1 /* 2 * Watchdog driver for SiByte SB1 SoCs 3 * 4 * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@onstor.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@redhat.com>, All Rights Reserved. 39 * http://www.redhat.com 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 #include <linux/module.h> 47 #include <linux/io.h> 48 #include <linux/uaccess.h> 49 #include <linux/fs.h> 50 #include <linux/reboot.h> 51 #include <linux/miscdevice.h> 52 #include <linux/watchdog.h> 53 #include <linux/interrupt.h> 54 55 #include <asm/sibyte/sb1250.h> 56 #include <asm/sibyte/sb1250_regs.h> 57 #include <asm/sibyte/sb1250_int.h> 58 #include <asm/sibyte/sb1250_scd.h> 59 60 61 /* 62 * set the initial count value of a timer 63 * 64 * wdog is the iomem address of the cfg register 65 */ 66 void sbwdog_set(char __iomem *wdog, unsigned long t) 67 { 68 __raw_writeb(0, wdog - 0x10); 69 __raw_writeq(t & 0x7fffffUL, wdog); 70 } 71 72 /* 73 * cause the timer to [re]load it's initial count and start counting 74 * all over again 75 * 76 * wdog is the iomem address of the cfg register 77 */ 78 void sbwdog_pet(char __iomem *wdog) 79 { 80 __raw_writeb(__raw_readb(wdog) | 1, wdog); 81 } 82 83 static unsigned long sbwdog_gate; /* keeps it to one thread only */ 84 static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0)); 85 static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1)); 86 static unsigned long timeout = 0x7fffffUL; /* useconds: 8.3ish secs. */ 87 static int expect_close; 88 89 static struct watchdog_info ident = { 90 .options = WDIOF_CARDRESET | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING, 91 .identity = "SiByte Watchdog", 92 }; 93 94 /* 95 * Allow only a single thread to walk the dog 96 */ 97 static int sbwdog_open(struct inode *inode, struct file *file) 98 { 99 nonseekable_open(inode, file); 100 if (test_and_set_bit(0, &sbwdog_gate)) { 101 return -EBUSY; 102 } 103 __module_get(THIS_MODULE); 104 105 /* 106 * Activate the timer 107 */ 108 sbwdog_set(user_dog, timeout); 109 __raw_writeb(1, user_dog); 110 111 return 0; 112 } 113 114 /* 115 * Put the dog back in the kennel. 116 */ 117 static int sbwdog_release(struct inode *inode, struct file *file) 118 { 119 if (expect_close == 42) { 120 __raw_writeb(0, user_dog); 121 module_put(THIS_MODULE); 122 } else { 123 printk(KERN_CRIT "%s: Unexpected close, not stopping watchdog!\n", 124 ident.identity); 125 sbwdog_pet(user_dog); 126 } 127 clear_bit(0, &sbwdog_gate); 128 expect_close = 0; 129 130 return 0; 131 } 132 133 /* 134 * 42 - the answer 135 */ 136 static ssize_t sbwdog_write(struct file *file, const char __user *data, 137 size_t len, loff_t *ppos) 138 { 139 int i; 140 141 if (len) { 142 /* 143 * restart the timer 144 */ 145 expect_close = 0; 146 147 for (i = 0; i != len; i++) { 148 char c; 149 150 if (get_user(c, data + i)) { 151 return -EFAULT; 152 } 153 if (c == 'V') { 154 expect_close = 42; 155 } 156 } 157 sbwdog_pet(user_dog); 158 } 159 160 return len; 161 } 162 163 static int sbwdog_ioctl(struct inode *inode, struct file *file, 164 unsigned int cmd, unsigned long arg) 165 { 166 int ret = -ENOTTY; 167 unsigned long time; 168 void __user *argp = (void __user *)arg; 169 int __user *p = argp; 170 171 switch (cmd) { 172 case WDIOC_GETSUPPORT: 173 ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 174 break; 175 176 case WDIOC_GETSTATUS: 177 case WDIOC_GETBOOTSTATUS: 178 ret = put_user(0, p); 179 break; 180 181 case WDIOC_SETTIMEOUT: 182 ret = get_user(time, p); 183 if (ret) { 184 break; 185 } 186 187 time *= 1000000; 188 if (time > 0x7fffffUL) { 189 ret = -EINVAL; 190 break; 191 } 192 timeout = time; 193 sbwdog_set(user_dog, timeout); 194 sbwdog_pet(user_dog); 195 196 case WDIOC_GETTIMEOUT: 197 /* 198 * get the remaining count from the ... count register 199 * which is 1*8 before the config register 200 */ 201 ret = put_user(__raw_readq(user_dog - 8) / 1000000, p); 202 break; 203 204 case WDIOC_KEEPALIVE: 205 sbwdog_pet(user_dog); 206 ret = 0; 207 break; 208 } 209 return ret; 210 } 211 212 /* 213 * Notifier for system down 214 */ 215 static int 216 sbwdog_notify_sys(struct notifier_block *this, unsigned long code, void *erf) 217 { 218 if (code == SYS_DOWN || code == SYS_HALT) { 219 /* 220 * sit and sit 221 */ 222 __raw_writeb(0, user_dog); 223 __raw_writeb(0, kern_dog); 224 } 225 226 return NOTIFY_DONE; 227 } 228 229 static const struct file_operations sbwdog_fops = 230 { 231 .owner = THIS_MODULE, 232 .llseek = no_llseek, 233 .write = sbwdog_write, 234 .ioctl = sbwdog_ioctl, 235 .open = sbwdog_open, 236 .release = sbwdog_release, 237 }; 238 239 static struct miscdevice sbwdog_miscdev = 240 { 241 .minor = WATCHDOG_MINOR, 242 .name = "watchdog", 243 .fops = &sbwdog_fops, 244 }; 245 246 static struct notifier_block sbwdog_notifier = { 247 .notifier_call = sbwdog_notify_sys, 248 }; 249 250 /* 251 * interrupt handler 252 * 253 * doesn't do a whole lot for user, but oh so cleverly written so kernel 254 * code can use it to re-up the watchdog, thereby saving the kernel from 255 * having to create and maintain a timer, just to tickle another timer, 256 * which is just so wrong. 257 */ 258 irqreturn_t sbwdog_interrupt(int irq, void *addr) 259 { 260 unsigned long wd_init; 261 char *wd_cfg_reg = (char *)addr; 262 u8 cfg; 263 264 cfg = __raw_readb(wd_cfg_reg); 265 wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff; 266 267 /* 268 * if it's the second watchdog timer, it's for those users 269 */ 270 if (wd_cfg_reg == user_dog) { 271 printk(KERN_CRIT 272 "%s in danger of initiating system reset in %ld.%01ld seconds\n", 273 ident.identity, wd_init / 1000000, (wd_init / 100000) % 10); 274 } else { 275 cfg |= 1; 276 } 277 278 __raw_writeb(cfg, wd_cfg_reg); 279 280 return IRQ_HANDLED; 281 } 282 283 static int __init sbwdog_init(void) 284 { 285 int ret; 286 287 /* 288 * register a reboot notifier 289 */ 290 ret = register_reboot_notifier(&sbwdog_notifier); 291 if (ret) { 292 printk (KERN_ERR "%s: cannot register reboot notifier (err=%d)\n", 293 ident.identity, ret); 294 return ret; 295 } 296 297 /* 298 * get the resources 299 */ 300 ret = misc_register(&sbwdog_miscdev); 301 if (ret == 0) { 302 printk(KERN_INFO "%s: timeout is %ld.%ld secs\n", ident.identity, 303 timeout / 1000000, (timeout / 100000) % 10); 304 } 305 306 ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED, 307 ident.identity, (void *)user_dog); 308 if (ret) { 309 printk(KERN_ERR "%s: failed to request irq 1 - %d\n", ident.identity, 310 ret); 311 misc_deregister(&sbwdog_miscdev); 312 } 313 314 return ret; 315 } 316 317 static void __exit sbwdog_exit(void) 318 { 319 misc_deregister(&sbwdog_miscdev); 320 } 321 322 module_init(sbwdog_init); 323 module_exit(sbwdog_exit); 324 325 MODULE_AUTHOR("Andrew Sharp <andy.sharp@onstor.com>"); 326 MODULE_DESCRIPTION("SiByte Watchdog"); 327 328 module_param(timeout, ulong, 0); 329 MODULE_PARM_DESC(timeout, 330 "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)"); 331 332 MODULE_LICENSE("GPL"); 333 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 334 335 /* 336 * example code that can be put in a platform code area to utilize the 337 * first watchdog timer for the kernels own purpose. 338 339 void 340 platform_wd_setup(void) 341 { 342 int ret; 343 344 ret = request_irq(0, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED, 345 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0)); 346 if (ret) { 347 printk(KERN_CRIT "Watchdog IRQ zero(0) failed to be requested - %d\n", 348 ret); 349 } 350 } 351 352 353 */ 354