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 static DEFINE_SPINLOCK(sbwd_lock); 61 62 /* 63 * set the initial count value of a timer 64 * 65 * wdog is the iomem address of the cfg register 66 */ 67 void sbwdog_set(char __iomem *wdog, unsigned long t) 68 { 69 spin_lock(&sbwd_lock); 70 __raw_writeb(0, wdog - 0x10); 71 __raw_writeq(t & 0x7fffffUL, wdog); 72 spin_unlock(&sbwd_lock); 73 } 74 75 /* 76 * cause the timer to [re]load it's initial count and start counting 77 * all over again 78 * 79 * wdog is the iomem address of the cfg register 80 */ 81 void sbwdog_pet(char __iomem *wdog) 82 { 83 spin_lock(&sbwd_lock); 84 __raw_writeb(__raw_readb(wdog) | 1, wdog); 85 spin_unlock(&sbwd_lock); 86 } 87 88 static unsigned long sbwdog_gate; /* keeps it to one thread only */ 89 static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0)); 90 static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1)); 91 static unsigned long timeout = 0x7fffffUL; /* useconds: 8.3ish secs. */ 92 static int expect_close; 93 94 static const struct watchdog_info ident = { 95 .options = WDIOF_CARDRESET | WDIOF_SETTIMEOUT | 96 WDIOF_KEEPALIVEPING, 97 .identity = "SiByte Watchdog", 98 }; 99 100 /* 101 * Allow only a single thread to walk the dog 102 */ 103 static int sbwdog_open(struct inode *inode, struct file *file) 104 { 105 nonseekable_open(inode, file); 106 if (test_and_set_bit(0, &sbwdog_gate)) 107 return -EBUSY; 108 __module_get(THIS_MODULE); 109 110 /* 111 * Activate the timer 112 */ 113 sbwdog_set(user_dog, timeout); 114 __raw_writeb(1, user_dog); 115 116 return 0; 117 } 118 119 /* 120 * Put the dog back in the kennel. 121 */ 122 static int sbwdog_release(struct inode *inode, struct file *file) 123 { 124 if (expect_close == 42) { 125 __raw_writeb(0, user_dog); 126 module_put(THIS_MODULE); 127 } else { 128 printk(KERN_CRIT 129 "%s: Unexpected close, not stopping watchdog!\n", 130 ident.identity); 131 sbwdog_pet(user_dog); 132 } 133 clear_bit(0, &sbwdog_gate); 134 expect_close = 0; 135 136 return 0; 137 } 138 139 /* 140 * 42 - the answer 141 */ 142 static ssize_t sbwdog_write(struct file *file, const char __user *data, 143 size_t len, loff_t *ppos) 144 { 145 int i; 146 147 if (len) { 148 /* 149 * restart the timer 150 */ 151 expect_close = 0; 152 153 for (i = 0; i != len; i++) { 154 char c; 155 156 if (get_user(c, data + i)) 157 return -EFAULT; 158 if (c == 'V') 159 expect_close = 42; 160 } 161 sbwdog_pet(user_dog); 162 } 163 164 return len; 165 } 166 167 static long sbwdog_ioctl(struct file *file, unsigned int cmd, 168 unsigned long arg) 169 { 170 int ret = -ENOTTY; 171 unsigned long time; 172 void __user *argp = (void __user *)arg; 173 int __user *p = argp; 174 175 switch (cmd) { 176 case WDIOC_GETSUPPORT: 177 ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 178 break; 179 180 case WDIOC_GETSTATUS: 181 case WDIOC_GETBOOTSTATUS: 182 ret = put_user(0, p); 183 break; 184 185 case WDIOC_KEEPALIVE: 186 sbwdog_pet(user_dog); 187 ret = 0; 188 break; 189 190 case WDIOC_SETTIMEOUT: 191 ret = get_user(time, p); 192 if (ret) 193 break; 194 195 time *= 1000000; 196 if (time > 0x7fffffUL) { 197 ret = -EINVAL; 198 break; 199 } 200 timeout = time; 201 sbwdog_set(user_dog, timeout); 202 sbwdog_pet(user_dog); 203 204 case WDIOC_GETTIMEOUT: 205 /* 206 * get the remaining count from the ... count register 207 * which is 1*8 before the config register 208 */ 209 ret = put_user(__raw_readq(user_dog - 8) / 1000000, p); 210 break; 211 } 212 return ret; 213 } 214 215 /* 216 * Notifier for system down 217 */ 218 static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code, 219 void *erf) 220 { 221 if (code == SYS_DOWN || code == SYS_HALT) { 222 /* 223 * sit and sit 224 */ 225 __raw_writeb(0, user_dog); 226 __raw_writeb(0, kern_dog); 227 } 228 229 return NOTIFY_DONE; 230 } 231 232 static const struct file_operations sbwdog_fops = { 233 .owner = THIS_MODULE, 234 .llseek = no_llseek, 235 .write = sbwdog_write, 236 .unlocked_ioctl = sbwdog_ioctl, 237 .open = sbwdog_open, 238 .release = sbwdog_release, 239 }; 240 241 static struct miscdevice sbwdog_miscdev = { 242 .minor = WATCHDOG_MINOR, 243 .name = "watchdog", 244 .fops = &sbwdog_fops, 245 }; 246 247 static struct notifier_block sbwdog_notifier = { 248 .notifier_call = sbwdog_notify_sys, 249 }; 250 251 /* 252 * interrupt handler 253 * 254 * doesn't do a whole lot for user, but oh so cleverly written so kernel 255 * code can use it to re-up the watchdog, thereby saving the kernel from 256 * having to create and maintain a timer, just to tickle another timer, 257 * which is just so wrong. 258 */ 259 irqreturn_t sbwdog_interrupt(int irq, void *addr) 260 { 261 unsigned long wd_init; 262 char *wd_cfg_reg = (char *)addr; 263 u8 cfg; 264 265 cfg = __raw_readb(wd_cfg_reg); 266 wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff; 267 268 /* 269 * if it's the second watchdog timer, it's for those users 270 */ 271 if (wd_cfg_reg == user_dog) 272 printk(KERN_CRIT 273 "%s in danger of initiating system reset in %ld.%01ld seconds\n", 274 ident.identity, wd_init / 1000000, (wd_init / 100000) % 10); 275 else 276 cfg |= 1; 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 293 "%s: cannot register reboot notifier (err=%d)\n", 294 ident.identity, ret); 295 return ret; 296 } 297 298 /* 299 * get the resources 300 */ 301 302 ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED, 303 ident.identity, (void *)user_dog); 304 if (ret) { 305 printk(KERN_ERR "%s: failed to request irq 1 - %d\n", 306 ident.identity, ret); 307 return ret; 308 } 309 310 ret = misc_register(&sbwdog_miscdev); 311 if (ret == 0) { 312 printk(KERN_INFO "%s: timeout is %ld.%ld secs\n", 313 ident.identity, 314 timeout / 1000000, (timeout / 100000) % 10); 315 } else 316 free_irq(1, (void *)user_dog); 317 return ret; 318 } 319 320 static void __exit sbwdog_exit(void) 321 { 322 misc_deregister(&sbwdog_miscdev); 323 } 324 325 module_init(sbwdog_init); 326 module_exit(sbwdog_exit); 327 328 MODULE_AUTHOR("Andrew Sharp <andy.sharp@onstor.com>"); 329 MODULE_DESCRIPTION("SiByte Watchdog"); 330 331 module_param(timeout, ulong, 0); 332 MODULE_PARM_DESC(timeout, 333 "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)"); 334 335 MODULE_LICENSE("GPL"); 336 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 337 338 /* 339 * example code that can be put in a platform code area to utilize the 340 * first watchdog timer for the kernels own purpose. 341 342 void platform_wd_setup(void) 343 { 344 int ret; 345 346 ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED, 347 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0)); 348 if (ret) { 349 printk(KERN_CRIT 350 "Watchdog IRQ zero(0) failed to be requested - %d\n", ret); 351 } 352 } 353 354 355 */ 356