1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	sun4v watchdog timer
4 *	(c) Copyright 2016 Oracle Corporation
5 *
6 *	Implement a simple watchdog driver using the built-in sun4v hypervisor
7 *	watchdog support. If time expires, the hypervisor stops or bounces
8 *	the guest domain.
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/errno.h>
14#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/moduleparam.h>
18#include <linux/watchdog.h>
19#include <asm/hypervisor.h>
20#include <asm/mdesc.h>
21
22#define WDT_TIMEOUT			60
23#define WDT_MAX_TIMEOUT			31536000
24#define WDT_MIN_TIMEOUT			1
25#define WDT_DEFAULT_RESOLUTION_MS	1000	/* 1 second */
26
27static unsigned int timeout;
28module_param(timeout, uint, 0);
29MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
30	__MODULE_STRING(WDT_TIMEOUT) ")");
31
32static bool nowayout = WATCHDOG_NOWAYOUT;
33module_param(nowayout, bool, S_IRUGO);
34MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
35	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
36
37static int sun4v_wdt_stop(struct watchdog_device *wdd)
38{
39	sun4v_mach_set_watchdog(0, NULL);
40
41	return 0;
42}
43
44static int sun4v_wdt_ping(struct watchdog_device *wdd)
45{
46	int hverr;
47
48	/*
49	 * HV watchdog timer will round up the timeout
50	 * passed in to the nearest multiple of the
51	 * watchdog resolution in milliseconds.
52	 */
53	hverr = sun4v_mach_set_watchdog(wdd->timeout * 1000, NULL);
54	if (hverr == HV_EINVAL)
55		return -EINVAL;
56
57	return 0;
58}
59
60static int sun4v_wdt_set_timeout(struct watchdog_device *wdd,
61				 unsigned int timeout)
62{
63	wdd->timeout = timeout;
64
65	return 0;
66}
67
68static const struct watchdog_info sun4v_wdt_ident = {
69	.options =	WDIOF_SETTIMEOUT |
70			WDIOF_MAGICCLOSE |
71			WDIOF_KEEPALIVEPING,
72	.identity =	"sun4v hypervisor watchdog",
73	.firmware_version = 0,
74};
75
76static const struct watchdog_ops sun4v_wdt_ops = {
77	.owner =	THIS_MODULE,
78	.start =	sun4v_wdt_ping,
79	.stop =		sun4v_wdt_stop,
80	.ping =		sun4v_wdt_ping,
81	.set_timeout =	sun4v_wdt_set_timeout,
82};
83
84static struct watchdog_device wdd = {
85	.info = &sun4v_wdt_ident,
86	.ops = &sun4v_wdt_ops,
87	.min_timeout = WDT_MIN_TIMEOUT,
88	.max_timeout = WDT_MAX_TIMEOUT,
89	.timeout = WDT_TIMEOUT,
90};
91
92static int __init sun4v_wdt_init(void)
93{
94	struct mdesc_handle *handle;
95	u64 node;
96	const u64 *value;
97	int err = 0;
98	unsigned long major = 1, minor = 1;
99
100	/*
101	 * There are 2 properties that can be set from the control
102	 * domain for the watchdog.
103	 * watchdog-resolution
104	 * watchdog-max-timeout
105	 *
106	 * We can expect a handle to be returned otherwise something
107	 * serious is wrong. Correct to return -ENODEV here.
108	 */
109
110	handle = mdesc_grab();
111	if (!handle)
112		return -ENODEV;
113
114	node = mdesc_node_by_name(handle, MDESC_NODE_NULL, "platform");
115	err = -ENODEV;
116	if (node == MDESC_NODE_NULL)
117		goto out_release;
118
119	/*
120	 * This is a safe way to validate if we are on the right
121	 * platform.
122	 */
123	if (sun4v_hvapi_register(HV_GRP_CORE, major, &minor))
124		goto out_hv_unreg;
125
126	/* Allow value of watchdog-resolution up to 1s (default) */
127	value = mdesc_get_property(handle, node, "watchdog-resolution", NULL);
128	err = -EINVAL;
129	if (value) {
130		if (*value == 0 ||
131		    *value > WDT_DEFAULT_RESOLUTION_MS)
132			goto out_hv_unreg;
133	}
134
135	value = mdesc_get_property(handle, node, "watchdog-max-timeout", NULL);
136	if (value) {
137		/*
138		 * If the property value (in ms) is smaller than
139		 * min_timeout, return -EINVAL.
140		 */
141		if (*value < wdd.min_timeout * 1000)
142			goto out_hv_unreg;
143
144		/*
145		 * If the property value is smaller than
146		 * default max_timeout  then set watchdog max_timeout to
147		 * the value of the property in seconds.
148		 */
149		if (*value < wdd.max_timeout * 1000)
150			wdd.max_timeout = *value  / 1000;
151	}
152
153	watchdog_init_timeout(&wdd, timeout, NULL);
154
155	watchdog_set_nowayout(&wdd, nowayout);
156
157	err = watchdog_register_device(&wdd);
158	if (err)
159		goto out_hv_unreg;
160
161	pr_info("initialized (timeout=%ds, nowayout=%d)\n",
162		 wdd.timeout, nowayout);
163
164	mdesc_release(handle);
165
166	return 0;
167
168out_hv_unreg:
169	sun4v_hvapi_unregister(HV_GRP_CORE);
170
171out_release:
172	mdesc_release(handle);
173	return err;
174}
175
176static void __exit sun4v_wdt_exit(void)
177{
178	sun4v_hvapi_unregister(HV_GRP_CORE);
179	watchdog_unregister_device(&wdd);
180}
181
182module_init(sun4v_wdt_init);
183module_exit(sun4v_wdt_exit);
184
185MODULE_AUTHOR("Wim Coekaerts <wim.coekaerts@oracle.com>");
186MODULE_DESCRIPTION("sun4v watchdog driver");
187MODULE_LICENSE("GPL");
188