at32ap700x_wdt.c

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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>
#include <linux/slab.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 bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 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 const struct watchdog_info at32_wdt_info = {
    .identity   = "at32ap700x watchdog",
    .options    = WDIOF_SETTIMEOUT |
              WDIOF_KEEPALIVEPING |
              WDIOF_MAGICCLOSE,
};

/*
 * Handle commands from user-space.
 */
static long at32_wdt_ioctl(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_GETSUPPORT:
        ret = copy_to_user(argp, &at32_wdt_info,
                sizeof(at32_wdt_info)) ? -EFAULT : 0;
        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;
    case WDIOC_KEEPALIVE:
        at32_wdt_pat();
        ret = 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;
    }

    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,
    .unlocked_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, resource_size(regs));
    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;
    wdt->miscdev.parent = &pdev->dev;

    platform_set_drvdata(pdev, wdt);

    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_register;
    }

    dev_info(&pdev->dev,
        "AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
        wdt->regs, wdt->timeout, nowayout);

    return 0;

err_register:
    platform_set_drvdata(pdev, NULL);
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

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:at32_wdt");

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 <[email protected]>");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);