1 /*
2  * mpc8xxx_wdt.c - MPC8xx/MPC83xx/MPC86xx watchdog userspace interface
3  *
4  * Authors: Dave Updegraff <dave@cray.org>
5  *	    Kumar Gala <galak@kernel.crashing.org>
6  *		Attribution: from 83xx_wst: Florian Schirmer <jolt@tuxbox.org>
7  *				..and from sc520_wdt
8  * Copyright (c) 2008  MontaVista Software, Inc.
9  *                     Anton Vorontsov <avorontsov@ru.mvista.com>
10  *
11  * Note: it appears that you can only actually ENABLE or DISABLE the thing
12  * once after POR. Once enabled, you cannot disable, and vice versa.
13  *
14  * This program is free software; you can redistribute  it and/or modify it
15  * under  the terms of  the GNU General  Public License as published by the
16  * Free Software Foundation;  either version 2 of the  License, or (at your
17  * option) any later version.
18  */
19 
20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21 
22 #include <linux/fs.h>
23 #include <linux/init.h>
24 #include <linux/kernel.h>
25 #include <linux/timer.h>
26 #include <linux/miscdevice.h>
27 #include <linux/of_address.h>
28 #include <linux/of_platform.h>
29 #include <linux/module.h>
30 #include <linux/watchdog.h>
31 #include <linux/io.h>
32 #include <linux/uaccess.h>
33 #include <sysdev/fsl_soc.h>
34 
35 struct mpc8xxx_wdt {
36 	__be32 res0;
37 	__be32 swcrr; /* System watchdog control register */
38 #define SWCRR_SWTC 0xFFFF0000 /* Software Watchdog Time Count. */
39 #define SWCRR_SWEN 0x00000004 /* Watchdog Enable bit. */
40 #define SWCRR_SWRI 0x00000002 /* Software Watchdog Reset/Interrupt Select bit.*/
41 #define SWCRR_SWPR 0x00000001 /* Software Watchdog Counter Prescale bit. */
42 	__be32 swcnr; /* System watchdog count register */
43 	u8 res1[2];
44 	__be16 swsrr; /* System watchdog service register */
45 	u8 res2[0xF0];
46 };
47 
48 struct mpc8xxx_wdt_type {
49 	int prescaler;
50 	bool hw_enabled;
51 };
52 
53 static struct mpc8xxx_wdt __iomem *wd_base;
54 static int mpc8xxx_wdt_init_late(void);
55 
56 static u16 timeout = 0xffff;
57 module_param(timeout, ushort, 0);
58 MODULE_PARM_DESC(timeout,
59 	"Watchdog timeout in ticks. (0<timeout<65536, default=65535)");
60 
61 static bool reset = 1;
62 module_param(reset, bool, 0);
63 MODULE_PARM_DESC(reset,
64 	"Watchdog Interrupt/Reset Mode. 0 = interrupt, 1 = reset");
65 
66 static bool nowayout = WATCHDOG_NOWAYOUT;
67 module_param(nowayout, bool, 0);
68 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
69 		 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
70 
71 /*
72  * We always prescale, but if someone really doesn't want to they can set this
73  * to 0
74  */
75 static int prescale = 1;
76 static unsigned int timeout_sec;
77 
78 static unsigned long wdt_is_open;
79 static DEFINE_SPINLOCK(wdt_spinlock);
80 
81 static void mpc8xxx_wdt_keepalive(void)
82 {
83 	/* Ping the WDT */
84 	spin_lock(&wdt_spinlock);
85 	out_be16(&wd_base->swsrr, 0x556c);
86 	out_be16(&wd_base->swsrr, 0xaa39);
87 	spin_unlock(&wdt_spinlock);
88 }
89 
90 static void mpc8xxx_wdt_timer_ping(unsigned long arg);
91 static DEFINE_TIMER(wdt_timer, mpc8xxx_wdt_timer_ping, 0, 0);
92 
93 static void mpc8xxx_wdt_timer_ping(unsigned long arg)
94 {
95 	mpc8xxx_wdt_keepalive();
96 	/* We're pinging it twice faster than needed, just to be sure. */
97 	mod_timer(&wdt_timer, jiffies + HZ * timeout_sec / 2);
98 }
99 
100 static void mpc8xxx_wdt_pr_warn(const char *msg)
101 {
102 	pr_crit("%s, expect the %s soon!\n", msg,
103 		reset ? "reset" : "machine check exception");
104 }
105 
106 static ssize_t mpc8xxx_wdt_write(struct file *file, const char __user *buf,
107 				 size_t count, loff_t *ppos)
108 {
109 	if (count)
110 		mpc8xxx_wdt_keepalive();
111 	return count;
112 }
113 
114 static int mpc8xxx_wdt_open(struct inode *inode, struct file *file)
115 {
116 	u32 tmp = SWCRR_SWEN;
117 	if (test_and_set_bit(0, &wdt_is_open))
118 		return -EBUSY;
119 
120 	/* Once we start the watchdog we can't stop it */
121 	if (nowayout)
122 		__module_get(THIS_MODULE);
123 
124 	/* Good, fire up the show */
125 	if (prescale)
126 		tmp |= SWCRR_SWPR;
127 	if (reset)
128 		tmp |= SWCRR_SWRI;
129 
130 	tmp |= timeout << 16;
131 
132 	out_be32(&wd_base->swcrr, tmp);
133 
134 	del_timer_sync(&wdt_timer);
135 
136 	return nonseekable_open(inode, file);
137 }
138 
139 static int mpc8xxx_wdt_release(struct inode *inode, struct file *file)
140 {
141 	if (!nowayout)
142 		mpc8xxx_wdt_timer_ping(0);
143 	else
144 		mpc8xxx_wdt_pr_warn("watchdog closed");
145 	clear_bit(0, &wdt_is_open);
146 	return 0;
147 }
148 
149 static long mpc8xxx_wdt_ioctl(struct file *file, unsigned int cmd,
150 							unsigned long arg)
151 {
152 	void __user *argp = (void __user *)arg;
153 	int __user *p = argp;
154 	static const struct watchdog_info ident = {
155 		.options = WDIOF_KEEPALIVEPING,
156 		.firmware_version = 1,
157 		.identity = "MPC8xxx",
158 	};
159 
160 	switch (cmd) {
161 	case WDIOC_GETSUPPORT:
162 		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
163 	case WDIOC_GETSTATUS:
164 	case WDIOC_GETBOOTSTATUS:
165 		return put_user(0, p);
166 	case WDIOC_KEEPALIVE:
167 		mpc8xxx_wdt_keepalive();
168 		return 0;
169 	case WDIOC_GETTIMEOUT:
170 		return put_user(timeout_sec, p);
171 	default:
172 		return -ENOTTY;
173 	}
174 }
175 
176 static const struct file_operations mpc8xxx_wdt_fops = {
177 	.owner		= THIS_MODULE,
178 	.llseek		= no_llseek,
179 	.write		= mpc8xxx_wdt_write,
180 	.unlocked_ioctl	= mpc8xxx_wdt_ioctl,
181 	.open		= mpc8xxx_wdt_open,
182 	.release	= mpc8xxx_wdt_release,
183 };
184 
185 static struct miscdevice mpc8xxx_wdt_miscdev = {
186 	.minor	= WATCHDOG_MINOR,
187 	.name	= "watchdog",
188 	.fops	= &mpc8xxx_wdt_fops,
189 };
190 
191 static const struct of_device_id mpc8xxx_wdt_match[];
192 static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
193 {
194 	int ret;
195 	const struct of_device_id *match;
196 	struct device_node *np = ofdev->dev.of_node;
197 	const struct mpc8xxx_wdt_type *wdt_type;
198 	u32 freq = fsl_get_sys_freq();
199 	bool enabled;
200 
201 	match = of_match_device(mpc8xxx_wdt_match, &ofdev->dev);
202 	if (!match)
203 		return -EINVAL;
204 	wdt_type = match->data;
205 
206 	if (!freq || freq == -1)
207 		return -EINVAL;
208 
209 	wd_base = of_iomap(np, 0);
210 	if (!wd_base)
211 		return -ENOMEM;
212 
213 	enabled = in_be32(&wd_base->swcrr) & SWCRR_SWEN;
214 	if (!enabled && wdt_type->hw_enabled) {
215 		pr_info("could not be enabled in software\n");
216 		ret = -ENOSYS;
217 		goto err_unmap;
218 	}
219 
220 	/* Calculate the timeout in seconds */
221 	if (prescale)
222 		timeout_sec = (timeout * wdt_type->prescaler) / freq;
223 	else
224 		timeout_sec = timeout / freq;
225 
226 #ifdef MODULE
227 	ret = mpc8xxx_wdt_init_late();
228 	if (ret)
229 		goto err_unmap;
230 #endif
231 
232 	pr_info("WDT driver for MPC8xxx initialized. mode:%s timeout=%d (%d seconds)\n",
233 		reset ? "reset" : "interrupt", timeout, timeout_sec);
234 
235 	/*
236 	 * If the watchdog was previously enabled or we're running on
237 	 * MPC8xxx, we should ping the wdt from the kernel until the
238 	 * userspace handles it.
239 	 */
240 	if (enabled)
241 		mpc8xxx_wdt_timer_ping(0);
242 	return 0;
243 err_unmap:
244 	iounmap(wd_base);
245 	wd_base = NULL;
246 	return ret;
247 }
248 
249 static int mpc8xxx_wdt_remove(struct platform_device *ofdev)
250 {
251 	mpc8xxx_wdt_pr_warn("watchdog removed");
252 	del_timer_sync(&wdt_timer);
253 	misc_deregister(&mpc8xxx_wdt_miscdev);
254 	iounmap(wd_base);
255 
256 	return 0;
257 }
258 
259 static const struct of_device_id mpc8xxx_wdt_match[] = {
260 	{
261 		.compatible = "mpc83xx_wdt",
262 		.data = &(struct mpc8xxx_wdt_type) {
263 			.prescaler = 0x10000,
264 		},
265 	},
266 	{
267 		.compatible = "fsl,mpc8610-wdt",
268 		.data = &(struct mpc8xxx_wdt_type) {
269 			.prescaler = 0x10000,
270 			.hw_enabled = true,
271 		},
272 	},
273 	{
274 		.compatible = "fsl,mpc823-wdt",
275 		.data = &(struct mpc8xxx_wdt_type) {
276 			.prescaler = 0x800,
277 		},
278 	},
279 	{},
280 };
281 MODULE_DEVICE_TABLE(of, mpc8xxx_wdt_match);
282 
283 static struct platform_driver mpc8xxx_wdt_driver = {
284 	.probe		= mpc8xxx_wdt_probe,
285 	.remove		= mpc8xxx_wdt_remove,
286 	.driver = {
287 		.name = "mpc8xxx_wdt",
288 		.owner = THIS_MODULE,
289 		.of_match_table = mpc8xxx_wdt_match,
290 	},
291 };
292 
293 /*
294  * We do wdt initialization in two steps: arch_initcall probes the wdt
295  * very early to start pinging the watchdog (misc devices are not yet
296  * available), and later module_init() just registers the misc device.
297  */
298 static int mpc8xxx_wdt_init_late(void)
299 {
300 	int ret;
301 
302 	if (!wd_base)
303 		return -ENODEV;
304 
305 	ret = misc_register(&mpc8xxx_wdt_miscdev);
306 	if (ret) {
307 		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
308 		       WATCHDOG_MINOR, ret);
309 		return ret;
310 	}
311 	return 0;
312 }
313 #ifndef MODULE
314 module_init(mpc8xxx_wdt_init_late);
315 #endif
316 
317 static int __init mpc8xxx_wdt_init(void)
318 {
319 	return platform_driver_register(&mpc8xxx_wdt_driver);
320 }
321 arch_initcall(mpc8xxx_wdt_init);
322 
323 static void __exit mpc8xxx_wdt_exit(void)
324 {
325 	platform_driver_unregister(&mpc8xxx_wdt_driver);
326 }
327 module_exit(mpc8xxx_wdt_exit);
328 
329 MODULE_AUTHOR("Dave Updegraff, Kumar Gala");
330 MODULE_DESCRIPTION("Driver for watchdog timer in MPC8xx/MPC83xx/MPC86xx "
331 		   "uProcessors");
332 MODULE_LICENSE("GPL");
333