Documentation: Add documentation for Processor MMIO Stale Data

[mirror_ubuntu-jammy-kernel.git] / drivers / watchdog / wdt.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *	Industrial Computer Source WDT501 driver
 *
 *	(c) Copyright 1996-1997 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *						All Rights Reserved.
 *
 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *	warranty for any of this software. This material is provided
 *	"AS-IS" and at no charge.
 *
 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *	Release 0.10.
 *
 *	Fixes
 *		Dave Gregorich	:	Modularisation and minor bugs
 *		Alan Cox	:	Added the watchdog ioctl() stuff
 *		Alan Cox	:	Fixed the reboot problem (as noted by
 *					Matt Crocker).
 *		Alan Cox	:	Added wdt= boot option
 *		Alan Cox	:	Cleaned up copy/user stuff
 *		Tim Hockin	:	Added insmod parameters, comment
 *					cleanup, parameterized timeout
 *		Tigran Aivazian	:	Restructured wdt_init() to handle
 *					failures
 *		Joel Becker	:	Added WDIOC_GET/SETTIMEOUT
 *		Matt Domsch	:	Added nowayout module option
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include "wd501p.h"

static unsigned long wdt_is_open;
static char expect_close;

/*
 *	Module parameters
 */

#define WD_TIMO 60			/* Default heartbeat = 60 seconds */

static int heartbeat = WD_TIMO;
static int wd_heartbeat;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat,
	"Watchdog heartbeat in seconds. (0 < heartbeat < 65536, default="
				__MODULE_STRING(WD_TIMO) ")");

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) ")");

/* You must set these - there is no sane way to probe for this board. */
static int io = 0x240;
static int irq = 11;

static DEFINE_SPINLOCK(wdt_lock);

module_param_hw(io, int, ioport, 0);
MODULE_PARM_DESC(io, "WDT io port (default=0x240)");
module_param_hw(irq, int, irq, 0);
MODULE_PARM_DESC(irq, "WDT irq (default=11)");

/* Support for the Fan Tachometer on the WDT501-P */
static int tachometer;
module_param(tachometer, int, 0);
MODULE_PARM_DESC(tachometer,
		"WDT501-P Fan Tachometer support (0=disable, default=0)");

static int type = 500;
module_param(type, int, 0);
MODULE_PARM_DESC(type,
		"WDT501-P Card type (500 or 501, default=500)");

/*
 *	Programming support
 */

static void wdt_ctr_mode(int ctr, int mode)
{
	ctr <<= 6;
	ctr |= 0x30;
	ctr |= (mode << 1);
	outb_p(ctr, WDT_CR);
}

static void wdt_ctr_load(int ctr, int val)
{
	outb_p(val&0xFF, WDT_COUNT0+ctr);
	outb_p(val>>8, WDT_COUNT0+ctr);
}

/**
 *	wdt_start:
 *
 *	Start the watchdog driver.
 */

static int wdt_start(void)
{
	unsigned long flags;
	spin_lock_irqsave(&wdt_lock, flags);
	inb_p(WDT_DC);			/* Disable watchdog */
	wdt_ctr_mode(0, 3);		/* Program CTR0 for Mode 3:
						Square Wave Generator */
	wdt_ctr_mode(1, 2);		/* Program CTR1 for Mode 2:
						Rate Generator */
	wdt_ctr_mode(2, 0);		/* Program CTR2 for Mode 0:
						Pulse on Terminal Count */
	wdt_ctr_load(0, 8948);		/* Count at 100Hz */
	wdt_ctr_load(1, wd_heartbeat);	/* Heartbeat */
	wdt_ctr_load(2, 65535);		/* Length of reset pulse */
	outb_p(0, WDT_DC);		/* Enable watchdog */
	spin_unlock_irqrestore(&wdt_lock, flags);
	return 0;
}

/**
 *	wdt_stop:
 *
 *	Stop the watchdog driver.
 */

static int wdt_stop(void)
{
	unsigned long flags;
	spin_lock_irqsave(&wdt_lock, flags);
	/* Turn the card off */
	inb_p(WDT_DC);			/* Disable watchdog */
	wdt_ctr_load(2, 0);		/* 0 length reset pulses now */
	spin_unlock_irqrestore(&wdt_lock, flags);
	return 0;
}

/**
 *	wdt_ping:
 *
 *	Reload counter one with the watchdog heartbeat. We don't bother
 *	reloading the cascade counter.
 */

static void wdt_ping(void)
{
	unsigned long flags;
	spin_lock_irqsave(&wdt_lock, flags);
	/* Write a watchdog value */
	inb_p(WDT_DC);			/* Disable watchdog */
	wdt_ctr_mode(1, 2);		/* Re-Program CTR1 for Mode 2:
							Rate Generator */
	wdt_ctr_load(1, wd_heartbeat);	/* Heartbeat */
	outb_p(0, WDT_DC);		/* Enable watchdog */
	spin_unlock_irqrestore(&wdt_lock, flags);
}

/**
 *	wdt_set_heartbeat:
 *	@t:		the new heartbeat value that needs to be set.
 *
 *	Set a new heartbeat value for the watchdog device. If the heartbeat
 *	value is incorrect we keep the old value and return -EINVAL. If
 *	successful we return 0.
 */

static int wdt_set_heartbeat(int t)
{
	if (t < 1 || t > 65535)
		return -EINVAL;

	heartbeat = t;
	wd_heartbeat = t * 100;
	return 0;
}

/**
 *	wdt_get_status:
 *
 *	Extract the status information from a WDT watchdog device. There are
 *	several board variants so we have to know which bits are valid. Some
 *	bits default to one and some to zero in order to be maximally painful.
 *
 *	we then map the bits onto the status ioctl flags.
 */

static int wdt_get_status(void)
{
	unsigned char new_status;
	int status = 0;
	unsigned long flags;

	spin_lock_irqsave(&wdt_lock, flags);
	new_status = inb_p(WDT_SR);
	spin_unlock_irqrestore(&wdt_lock, flags);

	if (new_status & WDC_SR_ISOI0)
		status |= WDIOF_EXTERN1;
	if (new_status & WDC_SR_ISII1)
		status |= WDIOF_EXTERN2;
	if (type == 501) {
		if (!(new_status & WDC_SR_TGOOD))
			status |= WDIOF_OVERHEAT;
		if (!(new_status & WDC_SR_PSUOVER))
			status |= WDIOF_POWEROVER;
		if (!(new_status & WDC_SR_PSUUNDR))
			status |= WDIOF_POWERUNDER;
		if (tachometer) {
			if (!(new_status & WDC_SR_FANGOOD))
				status |= WDIOF_FANFAULT;
		}
	}
	return status;
}

/**
 *	wdt_get_temperature:
 *
 *	Reports the temperature in degrees Fahrenheit. The API is in
 *	farenheit. It was designed by an imperial measurement luddite.
 */

static int wdt_get_temperature(void)
{
	unsigned short c;
	unsigned long flags;

	spin_lock_irqsave(&wdt_lock, flags);
	c = inb_p(WDT_RT);
	spin_unlock_irqrestore(&wdt_lock, flags);
	return (c * 11 / 15) + 7;
}

static void wdt_decode_501(int status)
{
	if (!(status & WDC_SR_TGOOD))
		pr_crit("Overheat alarm (%d)\n", inb_p(WDT_RT));
	if (!(status & WDC_SR_PSUOVER))
		pr_crit("PSU over voltage\n");
	if (!(status & WDC_SR_PSUUNDR))
		pr_crit("PSU under voltage\n");
}

/**
 *	wdt_interrupt:
 *	@irq:		Interrupt number
 *	@dev_id:	Unused as we don't allow multiple devices.
 *
 *	Handle an interrupt from the board. These are raised when the status
 *	map changes in what the board considers an interesting way. That means
 *	a failure condition occurring.
 */

static irqreturn_t wdt_interrupt(int irq, void *dev_id)
{
	/*
	 *	Read the status register see what is up and
	 *	then printk it.
	 */
	unsigned char status;

	spin_lock(&wdt_lock);
	status = inb_p(WDT_SR);

	pr_crit("WDT status %d\n", status);

	if (type == 501) {
		wdt_decode_501(status);
		if (tachometer) {
			if (!(status & WDC_SR_FANGOOD))
				pr_crit("Possible fan fault\n");
		}
	}
	if (!(status & WDC_SR_WCCR)) {
#ifdef SOFTWARE_REBOOT
#ifdef ONLY_TESTING
		pr_crit("Would Reboot\n");
#else
		pr_crit("Initiating system reboot\n");
		emergency_restart();
#endif
#else
		pr_crit("Reset in 5ms\n");
#endif
	}
	spin_unlock(&wdt_lock);
	return IRQ_HANDLED;
}


/**
 *	wdt_write:
 *	@file: file handle to the watchdog
 *	@buf: buffer to write (unused as data does not matter here
 *	@count: count of bytes
 *	@ppos: pointer to the position to write. No seeks allowed
 *
 *	A write to a watchdog device is defined as a keepalive signal. Any
 *	write of data will do, as we we don't define content meaning.
 */

static ssize_t wdt_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	if (count) {
		if (!nowayout) {
			size_t i;

			/* In case it was set long ago */
			expect_close = 0;

			for (i = 0; i != count; i++) {
				char c;
				if (get_user(c, buf + i))
					return -EFAULT;
				if (c == 'V')
					expect_close = 42;
			}
		}
		wdt_ping();
	}
	return count;
}

/**
 *	wdt_ioctl:
 *	@file: file handle to the device
 *	@cmd: watchdog command
 *	@arg: argument pointer
 *
 *	The watchdog API defines a common set of functions for all watchdogs
 *	according to their available features. We only actually usefully support
 *	querying capabilities and current status.
 */

static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_heartbeat;
	int status;

	struct watchdog_info ident = {
		.options =		WDIOF_SETTIMEOUT|
					WDIOF_MAGICCLOSE|
					WDIOF_KEEPALIVEPING,
		.firmware_version =	1,
		.identity =		"WDT500/501",
	};

	/* Add options according to the card we have */
	ident.options |= (WDIOF_EXTERN1|WDIOF_EXTERN2);
	if (type == 501) {
		ident.options |= (WDIOF_OVERHEAT|WDIOF_POWERUNDER|
							WDIOF_POWEROVER);
		if (tachometer)
			ident.options |= WDIOF_FANFAULT;
	}

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
	case WDIOC_GETSTATUS:
		status = wdt_get_status();
		return put_user(status, p);
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);
	case WDIOC_KEEPALIVE:
		wdt_ping();
		return 0;
	case WDIOC_SETTIMEOUT:
		if (get_user(new_heartbeat, p))
			return -EFAULT;
		if (wdt_set_heartbeat(new_heartbeat))
			return -EINVAL;
		wdt_ping();
		fallthrough;
	case WDIOC_GETTIMEOUT:
		return put_user(heartbeat, p);
	default:
		return -ENOTTY;
	}
}

/**
 *	wdt_open:
 *	@inode: inode of device
 *	@file: file handle to device
 *
 *	The watchdog device has been opened. The watchdog device is single
 *	open and on opening we load the counters. Counter zero is a 100Hz
 *	cascade, into counter 1 which downcounts to reboot. When the counter
 *	triggers counter 2 downcounts the length of the reset pulse which
 *	set set to be as long as possible.
 */

static int wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(0, &wdt_is_open))
		return -EBUSY;
	/*
	 *	Activate
	 */
	wdt_start();
	return stream_open(inode, file);
}

/**
 *	wdt_release:
 *	@inode: inode to board
 *	@file: file handle to board
 *
 *	The watchdog has a configurable API. There is a religious dispute
 *	between people who want their watchdog to be able to shut down and
 *	those who want to be sure if the watchdog manager dies the machine
 *	reboots. In the former case we disable the counters, in the latter
 *	case you have to open it again very soon.
 */

static int wdt_release(struct inode *inode, struct file *file)
{
	if (expect_close == 42) {
		wdt_stop();
		clear_bit(0, &wdt_is_open);
	} else {
		pr_crit("WDT device closed unexpectedly.  WDT will not stop!\n");
		wdt_ping();
	}
	expect_close = 0;
	return 0;
}

/**
 *	wdt_temp_read:
 *	@file: file handle to the watchdog board
 *	@buf: buffer to write 1 byte into
 *	@count: length of buffer
 *	@ptr: offset (no seek allowed)
 *
 *	Temp_read reports the temperature in degrees Fahrenheit. The API is in
 *	farenheit. It was designed by an imperial measurement luddite.
 */

static ssize_t wdt_temp_read(struct file *file, char __user *buf,
						size_t count, loff_t *ptr)
{
	int temperature = wdt_get_temperature();

	if (copy_to_user(buf, &temperature, 1))
		return -EFAULT;

	return 1;
}

/**
 *	wdt_temp_open:
 *	@inode: inode of device
 *	@file: file handle to device
 *
 *	The temperature device has been opened.
 */

static int wdt_temp_open(struct inode *inode, struct file *file)
{
	return stream_open(inode, file);
}

/**
 *	wdt_temp_release:
 *	@inode: inode to board
 *	@file: file handle to board
 *
 *	The temperature device has been closed.
 */

static int wdt_temp_release(struct inode *inode, struct file *file)
{
	return 0;
}

/**
 *	wdt_notify_sys:
 *	@this: our notifier block
 *	@code: the event being reported
 *	@unused: unused
 *
 *	Our notifier is called on system shutdowns. We want to turn the card
 *	off at reboot otherwise the machine will reboot again during memory
 *	test or worse yet during the following fsck. This would suck, in fact
 *	trust me - if it happens it does suck.
 */

static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
	void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		wdt_stop();
	return NOTIFY_DONE;
}

/*
 *	Kernel Interfaces
 */


static const struct file_operations wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= wdt_write,
	.unlocked_ioctl	= wdt_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
	.open		= wdt_open,
	.release	= wdt_release,
};

static struct miscdevice wdt_miscdev = {
	.minor	= WATCHDOG_MINOR,
	.name	= "watchdog",
	.fops	= &wdt_fops,
};

static const struct file_operations wdt_temp_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.read		= wdt_temp_read,
	.open		= wdt_temp_open,
	.release	= wdt_temp_release,
};

static struct miscdevice temp_miscdev = {
	.minor	= TEMP_MINOR,
	.name	= "temperature",
	.fops	= &wdt_temp_fops,
};

/*
 *	The WDT card 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,
};

/**
 *	wdt_exit:
 *
 *	Unload the watchdog. You cannot do this with any file handles open.
 *	If your watchdog is set to continue ticking on close and you unload
 *	it, well it keeps ticking. We won't get the interrupt but the board
 *	will not touch PC memory so all is fine. You just have to load a new
 *	module in 60 seconds or reboot.
 */

static void __exit wdt_exit(void)
{
	misc_deregister(&wdt_miscdev);
	if (type == 501)
		misc_deregister(&temp_miscdev);
	unregister_reboot_notifier(&wdt_notifier);
	free_irq(irq, NULL);
	release_region(io, 8);
}

/**
 *	wdt_init:
 *
 *	Set up the WDT watchdog board. All we have to do is grab the
 *	resources we require and bitch if anyone beat us to them.
 *	The open() function will actually kick the board off.
 */

static int __init wdt_init(void)
{
	int ret;

	if (type != 500 && type != 501) {
		pr_err("unknown card type '%d'\n", type);
		return -ENODEV;
	}

	/* Check that the heartbeat value is within it's range;
	   if not reset to the default */
	if (wdt_set_heartbeat(heartbeat)) {
		wdt_set_heartbeat(WD_TIMO);
		pr_info("heartbeat value must be 0 < heartbeat < 65536, using %d\n",
			WD_TIMO);
	}

	if (!request_region(io, 8, "wdt501p")) {
		pr_err("I/O address 0x%04x already in use\n", io);
		ret = -EBUSY;
		goto out;
	}

	ret = request_irq(irq, wdt_interrupt, 0, "wdt501p", NULL);
	if (ret) {
		pr_err("IRQ %d is not free\n", irq);
		goto outreg;
	}

	ret = register_reboot_notifier(&wdt_notifier);
	if (ret) {
		pr_err("cannot register reboot notifier (err=%d)\n", ret);
		goto outirq;
	}

	if (type == 501) {
		ret = misc_register(&temp_miscdev);
		if (ret) {
			pr_err("cannot register miscdev on minor=%d (err=%d)\n",
			       TEMP_MINOR, ret);
			goto outrbt;
		}
	}

	ret = misc_register(&wdt_miscdev);
	if (ret) {
		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
		       WATCHDOG_MINOR, ret);
		goto outmisc;
	}

	pr_info("WDT500/501-P driver 0.10 at 0x%04x (Interrupt %d). heartbeat=%d sec (nowayout=%d)\n",
		io, irq, heartbeat, nowayout);
	if (type == 501)
		pr_info("Fan Tachometer is %s\n",
			tachometer ? "Enabled" : "Disabled");
	return 0;

outmisc:
	if (type == 501)
		misc_deregister(&temp_miscdev);
outrbt:
	unregister_reboot_notifier(&wdt_notifier);
outirq:
	free_irq(irq, NULL);
outreg:
	release_region(io, 8);
out:
	return ret;
}

module_init(wdt_init);
module_exit(wdt_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Driver for ISA ICS watchdog cards (WDT500/501)");
MODULE_LICENSE("GPL");