1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * AMD Elan SC520 processor Watchdog Timer driver 4 * 5 * Based on acquirewdt.c by Alan Cox, 6 * and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net> 7 * 8 * The authors do NOT admit liability nor provide warranty for 9 * any of this software. This material is provided "AS-IS" in 10 * the hope that it may be useful for others. 11 * 12 * (c) Copyright 2001 Scott Jennings <linuxdrivers@oro.net> 13 * 9/27 - 2001 [Initial release] 14 * 15 * Additional fixes Alan Cox 16 * - Fixed formatting 17 * - Removed debug printks 18 * - Fixed SMP built kernel deadlock 19 * - Switched to private locks not lock_kernel 20 * - Used ioremap/writew/readw 21 * - Added NOWAYOUT support 22 * 4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com> 23 * - Change comments 24 * - Eliminate fop_llseek 25 * - Change CONFIG_WATCHDOG_NOWAYOUT semantics 26 * - Add KERN_* tags to printks 27 * - fix possible wdt_is_open race 28 * - Report proper capabilities in watchdog_info 29 * - Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT, 30 * GETTIMEOUT, SETOPTIONS} ioctls 31 * 09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be> 32 * - cleanup of trailing spaces 33 * - added extra printk's for startup problems 34 * - use module_param 35 * - made timeout (the emulated heartbeat) a module_param 36 * - made the keepalive ping an internal subroutine 37 * 3/27 - 2004 Changes by Sean Young <sean@mess.org> 38 * - set MMCR_BASE to 0xfffef000 39 * - CBAR does not need to be read 40 * - removed debugging printks 41 * 42 * This WDT driver is different from most other Linux WDT 43 * drivers in that the driver will ping the watchdog by itself, 44 * because this particular WDT has a very short timeout (1.6 45 * seconds) and it would be insane to count on any userspace 46 * daemon always getting scheduled within that time frame. 47 * 48 * This driver uses memory mapped IO, and spinlock. 49 */ 50 51 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 52 53 #include <linux/module.h> 54 #include <linux/moduleparam.h> 55 #include <linux/types.h> 56 #include <linux/timer.h> 57 #include <linux/miscdevice.h> 58 #include <linux/watchdog.h> 59 #include <linux/fs.h> 60 #include <linux/ioport.h> 61 #include <linux/notifier.h> 62 #include <linux/reboot.h> 63 #include <linux/init.h> 64 #include <linux/jiffies.h> 65 #include <linux/io.h> 66 #include <linux/uaccess.h> 67 68 69 /* 70 * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7) 71 * 72 * 0: 492us 2: 1.01s 4: 4.03s 6: 16.22s 73 * 1: 503ms 3: 2.01s 5: 8.05s 7: 32.21s 74 * 75 * We will program the SC520 watchdog for a timeout of 2.01s. 76 * If we reset the watchdog every ~250ms we should be safe. 77 */ 78 79 #define WDT_INTERVAL (HZ/4+1) 80 81 /* 82 * We must not require too good response from the userspace daemon. 83 * Here we require the userspace daemon to send us a heartbeat 84 * char to /dev/watchdog every 30 seconds. 85 */ 86 87 #define WATCHDOG_TIMEOUT 30 /* 30 sec default timeout */ 88 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */ 89 static int timeout = WATCHDOG_TIMEOUT; 90 module_param(timeout, int, 0); 91 MODULE_PARM_DESC(timeout, 92 "Watchdog timeout in seconds. (1 <= timeout <= 3600, default=" 93 __MODULE_STRING(WATCHDOG_TIMEOUT) ")"); 94 95 static bool nowayout = WATCHDOG_NOWAYOUT; 96 module_param(nowayout, bool, 0); 97 MODULE_PARM_DESC(nowayout, 98 "Watchdog cannot be stopped once started (default=" 99 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 100 101 /* 102 * AMD Elan SC520 - Watchdog Timer Registers 103 */ 104 #define MMCR_BASE 0xfffef000 /* The default base address */ 105 #define OFFS_WDTMRCTL 0xCB0 /* Watchdog Timer Control Register */ 106 107 /* WDT Control Register bit definitions */ 108 #define WDT_EXP_SEL_01 0x0001 /* [01] Time-out = 496 us (with 33 Mhz clk). */ 109 #define WDT_EXP_SEL_02 0x0002 /* [02] Time-out = 508 ms (with 33 Mhz clk). */ 110 #define WDT_EXP_SEL_03 0x0004 /* [03] Time-out = 1.02 s (with 33 Mhz clk). */ 111 #define WDT_EXP_SEL_04 0x0008 /* [04] Time-out = 2.03 s (with 33 Mhz clk). */ 112 #define WDT_EXP_SEL_05 0x0010 /* [05] Time-out = 4.07 s (with 33 Mhz clk). */ 113 #define WDT_EXP_SEL_06 0x0020 /* [06] Time-out = 8.13 s (with 33 Mhz clk). */ 114 #define WDT_EXP_SEL_07 0x0040 /* [07] Time-out = 16.27s (with 33 Mhz clk). */ 115 #define WDT_EXP_SEL_08 0x0080 /* [08] Time-out = 32.54s (with 33 Mhz clk). */ 116 #define WDT_IRQ_FLG 0x1000 /* [12] Interrupt Request Flag */ 117 #define WDT_WRST_ENB 0x4000 /* [14] Watchdog Timer Reset Enable */ 118 #define WDT_ENB 0x8000 /* [15] Watchdog Timer Enable */ 119 120 static __u16 __iomem *wdtmrctl; 121 122 static void wdt_timer_ping(struct timer_list *); 123 static DEFINE_TIMER(timer, wdt_timer_ping); 124 static unsigned long next_heartbeat; 125 static unsigned long wdt_is_open; 126 static char wdt_expect_close; 127 static DEFINE_SPINLOCK(wdt_spinlock); 128 129 /* 130 * Whack the dog 131 */ 132 133 static void wdt_timer_ping(struct timer_list *unused) 134 { 135 /* If we got a heartbeat pulse within the WDT_US_INTERVAL 136 * we agree to ping the WDT 137 */ 138 if (time_before(jiffies, next_heartbeat)) { 139 /* Ping the WDT */ 140 spin_lock(&wdt_spinlock); 141 writew(0xAAAA, wdtmrctl); 142 writew(0x5555, wdtmrctl); 143 spin_unlock(&wdt_spinlock); 144 145 /* Re-set the timer interval */ 146 mod_timer(&timer, jiffies + WDT_INTERVAL); 147 } else 148 pr_warn("Heartbeat lost! Will not ping the watchdog\n"); 149 } 150 151 /* 152 * Utility routines 153 */ 154 155 static void wdt_config(int writeval) 156 { 157 unsigned long flags; 158 159 /* buy some time (ping) */ 160 spin_lock_irqsave(&wdt_spinlock, flags); 161 readw(wdtmrctl); /* ensure write synchronization */ 162 writew(0xAAAA, wdtmrctl); 163 writew(0x5555, wdtmrctl); 164 /* unlock WDT = make WDT configuration register writable one time */ 165 writew(0x3333, wdtmrctl); 166 writew(0xCCCC, wdtmrctl); 167 /* write WDT configuration register */ 168 writew(writeval, wdtmrctl); 169 spin_unlock_irqrestore(&wdt_spinlock, flags); 170 } 171 172 static int wdt_startup(void) 173 { 174 next_heartbeat = jiffies + (timeout * HZ); 175 176 /* Start the timer */ 177 mod_timer(&timer, jiffies + WDT_INTERVAL); 178 179 /* Start the watchdog */ 180 wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04); 181 182 pr_info("Watchdog timer is now enabled\n"); 183 return 0; 184 } 185 186 static int wdt_turnoff(void) 187 { 188 /* Stop the timer */ 189 del_timer_sync(&timer); 190 191 /* Stop the watchdog */ 192 wdt_config(0); 193 194 pr_info("Watchdog timer is now disabled...\n"); 195 return 0; 196 } 197 198 static int wdt_keepalive(void) 199 { 200 /* user land ping */ 201 next_heartbeat = jiffies + (timeout * HZ); 202 return 0; 203 } 204 205 static int wdt_set_heartbeat(int t) 206 { 207 if ((t < 1) || (t > 3600)) /* arbitrary upper limit */ 208 return -EINVAL; 209 210 timeout = t; 211 return 0; 212 } 213 214 /* 215 * /dev/watchdog handling 216 */ 217 218 static ssize_t fop_write(struct file *file, const char __user *buf, 219 size_t count, loff_t *ppos) 220 { 221 /* See if we got the magic character 'V' and reload the timer */ 222 if (count) { 223 if (!nowayout) { 224 size_t ofs; 225 226 /* note: just in case someone wrote the magic character 227 * five months ago... */ 228 wdt_expect_close = 0; 229 230 /* now scan */ 231 for (ofs = 0; ofs != count; ofs++) { 232 char c; 233 if (get_user(c, buf + ofs)) 234 return -EFAULT; 235 if (c == 'V') 236 wdt_expect_close = 42; 237 } 238 } 239 240 /* Well, anyhow someone wrote to us, we should 241 return that favour */ 242 wdt_keepalive(); 243 } 244 return count; 245 } 246 247 static int fop_open(struct inode *inode, struct file *file) 248 { 249 /* Just in case we're already talking to someone... */ 250 if (test_and_set_bit(0, &wdt_is_open)) 251 return -EBUSY; 252 if (nowayout) 253 __module_get(THIS_MODULE); 254 255 /* Good, fire up the show */ 256 wdt_startup(); 257 return stream_open(inode, file); 258 } 259 260 static int fop_close(struct inode *inode, struct file *file) 261 { 262 if (wdt_expect_close == 42) 263 wdt_turnoff(); 264 else { 265 pr_crit("Unexpected close, not stopping watchdog!\n"); 266 wdt_keepalive(); 267 } 268 clear_bit(0, &wdt_is_open); 269 wdt_expect_close = 0; 270 return 0; 271 } 272 273 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 274 { 275 void __user *argp = (void __user *)arg; 276 int __user *p = argp; 277 static const struct watchdog_info ident = { 278 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT 279 | WDIOF_MAGICCLOSE, 280 .firmware_version = 1, 281 .identity = "SC520", 282 }; 283 284 switch (cmd) { 285 case WDIOC_GETSUPPORT: 286 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 287 case WDIOC_GETSTATUS: 288 case WDIOC_GETBOOTSTATUS: 289 return put_user(0, p); 290 case WDIOC_SETOPTIONS: 291 { 292 int new_options, retval = -EINVAL; 293 294 if (get_user(new_options, p)) 295 return -EFAULT; 296 297 if (new_options & WDIOS_DISABLECARD) { 298 wdt_turnoff(); 299 retval = 0; 300 } 301 302 if (new_options & WDIOS_ENABLECARD) { 303 wdt_startup(); 304 retval = 0; 305 } 306 307 return retval; 308 } 309 case WDIOC_KEEPALIVE: 310 wdt_keepalive(); 311 return 0; 312 case WDIOC_SETTIMEOUT: 313 { 314 int new_timeout; 315 316 if (get_user(new_timeout, p)) 317 return -EFAULT; 318 319 if (wdt_set_heartbeat(new_timeout)) 320 return -EINVAL; 321 322 wdt_keepalive(); 323 } 324 fallthrough; 325 case WDIOC_GETTIMEOUT: 326 return put_user(timeout, p); 327 default: 328 return -ENOTTY; 329 } 330 } 331 332 static const struct file_operations wdt_fops = { 333 .owner = THIS_MODULE, 334 .llseek = no_llseek, 335 .write = fop_write, 336 .open = fop_open, 337 .release = fop_close, 338 .unlocked_ioctl = fop_ioctl, 339 .compat_ioctl = compat_ptr_ioctl, 340 }; 341 342 static struct miscdevice wdt_miscdev = { 343 .minor = WATCHDOG_MINOR, 344 .name = "watchdog", 345 .fops = &wdt_fops, 346 }; 347 348 /* 349 * Notifier for system down 350 */ 351 352 static int wdt_notify_sys(struct notifier_block *this, unsigned long code, 353 void *unused) 354 { 355 if (code == SYS_DOWN || code == SYS_HALT) 356 wdt_turnoff(); 357 return NOTIFY_DONE; 358 } 359 360 /* 361 * The WDT needs to learn about soft shutdowns in order to 362 * turn the timebomb registers off. 363 */ 364 365 static struct notifier_block wdt_notifier = { 366 .notifier_call = wdt_notify_sys, 367 }; 368 369 static void __exit sc520_wdt_unload(void) 370 { 371 if (!nowayout) 372 wdt_turnoff(); 373 374 /* Deregister */ 375 misc_deregister(&wdt_miscdev); 376 unregister_reboot_notifier(&wdt_notifier); 377 iounmap(wdtmrctl); 378 } 379 380 static int __init sc520_wdt_init(void) 381 { 382 int rc = -EBUSY; 383 384 /* Check that the timeout value is within it's range ; 385 if not reset to the default */ 386 if (wdt_set_heartbeat(timeout)) { 387 wdt_set_heartbeat(WATCHDOG_TIMEOUT); 388 pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n", 389 WATCHDOG_TIMEOUT); 390 } 391 392 wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2); 393 if (!wdtmrctl) { 394 pr_err("Unable to remap memory\n"); 395 rc = -ENOMEM; 396 goto err_out_region2; 397 } 398 399 rc = register_reboot_notifier(&wdt_notifier); 400 if (rc) { 401 pr_err("cannot register reboot notifier (err=%d)\n", rc); 402 goto err_out_ioremap; 403 } 404 405 rc = misc_register(&wdt_miscdev); 406 if (rc) { 407 pr_err("cannot register miscdev on minor=%d (err=%d)\n", 408 WATCHDOG_MINOR, rc); 409 goto err_out_notifier; 410 } 411 412 pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n", 413 timeout, nowayout); 414 415 return 0; 416 417 err_out_notifier: 418 unregister_reboot_notifier(&wdt_notifier); 419 err_out_ioremap: 420 iounmap(wdtmrctl); 421 err_out_region2: 422 return rc; 423 } 424 425 module_init(sc520_wdt_init); 426 module_exit(sc520_wdt_unload); 427 428 MODULE_AUTHOR("Scott and Bill Jennings"); 429 MODULE_DESCRIPTION( 430 "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor"); 431 MODULE_LICENSE("GPL"); 432