// SPDX-License-Identifier: GPL-2.0+
/*
* Acquire Single Board Computer Watchdog Timer driver
*
* Based on wdt.c. Original copyright messages:
*
* (c) Copyright 1996 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>
*
* 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
* Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
* Can't add timeout - driver doesn't allow changing value
*/
/*
* Theory of Operation:
* The Watch-Dog Timer is provided to ensure that standalone
* Systems can always recover from catastrophic conditions that
* caused the CPU to crash. This condition may have occurred by
* external EMI or a software bug. When the CPU stops working
* correctly, hardware on the board will either perform a hardware
* reset (cold boot) or a non-maskable interrupt (NMI) to bring the
* system back to a known state.
*
* The Watch-Dog Timer is controlled by two I/O Ports.
* 443 hex - Read - Enable or refresh the Watch-Dog Timer
* 043 hex - Read - Disable the Watch-Dog Timer
*
* To enable the Watch-Dog Timer, a read from I/O port 443h must
* be performed. This will enable and activate the countdown timer
* which will eventually time out and either reset the CPU or cause
* an NMI depending on the setting of a jumper. To ensure that this
* reset condition does not occur, the Watch-Dog Timer must be
* periodically refreshed by reading the same I/O port 443h.
* The Watch-Dog Timer is disabled by reading I/O port 043h.
*
* The Watch-Dog Timer Time-Out Period is set via jumpers.
* It can be 1, 2, 10, 20, 110 or 220 seconds.
*/
/*
* Includes, defines, variables, module parameters, ...
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
/* Includes */
#include <linux/module.h> /* For module specific items */
#include <linux/moduleparam.h> /* For new moduleparam's */
#include <linux/types.h> /* For standard types (like size_t) */
#include <linux/errno.h> /* For the -ENODEV/... values */
#include <linux/kernel.h> /* For printk/panic/... */
#include <linux/miscdevice.h> /* For struct miscdevice */
#include <linux/watchdog.h> /* For the watchdog specific items */
#include <linux/fs.h> /* For file operations */
#include <linux/ioport.h> /* For io-port access */
#include <linux/platform_device.h> /* For platform_driver framework */
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
#include <linux/io.h> /* For inb/outb/... */
/* Module information */
#define DRV_NAME "acquirewdt"
#define WATCHDOG_NAME "Acquire WDT"
/* There is no way to see what the correct time-out period is */
#define WATCHDOG_HEARTBEAT 0
/* internal variables */
/* the watchdog platform device */
static struct platform_device *acq_platform_device;
static unsigned long acq_is_open;
static char expect_close;
/* module parameters */
/* You must set this - there is no sane way to probe for this board. */
static int wdt_stop = 0x43;
module_param(wdt_stop, int, 0);
MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
/* You must set this - there is no sane way to probe for this board. */
static int wdt_start = 0x443;
module_param(wdt_start, int, 0);
MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
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) ")");
/*
* Watchdog Operations
*/
static void acq_keepalive(void)
{
/* Write a watchdog value */
inb_p(wdt_start);
}
static void acq_stop(void)
{
/* Turn the card off */
inb_p(wdt_stop);
}
/*
* /dev/watchdog handling
*/
static ssize_t acq_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 i;
/* note: just in case someone wrote the magic character
five months ago... */
expect_close = 0;
/* scan to see whether or not we got the
magic character */
for (i = 0; i != count; i++) {
char c;
if (get_user(c, buf + i))
return -EFAULT;
if (c == 'V')
expect_close = 42;
}
}
/* Well, anyhow someone wrote to us, we should
return that favour */
acq_keepalive();
}
return count;
}
static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
int options, retval = -EINVAL;
void __user *argp = (void __user *)arg;
int __user *p = argp;
static const struct watchdog_info ident = {
.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
.firmware_version = 1,
.identity = WATCHDOG_NAME,
};
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:
{
if (get_user(options, p))
return -EFAULT;
if (options & WDIOS_DISABLECARD) {
acq_stop();
retval = 0;
}
if (options & WDIOS_ENABLECARD) {
acq_keepalive();
retval = 0;
}
return retval;
}
case WDIOC_KEEPALIVE:
acq_keepalive();
return 0;
case WDIOC_GETTIMEOUT:
return put_user(WATCHDOG_HEARTBEAT, p);
default:
return -ENOTTY;
}
}
static int acq_open(struct inode *inode, struct file *file)
{
if (test_and_set_bit(0, &acq_is_open))
return -EBUSY;
if (nowayout)
__module_get(THIS_MODULE);
/* Activate */
acq_keepalive();
return stream_open(inode, file);
}
static int acq_close(struct inode *inode, struct file *file)
{
if (expect_close == 42) {
acq_stop();
} else {
pr_crit("Unexpected close, not stopping watchdog!\n");
acq_keepalive();
}
clear_bit(0, &acq_is_open);
expect_close = 0;
return 0;
}
/*
* Kernel Interfaces
*/
static const struct file_operations acq_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.write = acq_write,
.unlocked_ioctl = acq_ioctl,
.open = acq_open,
.release = acq_close,
};
static struct miscdevice acq_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &acq_fops,
};
/*
* Init & exit routines
*/
static int __init acq_probe(struct platform_device *dev)
{
int ret;
if (wdt_stop != wdt_start) {
if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
pr_err("I/O address 0x%04x already in use\n", wdt_stop);
ret = -EIO;
goto out;
}
}
if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
pr_err("I/O address 0x%04x already in use\n", wdt_start);
ret = -EIO;
goto unreg_stop;
}
ret = misc_register(&acq_miscdev);
if (ret != 0) {
pr_err("cannot register miscdev on minor=%d (err=%d)\n",
WATCHDOG_MINOR, ret);
goto unreg_regions;
}
pr_info("initialized. (nowayout=%d)\n", nowayout);
return 0;
unreg_regions:
release_region(wdt_start, 1);
unreg_stop:
if (wdt_stop != wdt_start)
release_region(wdt_stop, 1);
out:
return ret;
}
static int acq_remove(struct platform_device *dev)
{
misc_deregister(&acq_miscdev);
release_region(wdt_start, 1);
if (wdt_stop != wdt_start)
release_region(wdt_stop, 1);
return 0;
}
static void acq_shutdown(struct platform_device *dev)
{
/* Turn the WDT off if we have a soft shutdown */
acq_stop();
}
static struct platform_driver acquirewdt_driver = {
.remove = acq_remove,
.shutdown = acq_shutdown,
.driver = {
.name = DRV_NAME,
},
};
static int __init acq_init(void)
{
int err;
pr_info("WDT driver for Acquire single board computer initialising\n");
acq_platform_device = platform_device_register_simple(DRV_NAME,
-1, NULL, 0);
if (IS_ERR(acq_platform_device))
return PTR_ERR(acq_platform_device);
err = platform_driver_probe(&acquirewdt_driver, acq_probe);
if (err)
goto unreg_platform_device;
return 0;
unreg_platform_device:
platform_device_unregister(acq_platform_device);
return err;
}
static void __exit acq_exit(void)
{
platform_device_unregister(acq_platform_device);
platform_driver_unregister(&acquirewdt_driver);
pr_info("Watchdog Module Unloaded\n");
}
module_init(acq_init);
module_exit(acq_exit);
MODULE_AUTHOR("David Woodhouse");
MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
MODULE_LICENSE("GPL");