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1/*2 * Watchdog driver for SiByte SB1 SoCs3 *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 watchdogs7 * on the Sibyte 12XX and 11XX SoCs available to the user. There are two8 * such devices available on the SoC, but it seems that there isn't an9 * 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 work14 * just well enough to really screw things up.15 *16 * It is a simple timer, and there is an interrupt that is raised the17 * first time the timer expires. The second time it expires, the chip18 * is reset and there is no way to redirect that NMI. Which could19 * be problematic in some cases where this chip is sitting on the HT20 * 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 is22 * 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 of28 * 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, unless32 * you previously wrote a 'V' to the fd, in which case it disables33 * the watchdog when you close the fd like some other drivers.34 *35 * Based on various other watchdog drivers, which are probably all36 * 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/or42 * modify it under the terms of the GNU General Public License43 * version 1 or 2 as published by the Free Software Foundation.44 *45 */46 47#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt48 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 63static DEFINE_SPINLOCK(sbwd_lock);64 65/*66 * set the initial count value of a timer67 *68 * wdog is the iomem address of the cfg register69 */70static 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 counting80 * all over again81 *82 * wdog is the iomem address of the cfg register83 */84static 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 91static unsigned long sbwdog_gate; /* keeps it to one thread only */92static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));93static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));94static unsigned long timeout = 0x7fffffUL; /* useconds: 8.3ish secs. */95static int expect_close;96 97static 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 dog105 */106static 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 timer115 */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 */125static 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 answer143 */144static 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 timer152 */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 169static 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 register210 * which is 1*8 before the config register211 */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 down220 */221static 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 sit227 */228 __raw_writeb(0, user_dog);229 __raw_writeb(0, kern_dog);230 }231 232 return NOTIFY_DONE;233}234 235static 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 244static struct miscdevice sbwdog_miscdev = {245 .minor = WATCHDOG_MINOR,246 .name = "watchdog",247 .fops = &sbwdog_fops,248};249 250static struct notifier_block sbwdog_notifier = {251 .notifier_call = sbwdog_notify_sys,252};253 254/*255 * interrupt handler256 *257 * doesn't do a whole lot for user, but oh so cleverly written so kernel258 * code can use it to re-up the watchdog, thereby saving the kernel from259 * having to create and maintain a timer, just to tickle another timer,260 * which is just so wrong.261 */262irqreturn_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 users273 */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 else280 cfg |= 1;281 282 __raw_writeb(cfg, wd_cfg_reg);283 284 return IRQ_HANDLED;285}286 287static int __init sbwdog_init(void)288{289 int ret;290 291 /*292 * register a reboot notifier293 */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 resources303 */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);321out:322 unregister_reboot_notifier(&sbwdog_notifier);323 324 return ret;325}326 327static 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 334module_init(sbwdog_init);335module_exit(sbwdog_exit);336 337MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");338MODULE_DESCRIPTION("SiByte Watchdog");339 340module_param(timeout, ulong, 0);341MODULE_PARM_DESC(timeout,342 "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");343 344MODULE_LICENSE("GPL");345 346/*347 * example code that can be put in a platform code area to utilize the348 * first watchdog timer for the kernels own purpose.349 350void 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