1/*
2 * Watchdog driver for SiByte SB1 SoCs
3 *
4 * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@lsi.com>
5 *
6 * This driver is intended to make the second of two hardware watchdogs
7 * on the Sibyte 12XX and 11XX SoCs available to the user.  There are two
8 * such devices available on the SoC, but it seems that there isn't an
9 * enumeration class for watchdogs in Linux like there is for RTCs.
10 * The second is used rather than the first because it uses IRQ 1,
11 * thereby avoiding all that IRQ 0 problematic nonsense.
12 *
13 * I have not tried this driver on a 1480 processor; it might work
14 * just well enough to really screw things up.
15 *
16 * It is a simple timer, and there is an interrupt that is raised the
17 * first time the timer expires.  The second time it expires, the chip
18 * is reset and there is no way to redirect that NMI.  Which could
19 * be problematic in some cases where this chip is sitting on the HT
20 * bus and has just taken responsibility for providing a cache block.
21 * Since the reset can't be redirected to the external reset pin, it is
22 * possible that other HT connected processors might hang and not reset.
23 * For Linux, a soft reset would probably be even worse than a hard reset.
24 * There you have it.
25 *
26 * The timer takes 23 bits of a 64 bit register (?) as a count value,
27 * and decrements the count every microsecond, for a max value of
28 * 0x7fffff usec or about 8.3ish seconds.
29 *
30 * This watchdog borrows some user semantics from the softdog driver,
31 * in that if you close the fd, it leaves the watchdog running, unless
32 * you previously wrote a 'V' to the fd, in which case it disables
33 * the watchdog when you close the fd like some other drivers.
34 *
35 * Based on various other watchdog drivers, which are probably all
36 * loosely based on something Alan Cox wrote years ago.
37 *
38 *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
39 *						All Rights Reserved.
40 *
41 *	This program is free software; you can redistribute it and/or
42 *	modify it under the terms of the GNU General Public License
43 *	version 1 or 2 as published by the Free Software Foundation.
44 *
45 */
46
47#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
48
49#include <linux/module.h>
50#include <linux/io.h>
51#include <linux/uaccess.h>
52#include <linux/fs.h>
53#include <linux/reboot.h>
54#include <linux/miscdevice.h>
55#include <linux/watchdog.h>
56#include <linux/interrupt.h>
57
58#include <asm/sibyte/sb1250.h>
59#include <asm/sibyte/sb1250_regs.h>
60#include <asm/sibyte/sb1250_int.h>
61#include <asm/sibyte/sb1250_scd.h>
62
63static DEFINE_SPINLOCK(sbwd_lock);
64
65/*
66 * set the initial count value of a timer
67 *
68 * wdog is the iomem address of the cfg register
69 */
70static void sbwdog_set(char __iomem *wdog, unsigned long t)
71{
72	spin_lock(&sbwd_lock);
73	__raw_writeb(0, wdog);
74	__raw_writeq(t & 0x7fffffUL, wdog - 0x10);
75	spin_unlock(&sbwd_lock);
76}
77
78/*
79 * cause the timer to [re]load it's initial count and start counting
80 * all over again
81 *
82 * wdog is the iomem address of the cfg register
83 */
84static void sbwdog_pet(char __iomem *wdog)
85{
86	spin_lock(&sbwd_lock);
87	__raw_writeb(__raw_readb(wdog) | 1, wdog);
88	spin_unlock(&sbwd_lock);
89}
90
91static unsigned long sbwdog_gate; /* keeps it to one thread only */
92static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));
93static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));
94static unsigned long timeout = 0x7fffffUL;	/* useconds: 8.3ish secs. */
95static int expect_close;
96
97static const struct watchdog_info ident = {
98	.options	= WDIOF_CARDRESET | WDIOF_SETTIMEOUT |
99					WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
100	.identity	= "SiByte Watchdog",
101};
102
103/*
104 * Allow only a single thread to walk the dog
105 */
106static int sbwdog_open(struct inode *inode, struct file *file)
107{
108	stream_open(inode, file);
109	if (test_and_set_bit(0, &sbwdog_gate))
110		return -EBUSY;
111	__module_get(THIS_MODULE);
112
113	/*
114	 * Activate the timer
115	 */
116	sbwdog_set(user_dog, timeout);
117	__raw_writeb(1, user_dog);
118
119	return 0;
120}
121
122/*
123 * Put the dog back in the kennel.
124 */
125static int sbwdog_release(struct inode *inode, struct file *file)
126{
127	if (expect_close == 42) {
128		__raw_writeb(0, user_dog);
129		module_put(THIS_MODULE);
130	} else {
131		pr_crit("%s: Unexpected close, not stopping watchdog!\n",
132			ident.identity);
133		sbwdog_pet(user_dog);
134	}
135	clear_bit(0, &sbwdog_gate);
136	expect_close = 0;
137
138	return 0;
139}
140
141/*
142 * 42 - the answer
143 */
144static ssize_t sbwdog_write(struct file *file, const char __user *data,
145			size_t len, loff_t *ppos)
146{
147	int i;
148
149	if (len) {
150		/*
151		 * restart the timer
152		 */
153		expect_close = 0;
154
155		for (i = 0; i != len; i++) {
156			char c;
157
158			if (get_user(c, data + i))
159				return -EFAULT;
160			if (c == 'V')
161				expect_close = 42;
162		}
163		sbwdog_pet(user_dog);
164	}
165
166	return len;
167}
168
169static long sbwdog_ioctl(struct file *file, unsigned int cmd,
170						unsigned long arg)
171{
172	int ret = -ENOTTY;
173	unsigned long time;
174	void __user *argp = (void __user *)arg;
175	int __user *p = argp;
176
177	switch (cmd) {
178	case WDIOC_GETSUPPORT:
179		ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
180		break;
181
182	case WDIOC_GETSTATUS:
183	case WDIOC_GETBOOTSTATUS:
184		ret = put_user(0, p);
185		break;
186
187	case WDIOC_KEEPALIVE:
188		sbwdog_pet(user_dog);
189		ret = 0;
190		break;
191
192	case WDIOC_SETTIMEOUT:
193		ret = get_user(time, p);
194		if (ret)
195			break;
196
197		time *= 1000000;
198		if (time > 0x7fffffUL) {
199			ret = -EINVAL;
200			break;
201		}
202		timeout = time;
203		sbwdog_set(user_dog, timeout);
204		sbwdog_pet(user_dog);
205		fallthrough;
206
207	case WDIOC_GETTIMEOUT:
208		/*
209		 * get the remaining count from the ... count register
210		 * which is 1*8 before the config register
211		 */
212		ret = put_user((u32)__raw_readq(user_dog - 8) / 1000000, p);
213		break;
214	}
215	return ret;
216}
217
218/*
219 *	Notifier for system down
220 */
221static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code,
222								void *erf)
223{
224	if (code == SYS_DOWN || code == SYS_HALT) {
225		/*
226		 * sit and sit
227		 */
228		__raw_writeb(0, user_dog);
229		__raw_writeb(0, kern_dog);
230	}
231
232	return NOTIFY_DONE;
233}
234
235static const struct file_operations sbwdog_fops = {
236	.owner		= THIS_MODULE,
237	.llseek		= no_llseek,
238	.write		= sbwdog_write,
239	.unlocked_ioctl	= sbwdog_ioctl,
240	.compat_ioctl	= compat_ptr_ioctl,
241	.open		= sbwdog_open,
242	.release	= sbwdog_release,
243};
244
245static struct miscdevice sbwdog_miscdev = {
246	.minor		= WATCHDOG_MINOR,
247	.name		= "watchdog",
248	.fops		= &sbwdog_fops,
249};
250
251static struct notifier_block sbwdog_notifier = {
252	.notifier_call	= sbwdog_notify_sys,
253};
254
255/*
256 * interrupt handler
257 *
258 * doesn't do a whole lot for user, but oh so cleverly written so kernel
259 * code can use it to re-up the watchdog, thereby saving the kernel from
260 * having to create and maintain a timer, just to tickle another timer,
261 * which is just so wrong.
262 */
263irqreturn_t sbwdog_interrupt(int irq, void *addr)
264{
265	unsigned long wd_init;
266	char *wd_cfg_reg = (char *)addr;
267	u8 cfg;
268
269	cfg = __raw_readb(wd_cfg_reg);
270	wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff;
271
272	/*
273	 * if it's the second watchdog timer, it's for those users
274	 */
275	if (wd_cfg_reg == user_dog)
276		pr_crit("%s in danger of initiating system reset "
277			"in %ld.%01ld seconds\n",
278			ident.identity,
279			wd_init / 1000000, (wd_init / 100000) % 10);
280	else
281		cfg |= 1;
282
283	__raw_writeb(cfg, wd_cfg_reg);
284
285	return IRQ_HANDLED;
286}
287
288static int __init sbwdog_init(void)
289{
290	int ret;
291
292	/*
293	 * register a reboot notifier
294	 */
295	ret = register_reboot_notifier(&sbwdog_notifier);
296	if (ret) {
297		pr_err("%s: cannot register reboot notifier (err=%d)\n",
298		       ident.identity, ret);
299		return ret;
300	}
301
302	/*
303	 * get the resources
304	 */
305
306	ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
307		ident.identity, (void *)user_dog);
308	if (ret) {
309		pr_err("%s: failed to request irq 1 - %d\n",
310		       ident.identity, ret);
311		goto out;
312	}
313
314	ret = misc_register(&sbwdog_miscdev);
315	if (ret == 0) {
316		pr_info("%s: timeout is %ld.%ld secs\n",
317			ident.identity,
318			timeout / 1000000, (timeout / 100000) % 10);
319		return 0;
320	}
321	free_irq(1, (void *)user_dog);
322out:
323	unregister_reboot_notifier(&sbwdog_notifier);
324
325	return ret;
326}
327
328static void __exit sbwdog_exit(void)
329{
330	misc_deregister(&sbwdog_miscdev);
331	free_irq(1, (void *)user_dog);
332	unregister_reboot_notifier(&sbwdog_notifier);
333}
334
335module_init(sbwdog_init);
336module_exit(sbwdog_exit);
337
338MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
339MODULE_DESCRIPTION("SiByte Watchdog");
340
341module_param(timeout, ulong, 0);
342MODULE_PARM_DESC(timeout,
343      "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");
344
345MODULE_LICENSE("GPL");
346
347/*
348 * example code that can be put in a platform code area to utilize the
349 * first watchdog timer for the kernels own purpose.
350
351void platform_wd_setup(void)
352{
353	int ret;
354
355	ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
356		"Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0));
357	if (ret) {
358		pr_crit("Watchdog IRQ zero(0) failed to be requested - %d\n", ret);
359	}
360}
361
362
363 */
364