1/*
  2 *	sun4v watchdog timer
  3 *	(c) Copyright 2016 Oracle Corporation
  4 *
  5 *	Implement a simple watchdog driver using the built-in sun4v hypervisor
  6 *	watchdog support. If time expires, the hypervisor stops or bounces
  7 *	the guest domain.
  8 *
  9 *	This program is free software; you can redistribute it and/or
 10 *	modify it under the terms of the GNU General Public License
 11 *	as published by the Free Software Foundation; either version
 12 *	2 of the License, or (at your option) any later version.
 13 */
 14
 15#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 16
 17#include <linux/errno.h>
 18#include <linux/init.h>
 19#include <linux/kernel.h>
 20#include <linux/module.h>
 21#include <linux/moduleparam.h>
 22#include <linux/watchdog.h>
 23#include <asm/hypervisor.h>
 24#include <asm/mdesc.h>
 25
 26#define WDT_TIMEOUT			60
 27#define WDT_MAX_TIMEOUT			31536000
 28#define WDT_MIN_TIMEOUT			1
 29#define WDT_DEFAULT_RESOLUTION_MS	1000	/* 1 second */
 30
 31static unsigned int timeout;
 32module_param(timeout, uint, 0);
 33MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
 34	__MODULE_STRING(WDT_TIMEOUT) ")");
 35
 36static bool nowayout = WATCHDOG_NOWAYOUT;
 37module_param(nowayout, bool, S_IRUGO);
 38MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 39	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 40
 41static int sun4v_wdt_stop(struct watchdog_device *wdd)
 42{
 43	sun4v_mach_set_watchdog(0, NULL);
 44
 45	return 0;
 46}
 47
 48static int sun4v_wdt_ping(struct watchdog_device *wdd)
 49{
 50	int hverr;
 51
 52	/*
 53	 * HV watchdog timer will round up the timeout
 54	 * passed in to the nearest multiple of the
 55	 * watchdog resolution in milliseconds.
 56	 */
 57	hverr = sun4v_mach_set_watchdog(wdd->timeout * 1000, NULL);
 58	if (hverr == HV_EINVAL)
 59		return -EINVAL;
 60
 61	return 0;
 62}
 63
 64static int sun4v_wdt_set_timeout(struct watchdog_device *wdd,
 65				 unsigned int timeout)
 66{
 67	wdd->timeout = timeout;
 68
 69	return 0;
 70}
 71
 72static const struct watchdog_info sun4v_wdt_ident = {
 73	.options =	WDIOF_SETTIMEOUT |
 74			WDIOF_MAGICCLOSE |
 75			WDIOF_KEEPALIVEPING,
 76	.identity =	"sun4v hypervisor watchdog",
 77	.firmware_version = 0,
 78};
 79
 80static struct watchdog_ops sun4v_wdt_ops = {
 81	.owner =	THIS_MODULE,
 82	.start =	sun4v_wdt_ping,
 83	.stop =		sun4v_wdt_stop,
 84	.ping =		sun4v_wdt_ping,
 85	.set_timeout =	sun4v_wdt_set_timeout,
 86};
 87
 88static struct watchdog_device wdd = {
 89	.info = &sun4v_wdt_ident,
 90	.ops = &sun4v_wdt_ops,
 91	.min_timeout = WDT_MIN_TIMEOUT,
 92	.max_timeout = WDT_MAX_TIMEOUT,
 93	.timeout = WDT_TIMEOUT,
 94};
 95
 96static int __init sun4v_wdt_init(void)
 97{
 98	struct mdesc_handle *handle;
 99	u64 node;
100	const u64 *value;
101	int err = 0;
102	unsigned long major = 1, minor = 1;
103
104	/*
105	 * There are 2 properties that can be set from the control
106	 * domain for the watchdog.
107	 * watchdog-resolution
108	 * watchdog-max-timeout
109	 *
110	 * We can expect a handle to be returned otherwise something
111	 * serious is wrong. Correct to return -ENODEV here.
112	 */
113
114	handle = mdesc_grab();
115	if (!handle)
116		return -ENODEV;
117
118	node = mdesc_node_by_name(handle, MDESC_NODE_NULL, "platform");
119	err = -ENODEV;
120	if (node == MDESC_NODE_NULL)
121		goto out_release;
122
123	/*
124	 * This is a safe way to validate if we are on the right
125	 * platform.
126	 */
127	if (sun4v_hvapi_register(HV_GRP_CORE, major, &minor))
128		goto out_hv_unreg;
129
130	/* Allow value of watchdog-resolution up to 1s (default) */
131	value = mdesc_get_property(handle, node, "watchdog-resolution", NULL);
132	err = -EINVAL;
133	if (value) {
134		if (*value == 0 ||
135		    *value > WDT_DEFAULT_RESOLUTION_MS)
136			goto out_hv_unreg;
137	}
138
139	value = mdesc_get_property(handle, node, "watchdog-max-timeout", NULL);
140	if (value) {
141		/*
142		 * If the property value (in ms) is smaller than
143		 * min_timeout, return -EINVAL.
144		 */
145		if (*value < wdd.min_timeout * 1000)
146			goto out_hv_unreg;
147
148		/*
149		 * If the property value is smaller than
150		 * default max_timeout  then set watchdog max_timeout to
151		 * the value of the property in seconds.
152		 */
153		if (*value < wdd.max_timeout * 1000)
154			wdd.max_timeout = *value  / 1000;
155	}
156
157	watchdog_init_timeout(&wdd, timeout, NULL);
158
159	watchdog_set_nowayout(&wdd, nowayout);
160
161	err = watchdog_register_device(&wdd);
162	if (err)
163		goto out_hv_unreg;
164
165	pr_info("initialized (timeout=%ds, nowayout=%d)\n",
166		 wdd.timeout, nowayout);
167
168	mdesc_release(handle);
169
170	return 0;
171
172out_hv_unreg:
173	sun4v_hvapi_unregister(HV_GRP_CORE);
174
175out_release:
176	mdesc_release(handle);
177	return err;
178}
179
180static void __exit sun4v_wdt_exit(void)
181{
182	sun4v_hvapi_unregister(HV_GRP_CORE);
183	watchdog_unregister_device(&wdd);
184}
185
186module_init(sun4v_wdt_init);
187module_exit(sun4v_wdt_exit);
188
189MODULE_AUTHOR("Wim Coekaerts <wim.coekaerts@oracle.com>");
190MODULE_DESCRIPTION("sun4v watchdog driver");
191MODULE_LICENSE("GPL");