/*
 * Watchdog driver for Technologic Systems TS-72xx based SBCs
 * (TS-7200, TS-7250 and TS-7260). These boards have external
 * glue logic CPLD chip, which includes programmable watchdog
 * timer.
 *
 * Copyright (c) 2009 Mika Westerberg <mika.westerberg@iki.fi>
 *
 * This driver is based on ep93xx_wdt and wm831x_wdt drivers.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/fs.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>

#define TS72XX_WDT_FEED_VAL             0x05
#define TS72XX_WDT_DEFAULT_TIMEOUT      8

static int timeout = TS72XX_WDT_DEFAULT_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. "
                          "(1 <= timeout <= 8, default="
                          __MODULE_STRING(TS72XX_WDT_DEFAULT_TIMEOUT)
                          ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");

/**
 * struct ts72xx_wdt - watchdog control structure
 * @lock: lock that protects this structure
 * @regval: watchdog timeout value suitable for control register
 * @flags: flags controlling watchdog device state
 * @control_reg: watchdog control register
 * @feed_reg: watchdog feed register
 * @pdev: back pointer to platform dev
 */
struct ts72xx_wdt {
        struct mutex    lock;
        int             regval;

#define TS72XX_WDT_BUSY_FLAG            1
#define TS72XX_WDT_EXPECT_CLOSE_FLAG    2
        int             flags;

        void __iomem    *control_reg;
        void __iomem    *feed_reg;

        struct platform_device *pdev;
};

static struct platform_device *ts72xx_wdt_pdev;

/*
 * TS-72xx Watchdog supports following timeouts (value written
 * to control register):
 *      value   description
 *      -------------------------
 *      0x00    watchdog disabled
 *      0x01    250ms
 *      0x02    500ms
 *      0x03    1s
 *      0x04    reserved
 *      0x05    2s
 *      0x06    4s
 *      0x07    8s
 *
 * Timeouts below 1s are not very usable so we don't
 * allow them at all.
 *
 * We provide two functions that convert between these:
 * timeout_to_regval() and regval_to_timeout().
 */
static const struct {
        int     timeout;
        int     regval;
} ts72xx_wdt_map[] = {
        { 1, 3 },
        { 2, 5 },
        { 4, 6 },
        { 8, 7 },
};

/**
 * timeout_to_regval() - converts given timeout to control register value
 * @new_timeout: timeout in seconds to be converted
 *
 * Function converts given @new_timeout into valid value that can
 * be programmed into watchdog control register. When conversion is
 * not possible, function returns %-EINVAL.
 */
static int timeout_to_regval(int new_timeout)
{
        int i;

        /* first limit it to 1 - 8 seconds */
        new_timeout = clamp_val(new_timeout, 1, 8);

        for (i = 0; i < ARRAY_SIZE(ts72xx_wdt_map); i++) {
                if (ts72xx_wdt_map[i].timeout >= new_timeout)
                        return ts72xx_wdt_map[i].regval;
        }

        return -EINVAL;
}

/**
 * regval_to_timeout() - converts control register value to timeout
 * @regval: control register value to be converted
 *
 * Function converts given @regval to timeout in seconds (1, 2, 4 or 8).
 * If @regval cannot be converted, function returns %-EINVAL.
 */
static int regval_to_timeout(int regval)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(ts72xx_wdt_map); i++) {
                if (ts72xx_wdt_map[i].regval == regval)
                        return ts72xx_wdt_map[i].timeout;
        }

        return -EINVAL;
}

/**
 * ts72xx_wdt_kick() - kick the watchdog
 * @wdt: watchdog to be kicked
 *
 * Called with @wdt->lock held.
 */
static inline void ts72xx_wdt_kick(struct ts72xx_wdt *wdt)
{
        __raw_writeb(TS72XX_WDT_FEED_VAL, wdt->feed_reg);
}

/**
 * ts72xx_wdt_start() - starts the watchdog timer
 * @wdt: watchdog to be started
 *
 * This function programs timeout to watchdog timer
 * and starts it.
 *
 * Called with @wdt->lock held.
 */
static void ts72xx_wdt_start(struct ts72xx_wdt *wdt)
{
        /*
         * To program the wdt, it first must be "fed" and
         * only after that (within 30 usecs) the configuration
         * can be changed.
         */
        ts72xx_wdt_kick(wdt);
        __raw_writeb((u8)wdt->regval, wdt->control_reg);
}

/**
 * ts72xx_wdt_stop() - stops the watchdog timer
 * @wdt: watchdog to be stopped
 *
 * Called with @wdt->lock held.
 */
static void ts72xx_wdt_stop(struct ts72xx_wdt *wdt)
{
        ts72xx_wdt_kick(wdt);
        __raw_writeb(0, wdt->control_reg);
}

static int ts72xx_wdt_open(struct inode *inode, struct file *file)
{
        struct ts72xx_wdt *wdt = platform_get_drvdata(ts72xx_wdt_pdev);
        int regval;

        /*
         * Try to convert default timeout to valid register
         * value first.
         */
        regval = timeout_to_regval(timeout);
        if (regval < 0) {
                dev_err(&wdt->pdev->dev,
                        "failed to convert timeout (%d) to register value\n",
                        timeout);
                return regval;
        }

        if (mutex_lock_interruptible(&wdt->lock))
                return -ERESTARTSYS;

        if ((wdt->flags & TS72XX_WDT_BUSY_FLAG) != 0) {
                mutex_unlock(&wdt->lock);
                return -EBUSY;
        }

        wdt->flags = TS72XX_WDT_BUSY_FLAG;
        wdt->regval = regval;
        file->private_data = wdt;

        ts72xx_wdt_start(wdt);

        mutex_unlock(&wdt->lock);
        return nonseekable_open(inode, file);
}

static int ts72xx_wdt_release(struct inode *inode, struct file *file)
{
        struct ts72xx_wdt *wdt = file->private_data;

        if (mutex_lock_interruptible(&wdt->lock))
                return -ERESTARTSYS;

        if ((wdt->flags & TS72XX_WDT_EXPECT_CLOSE_FLAG) != 0) {
                ts72xx_wdt_stop(wdt);
        } else {
                dev_warn(&wdt->pdev->dev,
                         "TS-72XX WDT device closed unexpectly. "
                         "Watchdog timer will not stop!\n");
                /*
                 * Kick it one more time, to give userland some time
                 * to recover (for example, respawning the kicker
                 * daemon).
                 */
                ts72xx_wdt_kick(wdt);
        }

        wdt->flags = 0;

        mutex_unlock(&wdt->lock);
        return 0;
}

static ssize_t ts72xx_wdt_write(struct file *file,
                                const char __user *data,
                                size_t len,
                                loff_t *ppos)
{
        struct ts72xx_wdt *wdt = file->private_data;

        if (!len)
                return 0;

        if (mutex_lock_interruptible(&wdt->lock))
                return -ERESTARTSYS;

        ts72xx_wdt_kick(wdt);

        /*
         * Support for magic character closing. User process
         * writes 'V' into the device, just before it is closed.
         * This means that we know that the wdt timer can be
         * stopped after user closes the device.
         */
        if (!nowayout) {
                int i;

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

                        /* In case it was set long ago */
                        wdt->flags &= ~TS72XX_WDT_EXPECT_CLOSE_FLAG;

                        if (get_user(c, data + i)) {
                                mutex_unlock(&wdt->lock);
                                return -EFAULT;
                        }
                        if (c == 'V') {
                                wdt->flags |= TS72XX_WDT_EXPECT_CLOSE_FLAG;
                                break;
                        }
                }
        }

        mutex_unlock(&wdt->lock);
        return len;
}

static const struct watchdog_info winfo = {
        .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
                                  WDIOF_MAGICCLOSE,
        .firmware_version       = 1,
        .identity               = "TS-72XX WDT",
};

static long ts72xx_wdt_ioctl(struct file *file, unsigned int cmd,
                             unsigned long arg)
{
        struct ts72xx_wdt *wdt = file->private_data;
        void __user *argp = (void __user *)arg;
        int __user *p = (int __user *)argp;
        int error = 0;

        if (mutex_lock_interruptible(&wdt->lock))
                return -ERESTARTSYS;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &winfo, sizeof(winfo)))
                        error = -EFAULT;
                break;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                error = put_user(0, p);
                break;

        case WDIOC_KEEPALIVE:
                ts72xx_wdt_kick(wdt);
                break;

        case WDIOC_SETOPTIONS: {
                int options;

                error = get_user(options, p);
                if (error)
                        break;

                error = -EINVAL;

                if ((options & WDIOS_DISABLECARD) != 0) {
                        ts72xx_wdt_stop(wdt);
                        error = 0;
                }
                if ((options & WDIOS_ENABLECARD) != 0) {
                        ts72xx_wdt_start(wdt);
                        error = 0;
                }

                break;
        }

        case WDIOC_SETTIMEOUT: {
                int new_timeout;
                int regval;

                error = get_user(new_timeout, p);
                if (error)
                        break;

                regval = timeout_to_regval(new_timeout);
                if (regval < 0) {
                        error = regval;
                        break;
                }
                ts72xx_wdt_stop(wdt);
                wdt->regval = regval;
                ts72xx_wdt_start(wdt);

                /*FALLTHROUGH*/
        }

        case WDIOC_GETTIMEOUT:
                error = put_user(regval_to_timeout(wdt->regval), p);
                break;

        default:
                error = -ENOTTY;
                break;
        }

        mutex_unlock(&wdt->lock);
        return error;
}

static const struct file_operations ts72xx_wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .open           = ts72xx_wdt_open,
        .release        = ts72xx_wdt_release,
        .write          = ts72xx_wdt_write,
        .unlocked_ioctl = ts72xx_wdt_ioctl,
};

static struct miscdevice ts72xx_wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &ts72xx_wdt_fops,
};

static int ts72xx_wdt_probe(struct platform_device *pdev)
{
        struct ts72xx_wdt *wdt;
        struct resource *r1, *r2;
        int error = 0;

        wdt = devm_kzalloc(&pdev->dev, sizeof(struct ts72xx_wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        r1 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        wdt->control_reg = devm_ioremap_resource(&pdev->dev, r1);
        if (IS_ERR(wdt->control_reg))
                return PTR_ERR(wdt->control_reg);

        r2 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
        wdt->feed_reg = devm_ioremap_resource(&pdev->dev, r2);
        if (IS_ERR(wdt->feed_reg))
                return PTR_ERR(wdt->feed_reg);

        platform_set_drvdata(pdev, wdt);
        ts72xx_wdt_pdev = pdev;
        wdt->pdev = pdev;
        mutex_init(&wdt->lock);

        /* make sure that the watchdog is disabled */
        ts72xx_wdt_stop(wdt);

        error = misc_register(&ts72xx_wdt_miscdev);
        if (error) {
                dev_err(&pdev->dev, "failed to register miscdev\n");
                return error;
        }

        dev_info(&pdev->dev, "TS-72xx Watchdog driver\n");

        return 0;
}

static int ts72xx_wdt_remove(struct platform_device *pdev)
{
        return misc_deregister(&ts72xx_wdt_miscdev);
}

static struct platform_driver ts72xx_wdt_driver = {
        .probe          = ts72xx_wdt_probe,
        .remove         = ts72xx_wdt_remove,
        .driver         = {
                .name   = "ts72xx-wdt",
        },
};

module_platform_driver(ts72xx_wdt_driver);

MODULE_AUTHOR("Mika Westerberg <mika.westerberg@iki.fi>");
MODULE_DESCRIPTION("TS-72xx SBC Watchdog");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ts72xx-wdt");