/*
 * Watchdog driver for IMX2 and later processors
 *
 *  Copyright (C) 2010 Wolfram Sang, Pengutronix e.K. <w.sang@pengutronix.de>
 *  Copyright (C) 2014 Freescale Semiconductor, Inc.
 *
 * some parts adapted by similar drivers from Darius Augulis and Vladimir
 * Zapolskiy, additional improvements by Wim Van Sebroeck.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * NOTE: MX1 has a slightly different Watchdog than MX2 and later:
 *
 *                      MX1:            MX2+:
 *                      ----            -----
 * Registers:           32-bit          16-bit
 * Stopable timer:      Yes             No
 * Need to enable clk:  No              Yes
 * Halt on suspend:     Manual          Can be automatic
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/notifier.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/regmap.h>
#include <linux/timer.h>
#include <linux/watchdog.h>

#define DRIVER_NAME "imx2-wdt"

#define IMX2_WDT_WCR            0x00            /* Control Register */
#define IMX2_WDT_WCR_WT         (0xFF << 8)     /* -> Watchdog Timeout Field */
#define IMX2_WDT_WCR_WRE        (1 << 3)        /* -> WDOG Reset Enable */
#define IMX2_WDT_WCR_WDE        (1 << 2)        /* -> Watchdog Enable */
#define IMX2_WDT_WCR_WDZST      (1 << 0)        /* -> Watchdog timer Suspend */

#define IMX2_WDT_WSR            0x02            /* Service Register */
#define IMX2_WDT_SEQ1           0x5555          /* -> service sequence 1 */
#define IMX2_WDT_SEQ2           0xAAAA          /* -> service sequence 2 */

#define IMX2_WDT_WRSR           0x04            /* Reset Status Register */
#define IMX2_WDT_WRSR_TOUT      (1 << 1)        /* -> Reset due to Timeout */

#define IMX2_WDT_WMCR           0x08            /* Misc Register */

#define IMX2_WDT_MAX_TIME       128
#define IMX2_WDT_DEFAULT_TIME   60              /* in seconds */

#define WDOG_SEC_TO_COUNT(s)    ((s * 2 - 1) << 8)

struct imx2_wdt_device {
        struct clk *clk;
        struct regmap *regmap;
        struct timer_list timer;        /* Pings the watchdog when closed */
        struct watchdog_device wdog;
        struct notifier_block restart_handler;
};

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 unsigned timeout = IMX2_WDT_DEFAULT_TIME;
module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
                                __MODULE_STRING(IMX2_WDT_DEFAULT_TIME) ")");

static const struct watchdog_info imx2_wdt_info = {
        .identity = "imx2+ watchdog",
        .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
};

static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
                                void *cmd)
{
        unsigned int wcr_enable = IMX2_WDT_WCR_WDE;
        struct imx2_wdt_device *wdev = container_of(this,
                                                    struct imx2_wdt_device,
                                                    restart_handler);
        /* Assert SRS signal */
        regmap_write(wdev->regmap, 0, wcr_enable);
        /*
         * Due to imx6q errata ERR004346 (WDOG: WDOG SRS bit requires to be
         * written twice), we add another two writes to ensure there must be at
         * least two writes happen in the same one 32kHz clock period.  We save
         * the target check here, since the writes shouldn't be a huge burden
         * for other platforms.
         */
        regmap_write(wdev->regmap, 0, wcr_enable);
        regmap_write(wdev->regmap, 0, wcr_enable);

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

        return NOTIFY_DONE;
}

static inline void imx2_wdt_setup(struct watchdog_device *wdog)
{
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
        u32 val;

        regmap_read(wdev->regmap, IMX2_WDT_WCR, &val);

        /* Suspend timer in low power mode, write once-only */
        val |= IMX2_WDT_WCR_WDZST;
        /* Strip the old watchdog Time-Out value */
        val &= ~IMX2_WDT_WCR_WT;
        /* Generate reset if WDOG times out */
        val &= ~IMX2_WDT_WCR_WRE;
        /* Keep Watchdog Disabled */
        val &= ~IMX2_WDT_WCR_WDE;
        /* Set the watchdog's Time-Out value */
        val |= WDOG_SEC_TO_COUNT(wdog->timeout);

        regmap_write(wdev->regmap, IMX2_WDT_WCR, val);

        /* enable the watchdog */
        val |= IMX2_WDT_WCR_WDE;
        regmap_write(wdev->regmap, IMX2_WDT_WCR, val);
}

static inline bool imx2_wdt_is_running(struct imx2_wdt_device *wdev)
{
        u32 val;

        regmap_read(wdev->regmap, IMX2_WDT_WCR, &val);

        return val & IMX2_WDT_WCR_WDE;
}

static int imx2_wdt_ping(struct watchdog_device *wdog)
{
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        regmap_write(wdev->regmap, IMX2_WDT_WSR, IMX2_WDT_SEQ1);
        regmap_write(wdev->regmap, IMX2_WDT_WSR, IMX2_WDT_SEQ2);
        return 0;
}

static void imx2_wdt_timer_ping(unsigned long arg)
{
        struct watchdog_device *wdog = (struct watchdog_device *)arg;
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        /* ping it every wdog->timeout / 2 seconds to prevent reboot */
        imx2_wdt_ping(wdog);
        mod_timer(&wdev->timer, jiffies + wdog->timeout * HZ / 2);
}

static int imx2_wdt_set_timeout(struct watchdog_device *wdog,
                                unsigned int new_timeout)
{
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        regmap_update_bits(wdev->regmap, IMX2_WDT_WCR, IMX2_WDT_WCR_WT,
                           WDOG_SEC_TO_COUNT(new_timeout));
        return 0;
}

static int imx2_wdt_start(struct watchdog_device *wdog)
{
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        if (imx2_wdt_is_running(wdev)) {
                /* delete the timer that pings the watchdog after close */
                del_timer_sync(&wdev->timer);
                imx2_wdt_set_timeout(wdog, wdog->timeout);
        } else
                imx2_wdt_setup(wdog);

        return imx2_wdt_ping(wdog);
}

static int imx2_wdt_stop(struct watchdog_device *wdog)
{
        /*
         * We don't need a clk_disable, it cannot be disabled once started.
         * We use a timer to ping the watchdog while /dev/watchdog is closed
         */
        imx2_wdt_timer_ping((unsigned long)wdog);
        return 0;
}

static inline void imx2_wdt_ping_if_active(struct watchdog_device *wdog)
{
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        if (imx2_wdt_is_running(wdev)) {
                imx2_wdt_set_timeout(wdog, wdog->timeout);
                imx2_wdt_timer_ping((unsigned long)wdog);
        }
}

static const struct watchdog_ops imx2_wdt_ops = {
        .owner = THIS_MODULE,
        .start = imx2_wdt_start,
        .stop = imx2_wdt_stop,
        .ping = imx2_wdt_ping,
        .set_timeout = imx2_wdt_set_timeout,
};

static const struct regmap_config imx2_wdt_regmap_config = {
        .reg_bits = 16,
        .reg_stride = 2,
        .val_bits = 16,
        .max_register = 0x8,
};

static int __init imx2_wdt_probe(struct platform_device *pdev)
{
        struct imx2_wdt_device *wdev;
        struct watchdog_device *wdog;
        struct resource *res;
        void __iomem *base;
        int ret;
        u32 val;

        wdev = devm_kzalloc(&pdev->dev, sizeof(*wdev), GFP_KERNEL);
        if (!wdev)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        wdev->regmap = devm_regmap_init_mmio_clk(&pdev->dev, NULL, base,
                                                 &imx2_wdt_regmap_config);
        if (IS_ERR(wdev->regmap)) {
                dev_err(&pdev->dev, "regmap init failed\n");
                return PTR_ERR(wdev->regmap);
        }

        wdev->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(wdev->clk)) {
                dev_err(&pdev->dev, "can't get Watchdog clock\n");
                return PTR_ERR(wdev->clk);
        }

        wdog                    = &wdev->wdog;
        wdog->info              = &imx2_wdt_info;
        wdog->ops               = &imx2_wdt_ops;
        wdog->min_timeout       = 1;
        wdog->max_timeout       = IMX2_WDT_MAX_TIME;

        clk_prepare_enable(wdev->clk);

        regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
        wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;

        wdog->timeout = clamp_t(unsigned, timeout, 1, IMX2_WDT_MAX_TIME);
        if (wdog->timeout != timeout)
                dev_warn(&pdev->dev, "Initial timeout out of range! Clamped from %u to %u\n",
                         timeout, wdog->timeout);

        platform_set_drvdata(pdev, wdog);
        watchdog_set_drvdata(wdog, wdev);
        watchdog_set_nowayout(wdog, nowayout);
        watchdog_init_timeout(wdog, timeout, &pdev->dev);

        setup_timer(&wdev->timer, imx2_wdt_timer_ping, (unsigned long)wdog);

        imx2_wdt_ping_if_active(wdog);

        /*
         * Disable the watchdog power down counter at boot. Otherwise the power
         * down counter will pull down the #WDOG interrupt line for one clock
         * cycle.
         */
        regmap_write(wdev->regmap, IMX2_WDT_WMCR, 0);

        ret = watchdog_register_device(wdog);
        if (ret) {
                dev_err(&pdev->dev, "cannot register watchdog device\n");
                return ret;
        }

        wdev->restart_handler.notifier_call = imx2_restart_handler;
        wdev->restart_handler.priority = 128;
        ret = register_restart_handler(&wdev->restart_handler);
        if (ret)
                dev_err(&pdev->dev, "cannot register restart handler\n");

        dev_info(&pdev->dev, "timeout %d sec (nowayout=%d)\n",
                 wdog->timeout, nowayout);

        return 0;
}

static int __exit imx2_wdt_remove(struct platform_device *pdev)
{
        struct watchdog_device *wdog = platform_get_drvdata(pdev);
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        unregister_restart_handler(&wdev->restart_handler);

        watchdog_unregister_device(wdog);

        if (imx2_wdt_is_running(wdev)) {
                del_timer_sync(&wdev->timer);
                imx2_wdt_ping(wdog);
                dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
        }
        return 0;
}

static void imx2_wdt_shutdown(struct platform_device *pdev)
{
        struct watchdog_device *wdog = platform_get_drvdata(pdev);
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        if (imx2_wdt_is_running(wdev)) {
                /*
                 * We are running, we need to delete the timer but will
                 * give max timeout before reboot will take place
                 */
                del_timer_sync(&wdev->timer);
                imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
                imx2_wdt_ping(wdog);
                dev_crit(&pdev->dev, "Device shutdown: Expect reboot!\n");
        }
}

#ifdef CONFIG_PM_SLEEP
/* Disable watchdog if it is active or non-active but still running */
static int imx2_wdt_suspend(struct device *dev)
{
        struct watchdog_device *wdog = dev_get_drvdata(dev);
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        /* The watchdog IP block is running */
        if (imx2_wdt_is_running(wdev)) {
                imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
                imx2_wdt_ping(wdog);

                /* The watchdog is not active */
                if (!watchdog_active(wdog))
                        del_timer_sync(&wdev->timer);
        }

        clk_disable_unprepare(wdev->clk);

        return 0;
}

/* Enable watchdog and configure it if necessary */
static int imx2_wdt_resume(struct device *dev)
{
        struct watchdog_device *wdog = dev_get_drvdata(dev);
        struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

        clk_prepare_enable(wdev->clk);

        if (watchdog_active(wdog) && !imx2_wdt_is_running(wdev)) {
                /*
                 * If the watchdog is still active and resumes
                 * from deep sleep state, need to restart the
                 * watchdog again.
                 */
                imx2_wdt_setup(wdog);
                imx2_wdt_set_timeout(wdog, wdog->timeout);
                imx2_wdt_ping(wdog);
        } else if (imx2_wdt_is_running(wdev)) {
                /* Resuming from non-deep sleep state. */
                imx2_wdt_set_timeout(wdog, wdog->timeout);
                imx2_wdt_ping(wdog);
                /*
                 * But the watchdog is not active, then start
                 * the timer again.
                 */
                if (!watchdog_active(wdog))
                        mod_timer(&wdev->timer,
                                  jiffies + wdog->timeout * HZ / 2);
        }

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(imx2_wdt_pm_ops, imx2_wdt_suspend,
                         imx2_wdt_resume);

static const struct of_device_id imx2_wdt_dt_ids[] = {
        { .compatible = "fsl,imx21-wdt", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx2_wdt_dt_ids);

static struct platform_driver imx2_wdt_driver = {
        .remove         = __exit_p(imx2_wdt_remove),
        .shutdown       = imx2_wdt_shutdown,
        .driver         = {
                .name   = DRIVER_NAME,
                .pm     = &imx2_wdt_pm_ops,
                .of_match_table = imx2_wdt_dt_ids,
        },
};

module_platform_driver_probe(imx2_wdt_driver, imx2_wdt_probe);

MODULE_AUTHOR("Wolfram Sang");
MODULE_DESCRIPTION("Watchdog driver for IMX2 and later");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" DRIVER_NAME);