gef_wdt.c

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/*
 * GE watchdog userspace interface
 *
 * Author:  Martyn Welch <[email protected]>
 *
 * Copyright 2008 GE Intelligent Platforms Embedded Systems, 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.
 *
 * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
 *   Author: James Chapman <[email protected]>
 */

/* TODO:
 * This driver does not provide support for the hardwares capability of sending
 * an interrupt at a programmable threshold.
 *
 * This driver currently can only support 1 watchdog - there are 2 in the
 * hardware that this driver supports. Thus one could be configured as a
 * process-based watchdog (via /dev/watchdog), the second (using the interrupt
 * capabilities) a kernel-based watchdog.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/compiler.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include <sysdev/fsl_soc.h>

/*
 * The watchdog configuration register contains a pair of 2-bit fields,
 *   1.  a reload field, bits 27-26, which triggers a reload of
 *       the countdown register, and
 *   2.  an enable field, bits 25-24, which toggles between
 *       enabling and disabling the watchdog timer.
 * Bit 31 is a read-only field which indicates whether the
 * watchdog timer is currently enabled.
 *
 * The low 24 bits contain the timer reload value.
 */
#define GEF_WDC_ENABLE_SHIFT    24
#define GEF_WDC_SERVICE_SHIFT   26
#define GEF_WDC_ENABLED_SHIFT   31

#define GEF_WDC_ENABLED_TRUE    1
#define GEF_WDC_ENABLED_FALSE   0

/* Flags bits */
#define GEF_WDOG_FLAG_OPENED    0

static unsigned long wdt_flags;
static int wdt_status;
static void __iomem *gef_wdt_regs;
static int gef_wdt_timeout;
static int gef_wdt_count;
static unsigned int bus_clk;
static char expect_close;
static DEFINE_SPINLOCK(gef_wdt_spinlock);

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) ")");


static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
{
    u32 data;
    u32 enabled;
    int ret = 0;

    spin_lock(&gef_wdt_spinlock);
    data = ioread32be(gef_wdt_regs);
    enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;

    /* only toggle the requested field if enabled state matches predicate */
    if ((enabled ^ enabled_predicate) == 0) {
        /* We write a 1, then a 2 -- to the appropriate field */
        data = (1 << field_shift) | gef_wdt_count;
        iowrite32be(data, gef_wdt_regs);

        data = (2 << field_shift) | gef_wdt_count;
        iowrite32be(data, gef_wdt_regs);
        ret = 1;
    }
    spin_unlock(&gef_wdt_spinlock);

    return ret;
}

static void gef_wdt_service(void)
{
    gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
        GEF_WDC_SERVICE_SHIFT);
}

static void gef_wdt_handler_enable(void)
{
    if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
                   GEF_WDC_ENABLE_SHIFT)) {
        gef_wdt_service();
        pr_notice("watchdog activated\n");
    }
}

static void gef_wdt_handler_disable(void)
{
    if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
                   GEF_WDC_ENABLE_SHIFT))
        pr_notice("watchdog deactivated\n");
}

static void gef_wdt_set_timeout(unsigned int timeout)
{
    /* maximum bus cycle count is 0xFFFFFFFF */
    if (timeout > 0xFFFFFFFF / bus_clk)
        timeout = 0xFFFFFFFF / bus_clk;

    /* Register only holds upper 24 bits, bit shifted into lower 24 */
    gef_wdt_count = (timeout * bus_clk) >> 8;
    gef_wdt_timeout = timeout;
}


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

            expect_close = 0;

            for (i = 0; i != len; i++) {
                char c;
                if (get_user(c, data + i))
                    return -EFAULT;
                if (c == 'V')
                    expect_close = 42;
            }
        }
        gef_wdt_service();
    }

    return len;
}

static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg)
{
    int timeout;
    int options;
    void __user *argp = (void __user *)arg;
    static const struct watchdog_info info = {
        .options =  WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
                WDIOF_KEEPALIVEPING,
        .firmware_version = 0,
        .identity = "GE watchdog",
    };

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user(argp, &info, sizeof(info)))
            return -EFAULT;
        break;

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        if (put_user(wdt_status, (int __user *)argp))
            return -EFAULT;
        wdt_status &= ~WDIOF_KEEPALIVEPING;
        break;

    case WDIOC_SETOPTIONS:
        if (get_user(options, (int __user *)argp))
            return -EFAULT;

        if (options & WDIOS_DISABLECARD)
            gef_wdt_handler_disable();

        if (options & WDIOS_ENABLECARD)
            gef_wdt_handler_enable();
        break;

    case WDIOC_KEEPALIVE:
        gef_wdt_service();
        wdt_status |= WDIOF_KEEPALIVEPING;
        break;

    case WDIOC_SETTIMEOUT:
        if (get_user(timeout, (int __user *)argp))
            return -EFAULT;
        gef_wdt_set_timeout(timeout);
        /* Fall through */

    case WDIOC_GETTIMEOUT:
        if (put_user(gef_wdt_timeout, (int __user *)argp))
            return -EFAULT;
        break;

    default:
        return -ENOTTY;
    }

    return 0;
}

static int gef_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
        return -EBUSY;

    if (nowayout)
        __module_get(THIS_MODULE);

    gef_wdt_handler_enable();

    return nonseekable_open(inode, file);
}

static int gef_wdt_release(struct inode *inode, struct file *file)
{
    if (expect_close == 42)
        gef_wdt_handler_disable();
    else {
        pr_crit("unexpected close, not stopping timer!\n");
        gef_wdt_service();
    }
    expect_close = 0;

    clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);

    return 0;
}

static const struct file_operations gef_wdt_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .write = gef_wdt_write,
    .unlocked_ioctl = gef_wdt_ioctl,
    .open = gef_wdt_open,
    .release = gef_wdt_release,
};

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


static int __devinit gef_wdt_probe(struct platform_device *dev)
{
    int timeout = 10;
    u32 freq;

    bus_clk = 133; /* in MHz */

    freq = fsl_get_sys_freq();
    if (freq != -1)
        bus_clk = freq;

    /* Map devices registers into memory */
    gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
    if (gef_wdt_regs == NULL)
        return -ENOMEM;

    gef_wdt_set_timeout(timeout);

    gef_wdt_handler_disable();  /* in case timer was already running */

    return misc_register(&gef_wdt_miscdev);
}

static int __devexit gef_wdt_remove(struct platform_device *dev)
{
    misc_deregister(&gef_wdt_miscdev);

    gef_wdt_handler_disable();

    iounmap(gef_wdt_regs);

    return 0;
}

static const struct of_device_id gef_wdt_ids[] = {
    {
        .compatible = "gef,fpga-wdt",
    },
    {},
};

static struct platform_driver gef_wdt_driver = {
    .driver = {
        .name = "gef_wdt",
        .owner = THIS_MODULE,
        .of_match_table = gef_wdt_ids,
    },
    .probe      = gef_wdt_probe,
};

static int __init gef_wdt_init(void)
{
    pr_info("GE watchdog driver\n");
    return platform_driver_register(&gef_wdt_driver);
}

static void __exit gef_wdt_exit(void)
{
    platform_driver_unregister(&gef_wdt_driver);
}

module_init(gef_wdt_init);
module_exit(gef_wdt_exit);

MODULE_AUTHOR("Martyn Welch <[email protected]>");
MODULE_DESCRIPTION("GE watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:gef_wdt");