/*
* drivers/char/watchdog/shwdt.c
*
* Watchdog driver for integrated watchdog in the SuperH processors.
*
* Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
* Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
*
* 19-Apr-2002 Rob Radez <rob@osinvestor.com>
* Added expect close support, made emulated timeout runtime changeable
* general cleanups, add some ioctls
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/notifier.h>
#include <linux/ioport.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/watchdog.h>
#define PFX "shwdt: "
/*
* Default clock division ratio is 5.25 msecs. For an additional table of
* values, consult the asm-sh/watchdog.h. Overload this at module load
* time.
*
* In order for this to work reliably we need to have HZ set to 1000 or
* something quite higher than 100 (or we need a proper high-res timer
* implementation that will deal with this properly), otherwise the 10ms
* resolution of a jiffy is enough to trigger the overflow. For things like
* the SH-4 and SH-5, this isn't necessarily that big of a problem, though
* for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
* necssary.
*
* As a result of this timing problem, the only modes that are particularly
* feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
* overflow periods respectively.
*
* Also, since we can't really expect userspace to be responsive enough
* before the overflow happens, we maintain two seperate timers .. One in
* the kernel for clearing out WOVF every 2ms or so (again, this depends on
* HZ == 1000), and another for monitoring userspace writes to the WDT device.
*
* As such, we currently use a configurable heartbeat interval which defaults
* to 30s. In this case, the userspace daemon is only responsible for periodic
* writes to the device before the next heartbeat is scheduled. If the daemon
* misses its deadline, the kernel timer will allow the WDT to overflow.
*/
static int clock_division_ratio = WTCSR_CKS_4096;
#define next_ping_period(cks) msecs_to_jiffies(cks - 4)
static unsigned long shwdt_is_open;
static struct watchdog_info sh_wdt_info;
static char shwdt_expect_close;
static struct timer_list timer;
static unsigned long next_heartbeat;
#define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */
static int heartbeat = WATCHDOG_HEARTBEAT; /* in seconds */
static int nowayout = WATCHDOG_NOWAYOUT;
/**
* sh_wdt_start - Start the Watchdog
*
* Starts the watchdog.
*/
static void sh_wdt_start(void)
{
__u8 csr;
next_heartbeat = jiffies + (heartbeat * HZ);
mod_timer(&timer, next_ping_period(clock_division_ratio));
csr = sh_wdt_read_csr();
csr |= WTCSR_WT | clock_division_ratio;
sh_wdt_write_csr(csr);
sh_wdt_write_cnt(0);
/*
* These processors have a bit of an inconsistent initialization
* process.. starting with SH-3, RSTS was moved to WTCSR, and the
* RSTCSR register was removed.
*
* On the SH-2 however, in addition with bits being in different
* locations, we must deal with RSTCSR outright..
*/
csr = sh_wdt_read_csr();
csr |= WTCSR_TME;
csr &= ~WTCSR_RSTS;
sh_wdt_write_csr(csr);
#ifdef CONFIG_CPU_SH2
/*
* Whoever came up with the RSTCSR semantics must've been smoking
* some of the good stuff, since in addition to the WTCSR/WTCNT write
* brain-damage, it's managed to fuck things up one step further..
*
* If we need to clear the WOVF bit, the upper byte has to be 0xa5..
* but if we want to touch RSTE or RSTS, the upper byte has to be
* 0x5a..
*/
csr = sh_wdt_read_rstcsr();
csr &= ~RSTCSR_RSTS;
sh_wdt_write_rstcsr(csr);
#endif
}
/**
* sh_wdt_stop - Stop the Watchdog
*
* Stops the watchdog.
*/
static void sh_wdt_stop(void)
{
__u8 csr;
del_timer(&timer);
csr = sh_wdt_read_csr();
csr &= ~WTCSR_TME;
sh_wdt_write_csr(csr);
}
/**
* sh_wdt_keepalive - Keep the Userspace Watchdog Alive
*
* The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
*/
static void sh_wdt_keepalive(void)
{
next_heartbeat = jiffies + (heartbeat * HZ);
}
/**
* sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
*
* Set the Userspace Watchdog heartbeat
*/
static int sh_wdt_set_heartbeat(int t)
{
if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
return -EINVAL;
heartbeat = t;
return 0;
}
/**
* sh_wdt_ping - Ping the Watchdog
*
* @data: Unused
*
* Clears overflow bit, resets timer counter.
*/
static void sh_wdt_ping(unsigned long data)
{
if (time_before(jiffies, next_heartbeat)) {
__u8 csr;
csr = sh_wdt_read_csr();
csr &= ~WTCSR_IOVF;
sh_wdt_write_csr(csr);
sh_wdt_write_cnt(0);
mod_timer(&timer, next_ping_period(clock_division_ratio));
} else {
printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
}
}
/**
* sh_wdt_open - Open the Device
*
* @inode: inode of device
* @file: file handle of device
*
* Watchdog device is opened and started.
*/
static int sh_wdt_open(struct inode *inode, struct file *file)
{
if (test_and_set_bit(0, &shwdt_is_open))
return -EBUSY;
if (nowayout)
__module_get(THIS_MODULE);
sh_wdt_start();
return nonseekable_open(inode, file);
}
/**
* sh_wdt_close - Close the Device
*
* @inode: inode of device
* @file: file handle of device
*
* Watchdog device is closed and stopped.
*/
static int sh_wdt_close(struct inode *inode, struct file *file)
{
if (shwdt_expect_close == 42) {
sh_wdt_stop();
} else {
printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
sh_wdt_keepalive();
}
clear_bit(0, &shwdt_is_open);
shwdt_expect_close = 0;
return 0;
}
/**
* sh_wdt_write - Write to Device
*
* @file: file handle of device
* @buf: buffer to write
* @count: length of buffer
* @ppos: offset
*
* Pings the watchdog on write.
*/
static ssize_t sh_wdt_write(struct file *file, const char *buf,
size_t count, loff_t *ppos)
{
if (count) {
if (!nowayout) {
size_t i;
shwdt_expect_close = 0;
for (i = 0; i != count; i++) {
char c;
if (get_user(c, buf + i))
return -EFAULT;
if (c == 'V')
shwdt_expect_close = 42;
}
}
sh_wdt_keepalive();
}
return count;
}
/**
* sh_wdt_ioctl - Query Device
*
* @inode: inode of device
* @file: file handle of device
* @cmd: watchdog command
* @arg: argument
*
* Query basic information from the device or ping it, as outlined by the
* watchdog API.
*/
static int sh_wdt_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
int new_heartbeat;
int options, retval = -EINVAL;
switch (cmd) {
case WDIOC_GETSUPPORT:
return copy_to_user((struct watchdog_info *)arg,
&sh_wdt_info,
sizeof(sh_wdt_info)) ? -EFAULT : 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
return put_user(0, (int *)arg);
case WDIOC_KEEPALIVE:
sh_wdt_keepalive();
return 0;
case WDIOC_SETTIMEOUT:
if (get_user(new_heartbeat, (int *)arg))
return -EFAULT;
if (sh_wdt_set_heartbeat(new_heartbeat))
return -EINVAL;
sh_wdt_keepalive();
/* Fall */
case WDIOC_GETTIMEOUT:
return put_user(heartbeat, (int *)arg);
case WDIOC_SETOPTIONS:
if (get_user(options, (int *)arg))
return -EFAULT;
if (options & WDIOS_DISABLECARD) {
sh_wdt_stop();
retval = 0;
}
if (options & WDIOS_ENABLECARD) {
sh_wdt_start();
retval = 0;
}
return retval;
default:
return -ENOIOCTLCMD;
}
return 0;
}
/**
* sh_wdt_notify_sys - Notifier Handler
*
* @this: notifier block
* @code: notifier event
* @unused: unused
*
* Handles specific events, such as turning off the watchdog during a
* shutdown event.
*/
static int sh_wdt_notify_sys(struct notifier_block *this,
unsigned long code, void *unused)
{
if (code == SYS_DOWN || code == SYS_HALT) {
sh_wdt_stop();
}
return NOTIFY_DONE;
}
static struct file_operations sh_wdt_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.write = sh_wdt_write,
.ioctl = sh_wdt_ioctl,
.open = sh_wdt_open,
.release = sh_wdt_close,
};
static struct watchdog_info sh_wdt_info = {
.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
.firmware_version = 1,
.identity = "SH WDT",
};
static struct notifier_block sh_wdt_notifier = {
.notifier_call = sh_wdt_notify_sys,
};
static struct miscdevice sh_wdt_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &sh_wdt_fops,
};
/**
* sh_wdt_init - Initialize module
*
* Registers the device and notifier handler. Actual device
* initialization is handled by sh_wdt_open().
*/
static int __init sh_wdt_init(void)
{
int rc;
if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
clock_division_ratio = WTCSR_CKS_4096;
printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
clock_division_ratio);
}
if (sh_wdt_set_heartbeat(heartbeat))
{
heartbeat = WATCHDOG_HEARTBEAT;
printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n",
heartbeat);
}
init_timer(&timer);
timer.function = sh_wdt_ping;
timer.data = 0;
rc = register_reboot_notifier(&sh_wdt_notifier);
if (rc) {
printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc);
return rc;
}
rc = misc_register(&sh_wdt_miscdev);
if (rc) {
printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n",
sh_wdt_miscdev.minor, rc);
unregister_reboot_notifier(&sh_wdt_notifier);
return rc;
}
printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
heartbeat, nowayout);
return 0;
}
/**
* sh_wdt_exit - Deinitialize module
*
* Unregisters the device and notifier handler. Actual device
* deinitialization is handled by sh_wdt_close().
*/
static void __exit sh_wdt_exit(void)
{
misc_deregister(&sh_wdt_miscdev);
unregister_reboot_notifier(&sh_wdt_notifier);
}
MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
MODULE_DESCRIPTION("SuperH watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
module_param(clock_division_ratio, int, 0);
MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
module_init(sh_wdt_init);
module_exit(sh_wdt_exit);
