// SPDX-License-Identifier: GPL-2.0-or-later /* * AMD Elan SC520 processor Watchdog Timer driver * * Based on acquirewdt.c by Alan Cox, * and sbc60xxwdt.c by Jakob Oestergaard * * The authors do NOT admit liability nor provide warranty for * any of this software. This material is provided "AS-IS" in * the hope that it may be useful for others. * * (c) Copyright 2001 Scott Jennings * 9/27 - 2001 [Initial release] * * Additional fixes Alan Cox * - Fixed formatting * - Removed debug printks * - Fixed SMP built kernel deadlock * - Switched to private locks not lock_kernel * - Used ioremap/writew/readw * - Added NOWAYOUT support * 4/12 - 2002 Changes by Rob Radez * - Change comments * - Eliminate fop_llseek * - Change CONFIG_WATCHDOG_NOWAYOUT semantics * - Add KERN_* tags to printks * - fix possible wdt_is_open race * - Report proper capabilities in watchdog_info * - Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT, * GETTIMEOUT, SETOPTIONS} ioctls * 09/8 - 2003 Changes by Wim Van Sebroeck * - cleanup of trailing spaces * - added extra printk's for startup problems * - use module_param * - made timeout (the emulated heartbeat) a module_param * - made the keepalive ping an internal subroutine * 3/27 - 2004 Changes by Sean Young * - set MMCR_BASE to 0xfffef000 * - CBAR does not need to be read * - removed debugging printks * * This WDT driver is different from most other Linux WDT * drivers in that the driver will ping the watchdog by itself, * because this particular WDT has a very short timeout (1.6 * seconds) and it would be insane to count on any userspace * daemon always getting scheduled within that time frame. * * This driver uses memory mapped IO, and spinlock. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7) * * 0: 492us 2: 1.01s 4: 4.03s 6: 16.22s * 1: 503ms 3: 2.01s 5: 8.05s 7: 32.21s * * We will program the SC520 watchdog for a timeout of 2.01s. * If we reset the watchdog every ~250ms we should be safe. */ #define WDT_INTERVAL (HZ/4+1) /* * We must not require too good response from the userspace daemon. * Here we require the userspace daemon to send us a heartbeat * char to /dev/watchdog every 30 seconds. */ #define WATCHDOG_TIMEOUT 30 /* 30 sec default timeout */ /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */ static int timeout = WATCHDOG_TIMEOUT; module_param(timeout, int, 0); MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1 <= timeout <= 3600, default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")"); static bool nowayout = WATCHDOG_NOWAYOUT; module_param(nowayout, bool, 0); MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); /* * AMD Elan SC520 - Watchdog Timer Registers */ #define MMCR_BASE 0xfffef000 /* The default base address */ #define OFFS_WDTMRCTL 0xCB0 /* Watchdog Timer Control Register */ /* WDT Control Register bit definitions */ #define WDT_EXP_SEL_01 0x0001 /* [01] Time-out = 496 us (with 33 Mhz clk). */ #define WDT_EXP_SEL_02 0x0002 /* [02] Time-out = 508 ms (with 33 Mhz clk). */ #define WDT_EXP_SEL_03 0x0004 /* [03] Time-out = 1.02 s (with 33 Mhz clk). */ #define WDT_EXP_SEL_04 0x0008 /* [04] Time-out = 2.03 s (with 33 Mhz clk). */ #define WDT_EXP_SEL_05 0x0010 /* [05] Time-out = 4.07 s (with 33 Mhz clk). */ #define WDT_EXP_SEL_06 0x0020 /* [06] Time-out = 8.13 s (with 33 Mhz clk). */ #define WDT_EXP_SEL_07 0x0040 /* [07] Time-out = 16.27s (with 33 Mhz clk). */ #define WDT_EXP_SEL_08 0x0080 /* [08] Time-out = 32.54s (with 33 Mhz clk). */ #define WDT_IRQ_FLG 0x1000 /* [12] Interrupt Request Flag */ #define WDT_WRST_ENB 0x4000 /* [14] Watchdog Timer Reset Enable */ #define WDT_ENB 0x8000 /* [15] Watchdog Timer Enable */ static __u16 __iomem *wdtmrctl; static void wdt_timer_ping(struct timer_list *); static DEFINE_TIMER(timer, wdt_timer_ping); static unsigned long next_heartbeat; static unsigned long wdt_is_open; static char wdt_expect_close; static DEFINE_SPINLOCK(wdt_spinlock); /* * Whack the dog */ static void wdt_timer_ping(struct timer_list *unused) { /* If we got a heartbeat pulse within the WDT_US_INTERVAL * we agree to ping the WDT */ if (time_before(jiffies, next_heartbeat)) { /* Ping the WDT */ spin_lock(&wdt_spinlock); writew(0xAAAA, wdtmrctl); writew(0x5555, wdtmrctl); spin_unlock(&wdt_spinlock); /* Re-set the timer interval */ mod_timer(&timer, jiffies + WDT_INTERVAL); } else pr_warn("Heartbeat lost! Will not ping the watchdog\n"); } /* * Utility routines */ static void wdt_config(int writeval) { unsigned long flags; /* buy some time (ping) */ spin_lock_irqsave(&wdt_spinlock, flags); readw(wdtmrctl); /* ensure write synchronization */ writew(0xAAAA, wdtmrctl); writew(0x5555, wdtmrctl); /* unlock WDT = make WDT configuration register writable one time */ writew(0x3333, wdtmrctl); writew(0xCCCC, wdtmrctl); /* write WDT configuration register */ writew(writeval, wdtmrctl); spin_unlock_irqrestore(&wdt_spinlock, flags); } static int wdt_startup(void) { next_heartbeat = jiffies + (timeout * HZ); /* Start the timer */ mod_timer(&timer, jiffies + WDT_INTERVAL); /* Start the watchdog */ wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04); pr_info("Watchdog timer is now enabled\n"); return 0; } static int wdt_turnoff(void) { /* Stop the timer */ del_timer_sync(&timer); /* Stop the watchdog */ wdt_config(0); pr_info("Watchdog timer is now disabled...\n"); return 0; } static int wdt_keepalive(void) { /* user land ping */ next_heartbeat = jiffies + (timeout * HZ); return 0; } static int wdt_set_heartbeat(int t) { if ((t < 1) || (t > 3600)) /* arbitrary upper limit */ return -EINVAL; timeout = t; return 0; } /* * /dev/watchdog handling */ static ssize_t fop_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { /* See if we got the magic character 'V' and reload the timer */ if (count) { if (!nowayout) { size_t ofs; /* note: just in case someone wrote the magic character * five months ago... */ wdt_expect_close = 0; /* now scan */ for (ofs = 0; ofs != count; ofs++) { char c; if (get_user(c, buf + ofs)) return -EFAULT; if (c == 'V') wdt_expect_close = 42; } } /* Well, anyhow someone wrote to us, we should return that favour */ wdt_keepalive(); } return count; } static int fop_open(struct inode *inode, struct file *file) { /* Just in case we're already talking to someone... */ if (test_and_set_bit(0, &wdt_is_open)) return -EBUSY; if (nowayout) __module_get(THIS_MODULE); /* Good, fire up the show */ wdt_startup(); return stream_open(inode, file); } static int fop_close(struct inode *inode, struct file *file) { if (wdt_expect_close == 42) wdt_turnoff(); else { pr_crit("Unexpected close, not stopping watchdog!\n"); wdt_keepalive(); } clear_bit(0, &wdt_is_open); wdt_expect_close = 0; return 0; } static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { void __user *argp = (void __user *)arg; int __user *p = argp; static const struct watchdog_info ident = { .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE, .firmware_version = 1, .identity = "SC520", }; switch (cmd) { case WDIOC_GETSUPPORT: return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; case WDIOC_GETSTATUS: case WDIOC_GETBOOTSTATUS: return put_user(0, p); case WDIOC_SETOPTIONS: { int new_options, retval = -EINVAL; if (get_user(new_options, p)) return -EFAULT; if (new_options & WDIOS_DISABLECARD) { wdt_turnoff(); retval = 0; } if (new_options & WDIOS_ENABLECARD) { wdt_startup(); retval = 0; } return retval; } case WDIOC_KEEPALIVE: wdt_keepalive(); return 0; case WDIOC_SETTIMEOUT: { int new_timeout; if (get_user(new_timeout, p)) return -EFAULT; if (wdt_set_heartbeat(new_timeout)) return -EINVAL; wdt_keepalive(); } fallthrough; case WDIOC_GETTIMEOUT: return put_user(timeout, p); default: return -ENOTTY; } } static const struct file_operations wdt_fops = { .owner = THIS_MODULE, .write = fop_write, .open = fop_open, .release = fop_close, .unlocked_ioctl = fop_ioctl, .compat_ioctl = compat_ptr_ioctl, }; static struct miscdevice wdt_miscdev = { .minor = WATCHDOG_MINOR, .name = "watchdog", .fops = &wdt_fops, }; /* * Notifier for system down */ static int wdt_notify_sys(struct notifier_block *this, unsigned long code, void *unused) { if (code == SYS_DOWN || code == SYS_HALT) wdt_turnoff(); return NOTIFY_DONE; } /* * The WDT needs to learn about soft shutdowns in order to * turn the timebomb registers off. */ static struct notifier_block wdt_notifier = { .notifier_call = wdt_notify_sys, }; static void __exit sc520_wdt_unload(void) { if (!nowayout) wdt_turnoff(); /* Deregister */ misc_deregister(&wdt_miscdev); unregister_reboot_notifier(&wdt_notifier); iounmap(wdtmrctl); } static int __init sc520_wdt_init(void) { int rc = -EBUSY; /* Check that the timeout value is within it's range ; if not reset to the default */ if (wdt_set_heartbeat(timeout)) { wdt_set_heartbeat(WATCHDOG_TIMEOUT); pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n", WATCHDOG_TIMEOUT); } wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2); if (!wdtmrctl) { pr_err("Unable to remap memory\n"); rc = -ENOMEM; goto err_out_region2; } rc = register_reboot_notifier(&wdt_notifier); if (rc) { pr_err("cannot register reboot notifier (err=%d)\n", rc); goto err_out_ioremap; } rc = misc_register(&wdt_miscdev); if (rc) { pr_err("cannot register miscdev on minor=%d (err=%d)\n", WATCHDOG_MINOR, rc); goto err_out_notifier; } pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n", timeout, nowayout); return 0; err_out_notifier: unregister_reboot_notifier(&wdt_notifier); err_out_ioremap: iounmap(wdtmrctl); err_out_region2: return rc; } module_init(sc520_wdt_init); module_exit(sc520_wdt_unload); MODULE_AUTHOR("Scott and Bill Jennings"); MODULE_DESCRIPTION( "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor"); MODULE_LICENSE("GPL");