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 static 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 static 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 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 */ 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 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 */ 221 static 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 } 234 235 static const struct file_operations sbwdog_fops = { 236 .owner = THIS_MODULE, 237 .write = sbwdog_write, 238 .unlocked_ioctl = sbwdog_ioctl, 239 .compat_ioctl = compat_ptr_ioctl, 240 .open = sbwdog_open, 241 .release = sbwdog_release, 242 }; 243 244 static struct miscdevice sbwdog_miscdev = { 245 .minor = WATCHDOG_MINOR, 246 .name = "watchdog", 247 .fops = &sbwdog_fops, 248 }; 249 250 static struct notifier_block sbwdog_notifier = { 251 .notifier_call = sbwdog_notify_sys, 252 }; 253 254 /* 255 * interrupt handler 256 * 257 * doesn't do a whole lot for user, but oh so cleverly written so kernel 258 * code can use it to re-up the watchdog, thereby saving the kernel from 259 * having to create and maintain a timer, just to tickle another timer, 260 * which is just so wrong. 261 */ 262 irqreturn_t sbwdog_interrupt(int irq, void *addr) 263 { 264 unsigned long wd_init; 265 char *wd_cfg_reg = (char *)addr; 266 u8 cfg; 267 268 cfg = __raw_readb(wd_cfg_reg); 269 wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff; 270 271 /* 272 * if it's the second watchdog timer, it's for those users 273 */ 274 if (wd_cfg_reg == user_dog) 275 pr_crit("%s in danger of initiating system reset " 276 "in %ld.%01ld seconds\n", 277 ident.identity, 278 wd_init / 1000000, (wd_init / 100000) % 10); 279 else 280 cfg |= 1; 281 282 __raw_writeb(cfg, wd_cfg_reg); 283 284 return IRQ_HANDLED; 285 } 286 287 static int __init sbwdog_init(void) 288 { 289 int ret; 290 291 /* 292 * register a reboot notifier 293 */ 294 ret = register_reboot_notifier(&sbwdog_notifier); 295 if (ret) { 296 pr_err("%s: cannot register reboot notifier (err=%d)\n", 297 ident.identity, ret); 298 return ret; 299 } 300 301 /* 302 * get the resources 303 */ 304 305 ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED, 306 ident.identity, (void *)user_dog); 307 if (ret) { 308 pr_err("%s: failed to request irq 1 - %d\n", 309 ident.identity, ret); 310 goto out; 311 } 312 313 ret = misc_register(&sbwdog_miscdev); 314 if (ret == 0) { 315 pr_info("%s: timeout is %ld.%ld secs\n", 316 ident.identity, 317 timeout / 1000000, (timeout / 100000) % 10); 318 return 0; 319 } 320 free_irq(1, (void *)user_dog); 321 out: 322 unregister_reboot_notifier(&sbwdog_notifier); 323 324 return ret; 325 } 326 327 static void __exit sbwdog_exit(void) 328 { 329 misc_deregister(&sbwdog_miscdev); 330 free_irq(1, (void *)user_dog); 331 unregister_reboot_notifier(&sbwdog_notifier); 332 } 333 334 module_init(sbwdog_init); 335 module_exit(sbwdog_exit); 336 337 MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>"); 338 MODULE_DESCRIPTION("SiByte Watchdog"); 339 340 module_param(timeout, ulong, 0); 341 MODULE_PARM_DESC(timeout, 342 "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)"); 343 344 MODULE_LICENSE("GPL"); 345 346 /* 347 * example code that can be put in a platform code area to utilize the 348 * first watchdog timer for the kernels own purpose. 349 350 void platform_wd_setup(void) 351 { 352 int ret; 353 354 ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED, 355 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0)); 356 if (ret) { 357 pr_crit("Watchdog IRQ zero(0) failed to be requested - %d\n", ret); 358 } 359 } 360 361 362 */ 363