1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	Xen Watchdog Driver
4 *
5 *	(c) Copyright 2010 Novell, Inc.
6 */
7
8#define DRV_NAME	"xen_wdt"
9
10#include <linux/bug.h>
11#include <linux/errno.h>
12#include <linux/fs.h>
13#include <linux/hrtimer.h>
14#include <linux/kernel.h>
15#include <linux/ktime.h>
16#include <linux/init.h>
17#include <linux/module.h>
18#include <linux/moduleparam.h>
19#include <linux/platform_device.h>
20#include <linux/watchdog.h>
21#include <xen/xen.h>
22#include <asm/xen/hypercall.h>
23#include <xen/interface/sched.h>
24
25static struct platform_device *platform_device;
26static struct sched_watchdog wdt;
27static time64_t wdt_expires;
28
29#define WATCHDOG_TIMEOUT 60 /* in seconds */
30static unsigned int timeout;
31module_param(timeout, uint, S_IRUGO);
32MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
33	"(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
34
35static bool nowayout = WATCHDOG_NOWAYOUT;
36module_param(nowayout, bool, S_IRUGO);
37MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
38	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
39
40static inline time64_t set_timeout(struct watchdog_device *wdd)
41{
42	wdt.timeout = wdd->timeout;
43	return ktime_get_seconds() + wdd->timeout;
44}
45
46static int xen_wdt_start(struct watchdog_device *wdd)
47{
48	time64_t expires;
49	int err;
50
51	expires = set_timeout(wdd);
52	if (!wdt.id)
53		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
54	else
55		err = -EBUSY;
56	if (err > 0) {
57		wdt.id = err;
58		wdt_expires = expires;
59		err = 0;
60	} else
61		BUG_ON(!err);
62
63	return err;
64}
65
66static int xen_wdt_stop(struct watchdog_device *wdd)
67{
68	int err = 0;
69
70	wdt.timeout = 0;
71	if (wdt.id)
72		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
73	if (!err)
74		wdt.id = 0;
75
76	return err;
77}
78
79static int xen_wdt_kick(struct watchdog_device *wdd)
80{
81	time64_t expires;
82	int err;
83
84	expires = set_timeout(wdd);
85	if (wdt.id)
86		err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
87	else
88		err = -ENXIO;
89	if (!err)
90		wdt_expires = expires;
91
92	return err;
93}
94
95static unsigned int xen_wdt_get_timeleft(struct watchdog_device *wdd)
96{
97	return wdt_expires - ktime_get_seconds();
98}
99
100static struct watchdog_info xen_wdt_info = {
101	.identity = DRV_NAME,
102	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
103};
104
105static const struct watchdog_ops xen_wdt_ops = {
106	.owner = THIS_MODULE,
107	.start = xen_wdt_start,
108	.stop = xen_wdt_stop,
109	.ping = xen_wdt_kick,
110	.get_timeleft = xen_wdt_get_timeleft,
111};
112
113static struct watchdog_device xen_wdt_dev = {
114	.info = &xen_wdt_info,
115	.ops = &xen_wdt_ops,
116	.timeout = WATCHDOG_TIMEOUT,
117};
118
119static int xen_wdt_probe(struct platform_device *pdev)
120{
121	struct device *dev = &pdev->dev;
122	struct sched_watchdog wd = { .id = ~0 };
123	int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
124
125	if (ret == -ENOSYS) {
126		dev_err(dev, "watchdog not supported by hypervisor\n");
127		return -ENODEV;
128	}
129
130	if (ret != -EINVAL) {
131		dev_err(dev, "unexpected hypervisor error (%d)\n", ret);
132		return -ENODEV;
133	}
134
135	watchdog_init_timeout(&xen_wdt_dev, timeout, NULL);
136	watchdog_set_nowayout(&xen_wdt_dev, nowayout);
137	watchdog_stop_on_reboot(&xen_wdt_dev);
138	watchdog_stop_on_unregister(&xen_wdt_dev);
139
140	ret = devm_watchdog_register_device(dev, &xen_wdt_dev);
141	if (ret)
142		return ret;
143
144	dev_info(dev, "initialized (timeout=%ds, nowayout=%d)\n",
145		 xen_wdt_dev.timeout, nowayout);
146
147	return 0;
148}
149
150static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
151{
152	typeof(wdt.id) id = wdt.id;
153	int rc = xen_wdt_stop(&xen_wdt_dev);
154
155	wdt.id = id;
156	return rc;
157}
158
159static int xen_wdt_resume(struct platform_device *dev)
160{
161	if (!wdt.id)
162		return 0;
163	wdt.id = 0;
164	return xen_wdt_start(&xen_wdt_dev);
165}
166
167static struct platform_driver xen_wdt_driver = {
168	.probe          = xen_wdt_probe,
169	.suspend        = xen_wdt_suspend,
170	.resume         = xen_wdt_resume,
171	.driver         = {
172		.name   = DRV_NAME,
173	},
174};
175
176static int __init xen_wdt_init_module(void)
177{
178	int err;
179
180	if (!xen_domain())
181		return -ENODEV;
182
183	err = platform_driver_register(&xen_wdt_driver);
184	if (err)
185		return err;
186
187	platform_device = platform_device_register_simple(DRV_NAME,
188								  -1, NULL, 0);
189	if (IS_ERR(platform_device)) {
190		err = PTR_ERR(platform_device);
191		platform_driver_unregister(&xen_wdt_driver);
192	}
193
194	return err;
195}
196
197static void __exit xen_wdt_cleanup_module(void)
198{
199	platform_device_unregister(platform_device);
200	platform_driver_unregister(&xen_wdt_driver);
201}
202
203module_init(xen_wdt_init_module);
204module_exit(xen_wdt_cleanup_module);
205
206MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
207MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
208MODULE_LICENSE("GPL");
209