/*
 * MPC5200 General Purpose Timer device driver
 *
 * Copyright (c) 2009 Secret Lab Technologies Ltd.
 * Copyright (c) 2008 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
 *
 * 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.
 *
 * This file is a driver for the the General Purpose Timer (gpt) devices
 * found on the MPC5200 SoC.  Each timer has an IO pin which can be used
 * for GPIO or can be used to raise interrupts.  The timer function can
 * be used independently from the IO pin, or it can be used to control
 * output signals or measure input signals.
 *
 * This driver supports the GPIO and IRQ controller functions of the GPT
 * device.  Timer functions are not yet supported.
 *
 * The timer gpt0 can be used as watchdog (wdt).  If the wdt mode is used,
 * this prevents the use of any gpt0 gpt function (i.e. they will fail with
 * -EBUSY).  Thus, the safety wdt function always has precedence over the gpt
 * function.  If the kernel has been compiled with CONFIG_WATCHDOG_NOWAYOUT,
 * this means that gpt0 is locked in wdt mode until the next reboot - this
 * may be a requirement in safety applications.
 *
 * To use the GPIO function, the following two properties must be added
 * to the device tree node for the gpt device (typically in the .dts file
 * for the board):
 *      gpio-controller;
 *      #gpio-cells = < 2 >;
 * This driver will register the GPIO pin if it finds the gpio-controller
 * property in the device tree.
 *
 * To use the IRQ controller function, the following two properties must
 * be added to the device tree node for the gpt device:
 *      interrupt-controller;
 *      #interrupt-cells = < 1 >;
 * The IRQ controller binding only uses one cell to specify the interrupt,
 * and the IRQ flags are encoded in the cell.  A cell is not used to encode
 * the IRQ number because the GPT only has a single IRQ source.  For flags,
 * a value of '1' means rising edge sensitive and '2' means falling edge.
 *
 * The GPIO and the IRQ controller functions can be used at the same time,
 * but in this use case the IO line will only work as an input.  Trying to
 * use it as a GPIO output will not work.
 *
 * When using the GPIO line as an output, it can either be driven as normal
 * IO, or it can be an Open Collector (OC) output.  At the moment it is the
 * responsibility of either the bootloader or the platform setup code to set
 * the output mode.  This driver does not change the output mode setting.
 */

#include <linux/device.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/watchdog.h>
#include <linux/miscdevice.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <asm/div64.h>
#include <asm/mpc52xx.h>

MODULE_DESCRIPTION("Freescale MPC52xx gpt driver");
MODULE_AUTHOR("Sascha Hauer, Grant Likely, Albrecht Dreß");
MODULE_LICENSE("GPL");

/**
 * struct mpc52xx_gpt - Private data structure for MPC52xx GPT driver
 * @dev: pointer to device structure
 * @regs: virtual address of GPT registers
 * @lock: spinlock to coordinate between different functions.
 * @gc: gpio_chip instance structure; used when GPIO is enabled
 * @irqhost: Pointer to irq_domain instance; used when IRQ mode is supported
 * @wdt_mode: only relevant for gpt0: bit 0 (MPC52xx_GPT_CAN_WDT) indicates
 *   if the gpt may be used as wdt, bit 1 (MPC52xx_GPT_IS_WDT) indicates
 *   if the timer is actively used as wdt which blocks gpt functions
 */
struct mpc52xx_gpt_priv {
        struct list_head list;          /* List of all GPT devices */
        struct device *dev;
        struct mpc52xx_gpt __iomem *regs;
        spinlock_t lock;
        struct irq_domain *irqhost;
        u32 ipb_freq;
        u8 wdt_mode;

#if defined(CONFIG_GPIOLIB)
        struct gpio_chip gc;
#endif
};

LIST_HEAD(mpc52xx_gpt_list);
DEFINE_MUTEX(mpc52xx_gpt_list_mutex);

#define MPC52xx_GPT_MODE_MS_MASK        (0x07)
#define MPC52xx_GPT_MODE_MS_IC          (0x01)
#define MPC52xx_GPT_MODE_MS_OC          (0x02)
#define MPC52xx_GPT_MODE_MS_PWM         (0x03)
#define MPC52xx_GPT_MODE_MS_GPIO        (0x04)

#define MPC52xx_GPT_MODE_GPIO_MASK      (0x30)
#define MPC52xx_GPT_MODE_GPIO_OUT_LOW   (0x20)
#define MPC52xx_GPT_MODE_GPIO_OUT_HIGH  (0x30)

#define MPC52xx_GPT_MODE_COUNTER_ENABLE (0x1000)
#define MPC52xx_GPT_MODE_CONTINUOUS     (0x0400)
#define MPC52xx_GPT_MODE_OPEN_DRAIN     (0x0200)
#define MPC52xx_GPT_MODE_IRQ_EN         (0x0100)
#define MPC52xx_GPT_MODE_WDT_EN         (0x8000)

#define MPC52xx_GPT_MODE_ICT_MASK       (0x030000)
#define MPC52xx_GPT_MODE_ICT_RISING     (0x010000)
#define MPC52xx_GPT_MODE_ICT_FALLING    (0x020000)
#define MPC52xx_GPT_MODE_ICT_TOGGLE     (0x030000)

#define MPC52xx_GPT_MODE_WDT_PING       (0xa5)

#define MPC52xx_GPT_STATUS_IRQMASK      (0x000f)

#define MPC52xx_GPT_CAN_WDT             (1 << 0)
#define MPC52xx_GPT_IS_WDT              (1 << 1)


/* ---------------------------------------------------------------------
 * Cascaded interrupt controller hooks
 */

static void mpc52xx_gpt_irq_unmask(struct irq_data *d)
{
        struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);
        unsigned long flags;

        spin_lock_irqsave(&gpt->lock, flags);
        setbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_IRQ_EN);
        spin_unlock_irqrestore(&gpt->lock, flags);
}

static void mpc52xx_gpt_irq_mask(struct irq_data *d)
{
        struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);
        unsigned long flags;

        spin_lock_irqsave(&gpt->lock, flags);
        clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_IRQ_EN);
        spin_unlock_irqrestore(&gpt->lock, flags);
}

static void mpc52xx_gpt_irq_ack(struct irq_data *d)
{
        struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);

        out_be32(&gpt->regs->status, MPC52xx_GPT_STATUS_IRQMASK);
}

static int mpc52xx_gpt_irq_set_type(struct irq_data *d, unsigned int flow_type)
{
        struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);
        unsigned long flags;
        u32 reg;

        dev_dbg(gpt->dev, "%s: virq=%i type=%x\n", __func__, d->irq, flow_type);

        spin_lock_irqsave(&gpt->lock, flags);
        reg = in_be32(&gpt->regs->mode) & ~MPC52xx_GPT_MODE_ICT_MASK;
        if (flow_type & IRQF_TRIGGER_RISING)
                reg |= MPC52xx_GPT_MODE_ICT_RISING;
        if (flow_type & IRQF_TRIGGER_FALLING)
                reg |= MPC52xx_GPT_MODE_ICT_FALLING;
        out_be32(&gpt->regs->mode, reg);
        spin_unlock_irqrestore(&gpt->lock, flags);

        return 0;
}

static struct irq_chip mpc52xx_gpt_irq_chip = {
        .name = "MPC52xx GPT",
        .irq_unmask = mpc52xx_gpt_irq_unmask,
        .irq_mask = mpc52xx_gpt_irq_mask,
        .irq_ack = mpc52xx_gpt_irq_ack,
        .irq_set_type = mpc52xx_gpt_irq_set_type,
};

void mpc52xx_gpt_irq_cascade(unsigned int virq, struct irq_desc *desc)
{
        struct mpc52xx_gpt_priv *gpt = irq_get_handler_data(virq);
        int sub_virq;
        u32 status;

        status = in_be32(&gpt->regs->status) & MPC52xx_GPT_STATUS_IRQMASK;
        if (status) {
                sub_virq = irq_linear_revmap(gpt->irqhost, 0);
                generic_handle_irq(sub_virq);
        }
}

static int mpc52xx_gpt_irq_map(struct irq_domain *h, unsigned int virq,
                               irq_hw_number_t hw)
{
        struct mpc52xx_gpt_priv *gpt = h->host_data;

        dev_dbg(gpt->dev, "%s: h=%p, virq=%i\n", __func__, h, virq);
        irq_set_chip_data(virq, gpt);
        irq_set_chip_and_handler(virq, &mpc52xx_gpt_irq_chip, handle_edge_irq);

        return 0;
}

static int mpc52xx_gpt_irq_xlate(struct irq_domain *h, struct device_node *ct,
                                 const u32 *intspec, unsigned int intsize,
                                 irq_hw_number_t *out_hwirq,
                                 unsigned int *out_flags)
{
        struct mpc52xx_gpt_priv *gpt = h->host_data;

        dev_dbg(gpt->dev, "%s: flags=%i\n", __func__, intspec[0]);

        if ((intsize < 1) || (intspec[0] > 3)) {
                dev_err(gpt->dev, "bad irq specifier in %s\n", ct->full_name);
                return -EINVAL;
        }

        *out_hwirq = 0; /* The GPT only has 1 IRQ line */
        *out_flags = intspec[0];

        return 0;
}

static const struct irq_domain_ops mpc52xx_gpt_irq_ops = {
        .map = mpc52xx_gpt_irq_map,
        .xlate = mpc52xx_gpt_irq_xlate,
};

static void
mpc52xx_gpt_irq_setup(struct mpc52xx_gpt_priv *gpt, struct device_node *node)
{
        int cascade_virq;
        unsigned long flags;
        u32 mode;

        cascade_virq = irq_of_parse_and_map(node, 0);
        if (!cascade_virq)
                return;

        gpt->irqhost = irq_domain_add_linear(node, 1, &mpc52xx_gpt_irq_ops, gpt);
        if (!gpt->irqhost) {
                dev_err(gpt->dev, "irq_domain_add_linear() failed\n");
                return;
        }

        irq_set_handler_data(cascade_virq, gpt);
        irq_set_chained_handler(cascade_virq, mpc52xx_gpt_irq_cascade);

        /* If the GPT is currently disabled, then change it to be in Input
         * Capture mode.  If the mode is non-zero, then the pin could be
         * already in use for something. */
        spin_lock_irqsave(&gpt->lock, flags);
        mode = in_be32(&gpt->regs->mode);
        if ((mode & MPC52xx_GPT_MODE_MS_MASK) == 0)
                out_be32(&gpt->regs->mode, mode | MPC52xx_GPT_MODE_MS_IC);
        spin_unlock_irqrestore(&gpt->lock, flags);

        dev_dbg(gpt->dev, "%s() complete. virq=%i\n", __func__, cascade_virq);
}


/* ---------------------------------------------------------------------
 * GPIOLIB hooks
 */
#if defined(CONFIG_GPIOLIB)
static inline struct mpc52xx_gpt_priv *gc_to_mpc52xx_gpt(struct gpio_chip *gc)
{
        return container_of(gc, struct mpc52xx_gpt_priv, gc);
}

static int mpc52xx_gpt_gpio_get(struct gpio_chip *gc, unsigned int gpio)
{
        struct mpc52xx_gpt_priv *gpt = gc_to_mpc52xx_gpt(gc);

        return (in_be32(&gpt->regs->status) >> 8) & 1;
}

static void
mpc52xx_gpt_gpio_set(struct gpio_chip *gc, unsigned int gpio, int v)
{
        struct mpc52xx_gpt_priv *gpt = gc_to_mpc52xx_gpt(gc);
        unsigned long flags;
        u32 r;

        dev_dbg(gpt->dev, "%s: gpio:%d v:%d\n", __func__, gpio, v);
        r = v ? MPC52xx_GPT_MODE_GPIO_OUT_HIGH : MPC52xx_GPT_MODE_GPIO_OUT_LOW;

        spin_lock_irqsave(&gpt->lock, flags);
        clrsetbits_be32(&gpt->regs->mode, MPC52xx_GPT_MODE_GPIO_MASK, r);
        spin_unlock_irqrestore(&gpt->lock, flags);
}

static int mpc52xx_gpt_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
{
        struct mpc52xx_gpt_priv *gpt = gc_to_mpc52xx_gpt(gc);
        unsigned long flags;

        dev_dbg(gpt->dev, "%s: gpio:%d\n", __func__, gpio);

        spin_lock_irqsave(&gpt->lock, flags);
        clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_GPIO_MASK);
        spin_unlock_irqrestore(&gpt->lock, flags);

        return 0;
}

static int
mpc52xx_gpt_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
        mpc52xx_gpt_gpio_set(gc, gpio, val);
        return 0;
}

static void
mpc52xx_gpt_gpio_setup(struct mpc52xx_gpt_priv *gpt, struct device_node *node)
{
        int rc;

        /* Only setup GPIO if the device tree claims the GPT is
         * a GPIO controller */
        if (!of_find_property(node, "gpio-controller", NULL))
                return;

        gpt->gc.label = kstrdup(node->full_name, GFP_KERNEL);
        if (!gpt->gc.label) {
                dev_err(gpt->dev, "out of memory\n");
                return;
        }

        gpt->gc.ngpio = 1;
        gpt->gc.direction_input  = mpc52xx_gpt_gpio_dir_in;
        gpt->gc.direction_output = mpc52xx_gpt_gpio_dir_out;
        gpt->gc.get = mpc52xx_gpt_gpio_get;
        gpt->gc.set = mpc52xx_gpt_gpio_set;
        gpt->gc.base = -1;
        gpt->gc.of_node = node;

        /* Setup external pin in GPIO mode */
        clrsetbits_be32(&gpt->regs->mode, MPC52xx_GPT_MODE_MS_MASK,
                        MPC52xx_GPT_MODE_MS_GPIO);

        rc = gpiochip_add(&gpt->gc);
        if (rc)
                dev_err(gpt->dev, "gpiochip_add() failed; rc=%i\n", rc);

        dev_dbg(gpt->dev, "%s() complete.\n", __func__);
}
#else /* defined(CONFIG_GPIOLIB) */
static void
mpc52xx_gpt_gpio_setup(struct mpc52xx_gpt_priv *p, struct device_node *np) { }
#endif /* defined(CONFIG_GPIOLIB) */

/***********************************************************************
 * Timer API
 */

/**
 * mpc52xx_gpt_from_irq - Return the GPT device associated with an IRQ number
 * @irq: irq of timer.
 */
struct mpc52xx_gpt_priv *mpc52xx_gpt_from_irq(int irq)
{
        struct mpc52xx_gpt_priv *gpt;
        struct list_head *pos;

        /* Iterate over the list of timers looking for a matching device */
        mutex_lock(&mpc52xx_gpt_list_mutex);
        list_for_each(pos, &mpc52xx_gpt_list) {
                gpt = container_of(pos, struct mpc52xx_gpt_priv, list);
                if (gpt->irqhost && irq == irq_linear_revmap(gpt->irqhost, 0)) {
                        mutex_unlock(&mpc52xx_gpt_list_mutex);
                        return gpt;
                }
        }
        mutex_unlock(&mpc52xx_gpt_list_mutex);

        return NULL;
}
EXPORT_SYMBOL(mpc52xx_gpt_from_irq);

static int mpc52xx_gpt_do_start(struct mpc52xx_gpt_priv *gpt, u64 period,
                                int continuous, int as_wdt)
{
        u32 clear, set;
        u64 clocks;
        u32 prescale;
        unsigned long flags;

        clear = MPC52xx_GPT_MODE_MS_MASK | MPC52xx_GPT_MODE_CONTINUOUS;
        set = MPC52xx_GPT_MODE_MS_GPIO | MPC52xx_GPT_MODE_COUNTER_ENABLE;
        if (as_wdt) {
                clear |= MPC52xx_GPT_MODE_IRQ_EN;
                set |= MPC52xx_GPT_MODE_WDT_EN;
        } else if (continuous)
                set |= MPC52xx_GPT_MODE_CONTINUOUS;

        /* Determine the number of clocks in the requested period.  64 bit
         * arithmatic is done here to preserve the precision until the value
         * is scaled back down into the u32 range.  Period is in 'ns', bus
         * frequency is in Hz. */
        clocks = period * (u64)gpt->ipb_freq;
        do_div(clocks, 1000000000); /* Scale it down to ns range */

        /* This device cannot handle a clock count greater than 32 bits */
        if (clocks > 0xffffffff)
                return -EINVAL;

        /* Calculate the prescaler and count values from the clocks value.
         * 'clocks' is the number of clock ticks in the period.  The timer
         * has 16 bit precision and a 16 bit prescaler.  Prescaler is
         * calculated by integer dividing the clocks by 0x10000 (shifting
         * down 16 bits) to obtain the smallest possible divisor for clocks
         * to get a 16 bit count value.
         *
         * Note: the prescale register is '1' based, not '0' based.  ie. a
         * value of '1' means divide the clock by one.  0xffff divides the
         * clock by 0xffff.  '0x0000' does not divide by zero, but wraps
         * around and divides by 0x10000.  That is why prescale must be
         * a u32 variable, not a u16, for this calculation. */
        prescale = (clocks >> 16) + 1;
        do_div(clocks, prescale);
        if (clocks > 0xffff) {
                pr_err("calculation error; prescale:%x clocks:%llx\n",
                       prescale, clocks);
                return -EINVAL;
        }

        /* Set and enable the timer, reject an attempt to use a wdt as gpt */
        spin_lock_irqsave(&gpt->lock, flags);
        if (as_wdt)
                gpt->wdt_mode |= MPC52xx_GPT_IS_WDT;
        else if ((gpt->wdt_mode & MPC52xx_GPT_IS_WDT) != 0) {
                spin_unlock_irqrestore(&gpt->lock, flags);
                return -EBUSY;
        }
        out_be32(&gpt->regs->count, prescale << 16 | clocks);
        clrsetbits_be32(&gpt->regs->mode, clear, set);
        spin_unlock_irqrestore(&gpt->lock, flags);

        return 0;
}

/**
 * mpc52xx_gpt_start_timer - Set and enable the GPT timer
 * @gpt: Pointer to gpt private data structure
 * @period: period of timer in ns; max. ~130s @ 33MHz IPB clock
 * @continuous: set to 1 to make timer continuous free running
 *
 * An interrupt will be generated every time the timer fires
 */
int mpc52xx_gpt_start_timer(struct mpc52xx_gpt_priv *gpt, u64 period,
                            int continuous)
{
        return mpc52xx_gpt_do_start(gpt, period, continuous, 0);
}
EXPORT_SYMBOL(mpc52xx_gpt_start_timer);

/**
 * mpc52xx_gpt_stop_timer - Stop a gpt
 * @gpt: Pointer to gpt private data structure
 *
 * Returns an error if attempting to stop a wdt
 */
int mpc52xx_gpt_stop_timer(struct mpc52xx_gpt_priv *gpt)
{
        unsigned long flags;

        /* reject the operation if the timer is used as watchdog (gpt 0 only) */
        spin_lock_irqsave(&gpt->lock, flags);
        if ((gpt->wdt_mode & MPC52xx_GPT_IS_WDT) != 0) {
                spin_unlock_irqrestore(&gpt->lock, flags);
                return -EBUSY;
        }

        clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_COUNTER_ENABLE);
        spin_unlock_irqrestore(&gpt->lock, flags);
        return 0;
}
EXPORT_SYMBOL(mpc52xx_gpt_stop_timer);

/**
 * mpc52xx_gpt_timer_period - Read the timer period
 * @gpt: Pointer to gpt private data structure
 *
 * Returns the timer period in ns
 */
u64 mpc52xx_gpt_timer_period(struct mpc52xx_gpt_priv *gpt)
{
        u64 period;
        u64 prescale;
        unsigned long flags;

        spin_lock_irqsave(&gpt->lock, flags);
        period = in_be32(&gpt->regs->count);
        spin_unlock_irqrestore(&gpt->lock, flags);

        prescale = period >> 16;
        period &= 0xffff;
        if (prescale == 0)
                prescale = 0x10000;
        period = period * prescale * 1000000000ULL;
        do_div(period, (u64)gpt->ipb_freq);
        return period;
}
EXPORT_SYMBOL(mpc52xx_gpt_timer_period);

#if defined(CONFIG_MPC5200_WDT)
/***********************************************************************
 * Watchdog API for gpt0
 */

#define WDT_IDENTITY        "mpc52xx watchdog on GPT0"

/* wdt_is_active stores whether or not the /dev/watchdog device is opened */
static unsigned long wdt_is_active;

/* wdt-capable gpt */
static struct mpc52xx_gpt_priv *mpc52xx_gpt_wdt;

/* low-level wdt functions */
static inline void mpc52xx_gpt_wdt_ping(struct mpc52xx_gpt_priv *gpt_wdt)
{
        unsigned long flags;

        spin_lock_irqsave(&gpt_wdt->lock, flags);
        out_8((u8 *) &gpt_wdt->regs->mode, MPC52xx_GPT_MODE_WDT_PING);
        spin_unlock_irqrestore(&gpt_wdt->lock, flags);
}

/* wdt misc device api */
static ssize_t mpc52xx_wdt_write(struct file *file, const char __user *data,
                                 size_t len, loff_t *ppos)
{
        struct mpc52xx_gpt_priv *gpt_wdt = file->private_data;
        mpc52xx_gpt_wdt_ping(gpt_wdt);
        return 0;
}

static const struct watchdog_info mpc5200_wdt_info = {
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
        .identity       = WDT_IDENTITY,
};

static long mpc52xx_wdt_ioctl(struct file *file, unsigned int cmd,
                              unsigned long arg)
{
        struct mpc52xx_gpt_priv *gpt_wdt = file->private_data;
        int __user *data = (int __user *)arg;
        int timeout;
        u64 real_timeout;
        int ret = 0;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                ret = copy_to_user(data, &mpc5200_wdt_info,
                                   sizeof(mpc5200_wdt_info));
                if (ret)
                        ret = -EFAULT;
                break;

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

        case WDIOC_KEEPALIVE:
                mpc52xx_gpt_wdt_ping(gpt_wdt);
                break;

        case WDIOC_SETTIMEOUT:
                ret = get_user(timeout, data);
                if (ret)
                        break;
                real_timeout = (u64) timeout * 1000000000ULL;
                ret = mpc52xx_gpt_do_start(gpt_wdt, real_timeout, 0, 1);
                if (ret)
                        break;
                /* fall through and return the timeout */

        case WDIOC_GETTIMEOUT:
                /* we need to round here as to avoid e.g. the following
                 * situation:
                 * - timeout requested is 1 second;
                 * - real timeout @33MHz is 999997090ns
                 * - the int divide by 10^9 will return 0.
                 */
                real_timeout =
                        mpc52xx_gpt_timer_period(gpt_wdt) + 500000000ULL;
                do_div(real_timeout, 1000000000ULL);
                timeout = (int) real_timeout;
                ret = put_user(timeout, data);
                break;

        default:
                ret = -ENOTTY;
        }
        return ret;
}

static int mpc52xx_wdt_open(struct inode *inode, struct file *file)
{
        int ret;

        /* sanity check */
        if (!mpc52xx_gpt_wdt)
                return -ENODEV;

        /* /dev/watchdog can only be opened once */
        if (test_and_set_bit(0, &wdt_is_active))
                return -EBUSY;

        /* Set and activate the watchdog with 30 seconds timeout */
        ret = mpc52xx_gpt_do_start(mpc52xx_gpt_wdt, 30ULL * 1000000000ULL,
                                   0, 1);
        if (ret) {
                clear_bit(0, &wdt_is_active);
                return ret;
        }

        file->private_data = mpc52xx_gpt_wdt;
        return nonseekable_open(inode, file);
}

static int mpc52xx_wdt_release(struct inode *inode, struct file *file)
{
        /* note: releasing the wdt in NOWAYOUT-mode does not stop it */
#if !defined(CONFIG_WATCHDOG_NOWAYOUT)
        struct mpc52xx_gpt_priv *gpt_wdt = file->private_data;
        unsigned long flags;

        spin_lock_irqsave(&gpt_wdt->lock, flags);
        clrbits32(&gpt_wdt->regs->mode,
                  MPC52xx_GPT_MODE_COUNTER_ENABLE | MPC52xx_GPT_MODE_WDT_EN);
        gpt_wdt->wdt_mode &= ~MPC52xx_GPT_IS_WDT;
        spin_unlock_irqrestore(&gpt_wdt->lock, flags);
#endif
        clear_bit(0, &wdt_is_active);
        return 0;
}


static const struct file_operations mpc52xx_wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = mpc52xx_wdt_write,
        .unlocked_ioctl = mpc52xx_wdt_ioctl,
        .open           = mpc52xx_wdt_open,
        .release        = mpc52xx_wdt_release,
};

static struct miscdevice mpc52xx_wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &mpc52xx_wdt_fops,
};

static int mpc52xx_gpt_wdt_init(void)
{
        int err;

        /* try to register the watchdog misc device */
        err = misc_register(&mpc52xx_wdt_miscdev);
        if (err)
                pr_err("%s: cannot register watchdog device\n", WDT_IDENTITY);
        else
                pr_info("%s: watchdog device registered\n", WDT_IDENTITY);
        return err;
}

static int mpc52xx_gpt_wdt_setup(struct mpc52xx_gpt_priv *gpt,
                                 const u32 *period)
{
        u64 real_timeout;

        /* remember the gpt for the wdt operation */
        mpc52xx_gpt_wdt = gpt;

        /* configure the wdt if the device tree contained a timeout */
        if (!period || *period == 0)
                return 0;

        real_timeout = (u64) *period * 1000000000ULL;
        if (mpc52xx_gpt_do_start(gpt, real_timeout, 0, 1))
                dev_warn(gpt->dev, "starting as wdt failed\n");
        else
                dev_info(gpt->dev, "watchdog set to %us timeout\n", *period);
        return 0;
}

#else

static int mpc52xx_gpt_wdt_init(void)
{
        return 0;
}

static inline int mpc52xx_gpt_wdt_setup(struct mpc52xx_gpt_priv *gpt,
                                        const u32 *period)
{
        return 0;
}

#endif  /*  CONFIG_MPC5200_WDT  */

/* ---------------------------------------------------------------------
 * of_platform bus binding code
 */
static int mpc52xx_gpt_probe(struct platform_device *ofdev)
{
        struct mpc52xx_gpt_priv *gpt;

        gpt = kzalloc(sizeof *gpt, GFP_KERNEL);
        if (!gpt)
                return -ENOMEM;

        spin_lock_init(&gpt->lock);
        gpt->dev = &ofdev->dev;
        gpt->ipb_freq = mpc5xxx_get_bus_frequency(ofdev->dev.of_node);
        gpt->regs = of_iomap(ofdev->dev.of_node, 0);
        if (!gpt->regs) {
                kfree(gpt);
                return -ENOMEM;
        }

        dev_set_drvdata(&ofdev->dev, gpt);

        mpc52xx_gpt_gpio_setup(gpt, ofdev->dev.of_node);
        mpc52xx_gpt_irq_setup(gpt, ofdev->dev.of_node);

        mutex_lock(&mpc52xx_gpt_list_mutex);
        list_add(&gpt->list, &mpc52xx_gpt_list);
        mutex_unlock(&mpc52xx_gpt_list_mutex);

        /* check if this device could be a watchdog */
        if (of_get_property(ofdev->dev.of_node, "fsl,has-wdt", NULL) ||
            of_get_property(ofdev->dev.of_node, "has-wdt", NULL)) {
                const u32 *on_boot_wdt;

                gpt->wdt_mode = MPC52xx_GPT_CAN_WDT;
                on_boot_wdt = of_get_property(ofdev->dev.of_node,
                                              "fsl,wdt-on-boot", NULL);
                if (on_boot_wdt) {
                        dev_info(gpt->dev, "used as watchdog\n");
                        gpt->wdt_mode |= MPC52xx_GPT_IS_WDT;
                } else
                        dev_info(gpt->dev, "can function as watchdog\n");
                mpc52xx_gpt_wdt_setup(gpt, on_boot_wdt);
        }

        return 0;
}

static int mpc52xx_gpt_remove(struct platform_device *ofdev)
{
        return -EBUSY;
}

static const struct of_device_id mpc52xx_gpt_match[] = {
        { .compatible = "fsl,mpc5200-gpt", },

        /* Depreciated compatible values; don't use for new dts files */
        { .compatible = "fsl,mpc5200-gpt-gpio", },
        { .compatible = "mpc5200-gpt", },
        {}
};

static struct platform_driver mpc52xx_gpt_driver = {
        .driver = {
                .name = "mpc52xx-gpt",
                .owner = THIS_MODULE,
                .of_match_table = mpc52xx_gpt_match,
        },
        .probe = mpc52xx_gpt_probe,
        .remove = mpc52xx_gpt_remove,
};

static int __init mpc52xx_gpt_init(void)
{
        return platform_driver_register(&mpc52xx_gpt_driver);
}

/* Make sure GPIOs and IRQs get set up before anyone tries to use them */
subsys_initcall(mpc52xx_gpt_init);
device_initcall(mpc52xx_gpt_wdt_init);