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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * AMD Elan SC520 processor Watchdog Timer driver4 *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 for9 * any of this software. This material is provided "AS-IS" in10 * 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 Cox16 * - Fixed formatting17 * - Removed debug printks18 * - Fixed SMP built kernel deadlock19 * - Switched to private locks not lock_kernel20 * - Used ioremap/writew/readw21 * - Added NOWAYOUT support22 * 4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>23 * - Change comments24 * - Eliminate fop_llseek25 * - Change CONFIG_WATCHDOG_NOWAYOUT semantics26 * - Add KERN_* tags to printks27 * - fix possible wdt_is_open race28 * - Report proper capabilities in watchdog_info29 * - Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,30 * GETTIMEOUT, SETOPTIONS} ioctls31 * 09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>32 * - cleanup of trailing spaces33 * - added extra printk's for startup problems34 * - use module_param35 * - made timeout (the emulated heartbeat) a module_param36 * - made the keepalive ping an internal subroutine37 * 3/27 - 2004 Changes by Sean Young <sean@mess.org>38 * - set MMCR_BASE to 0xfffef00039 * - CBAR does not need to be read40 * - removed debugging printks41 *42 * This WDT driver is different from most other Linux WDT43 * drivers in that the driver will ping the watchdog by itself,44 * because this particular WDT has a very short timeout (1.645 * seconds) and it would be insane to count on any userspace46 * 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 ": " fmt52 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: 16.22s73 * 1: 503ms 3: 2.01s 5: 8.05s 7: 32.21s74 *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 heartbeat84 * 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 */89static int timeout = WATCHDOG_TIMEOUT;90module_param(timeout, int, 0);91MODULE_PARM_DESC(timeout,92 "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="93 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");94 95static bool nowayout = WATCHDOG_NOWAYOUT;96module_param(nowayout, bool, 0);97MODULE_PARM_DESC(nowayout,98 "Watchdog cannot be stopped once started (default="99 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");100 101/*102 * AMD Elan SC520 - Watchdog Timer Registers103 */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 120static __u16 __iomem *wdtmrctl;121 122static void wdt_timer_ping(struct timer_list *);123static DEFINE_TIMER(timer, wdt_timer_ping);124static unsigned long next_heartbeat;125static unsigned long wdt_is_open;126static char wdt_expect_close;127static DEFINE_SPINLOCK(wdt_spinlock);128 129/*130 * Whack the dog131 */132 133static void wdt_timer_ping(struct timer_list *unused)134{135 /* If we got a heartbeat pulse within the WDT_US_INTERVAL136 * we agree to ping the WDT137 */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 } else148 pr_warn("Heartbeat lost! Will not ping the watchdog\n");149}150 151/*152 * Utility routines153 */154 155static 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 172static 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 186static 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 198static int wdt_keepalive(void)199{200 /* user land ping */201 next_heartbeat = jiffies + (timeout * HZ);202 return 0;203}204 205static 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 handling216 */217 218static 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 character227 * 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 should241 return that favour */242 wdt_keepalive();243 }244 return count;245}246 247static 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 260static 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 273static 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_SETTIMEOUT279 | 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 332static const struct file_operations wdt_fops = {333 .owner = THIS_MODULE,334 .write = fop_write,335 .open = fop_open,336 .release = fop_close,337 .unlocked_ioctl = fop_ioctl,338 .compat_ioctl = compat_ptr_ioctl,339};340 341static struct miscdevice wdt_miscdev = {342 .minor = WATCHDOG_MINOR,343 .name = "watchdog",344 .fops = &wdt_fops,345};346 347/*348 * Notifier for system down349 */350 351static int wdt_notify_sys(struct notifier_block *this, unsigned long code,352 void *unused)353{354 if (code == SYS_DOWN || code == SYS_HALT)355 wdt_turnoff();356 return NOTIFY_DONE;357}358 359/*360 * The WDT needs to learn about soft shutdowns in order to361 * turn the timebomb registers off.362 */363 364static struct notifier_block wdt_notifier = {365 .notifier_call = wdt_notify_sys,366};367 368static void __exit sc520_wdt_unload(void)369{370 if (!nowayout)371 wdt_turnoff();372 373 /* Deregister */374 misc_deregister(&wdt_miscdev);375 unregister_reboot_notifier(&wdt_notifier);376 iounmap(wdtmrctl);377}378 379static int __init sc520_wdt_init(void)380{381 int rc = -EBUSY;382 383 /* Check that the timeout value is within it's range ;384 if not reset to the default */385 if (wdt_set_heartbeat(timeout)) {386 wdt_set_heartbeat(WATCHDOG_TIMEOUT);387 pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",388 WATCHDOG_TIMEOUT);389 }390 391 wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);392 if (!wdtmrctl) {393 pr_err("Unable to remap memory\n");394 rc = -ENOMEM;395 goto err_out_region2;396 }397 398 rc = register_reboot_notifier(&wdt_notifier);399 if (rc) {400 pr_err("cannot register reboot notifier (err=%d)\n", rc);401 goto err_out_ioremap;402 }403 404 rc = misc_register(&wdt_miscdev);405 if (rc) {406 pr_err("cannot register miscdev on minor=%d (err=%d)\n",407 WATCHDOG_MINOR, rc);408 goto err_out_notifier;409 }410 411 pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",412 timeout, nowayout);413 414 return 0;415 416err_out_notifier:417 unregister_reboot_notifier(&wdt_notifier);418err_out_ioremap:419 iounmap(wdtmrctl);420err_out_region2:421 return rc;422}423 424module_init(sc520_wdt_init);425module_exit(sc520_wdt_unload);426 427MODULE_AUTHOR("Scott and Bill Jennings");428MODULE_DESCRIPTION(429 "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");430MODULE_LICENSE("GPL");431