb_svc *svc)
108{
109	struct gb_svc_watchdog *watchdog;
110	int retval;
111
112	if (svc->watchdog)
113		return 0;
114
115	watchdog = kmalloc(sizeof(*watchdog), GFP_KERNEL);
116	if (!watchdog)
117		return -ENOMEM;
118
119	watchdog->enabled = false;
120	watchdog->svc = svc;
121	INIT_DELAYED_WORK(&watchdog->work, do_work);
122	svc->watchdog = watchdog;
123
124	watchdog->pm_notifier.notifier_call = svc_watchdog_pm_notifier;
125	retval = register_pm_notifier(&watchdog->pm_notifier);
126	if (retval) {
127		dev_err(&svc->dev, "error registering pm notifier(%d)\n",
128			retval);
129		goto svc_watchdog_create_err;
130	}
131
132	retval = gb_svc_watchdog_enable(svc);
133	if (retval) {
134		dev_err(&svc->dev, "error enabling watchdog (%d)\n", retval);
135		unregister_pm_notifier(&watchdog->pm_notifier);
136		goto svc_watchdog_create_err;
137	}
138	return retval;
139
140svc_watchdog_create_err:
141	svc->watchdog = NULL;
142	kfree(watchdog);
143
144	return retval;
145}
146
147void gb_svc_watchdog_destroy(struct gb_svc *svc)
148{
149	struct gb_svc_watchdog *watchdog = svc->watchdog;
150
151	if (!watchdog)
152		return;
153
154	unregister_pm_notifier(&watchdog->pm_notifier);
155	gb_svc_watchdog_disable(svc);
156	svc->watchdog = NULL;
157	kfree(watchdog);
158}
159
160bool gb_svc_watchdog_enabled(struct gb_svc *svc)
161{
162	if (!svc || !svc->watchdog)
163		return false;
164	return svc->watchdog->enabled;
165}
166
167int gb_svc_watchdog_enable(struct gb_svc *svc)
168{
169	struct gb_svc_watchdog *watchdog;
170
171	if (!svc->watchdog)
172		return -ENODEV;
173
174	watchdog = svc->watchdog;
175	if (watchdog->enabled)
176		return 0;
177
178	watchdog->enabled = true;
179	schedule_delayed_work(&watchdog->work, SVC_WATCHDOG_PERIOD);
180	return 0;
181}
182
183int gb_svc_watchdog_disable(struct gb_svc *svc)
184{
185	struct gb_svc_watchdog *watchdog;
186
187	if (!svc->watchdog)
188		return -ENODEV;
189
190	watchdog = svc->watchdog;
191	if (!watchdog->enabled)
192		return 0;
193
194	watchdog->enabled = false;
195	cancel_delayed_work_sync(&watchdog->work);
196	return 0;
197}
198