1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Watchdog driver for z/VM and LPAR using the diag 288 interface.
  4 *
  5 * Under z/VM, expiration of the watchdog will send a "system restart" command
  6 * to CP.
  7 *
  8 * The command can be altered using the module parameter "cmd". This is
  9 * not recommended because it's only supported on z/VM but not whith LPAR.
 10 *
 11 * On LPAR, the watchdog will always trigger a system restart. the module
 12 * paramter cmd is meaningless here.
 13 *
 14 *
 15 * Copyright IBM Corp. 2004, 2013
 16 * Author(s): Arnd Bergmann (arndb@de.ibm.com)
 17 *	      Philipp Hachtmann (phacht@de.ibm.com)
 18 *
 19 */
 20
 21#define KMSG_COMPONENT "diag288_wdt"
 22#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 23
 24#include <linux/init.h>
 25#include <linux/kernel.h>
 26#include <linux/module.h>
 27#include <linux/moduleparam.h>
 28#include <linux/slab.h>
 29#include <linux/watchdog.h>
 30#include <asm/ebcdic.h>
 31#include <asm/diag.h>
 32#include <linux/io.h>
 33
 34#define MAX_CMDLEN 240
 35#define DEFAULT_CMD "SYSTEM RESTART"
 36
 37#define MIN_INTERVAL 15     /* Minimal time supported by diag88 */
 38#define MAX_INTERVAL 3600   /* One hour should be enough - pure estimation */
 39
 40#define WDT_DEFAULT_TIMEOUT 30
 41
 42/* Function codes - init, change, cancel */
 43#define WDT_FUNC_INIT 0
 44#define WDT_FUNC_CHANGE 1
 45#define WDT_FUNC_CANCEL 2
 46#define WDT_FUNC_CONCEAL 0x80000000
 47
 48/* Action codes for LPAR watchdog */
 49#define LPARWDT_RESTART 0
 50
 51static char wdt_cmd[MAX_CMDLEN] = DEFAULT_CMD;
 52static bool conceal_on;
 53static bool nowayout_info = WATCHDOG_NOWAYOUT;
 54
 55MODULE_LICENSE("GPL");
 56MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
 57MODULE_AUTHOR("Philipp Hachtmann <phacht@de.ibm.com>");
 58
 59MODULE_DESCRIPTION("System z diag288  Watchdog Timer");
 60
 61module_param_string(cmd, wdt_cmd, MAX_CMDLEN, 0644);
 62MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers (z/VM only)");
 63
 64module_param_named(conceal, conceal_on, bool, 0644);
 65MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog is active (z/VM only)");
 66
 67module_param_named(nowayout, nowayout_info, bool, 0444);
 68MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default = CONFIG_WATCHDOG_NOWAYOUT)");
 69
 70MODULE_ALIAS("vmwatchdog");
 71
 72static char *cmd_buf;
 73
 74static int diag288(unsigned int func, unsigned int timeout,
 75		   unsigned long action, unsigned int len)
 76{
 77	union register_pair r1 = { .even = func, .odd = timeout, };
 78	union register_pair r3 = { .even = action, .odd = len, };
 79	int err;
 80
 81	diag_stat_inc(DIAG_STAT_X288);
 82
 83	err = -EINVAL;
 84	asm volatile(
 85		"	diag	%[r1],%[r3],0x288\n"
 86		"0:	la	%[err],0\n"
 87		"1:\n"
 88		EX_TABLE(0b, 1b)
 89		: [err] "+d" (err)
 90		: [r1] "d" (r1.pair), [r3] "d" (r3.pair)
 91		: "cc", "memory");
 92	return err;
 93}
 94
 95static int diag288_str(unsigned int func, unsigned int timeout, char *cmd)
 96{
 97	ssize_t len;
 98
 99	len = strscpy(cmd_buf, cmd, MAX_CMDLEN);
100	if (len < 0)
101		return len;
102	ASCEBC(cmd_buf, MAX_CMDLEN);
103	EBC_TOUPPER(cmd_buf, MAX_CMDLEN);
104
105	return diag288(func, timeout, virt_to_phys(cmd_buf), len);
106}
107
108static int wdt_start(struct watchdog_device *dev)
109{
110	int ret;
111	unsigned int func;
112
113	if (MACHINE_IS_VM) {
114		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
115			: WDT_FUNC_INIT;
116		ret = diag288_str(func, dev->timeout, wdt_cmd);
117		WARN_ON(ret != 0);
118	} else {
119		ret = diag288(WDT_FUNC_INIT, dev->timeout, LPARWDT_RESTART, 0);
120	}
121
122	if (ret) {
123		pr_err("The watchdog cannot be activated\n");
124		return ret;
125	}
126	return 0;
127}
128
129static int wdt_stop(struct watchdog_device *dev)
130{
131	return diag288(WDT_FUNC_CANCEL, 0, 0, 0);
132}
133
134static int wdt_ping(struct watchdog_device *dev)
135{
136	int ret;
137	unsigned int func;
138
139	if (MACHINE_IS_VM) {
140		/*
141		 * It seems to be ok to z/VM to use the init function to
142		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
143		 * be used when the watchdog is running.
144		 */
145		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
146			: WDT_FUNC_INIT;
147
148		ret = diag288_str(func, dev->timeout, wdt_cmd);
149		WARN_ON(ret != 0);
150	} else {
151		ret = diag288(WDT_FUNC_CHANGE, dev->timeout, 0, 0);
152	}
153
154	if (ret)
155		pr_err("The watchdog timer cannot be started or reset\n");
156	return ret;
157}
158
159static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
160{
161	dev->timeout = new_to;
162	return wdt_ping(dev);
163}
164
165static const struct watchdog_ops wdt_ops = {
166	.owner = THIS_MODULE,
167	.start = wdt_start,
168	.stop = wdt_stop,
169	.ping = wdt_ping,
170	.set_timeout = wdt_set_timeout,
171};
172
173static const struct watchdog_info wdt_info = {
174	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
175	.firmware_version = 0,
176	.identity = "z Watchdog",
177};
178
179static struct watchdog_device wdt_dev = {
180	.parent = NULL,
181	.info = &wdt_info,
182	.ops = &wdt_ops,
183	.bootstatus = 0,
184	.timeout = WDT_DEFAULT_TIMEOUT,
185	.min_timeout = MIN_INTERVAL,
186	.max_timeout = MAX_INTERVAL,
187};
188
189static int __init diag288_init(void)
190{
191	int ret;
192
193	watchdog_set_nowayout(&wdt_dev, nowayout_info);
194
195	if (MACHINE_IS_VM) {
196		cmd_buf = kmalloc(MAX_CMDLEN, GFP_KERNEL);
197		if (!cmd_buf) {
198			pr_err("The watchdog cannot be initialized\n");
199			return -ENOMEM;
200		}
201
202		ret = diag288_str(WDT_FUNC_INIT, MIN_INTERVAL, "BEGIN");
203		if (ret != 0) {
204			pr_err("The watchdog cannot be initialized\n");
205			kfree(cmd_buf);
206			return -EINVAL;
207		}
208	} else {
209		if (diag288(WDT_FUNC_INIT, WDT_DEFAULT_TIMEOUT,
210			    LPARWDT_RESTART, 0)) {
211			pr_err("The watchdog cannot be initialized\n");
212			return -EINVAL;
213		}
214	}
215
216	if (diag288(WDT_FUNC_CANCEL, 0, 0, 0)) {
217		pr_err("The watchdog cannot be deactivated\n");
218		return -EINVAL;
219	}
220
221	return watchdog_register_device(&wdt_dev);
222}
223
224static void __exit diag288_exit(void)
225{
226	watchdog_unregister_device(&wdt_dev);
227	kfree(cmd_buf);
228}
229
230module_init(diag288_init);
231module_exit(diag288_exit);