/*
 * PIKA FPGA based Watchdog Timer
 *
 * Copyright (c) 2008 PIKA Technologies
 *   Sean MacLennan <smaclennan@pikatech.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/bitops.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>

#define DRV_NAME "PIKA-WDT"

/* Hardware timeout in seconds */
#define WDT_HW_TIMEOUT 2

/* Timer heartbeat (500ms) */
#define WDT_TIMEOUT     (HZ/2)

/* User land timeout */
#define WDT_HEARTBEAT 15
static int heartbeat = WDT_HEARTBEAT;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
        "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");

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) ")");

static struct {
        void __iomem *fpga;
        unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
        unsigned long open;
        char expect_close;
        int bootstatus;
        struct timer_list timer;        /* The timer that pings the watchdog */
} pikawdt_private;

static struct watchdog_info ident __ro_after_init = {
        .identity       = DRV_NAME,
        .options        = WDIOF_CARDRESET |
                          WDIOF_SETTIMEOUT |
                          WDIOF_KEEPALIVEPING |
                          WDIOF_MAGICCLOSE,
};

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static inline void pikawdt_reset(void)
{
        /* -- FPGA: Reset Control Register (32bit R/W) (Offset: 0x14) --
         * Bit 7,    WTCHDG_EN: When set to 1, the watchdog timer is enabled.
         *           Once enabled, it cannot be disabled. The watchdog can be
         *           kicked by performing any write access to the reset
         *           control register (this register).
         * Bit 8-11, WTCHDG_TIMEOUT_SEC: Sets the watchdog timeout value in
         *           seconds. Valid ranges are 1 to 15 seconds. The value can
         *           be modified dynamically.
         */
        unsigned reset = in_be32(pikawdt_private.fpga + 0x14);
        /* enable with max timeout - 15 seconds */
        reset |= (1 << 7) + (WDT_HW_TIMEOUT << 8);
        out_be32(pikawdt_private.fpga + 0x14, reset);
}

/*
 * Timer tick
 */
static void pikawdt_ping(struct timer_list *unused)
{
        if (time_before(jiffies, pikawdt_private.next_heartbeat) ||
                        (!nowayout && !pikawdt_private.open)) {
                pikawdt_reset();
                mod_timer(&pikawdt_private.timer, jiffies + WDT_TIMEOUT);
        } else
                pr_crit("I will reset your machine !\n");
}


static void pikawdt_keepalive(void)
{
        pikawdt_private.next_heartbeat = jiffies + heartbeat * HZ;
}

static void pikawdt_start(void)
{
        pikawdt_keepalive();
        mod_timer(&pikawdt_private.timer, jiffies + WDT_TIMEOUT);
}

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int pikawdt_open(struct inode *inode, struct file *file)
{
        /* /dev/watchdog can only be opened once */
        if (test_and_set_bit(0, &pikawdt_private.open))
                return -EBUSY;

        pikawdt_start();

        return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 */
static int pikawdt_release(struct inode *inode, struct file *file)
{
        /* stop internal ping */
        if (!pikawdt_private.expect_close)
                del_timer(&pikawdt_private.timer);

        clear_bit(0, &pikawdt_private.open);
        pikawdt_private.expect_close = 0;
        return 0;
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t pikawdt_write(struct file *file, const char __user *data,
                             size_t len, loff_t *ppos)
{
        if (!len)
                return 0;

        /* Scan for magic character */
        if (!nowayout) {
                size_t i;

                pikawdt_private.expect_close = 0;

                for (i = 0; i < len; i++) {
                        char c;
                        if (get_user(c, data + i))
                                return -EFAULT;
                        if (c == 'V') {
                                pikawdt_private.expect_close = 42;
                                break;
                        }
                }
        }

        pikawdt_keepalive();

        return len;
}

/*
 * Handle commands from user-space.
 */
static long pikawdt_ioctl(struct file *file,
                unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        int new_value;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;

        case WDIOC_GETSTATUS:
                return put_user(0, p);

        case WDIOC_GETBOOTSTATUS:
                return put_user(pikawdt_private.bootstatus, p);

        case WDIOC_KEEPALIVE:
                pikawdt_keepalive();
                return 0;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_value, p))
                        return -EFAULT;

                heartbeat = new_value;
                pikawdt_keepalive();

                return put_user(new_value, p);  /* return current value */

        case WDIOC_GETTIMEOUT:
                return put_user(heartbeat, p);
        }
        return -ENOTTY;
}


static const struct file_operations pikawdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .open           = pikawdt_open,
        .release        = pikawdt_release,
        .write          = pikawdt_write,
        .unlocked_ioctl = pikawdt_ioctl,
};

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

static int __init pikawdt_init(void)
{
        struct device_node *np;
        void __iomem *fpga;
        static u32 post1;
        int ret;

        np = of_find_compatible_node(NULL, NULL, "pika,fpga");
        if (np == NULL) {
                pr_err("Unable to find fpga\n");
                return -ENOENT;
        }

        pikawdt_private.fpga = of_iomap(np, 0);
        of_node_put(np);
        if (pikawdt_private.fpga == NULL) {
                pr_err("Unable to map fpga\n");
                return -ENOMEM;
        }

        ident.firmware_version = in_be32(pikawdt_private.fpga + 0x1c) & 0xffff;

        /* POST information is in the sd area. */
        np = of_find_compatible_node(NULL, NULL, "pika,fpga-sd");
        if (np == NULL) {
                pr_err("Unable to find fpga-sd\n");
                ret = -ENOENT;
                goto out;
        }

        fpga = of_iomap(np, 0);
        of_node_put(np);
        if (fpga == NULL) {
                pr_err("Unable to map fpga-sd\n");
                ret = -ENOMEM;
                goto out;
        }

        /* -- FPGA: POST Test Results Register 1 (32bit R/W) (Offset: 0x4040) --
         * Bit 31,   WDOG: Set to 1 when the last reset was caused by a watchdog
         *           timeout.
         */
        post1 = in_be32(fpga + 0x40);
        if (post1 & 0x80000000)
                pikawdt_private.bootstatus = WDIOF_CARDRESET;

        iounmap(fpga);

        timer_setup(&pikawdt_private.timer, pikawdt_ping, 0);

        ret = misc_register(&pikawdt_miscdev);
        if (ret) {
                pr_err("Unable to register miscdev\n");
                goto out;
        }

        pr_info("initialized. heartbeat=%d sec (nowayout=%d)\n",
                heartbeat, nowayout);
        return 0;

out:
        iounmap(pikawdt_private.fpga);
        return ret;
}

static void __exit pikawdt_exit(void)
{
        misc_deregister(&pikawdt_miscdev);

        iounmap(pikawdt_private.fpga);
}

module_init(pikawdt_init);
module_exit(pikawdt_exit);

MODULE_AUTHOR("Sean MacLennan <smaclennan@pikatech.com>");
MODULE_DESCRIPTION("PIKA FPGA based Watchdog Timer");
MODULE_LICENSE("GPL");