/*
 * drivers/char/watchdog/iop_wdt.c
 *
 * WDT driver for Intel I/O Processors
 * Copyright (C) 2005, Intel Corporation.
 *
 * Based on ixp4xx driver, Copyright 2004 (c) MontaVista, Software, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 *      Curt E Bruns <curt.e.bruns@intel.com>
 *      Peter Milne <peter.milne@d-tacq.com>
 *      Dan Williams <dan.j.williams@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>
#include <mach/hardware.h>

static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned long wdt_status;
static unsigned long boot_status;
static DEFINE_SPINLOCK(wdt_lock);

#define WDT_IN_USE              0
#define WDT_OK_TO_CLOSE         1
#define WDT_ENABLED             2

static unsigned long iop_watchdog_timeout(void)
{
        return (0xffffffffUL / get_iop_tick_rate());
}

/**
 * wdt_supports_disable - determine if we are accessing a iop13xx watchdog
 * or iop3xx by whether it has a disable command
 */
static int wdt_supports_disable(void)
{
        int can_disable;

        if (IOP_WDTCR_EN_ARM != IOP_WDTCR_DIS_ARM)
                can_disable = 1;
        else
                can_disable = 0;

        return can_disable;
}

static void wdt_enable(void)
{
        /* Arm and enable the Timer to starting counting down from 0xFFFF.FFFF
         * Takes approx. 10.7s to timeout
         */
        spin_lock(&wdt_lock);
        write_wdtcr(IOP_WDTCR_EN_ARM);
        write_wdtcr(IOP_WDTCR_EN);
        spin_unlock(&wdt_lock);
}

/* returns 0 if the timer was successfully disabled */
static int wdt_disable(void)
{
        /* Stop Counting */
        if (wdt_supports_disable()) {
                spin_lock(&wdt_lock);
                write_wdtcr(IOP_WDTCR_DIS_ARM);
                write_wdtcr(IOP_WDTCR_DIS);
                clear_bit(WDT_ENABLED, &wdt_status);
                spin_unlock(&wdt_lock);
                pr_info("Disabled\n");
                return 0;
        } else
                return 1;
}

static int iop_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(WDT_IN_USE, &wdt_status))
                return -EBUSY;

        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
        wdt_enable();
        set_bit(WDT_ENABLED, &wdt_status);
        return nonseekable_open(inode, file);
}

static ssize_t iop_wdt_write(struct file *file, const char *data, size_t len,
                  loff_t *ppos)
{
        if (len) {
                if (!nowayout) {
                        size_t i;

                        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

                        for (i = 0; i != len; i++) {
                                char c;

                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        set_bit(WDT_OK_TO_CLOSE, &wdt_status);
                        }
                }
                wdt_enable();
        }
        return len;
}

static const struct watchdog_info ident = {
        .options = WDIOF_CARDRESET | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
        .identity = "iop watchdog",
};

static long iop_wdt_ioctl(struct file *file,
                                unsigned int cmd, unsigned long arg)
{
        int options;
        int ret = -ENOTTY;
        int __user *argp = (int __user *)arg;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        ret = -EFAULT;
                else
                        ret = 0;
                break;

        case WDIOC_GETSTATUS:
                ret = put_user(0, argp);
                break;

        case WDIOC_GETBOOTSTATUS:
                ret = put_user(boot_status, argp);
                break;

        case WDIOC_SETOPTIONS:
                if (get_user(options, (int *)arg))
                        return -EFAULT;

                if (options & WDIOS_DISABLECARD) {
                        if (!nowayout) {
                                if (wdt_disable() == 0) {
                                        set_bit(WDT_OK_TO_CLOSE, &wdt_status);
                                        ret = 0;
                                } else
                                        ret = -ENXIO;
                        } else
                                ret = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        wdt_enable();
                        ret = 0;
                }
                break;

        case WDIOC_KEEPALIVE:
                wdt_enable();
                ret = 0;
                break;

        case WDIOC_GETTIMEOUT:
                ret = put_user(iop_watchdog_timeout(), argp);
                break;
        }
        return ret;
}

static int iop_wdt_release(struct inode *inode, struct file *file)
{
        int state = 1;
        if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
                if (test_bit(WDT_ENABLED, &wdt_status))
                        state = wdt_disable();

        /* if the timer is not disabled reload and notify that we are still
         * going down
         */
        if (state != 0) {
                wdt_enable();
                pr_crit("Device closed unexpectedly - reset in %lu seconds\n",
                        iop_watchdog_timeout());
        }

        clear_bit(WDT_IN_USE, &wdt_status);
        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

        return 0;
}

static const struct file_operations iop_wdt_fops = {
        .owner = THIS_MODULE,
        .llseek = no_llseek,
        .write = iop_wdt_write,
        .unlocked_ioctl = iop_wdt_ioctl,
        .open = iop_wdt_open,
        .release = iop_wdt_release,
};

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

static int __init iop_wdt_init(void)
{
        int ret;

        /* check if the reset was caused by the watchdog timer */
        boot_status = (read_rcsr() & IOP_RCSR_WDT) ? WDIOF_CARDRESET : 0;

        /* Configure Watchdog Timeout to cause an Internal Bus (IB) Reset
         * NOTE: An IB Reset will Reset both cores in the IOP342
         */
        write_wdtsr(IOP13XX_WDTCR_IB_RESET);

        /* Register after we have the device set up so we cannot race
           with an open */
        ret = misc_register(&iop_wdt_miscdev);
        if (ret == 0)
                pr_info("timeout %lu sec\n", iop_watchdog_timeout());

        return ret;
}

static void __exit iop_wdt_exit(void)
{
        misc_deregister(&iop_wdt_miscdev);
}

module_init(iop_wdt_init);
module_exit(iop_wdt_exit);

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");

MODULE_AUTHOR("Curt E Bruns <curt.e.bruns@intel.com>");
MODULE_DESCRIPTION("iop watchdog timer driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);