m54xx_wdt.c

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/*
 * drivers/watchdog/m54xx_wdt.c
 *
 * Watchdog driver for ColdFire MCF547x & MCF548x processors
 * Copyright 2010 (c) Philippe De Muyter <[email protected]>
 *
 * Adapted from the IXP4xx watchdog driver, which carries these notices:
 *
 *  Author: Deepak Saxena <[email protected]>
 *
 *  Copyright 2004 (c) MontaVista, Software, Inc.
 *  Based on sa1100 driver, Copyright (C) 2000 Oleg Drokin <[email protected]>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/ioport.h>
#include <linux/uaccess.h>

#include <asm/coldfire.h>
#include <asm/m54xxsim.h>
#include <asm/m54xxgpt.h>

static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned int heartbeat = 30; /* (secs) Default is 0.5 minute */
static unsigned long wdt_status;

#define WDT_IN_USE      0
#define WDT_OK_TO_CLOSE     1

static void wdt_enable(void)
{
    unsigned int gms0;

    /* preserve GPIO usage, if any */
    gms0 = __raw_readl(MCF_GPT_GMS0);
    if (gms0 & MCF_GPT_GMS_TMS_GPIO)
        gms0 &= (MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_GPIO_MASK
                            | MCF_GPT_GMS_OD);
    else
        gms0 = MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_OD;
    __raw_writel(gms0, MCF_GPT_GMS0);
    __raw_writel(MCF_GPT_GCIR_PRE(heartbeat*(MCF_BUSCLK/0xffff)) |
            MCF_GPT_GCIR_CNT(0xffff), MCF_GPT_GCIR0);
    gms0 |= MCF_GPT_GMS_OCPW(0xA5) | MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE;
    __raw_writel(gms0, MCF_GPT_GMS0);
}

static void wdt_disable(void)
{
    unsigned int gms0;

    /* disable watchdog */
    gms0 = __raw_readl(MCF_GPT_GMS0);
    gms0 &= ~(MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE);
    __raw_writel(gms0, MCF_GPT_GMS0);
}

static void wdt_keepalive(void)
{
    unsigned int gms0;

    gms0 = __raw_readl(MCF_GPT_GMS0);
    gms0 |= MCF_GPT_GMS_OCPW(0xA5);
    __raw_writel(gms0, MCF_GPT_GMS0);
}

static int m54xx_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(WDT_IN_USE, &wdt_status))
        return -EBUSY;

    clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
    wdt_enable();
    return nonseekable_open(inode, file);
}

static ssize_t m54xx_wdt_write(struct file *file, const char *data,
                        size_t len, loff_t *ppos)
{
    if (len) {
        if (!nowayout) {
            size_t i;

            clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

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

                if (get_user(c, data + i))
                    return -EFAULT;
                if (c == 'V')
                    set_bit(WDT_OK_TO_CLOSE, &wdt_status);
            }
        }
        wdt_keepalive();
    }
    return len;
}

static const struct watchdog_info ident = {
    .options    = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT |
                WDIOF_KEEPALIVEPING,
    .identity   = "Coldfire M54xx Watchdog",
};

static long m54xx_wdt_ioctl(struct file *file, unsigned int cmd,
                             unsigned long arg)
{
    int ret = -ENOTTY;
    int time;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        ret = copy_to_user((struct watchdog_info *)arg, &ident,
                   sizeof(ident)) ? -EFAULT : 0;
        break;

    case WDIOC_GETSTATUS:
        ret = put_user(0, (int *)arg);
        break;

    case WDIOC_GETBOOTSTATUS:
        ret = put_user(0, (int *)arg);
        break;

    case WDIOC_KEEPALIVE:
        wdt_keepalive();
        ret = 0;
        break;

    case WDIOC_SETTIMEOUT:
        ret = get_user(time, (int *)arg);
        if (ret)
            break;

        if (time <= 0 || time > 30) {
            ret = -EINVAL;
            break;
        }

        heartbeat = time;
        wdt_enable();
        /* Fall through */

    case WDIOC_GETTIMEOUT:
        ret = put_user(heartbeat, (int *)arg);
        break;
    }
    return ret;
}

static int m54xx_wdt_release(struct inode *inode, struct file *file)
{
    if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
        wdt_disable();
    else {
        pr_crit("Device closed unexpectedly - timer will not stop\n");
        wdt_keepalive();
    }
    clear_bit(WDT_IN_USE, &wdt_status);
    clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

    return 0;
}


static const struct file_operations m54xx_wdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = m54xx_wdt_write,
    .unlocked_ioctl = m54xx_wdt_ioctl,
    .open       = m54xx_wdt_open,
    .release    = m54xx_wdt_release,
};

static struct miscdevice m54xx_wdt_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &m54xx_wdt_fops,
};

static int __init m54xx_wdt_init(void)
{
    if (!request_mem_region(MCF_GPT_GCIR0, 4, "Coldfire M54xx Watchdog")) {
        pr_warn("I/O region busy\n");
        return -EBUSY;
    }
    pr_info("driver is loaded\n");

    return misc_register(&m54xx_wdt_miscdev);
}

static void __exit m54xx_wdt_exit(void)
{
    misc_deregister(&m54xx_wdt_miscdev);
    release_mem_region(MCF_GPT_GCIR0, 4);
}

module_init(m54xx_wdt_init);
module_exit(m54xx_wdt_exit);

MODULE_AUTHOR("Philippe De Muyter <[email protected]>");
MODULE_DESCRIPTION("Coldfire M54xx Watchdog");

module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds (default 30s)");

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");

MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);