booke_wdt.c

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/*
 * Watchdog timer for PowerPC Book-E systems
 *
 * Author: Matthew McClintock
 * Maintainer: Kumar Gala <[email protected]>
 *
 * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/smp.h>
#include <linux/miscdevice.h>
#include <linux/notifier.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>

#include <asm/reg_booke.h>
#include <asm/time.h>
#include <asm/div64.h>

/* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
 * Also, the wdt_period sets the watchdog timer period timeout.
 * For E500 cpus the wdt_period sets which bit changing from 0->1 will
 * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
 * first time nothing will happen, the second time a watchdog exception will
 * occur, and the final time the board will reset.
 */

u32 booke_wdt_enabled;
u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;

#ifdef  CONFIG_PPC_FSL_BOOK3E
#define WDTP(x)     ((((x)&0x3)<<30)|(((x)&0x3c)<<15))
#define WDTP_MASK   (WDTP(0x3f))
#else
#define WDTP(x)     (TCR_WP(x))
#define WDTP_MASK   (TCR_WP_MASK)
#endif

static DEFINE_SPINLOCK(booke_wdt_lock);

/* For the specified period, determine the number of seconds
 * corresponding to the reset time.  There will be a watchdog
 * exception at approximately 3/5 of this time.
 *
 * The formula to calculate this is given by:
 * 2.5 * (2^(63-period+1)) / timebase_freq
 *
 * In order to simplify things, we assume that period is
 * at least 1.  This will still result in a very long timeout.
 */
static unsigned long long period_to_sec(unsigned int period)
{
    unsigned long long tmp = 1ULL << (64 - period);
    unsigned long tmp2 = ppc_tb_freq;

    /* tmp may be a very large number and we don't want to overflow,
     * so divide the timebase freq instead of multiplying tmp
     */
    tmp2 = tmp2 / 5 * 2;

    do_div(tmp, tmp2);
    return tmp;
}

/*
 * This procedure will find the highest period which will give a timeout
 * greater than the one required. e.g. for a bus speed of 66666666 and
 * and a parameter of 2 secs, then this procedure will return a value of 38.
 */
static unsigned int sec_to_period(unsigned int secs)
{
    unsigned int period;
    for (period = 63; period > 0; period--) {
        if (period_to_sec(period) >= secs)
            return period;
    }
    return 0;
}

static void __booke_wdt_set(void *data)
{
    u32 val;

    val = mfspr(SPRN_TCR);
    val &= ~WDTP_MASK;
    val |= WDTP(booke_wdt_period);

    mtspr(SPRN_TCR, val);
}

static void booke_wdt_set(void)
{
    on_each_cpu(__booke_wdt_set, NULL, 0);
}

static void __booke_wdt_ping(void *data)
{
    mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
}

static void booke_wdt_ping(void)
{
    on_each_cpu(__booke_wdt_ping, NULL, 0);
}

static void __booke_wdt_enable(void *data)
{
    u32 val;

    /* clear status before enabling watchdog */
    __booke_wdt_ping(NULL);
    val = mfspr(SPRN_TCR);
    val &= ~WDTP_MASK;
    val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(booke_wdt_period));

    mtspr(SPRN_TCR, val);
}

static void __booke_wdt_disable(void *data)
{
    u32 val;

    val = mfspr(SPRN_TCR);
    val &= ~(TCR_WIE | WDTP_MASK);
    mtspr(SPRN_TCR, val);

    /* clear status to make sure nothing is pending */
    __booke_wdt_ping(NULL);

}

static ssize_t booke_wdt_write(struct file *file, const char __user *buf,
                size_t count, loff_t *ppos)
{
    booke_wdt_ping();
    return count;
}

static struct watchdog_info ident = {
    .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
    .identity = "PowerPC Book-E Watchdog",
};

static long booke_wdt_ioctl(struct file *file,
                unsigned int cmd, unsigned long arg)
{
    u32 tmp = 0;
    u32 __user *p = (u32 __user *)arg;

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user(p, &ident, sizeof(ident)) ? -EFAULT : 0;
    case WDIOC_GETSTATUS:
        return put_user(0, p);
    case WDIOC_GETBOOTSTATUS:
        /* XXX: something is clearing TSR */
        tmp = mfspr(SPRN_TSR) & TSR_WRS(3);
        /* returns CARDRESET if last reset was caused by the WDT */
        return put_user((tmp ? WDIOF_CARDRESET : 0), p);
    case WDIOC_SETOPTIONS:
        if (get_user(tmp, p))
            return -EFAULT;
        if (tmp == WDIOS_ENABLECARD) {
            booke_wdt_ping();
            break;
        } else
            return -EINVAL;
        return 0;
    case WDIOC_KEEPALIVE:
        booke_wdt_ping();
        return 0;
    case WDIOC_SETTIMEOUT:
        if (get_user(tmp, p))
            return -EFAULT;
#ifdef  CONFIG_PPC_FSL_BOOK3E
        /* period of 1 gives the largest possible timeout */
        if (tmp > period_to_sec(1))
            return -EINVAL;
        booke_wdt_period = sec_to_period(tmp);
#else
        booke_wdt_period = tmp;
#endif
        booke_wdt_set();
        /* Fall */
    case WDIOC_GETTIMEOUT:
#ifdef  CONFIG_FSL_BOOKE
        return put_user(period_to_sec(booke_wdt_period), p);
#else
        return put_user(booke_wdt_period, p);
#endif
    default:
        return -ENOTTY;
    }

    return 0;
}

/* wdt_is_active stores wether or not the /dev/watchdog device is opened */
static unsigned long wdt_is_active;

static int booke_wdt_open(struct inode *inode, struct file *file)
{
    /* /dev/watchdog can only be opened once */
    if (test_and_set_bit(0, &wdt_is_active))
        return -EBUSY;

    spin_lock(&booke_wdt_lock);
    if (booke_wdt_enabled == 0) {
        booke_wdt_enabled = 1;
        on_each_cpu(__booke_wdt_enable, NULL, 0);
        pr_debug("watchdog enabled (timeout = %llu sec)\n",
             period_to_sec(booke_wdt_period));
    }
    spin_unlock(&booke_wdt_lock);

    return nonseekable_open(inode, file);
}

static int booke_wdt_release(struct inode *inode, struct file *file)
{
#ifndef CONFIG_WATCHDOG_NOWAYOUT
    /* Normally, the watchdog is disabled when /dev/watchdog is closed, but
     * if CONFIG_WATCHDOG_NOWAYOUT is defined, then it means that the
     * watchdog should remain enabled.  So we disable it only if
     * CONFIG_WATCHDOG_NOWAYOUT is not defined.
     */
    on_each_cpu(__booke_wdt_disable, NULL, 0);
    booke_wdt_enabled = 0;
    pr_debug("watchdog disabled\n");
#endif

    clear_bit(0, &wdt_is_active);

    return 0;
}

static const struct file_operations booke_wdt_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .write = booke_wdt_write,
    .unlocked_ioctl = booke_wdt_ioctl,
    .open = booke_wdt_open,
    .release = booke_wdt_release,
};

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

static void __exit booke_wdt_exit(void)
{
    misc_deregister(&booke_wdt_miscdev);
}

static int __init booke_wdt_init(void)
{
    int ret = 0;

    pr_info("powerpc book-e watchdog driver loaded\n");
    ident.firmware_version = cur_cpu_spec->pvr_value;

    ret = misc_register(&booke_wdt_miscdev);
    if (ret) {
        pr_err("cannot register device (minor=%u, ret=%i)\n",
               WATCHDOG_MINOR, ret);
        return ret;
    }

    spin_lock(&booke_wdt_lock);
    if (booke_wdt_enabled == 1) {
        pr_info("watchdog enabled (timeout = %llu sec)\n",
            period_to_sec(booke_wdt_period));
        on_each_cpu(__booke_wdt_enable, NULL, 0);
    }
    spin_unlock(&booke_wdt_lock);

    return ret;
}

module_init(booke_wdt_init);
module_exit(booke_wdt_exit);

MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
MODULE_LICENSE("GPL");