dw_wdt.c

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/*
 * Copyright 2010-2011 Picochip Ltd., Jamie Iles
 * http://www.picochip.com
 *
 * 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 implements a driver for the Synopsys DesignWare watchdog device
 * in the many ARM subsystems. The watchdog has 16 different timeout periods
 * and these are a function of the input clock frequency.
 *
 * The DesignWare watchdog cannot be stopped once it has been started so we
 * use a software timer to implement a ping that will keep the watchdog alive.
 * If we receive an expected close for the watchdog then we keep the timer
 * running, otherwise the timer is stopped and the watchdog will expire.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pm.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/timer.h>
#include <linux/uaccess.h>
#include <linux/watchdog.h>

#define WDOG_CONTROL_REG_OFFSET         0x00
#define WDOG_CONTROL_REG_WDT_EN_MASK        0x01
#define WDOG_TIMEOUT_RANGE_REG_OFFSET       0x04
#define WDOG_CURRENT_COUNT_REG_OFFSET       0x08
#define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
#define WDOG_COUNTER_RESTART_KICK_VALUE     0x76

/* The maximum TOP (timeout period) value that can be set in the watchdog. */
#define DW_WDT_MAX_TOP      15

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) ")");

#define WDT_TIMEOUT     (HZ / 2)

static struct {
    spinlock_t      lock;
    void __iomem        *regs;
    struct clk      *clk;
    unsigned long       in_use;
    unsigned long       next_heartbeat;
    struct timer_list   timer;
    int         expect_close;
} dw_wdt;

static inline int dw_wdt_is_enabled(void)
{
    return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
        WDOG_CONTROL_REG_WDT_EN_MASK;
}

static inline int dw_wdt_top_in_seconds(unsigned top)
{
    /*
     * There are 16 possible timeout values in 0..15 where the number of
     * cycles is 2 ^ (16 + i) and the watchdog counts down.
     */
    return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
}

static int dw_wdt_get_top(void)
{
    int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;

    return dw_wdt_top_in_seconds(top);
}

static inline void dw_wdt_set_next_heartbeat(void)
{
    dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
}

static int dw_wdt_set_top(unsigned top_s)
{
    int i, top_val = DW_WDT_MAX_TOP;

    /*
     * Iterate over the timeout values until we find the closest match. We
     * always look for >=.
     */
    for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
        if (dw_wdt_top_in_seconds(i) >= top_s) {
            top_val = i;
            break;
        }

    /* Set the new value in the watchdog. */
    writel(top_val, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);

    dw_wdt_set_next_heartbeat();

    return dw_wdt_top_in_seconds(top_val);
}

static void dw_wdt_keepalive(void)
{
    writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
           WDOG_COUNTER_RESTART_REG_OFFSET);
}

static void dw_wdt_ping(unsigned long data)
{
    if (time_before(jiffies, dw_wdt.next_heartbeat) ||
        (!nowayout && !dw_wdt.in_use)) {
        dw_wdt_keepalive();
        mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
    } else
        pr_crit("keepalive missed, machine will reset\n");
}

static int dw_wdt_open(struct inode *inode, struct file *filp)
{
    if (test_and_set_bit(0, &dw_wdt.in_use))
        return -EBUSY;

    /* Make sure we don't get unloaded. */
    __module_get(THIS_MODULE);

    spin_lock(&dw_wdt.lock);
    if (!dw_wdt_is_enabled()) {
        /*
         * The watchdog is not currently enabled. Set the timeout to
         * the maximum and then start it.
         */
        dw_wdt_set_top(DW_WDT_MAX_TOP);
        writel(WDOG_CONTROL_REG_WDT_EN_MASK,
               dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
    }

    dw_wdt_set_next_heartbeat();

    spin_unlock(&dw_wdt.lock);

    return nonseekable_open(inode, filp);
}

ssize_t dw_wdt_write(struct file *filp, const char __user *buf, size_t len,
             loff_t *offset)
{
    if (!len)
        return 0;

    if (!nowayout) {
        size_t i;

        dw_wdt.expect_close = 0;

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

            if (get_user(c, buf + i))
                return -EFAULT;

            if (c == 'V') {
                dw_wdt.expect_close = 1;
                break;
            }
        }
    }

    dw_wdt_set_next_heartbeat();
    mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);

    return len;
}

static u32 dw_wdt_time_left(void)
{
    return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
        clk_get_rate(dw_wdt.clk);
}

static const struct watchdog_info dw_wdt_ident = {
    .options    = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
              WDIOF_MAGICCLOSE,
    .identity   = "Synopsys DesignWare Watchdog",
};

static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    unsigned long val;
    int timeout;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user((struct watchdog_info *)arg, &dw_wdt_ident,
                    sizeof(dw_wdt_ident)) ? -EFAULT : 0;

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, (int *)arg);

    case WDIOC_KEEPALIVE:
        dw_wdt_set_next_heartbeat();
        return 0;

    case WDIOC_SETTIMEOUT:
        if (get_user(val, (int __user *)arg))
            return -EFAULT;
        timeout = dw_wdt_set_top(val);
        return put_user(timeout , (int __user *)arg);

    case WDIOC_GETTIMEOUT:
        return put_user(dw_wdt_get_top(), (int __user *)arg);

    case WDIOC_GETTIMELEFT:
        /* Get the time left until expiry. */
        if (get_user(val, (int __user *)arg))
            return -EFAULT;
        return put_user(dw_wdt_time_left(), (int __user *)arg);

    default:
        return -ENOTTY;
    }
}

static int dw_wdt_release(struct inode *inode, struct file *filp)
{
    clear_bit(0, &dw_wdt.in_use);

    if (!dw_wdt.expect_close) {
        del_timer(&dw_wdt.timer);

        if (!nowayout)
            pr_crit("unexpected close, system will reboot soon\n");
        else
            pr_crit("watchdog cannot be disabled, system will reboot soon\n");
    }

    dw_wdt.expect_close = 0;

    return 0;
}

#ifdef CONFIG_PM
static int dw_wdt_suspend(struct device *dev)
{
    clk_disable(dw_wdt.clk);

    return 0;
}

static int dw_wdt_resume(struct device *dev)
{
    int err = clk_enable(dw_wdt.clk);

    if (err)
        return err;

    dw_wdt_keepalive();

    return 0;
}

static const struct dev_pm_ops dw_wdt_pm_ops = {
    .suspend    = dw_wdt_suspend,
    .resume     = dw_wdt_resume,
};
#endif /* CONFIG_PM */

static const struct file_operations wdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .open       = dw_wdt_open,
    .write      = dw_wdt_write,
    .unlocked_ioctl = dw_wdt_ioctl,
    .release    = dw_wdt_release
};

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

static int __devinit dw_wdt_drv_probe(struct platform_device *pdev)
{
    int ret;
    struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

    if (!mem)
        return -EINVAL;

    dw_wdt.regs = devm_request_and_ioremap(&pdev->dev, mem);
    if (!dw_wdt.regs)
        return -ENOMEM;

    dw_wdt.clk = clk_get(&pdev->dev, NULL);
    if (IS_ERR(dw_wdt.clk))
        return PTR_ERR(dw_wdt.clk);

    ret = clk_enable(dw_wdt.clk);
    if (ret)
        goto out_put_clk;

    spin_lock_init(&dw_wdt.lock);

    ret = misc_register(&dw_wdt_miscdev);
    if (ret)
        goto out_disable_clk;

    dw_wdt_set_next_heartbeat();
    setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
    mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);

    return 0;

out_disable_clk:
    clk_disable(dw_wdt.clk);
out_put_clk:
    clk_put(dw_wdt.clk);

    return ret;
}

static int __devexit dw_wdt_drv_remove(struct platform_device *pdev)
{
    misc_deregister(&dw_wdt_miscdev);

    clk_disable(dw_wdt.clk);
    clk_put(dw_wdt.clk);

    return 0;
}

static struct platform_driver dw_wdt_driver = {
    .probe      = dw_wdt_drv_probe,
    .remove     = __devexit_p(dw_wdt_drv_remove),
    .driver     = {
        .name   = "dw_wdt",
        .owner  = THIS_MODULE,
#ifdef CONFIG_PM
        .pm = &dw_wdt_pm_ops,
#endif /* CONFIG_PM */
    },
};

module_platform_driver(dw_wdt_driver);

MODULE_AUTHOR("Jamie Iles");
MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);