ar7_wdt.c

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/*
 * drivers/watchdog/ar7_wdt.c
 *
 * Copyright (C) 2007 Nicolas Thill <[email protected]>
 * Copyright (c) 2005 Enrik Berkhan <[email protected]>
 *
 * Some code taken from:
 * National Semiconductor SCx200 Watchdog support
 * Copyright (c) 2001,2002 Christer Weinigel <[email protected]>
 *
 * 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 program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/clk.h>

#include <asm/addrspace.h>
#include <asm/mach-ar7/ar7.h>

#define LONGNAME "TI AR7 Watchdog Timer"

MODULE_AUTHOR("Nicolas Thill <[email protected]>");
MODULE_DESCRIPTION(LONGNAME);
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

static int margin = 60;
module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds");

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

#define READ_REG(x) readl((void __iomem *)&(x))
#define WRITE_REG(x, v) writel((v), (void __iomem *)&(x))

struct ar7_wdt {
    u32 kick_lock;
    u32 kick;
    u32 change_lock;
    u32 change;
    u32 disable_lock;
    u32 disable;
    u32 prescale_lock;
    u32 prescale;
};

static unsigned long wdt_is_open;
static unsigned expect_close;
static DEFINE_SPINLOCK(wdt_lock);

/* XXX currently fixed, allows max margin ~68.72 secs */
#define prescale_value 0xffff

/* Resource of the WDT registers */
static struct resource *ar7_regs_wdt;
/* Pointer to the remapped WDT IO space */
static struct ar7_wdt *ar7_wdt;

static struct clk *vbus_clk;

static void ar7_wdt_kick(u32 value)
{
    WRITE_REG(ar7_wdt->kick_lock, 0x5555);
    if ((READ_REG(ar7_wdt->kick_lock) & 3) == 1) {
        WRITE_REG(ar7_wdt->kick_lock, 0xaaaa);
        if ((READ_REG(ar7_wdt->kick_lock) & 3) == 3) {
            WRITE_REG(ar7_wdt->kick, value);
            return;
        }
    }
    pr_err("failed to unlock WDT kick reg\n");
}

static void ar7_wdt_prescale(u32 value)
{
    WRITE_REG(ar7_wdt->prescale_lock, 0x5a5a);
    if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 1) {
        WRITE_REG(ar7_wdt->prescale_lock, 0xa5a5);
        if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 3) {
            WRITE_REG(ar7_wdt->prescale, value);
            return;
        }
    }
    pr_err("failed to unlock WDT prescale reg\n");
}

static void ar7_wdt_change(u32 value)
{
    WRITE_REG(ar7_wdt->change_lock, 0x6666);
    if ((READ_REG(ar7_wdt->change_lock) & 3) == 1) {
        WRITE_REG(ar7_wdt->change_lock, 0xbbbb);
        if ((READ_REG(ar7_wdt->change_lock) & 3) == 3) {
            WRITE_REG(ar7_wdt->change, value);
            return;
        }
    }
    pr_err("failed to unlock WDT change reg\n");
}

static void ar7_wdt_disable(u32 value)
{
    WRITE_REG(ar7_wdt->disable_lock, 0x7777);
    if ((READ_REG(ar7_wdt->disable_lock) & 3) == 1) {
        WRITE_REG(ar7_wdt->disable_lock, 0xcccc);
        if ((READ_REG(ar7_wdt->disable_lock) & 3) == 2) {
            WRITE_REG(ar7_wdt->disable_lock, 0xdddd);
            if ((READ_REG(ar7_wdt->disable_lock) & 3) == 3) {
                WRITE_REG(ar7_wdt->disable, value);
                return;
            }
        }
    }
    pr_err("failed to unlock WDT disable reg\n");
}

static void ar7_wdt_update_margin(int new_margin)
{
    u32 change;
    u32 vbus_rate;

    vbus_rate = clk_get_rate(vbus_clk);
    change = new_margin * (vbus_rate / prescale_value);
    if (change < 1)
        change = 1;
    if (change > 0xffff)
        change = 0xffff;
    ar7_wdt_change(change);
    margin = change * prescale_value / vbus_rate;
    pr_info("timer margin %d seconds (prescale %d, change %d, freq %d)\n",
        margin, prescale_value, change, vbus_rate);
}

static void ar7_wdt_enable_wdt(void)
{
    pr_debug("enabling watchdog timer\n");
    ar7_wdt_disable(1);
    ar7_wdt_kick(1);
}

static void ar7_wdt_disable_wdt(void)
{
    pr_debug("disabling watchdog timer\n");
    ar7_wdt_disable(0);
}

static int ar7_wdt_open(struct inode *inode, struct file *file)
{
    /* only allow one at a time */
    if (test_and_set_bit(0, &wdt_is_open))
        return -EBUSY;
    ar7_wdt_enable_wdt();
    expect_close = 0;

    return nonseekable_open(inode, file);
}

static int ar7_wdt_release(struct inode *inode, struct file *file)
{
    if (!expect_close)
        pr_warn("watchdog device closed unexpectedly, will not disable the watchdog timer\n");
    else if (!nowayout)
        ar7_wdt_disable_wdt();
    clear_bit(0, &wdt_is_open);
    return 0;
}

static ssize_t ar7_wdt_write(struct file *file, const char *data,
                 size_t len, loff_t *ppos)
{
    /* check for a magic close character */
    if (len) {
        size_t i;

        spin_lock(&wdt_lock);
        ar7_wdt_kick(1);
        spin_unlock(&wdt_lock);

        expect_close = 0;
        for (i = 0; i < len; ++i) {
            char c;
            if (get_user(c, data + i))
                return -EFAULT;
            if (c == 'V')
                expect_close = 1;
        }

    }
    return len;
}

static long ar7_wdt_ioctl(struct file *file,
                    unsigned int cmd, unsigned long arg)
{
    static const struct watchdog_info ident = {
        .identity = LONGNAME,
        .firmware_version = 1,
        .options = (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                        WDIOF_MAGICCLOSE),
    };
    int new_margin;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user((struct watchdog_info *)arg, &ident,
                sizeof(ident)))
            return -EFAULT;
        return 0;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        if (put_user(0, (int *)arg))
            return -EFAULT;
        return 0;
    case WDIOC_KEEPALIVE:
        ar7_wdt_kick(1);
        return 0;
    case WDIOC_SETTIMEOUT:
        if (get_user(new_margin, (int *)arg))
            return -EFAULT;
        if (new_margin < 1)
            return -EINVAL;

        spin_lock(&wdt_lock);
        ar7_wdt_update_margin(new_margin);
        ar7_wdt_kick(1);
        spin_unlock(&wdt_lock);

    case WDIOC_GETTIMEOUT:
        if (put_user(margin, (int *)arg))
            return -EFAULT;
        return 0;
    default:
        return -ENOTTY;
    }
}

static const struct file_operations ar7_wdt_fops = {
    .owner      = THIS_MODULE,
    .write      = ar7_wdt_write,
    .unlocked_ioctl = ar7_wdt_ioctl,
    .open       = ar7_wdt_open,
    .release    = ar7_wdt_release,
    .llseek     = no_llseek,
};

static struct miscdevice ar7_wdt_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &ar7_wdt_fops,
};

static int __devinit ar7_wdt_probe(struct platform_device *pdev)
{
    int rc;

    ar7_regs_wdt =
        platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
    if (!ar7_regs_wdt) {
        pr_err("could not get registers resource\n");
        return -ENODEV;
    }

    ar7_wdt = devm_request_and_ioremap(&pdev->dev, ar7_regs_wdt);
    if (!ar7_wdt) {
        pr_err("could not ioremap registers\n");
        return -ENXIO;
    }

    vbus_clk = clk_get(NULL, "vbus");
    if (IS_ERR(vbus_clk)) {
        pr_err("could not get vbus clock\n");
        return PTR_ERR(vbus_clk);
    }

    ar7_wdt_disable_wdt();
    ar7_wdt_prescale(prescale_value);
    ar7_wdt_update_margin(margin);

    rc = misc_register(&ar7_wdt_miscdev);
    if (rc) {
        pr_err("unable to register misc device\n");
        goto out;
    }
    return 0;

out:
    clk_put(vbus_clk);
    vbus_clk = NULL;
    return rc;
}

static int __devexit ar7_wdt_remove(struct platform_device *pdev)
{
    misc_deregister(&ar7_wdt_miscdev);
    clk_put(vbus_clk);
    vbus_clk = NULL;
    return 0;
}

static void ar7_wdt_shutdown(struct platform_device *pdev)
{
    if (!nowayout)
        ar7_wdt_disable_wdt();
}

static struct platform_driver ar7_wdt_driver = {
    .probe = ar7_wdt_probe,
    .remove = __devexit_p(ar7_wdt_remove),
    .shutdown = ar7_wdt_shutdown,
    .driver = {
        .owner = THIS_MODULE,
        .name = "ar7_wdt",
    },
};

module_platform_driver(ar7_wdt_driver);