/*
 * 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/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 <linux/mm.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 void sh_wdt_ping(unsigned long data);

static unsigned long shwdt_is_open;
static struct watchdog_info sh_wdt_info;
static char shwdt_expect_close;
static DEFINE_TIMER(timer, sh_wdt_ping, 0, 0);
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 inline 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 (unlikely((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_mmap - map WDT/CPG registers into userspace
 *      @file: file structure for the device
 *      @vma: VMA to map the registers into
 *
 *      A simple mmap() implementation for the corner cases where the counter
 *      needs to be mapped in userspace directly. Due to the relatively small
 *      size of the area, neighbouring registers not necessarily tied to the
 *      CPG will also be accessible through the register page, so this remains
 *      configurable for users that really know what they're doing.
 *
 *      Additionaly, the register page maps in the CPG register base relative
 *      to the nearest page-aligned boundary, which requires that userspace do
 *      the appropriate CPU subtype math for calculating the page offset for
 *      the counter value.
 */
static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)
{
        int ret = -ENOSYS;

#ifdef CONFIG_SH_WDT_MMAP
        unsigned long addr;

        /* Only support the simple cases where we map in a register page. */
        if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
                return -EINVAL;

        /*
         * Pick WTCNT as the start, it's usually the first register after the
         * FRQCR, and neither one are generally page-aligned out of the box.
         */
        addr = WTCNT & ~(PAGE_SIZE - 1);

        vma->vm_flags |= VM_IO;
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
                               PAGE_SIZE, vma->vm_page_prot)) {
                printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
                       __FUNCTION__);
                return -EAGAIN;
        }

        ret = 0;
#endif

        return ret;
}

/**
 *      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 -ENOTTY;
        }

        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 const 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,
        .mmap           = sh_wdt_mmap,
};

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);
        }

        rc = sh_wdt_set_heartbeat(heartbeat);
        if (unlikely(rc)) {
                heartbeat = WATCHDOG_HEARTBEAT;
                printk(KERN_INFO PFX "heartbeat value must "
                       "be 1<=x<=3600, using %d\n", heartbeat);
        }

        rc = register_reboot_notifier(&sh_wdt_notifier);
        if (unlikely(rc)) {
                printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n",
                       rc);
                return rc;
        }

        rc = misc_register(&sh_wdt_miscdev);
        if (unlikely(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). (default=" __MODULE_STRING(clock_division_ratio) ")");

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=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

module_init(sh_wdt_init);
module_exit(sh_wdt_exit);