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 63 static 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 */ 70 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 */ 84 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 91 static unsigned long sbwdog_gate; /* keeps it to one thread only */ 92 static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0)); 93 static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1)); 94 static unsigned long timeout = 0x7fffffUL; /* useconds: 8.3ish secs. */ 95 static int expect_close; 96 97 static 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 */ 106 static int sbwdog_open(struct inode *inode, struct file *file) 107 { 108 nonseekable_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 */ 125 static 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 */ 144 static 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 } 168 169 static 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); 205 206 case WDIOC_GETTIMEOUT: 207 /* 208 * get the remaining count from the ... count register 209 * which is 1*8 before the config register 210 */ 211 ret = put_user((u32)__raw_readq(user_dog - 8) / 1000000, p); 212 break; 213 } 214 return ret; 215 } 216 217 /* 218 * Notifier for system down 219 */ 220 static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code, 221 void *erf) 222 { 223 if (code == SYS_DOWN || code == SYS_HALT) { 224 /* 225 * sit and sit 226 */ 227 __raw_writeb(0, user_dog); 228 __raw_writeb(0, kern_dog); 229 } 230 231 return NOTIFY_DONE; 232 } 233 234 static const struct file_operations sbwdog_fops = { 235 .owner = THIS_MODULE, 236 .llseek = no_llseek, 237 .write = sbwdog_write, 238 .unlocked_ioctl = sbwdog_ioctl, 239 .open = sbwdog_open, 240 .release = sbwdog_release, 241 }; 242 243 static struct miscdevice sbwdog_miscdev = { 244 .minor = WATCHDOG_MINOR, 245 .name = "watchdog", 246 .fops = &sbwdog_fops, 247 }; 248 249 static struct notifier_block sbwdog_notifier = { 250 .notifier_call = sbwdog_notify_sys, 251 }; 252 253 /* 254 * interrupt handler 255 * 256 * doesn't do a whole lot for user, but oh so cleverly written so kernel 257 * code can use it to re-up the watchdog, thereby saving the kernel from 258 * having to create and maintain a timer, just to tickle another timer, 259 * which is just so wrong. 260 */ 261 irqreturn_t sbwdog_interrupt(int irq, void *addr) 262 { 263 unsigned long wd_init; 264 char *wd_cfg_reg = (char *)addr; 265 u8 cfg; 266 267 cfg = __raw_readb(wd_cfg_reg); 268 wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff; 269 270 /* 271 * if it's the second watchdog timer, it's for those users 272 */ 273 if (wd_cfg_reg == user_dog) 274 pr_crit("%s in danger of initiating system reset " 275 "in %ld.%01ld seconds\n", 276 ident.identity, 277 wd_init / 1000000, (wd_init / 100000) % 10); 278 else 279 cfg |= 1; 280 281 __raw_writeb(cfg, wd_cfg_reg); 282 283 return IRQ_HANDLED; 284 } 285 286 static int __init sbwdog_init(void) 287 { 288 int ret; 289 290 /* 291 * register a reboot notifier 292 */ 293 ret = register_reboot_notifier(&sbwdog_notifier); 294 if (ret) { 295 pr_err("%s: cannot register reboot notifier (err=%d)\n", 296 ident.identity, ret); 297 return ret; 298 } 299 300 /* 301 * get the resources 302 */ 303 304 ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED, 305 ident.identity, (void *)user_dog); 306 if (ret) { 307 pr_err("%s: failed to request irq 1 - %d\n", 308 ident.identity, ret); 309 goto out; 310 } 311 312 ret = misc_register(&sbwdog_miscdev); 313 if (ret == 0) { 314 pr_info("%s: timeout is %ld.%ld secs\n", 315 ident.identity, 316 timeout / 1000000, (timeout / 100000) % 10); 317 return 0; 318 } 319 free_irq(1, (void *)user_dog); 320 out: 321 unregister_reboot_notifier(&sbwdog_notifier); 322 323 return ret; 324 } 325 326 static void __exit sbwdog_exit(void) 327 { 328 misc_deregister(&sbwdog_miscdev); 329 free_irq(1, (void *)user_dog); 330 unregister_reboot_notifier(&sbwdog_notifier); 331 } 332 333 module_init(sbwdog_init); 334 module_exit(sbwdog_exit); 335 336 MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>"); 337 MODULE_DESCRIPTION("SiByte Watchdog"); 338 339 module_param(timeout, ulong, 0); 340 MODULE_PARM_DESC(timeout, 341 "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)"); 342 343 MODULE_LICENSE("GPL"); 344 345 /* 346 * example code that can be put in a platform code area to utilize the 347 * first watchdog timer for the kernels own purpose. 348 349 void platform_wd_setup(void) 350 { 351 int ret; 352 353 ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED, 354 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0)); 355 if (ret) { 356 pr_crit("Watchdog IRQ zero(0) failed to be requested - %d\n", ret); 357 } 358 } 359 360 361 */ 362