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/*

 * Watchdog driver for Atmel AT32AP700X devices

 *

 * Copyright (C) 2005-2006 Atmel Corporation

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 *

 * Errata: WDT Clear is blocked after WDT Reset

 *

 * A watchdog timer event will, after reset, block writes to the WDT_CLEAR

 * register, preventing the program to clear the next Watchdog Timer Reset.

 *

 * If you still want to use the WDT after a WDT reset a small code can be

 * insterted at the startup checking the AVR32_PM.rcause register for WDT reset

 * and use a GPIO pin to reset the system. This method requires that one of the

 * GPIO pins are available and connected externally to the RESET_N pin. After

 * the GPIO pin has pulled down the reset line the GPIO will be reset and leave

 * the pin tristated with pullup.

 */

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/miscdevice.h>

#include <linux/fs.h>

#include <linux/platform_device.h>

#include <linux/watchdog.h>

#include <linux/uaccess.h>

#include <linux/io.h>

#include <linux/spinlock.h>

#define TIMEOUT_MIN             1

#define TIMEOUT_MAX             2

#define TIMEOUT_DEFAULT         TIMEOUT_MAX

/* module parameters */

static int timeout =  TIMEOUT_DEFAULT;

module_param(timeout, int, 0);

MODULE_PARM_DESC(timeout,

                "Timeout value. Limited to be 1 or 2 seconds. (default="

                __MODULE_STRING(TIMEOUT_DEFAULT) ")");

static int nowayout = WATCHDOG_NOWAYOUT;

module_param(nowayout, int, 0);

MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="

                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/* Watchdog registers and write/read macro */

#define WDT_CTRL                0x00

#define WDT_CTRL_EN                0

#define WDT_CTRL_PSEL              8

#define WDT_CTRL_KEY              24

#define WDT_CLR                 0x04

#define WDT_RCAUSE              0x10

#define WDT_RCAUSE_POR             0

#define WDT_RCAUSE_EXT             2

#define WDT_RCAUSE_WDT             3

#define WDT_RCAUSE_JTAG            4

#define WDT_RCAUSE_SERP            5

#define WDT_BIT(name)           (1 << WDT_##name)

#define WDT_BF(name, value)     ((value) << WDT_##name)

#define wdt_readl(dev, reg)                             \

        __raw_readl((dev)->regs + WDT_##reg)

#define wdt_writel(dev, reg, value)                     \

        __raw_writel((value), (dev)->regs + WDT_##reg)

struct wdt_at32ap700x {

        void __iomem            *regs;

        spinlock_t              io_lock;

        int                     timeout;

        int                     boot_status;

        unsigned long           users;

        struct miscdevice       miscdev;

};

static struct wdt_at32ap700x *wdt;

static char expect_release;

/*

 * Disable the watchdog.

 */

static inline void at32_wdt_stop(void)

{

        unsigned long psel;

        spin_lock(&wdt->io_lock);

        psel = wdt_readl(wdt, CTRL) & WDT_BF(CTRL_PSEL, 0x0f);

        wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0x55));

        wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0xaa));

        spin_unlock(&wdt->io_lock);

}

/*

 * Enable and reset the watchdog.

 */

static inline void at32_wdt_start(void)

{

        /* 0xf is 2^16 divider = 2 sec, 0xe is 2^15 divider = 1 sec */

        unsigned long psel = (wdt->timeout > 1) ? 0xf : 0xe;

        spin_lock(&wdt->io_lock);

        wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)

                        | WDT_BF(CTRL_PSEL, psel)

                        | WDT_BF(CTRL_KEY, 0x55));

        wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)

                        | WDT_BF(CTRL_PSEL, psel)

                        | WDT_BF(CTRL_KEY, 0xaa));

        spin_unlock(&wdt->io_lock);

}

/*

 * Pat the watchdog timer.

 */

static inline void at32_wdt_pat(void)

{

        spin_lock(&wdt->io_lock);

        wdt_writel(wdt, CLR, 0x42);

        spin_unlock(&wdt->io_lock);

}

/*

 * Watchdog device is opened, and watchdog starts running.

 */

static int at32_wdt_open(struct inode *inode, struct file *file)

{

        if (test_and_set_bit(1, &wdt->users))

                return -EBUSY;

        at32_wdt_start();

        return nonseekable_open(inode, file);

}

/*

 * Close the watchdog device.

 */

static int at32_wdt_close(struct inode *inode, struct file *file)

{

        if (expect_release == 42) {

                at32_wdt_stop();

        } else {

                dev_dbg(wdt->miscdev.parent,

                        "unexpected close, not stopping watchdog!\n");

                at32_wdt_pat();

        }

        clear_bit(1, &wdt->users);

        expect_release = 0;

        return 0;

}

/*

 * Change the watchdog time interval.

 */

static int at32_wdt_settimeout(int time)

{

        /*

         * All counting occurs at 1 / SLOW_CLOCK (32 kHz) and max prescaler is

         * 2 ^ 16 allowing up to 2 seconds timeout.

         */

        if ((time < TIMEOUT_MIN) || (time > TIMEOUT_MAX))

                return -EINVAL;

        /*

         * Set new watchdog time. It will be used when at32_wdt_start() is

         * called.

         */

        wdt->timeout = time;

        return 0;

}

/*

 * Get the watchdog status.

 */

static int at32_wdt_get_status(void)

{

        int rcause;

        int status = 0;

        rcause = wdt_readl(wdt, RCAUSE);

        switch (rcause) {

        case WDT_BIT(RCAUSE_EXT):

                status = WDIOF_EXTERN1;

                break;

        case WDT_BIT(RCAUSE_WDT):

                status = WDIOF_CARDRESET;

                break;

        case WDT_BIT(RCAUSE_POR):  /* fall through */

        case WDT_BIT(RCAUSE_JTAG): /* fall through */

        case WDT_BIT(RCAUSE_SERP): /* fall through */

        default:

                break;

        }

        return status;

}

static struct watchdog_info at32_wdt_info = {

        .identity       = "at32ap700x watchdog",

        .options        = WDIOF_SETTIMEOUT |

                          WDIOF_KEEPALIVEPING |

                          WDIOF_MAGICCLOSE,

};

/*

 * Handle commands from user-space.

 */

static int at32_wdt_ioctl(struct inode *inode, struct file *file,

                unsigned int cmd, unsigned long arg)

{

        int ret = -ENOTTY;

        int time;

        void __user *argp = (void __user *)arg;

        int __user *p = argp;

        switch (cmd) {

        case WDIOC_KEEPALIVE:

                at32_wdt_pat();

                ret = 0;

                break;

        case WDIOC_GETSUPPORT:

                ret = copy_to_user(argp, &at32_wdt_info,

                                sizeof(at32_wdt_info)) ? -EFAULT : 0;

                break;

        case WDIOC_SETTIMEOUT:

                ret = get_user(time, p);

                if (ret)

                        break;

                ret = at32_wdt_settimeout(time);

                if (ret)

                        break;

                /* Enable new time value */

                at32_wdt_start();

                /* fall through */

        case WDIOC_GETTIMEOUT:

                ret = put_user(wdt->timeout, p);

                break;

        case WDIOC_GETSTATUS:

                ret = put_user(0, p);

                break;

        case WDIOC_GETBOOTSTATUS:

                ret = put_user(wdt->boot_status, p);

                break;

        case WDIOC_SETOPTIONS:

                ret = get_user(time, p);

                if (ret)

                        break;

                if (time & WDIOS_DISABLECARD)

                        at32_wdt_stop();

                if (time & WDIOS_ENABLECARD)

                        at32_wdt_start();

                ret = 0;

                break;

        }

        return ret;

}

static ssize_t at32_wdt_write(struct file *file, const char __user *data,

                                size_t len, loff_t *ppos)

{

        /* See if we got the magic character 'V' and reload the timer */

        if (len) {

                if (!nowayout) {

                        size_t i;

                        /*

                         * note: just in case someone wrote the magic

                         * character five months ago...

                         */

                        expect_release = 0;

                        /*

                         * scan to see whether or not we got the magic

                         * character

                         */

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

                                char c;

                                if (get_user(c, data+i))

                                        return -EFAULT;

                                if (c == 'V')

                                        expect_release = 42;

                        }

                }

                /* someone wrote to us, we should pat the watchdog */

                at32_wdt_pat();

        }

        return len;

}

static const struct file_operations at32_wdt_fops = {

        .owner          = THIS_MODULE,

        .llseek         = no_llseek,

        .ioctl          = at32_wdt_ioctl,

        .open           = at32_wdt_open,

        .release        = at32_wdt_close,

        .write          = at32_wdt_write,

};

static int __init at32_wdt_probe(struct platform_device *pdev)

{

        struct resource *regs;

        int ret;

        if (wdt) {

                dev_dbg(&pdev->dev, "only 1 wdt instance supported.\n");

                return -EBUSY;

        }

        regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        if (!regs) {

                dev_dbg(&pdev->dev, "missing mmio resource\n");

                return -ENXIO;

        }

        wdt = kzalloc(sizeof(struct wdt_at32ap700x), GFP_KERNEL);

        if (!wdt) {

                dev_dbg(&pdev->dev, "no memory for wdt structure\n");

                return -ENOMEM;

        }

        wdt->regs = ioremap(regs->start, regs->end - regs->start + 1);

        if (!wdt->regs) {

                ret = -ENOMEM;

                dev_dbg(&pdev->dev, "could not map I/O memory\n");

                goto err_free;

        }

        spin_lock_init(&wdt->io_lock);

        wdt->boot_status = at32_wdt_get_status();

        /* Work-around for watchdog silicon errata. */

        if (wdt->boot_status & WDIOF_CARDRESET) {

                dev_info(&pdev->dev, "CPU must be reset with external "

                                "reset or POR due to silicon errata.\n");

                ret = -EIO;

                goto err_iounmap;

        } else {

                wdt->users = 0;

        }

        wdt->miscdev.minor = WATCHDOG_MINOR;

        wdt->miscdev.name = "watchdog";

        wdt->miscdev.fops = &at32_wdt_fops;

        if (at32_wdt_settimeout(timeout)) {

                at32_wdt_settimeout(TIMEOUT_DEFAULT);

                dev_dbg(&pdev->dev,

                        "default timeout invalid, set to %d sec.\n",

                        TIMEOUT_DEFAULT);

        }

        ret = misc_register(&wdt->miscdev);

        if (ret) {

                dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");

                goto err_iounmap;

        }

        platform_set_drvdata(pdev, wdt);

        wdt->miscdev.parent = &pdev->dev;

        dev_info(&pdev->dev,

                "AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",

                wdt->regs, wdt->timeout, nowayout);

        return 0;

err_iounmap:

        iounmap(wdt->regs);

err_free:

        kfree(wdt);

        wdt = NULL;

        return ret;

}

static int __exit at32_wdt_remove(struct platform_device *pdev)

{

        if (wdt && platform_get_drvdata(pdev) == wdt) {

                /* Stop the timer before we leave */

                if (!nowayout)

                        at32_wdt_stop();

                misc_deregister(&wdt->miscdev);

                iounmap(wdt->regs);

                kfree(wdt);

                wdt = NULL;

                platform_set_drvdata(pdev, NULL);

        }

        return 0;

}

static void at32_wdt_shutdown(struct platform_device *pdev)

{

        at32_wdt_stop();

}

#ifdef CONFIG_PM

static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)

{

        at32_wdt_stop();

        return 0;

}

static int at32_wdt_resume(struct platform_device *pdev)

{

        if (wdt->users)

                at32_wdt_start();

        return 0;

}

#else

#define at32_wdt_suspend NULL

#define at32_wdt_resume NULL

#endif

static struct platform_driver at32_wdt_driver = {

        .remove         = __exit_p(at32_wdt_remove),

        .suspend        = at32_wdt_suspend,

        .resume         = at32_wdt_resume,

        .driver         = {

                .name   = "at32_wdt",

                .owner  = THIS_MODULE,

        },

        .shutdown       = at32_wdt_shutdown,

};

static int __init at32_wdt_init(void)

{

        return platform_driver_probe(&at32_wdt_driver, at32_wdt_probe);

}

module_init(at32_wdt_init);

static void __exit at32_wdt_exit(void)

{

        platform_driver_unregister(&at32_wdt_driver);

}

module_exit(at32_wdt_exit);

MODULE_AUTHOR("Hans-Christian Egtvedt <hcegtvedt@atmel.com>");

MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");

MODULE_LICENSE("GPL");

MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);