Linux 4.2.1

[linux/fpc-iii.git] / drivers / watchdog / dw_wdt.c

/*
 * 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 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/delay.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/notifier.h>
#include <linux/of.h>
#include <linux/pm.h>
#include <linux/platform_device.h>
#include <linux/reboot.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_TIMEOUT_RANGE_TOPINIT_SHIFT    4
#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

#define DW_WDT_DEFAULT_SECONDS  30

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 {
        void __iomem            *regs;
        struct clk              *clk;
        unsigned long           in_use;
        unsigned long           next_heartbeat;
        struct timer_list       timer;
        int                     expect_close;
        struct notifier_block   restart_handler;
} 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 void dw_wdt_keepalive(void)
{
        writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
               WDOG_COUNTER_RESTART_REG_OFFSET);
}

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.  Some versions of dw_wdt
         * have have TOPINIT in the TIMEOUT_RANGE register (as per
         * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1).  On those we
         * effectively get a pat of the watchdog right here.
         */
        writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
                dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);

        /*
         * Add an explicit pat to handle versions of the watchdog that
         * don't have TOPINIT.  This won't hurt on versions that have
         * it.
         */
        dw_wdt_keepalive();

        dw_wdt_set_next_heartbeat();

        return dw_wdt_top_in_seconds(top_val);
}

static int dw_wdt_restart_handle(struct notifier_block *this,
                                unsigned long mode, void *cmd)
{
        u32 val;

        writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
        val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
        if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
                writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
                        WDOG_COUNTER_RESTART_REG_OFFSET);
        else
                writel(WDOG_CONTROL_REG_WDT_EN_MASK,
                       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);

        /* wait for reset to assert... */
        mdelay(500);

        return NOTIFY_DONE;
}

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);

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

        dw_wdt_set_next_heartbeat();

        return nonseekable_open(inode, filp);
}

static 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();
        dw_wdt_keepalive();
        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((void __user *)arg, &dw_wdt_ident,
                                    sizeof(dw_wdt_ident)) ? -EFAULT : 0;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, (int __user *)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_SLEEP
static int dw_wdt_suspend(struct device *dev)
{
        clk_disable_unprepare(dw_wdt.clk);

        return 0;
}

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

        if (err)
                return err;

        dw_wdt_keepalive();

        return 0;
}
#endif /* CONFIG_PM_SLEEP */

static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);

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

        dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(dw_wdt.regs))
                return PTR_ERR(dw_wdt.regs);

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

        ret = clk_prepare_enable(dw_wdt.clk);
        if (ret)
                return ret;

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

        dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
        dw_wdt.restart_handler.priority = 128;
        ret = register_restart_handler(&dw_wdt.restart_handler);
        if (ret)
                pr_warn("cannot register restart handler\n");

        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_unprepare(dw_wdt.clk);

        return ret;
}

static int dw_wdt_drv_remove(struct platform_device *pdev)
{
        unregister_restart_handler(&dw_wdt.restart_handler);

        misc_deregister(&dw_wdt_miscdev);

        clk_disable_unprepare(dw_wdt.clk);

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id dw_wdt_of_match[] = {
        { .compatible = "snps,dw-wdt", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
#endif

static struct platform_driver dw_wdt_driver = {
        .probe          = dw_wdt_drv_probe,
        .remove         = dw_wdt_drv_remove,
        .driver         = {
                .name   = "dw_wdt",
                .of_match_table = of_match_ptr(dw_wdt_of_match),
                .pm     = &dw_wdt_pm_ops,
        },
};

module_platform_driver(dw_wdt_driver);

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