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(lock: &sbwd_lock);
73 __raw_writeb(val: 0, addr: wdog);
74 __raw_writeq(val: t & 0x7fffffUL, addr: wdog - 0x10);
75 spin_unlock(lock: &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(lock: &sbwd_lock);
87 __raw_writeb(__raw_readb(addr: wdog) | 1, addr: wdog);
88 spin_unlock(lock: &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, filp: file);
109 if (test_and_set_bit(nr: 0, addr: &sbwdog_gate))
110 return -EBUSY;
111 __module_get(THIS_MODULE);
112
113 /*
114 * Activate the timer
115 */
116 sbwdog_set(wdog: user_dog, t: timeout);
117 __raw_writeb(val: 1, addr: 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(val: 0, addr: 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(wdog: user_dog);
134 }
135 clear_bit(nr: 0, addr: &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(wdog: 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(to: argp, from: &ident, n: 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(wdog: 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(wdog: user_dog, t: timeout);
204 sbwdog_pet(wdog: 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(val: 0, addr: user_dog);
229 __raw_writeb(val: 0, addr: 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(addr: wd_cfg_reg);
270 wd_init = __raw_readq(addr: 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(val: cfg, addr: 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(irq: 1, handler: sbwdog_interrupt, IRQF_SHARED,
307 name: ident.identity, dev: (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(misc: &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(misc: &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

source code of linux/drivers/watchdog/sb_wdog.c