/*
 * drivers/char/watchdog/sp805-wdt.c
 *
 * Watchdog driver for ARM SP805 watchdog module
 *
 * Copyright (C) 2010 ST Microelectronics
 * Viresh Kumar <viresh.linux@gmail.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2 or later. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/device.h>
#include <linux/resource.h>
#include <linux/amba/bus.h>
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/watchdog.h>

/* default timeout in seconds */
#define DEFAULT_TIMEOUT         60

#define MODULE_NAME             "sp805-wdt"

/* watchdog register offsets and masks */
#define WDTLOAD                 0x000
        #define LOAD_MIN        0x00000001
        #define LOAD_MAX        0xFFFFFFFF
#define WDTVALUE                0x004
#define WDTCONTROL              0x008
        /* control register masks */
        #define INT_ENABLE      (1 << 0)
        #define RESET_ENABLE    (1 << 1)
#define WDTINTCLR               0x00C
#define WDTRIS                  0x010
#define WDTMIS                  0x014
        #define INT_MASK        (1 << 0)
#define WDTLOCK                 0xC00
        #define UNLOCK          0x1ACCE551
        #define LOCK            0x00000001

/**
 * struct sp805_wdt: sp805 wdt device structure
 * @wdd: instance of struct watchdog_device
 * @lock: spin lock protecting dev structure and io access
 * @base: base address of wdt
 * @clk: clock structure of wdt
 * @adev: amba device structure of wdt
 * @status: current status of wdt
 * @load_val: load value to be set for current timeout
 * @timeout: current programmed timeout
 */
struct sp805_wdt {
        struct watchdog_device          wdd;
        spinlock_t                      lock;
        void __iomem                    *base;
        struct clk                      *clk;
        struct amba_device              *adev;
        unsigned int                    load_val;
        unsigned int                    timeout;
};

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                "Set to 1 to keep watchdog running after device release");

/* This routine finds load value that will reset system in required timout */
static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
{
        struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
        u64 load, rate;

        rate = clk_get_rate(wdt->clk);

        /*
         * sp805 runs counter with given value twice, after the end of first
         * counter it gives an interrupt and then starts counter again. If
         * interrupt already occurred then it resets the system. This is why
         * load is half of what should be required.
         */
        load = div_u64(rate, 2) * timeout - 1;

        load = (load > LOAD_MAX) ? LOAD_MAX : load;
        load = (load < LOAD_MIN) ? LOAD_MIN : load;

        spin_lock(&wdt->lock);
        wdt->load_val = load;
        /* roundup timeout to closest positive integer value */
        wdt->timeout = div_u64((load + 1) * 2 + (rate / 2), rate);
        spin_unlock(&wdt->lock);

        return 0;
}

/* returns number of seconds left for reset to occur */
static unsigned int wdt_timeleft(struct watchdog_device *wdd)
{
        struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
        u64 load, rate;

        rate = clk_get_rate(wdt->clk);

        spin_lock(&wdt->lock);
        load = readl_relaxed(wdt->base + WDTVALUE);

        /*If the interrupt is inactive then time left is WDTValue + WDTLoad. */
        if (!(readl_relaxed(wdt->base + WDTRIS) & INT_MASK))
                load += wdt->load_val + 1;
        spin_unlock(&wdt->lock);

        return div_u64(load, rate);
}

static int wdt_config(struct watchdog_device *wdd, bool ping)
{
        struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
        int ret;

        if (!ping) {

                ret = clk_prepare_enable(wdt->clk);
                if (ret) {
                        dev_err(&wdt->adev->dev, "clock enable fail");
                        return ret;
                }
        }

        spin_lock(&wdt->lock);

        writel_relaxed(UNLOCK, wdt->base + WDTLOCK);
        writel_relaxed(wdt->load_val, wdt->base + WDTLOAD);

        if (!ping) {
                writel_relaxed(INT_MASK, wdt->base + WDTINTCLR);
                writel_relaxed(INT_ENABLE | RESET_ENABLE, wdt->base +
                                WDTCONTROL);
        }

        writel_relaxed(LOCK, wdt->base + WDTLOCK);

        /* Flush posted writes. */
        readl_relaxed(wdt->base + WDTLOCK);
        spin_unlock(&wdt->lock);

        return 0;
}

static int wdt_ping(struct watchdog_device *wdd)
{
        return wdt_config(wdd, true);
}

/* enables watchdog timers reset */
static int wdt_enable(struct watchdog_device *wdd)
{
        return wdt_config(wdd, false);
}

/* disables watchdog timers reset */
static int wdt_disable(struct watchdog_device *wdd)
{
        struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);

        spin_lock(&wdt->lock);

        writel_relaxed(UNLOCK, wdt->base + WDTLOCK);
        writel_relaxed(0, wdt->base + WDTCONTROL);
        writel_relaxed(LOCK, wdt->base + WDTLOCK);

        /* Flush posted writes. */
        readl_relaxed(wdt->base + WDTLOCK);
        spin_unlock(&wdt->lock);

        clk_disable_unprepare(wdt->clk);

        return 0;
}

static const struct watchdog_info wdt_info = {
        .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
        .identity = MODULE_NAME,
};

static const struct watchdog_ops wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = wdt_enable,
        .stop           = wdt_disable,
        .ping           = wdt_ping,
        .set_timeout    = wdt_setload,
        .get_timeleft   = wdt_timeleft,
};

static int
sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
{
        struct sp805_wdt *wdt;
        int ret = 0;

        if (!devm_request_mem_region(&adev->dev, adev->res.start,
                                resource_size(&adev->res), "sp805_wdt")) {
                dev_warn(&adev->dev, "Failed to get memory region resource\n");
                ret = -ENOENT;
                goto err;
        }

        wdt = devm_kzalloc(&adev->dev, sizeof(*wdt), GFP_KERNEL);
        if (!wdt) {
                dev_warn(&adev->dev, "Kzalloc failed\n");
                ret = -ENOMEM;
                goto err;
        }

        wdt->base = devm_ioremap(&adev->dev, adev->res.start,
                        resource_size(&adev->res));
        if (!wdt->base) {
                ret = -ENOMEM;
                dev_warn(&adev->dev, "ioremap fail\n");
                goto err;
        }

        wdt->clk = devm_clk_get(&adev->dev, NULL);
        if (IS_ERR(wdt->clk)) {
                dev_warn(&adev->dev, "Clock not found\n");
                ret = PTR_ERR(wdt->clk);
                goto err;
        }

        wdt->adev = adev;
        wdt->wdd.info = &wdt_info;
        wdt->wdd.ops = &wdt_ops;

        spin_lock_init(&wdt->lock);
        watchdog_set_nowayout(&wdt->wdd, nowayout);
        watchdog_set_drvdata(&wdt->wdd, wdt);
        wdt_setload(&wdt->wdd, DEFAULT_TIMEOUT);

        ret = watchdog_register_device(&wdt->wdd);
        if (ret) {
                dev_err(&adev->dev, "watchdog_register_device() failed: %d\n",
                                ret);
                goto err;
        }
        amba_set_drvdata(adev, wdt);

        dev_info(&adev->dev, "registration successful\n");
        return 0;

err:
        dev_err(&adev->dev, "Probe Failed!!!\n");
        return ret;
}

static int sp805_wdt_remove(struct amba_device *adev)
{
        struct sp805_wdt *wdt = amba_get_drvdata(adev);

        watchdog_unregister_device(&wdt->wdd);
        watchdog_set_drvdata(&wdt->wdd, NULL);

        return 0;
}

static int __maybe_unused sp805_wdt_suspend(struct device *dev)
{
        struct sp805_wdt *wdt = dev_get_drvdata(dev);

        if (watchdog_active(&wdt->wdd))
                return wdt_disable(&wdt->wdd);

        return 0;
}

static int __maybe_unused sp805_wdt_resume(struct device *dev)
{
        struct sp805_wdt *wdt = dev_get_drvdata(dev);

        if (watchdog_active(&wdt->wdd))
                return wdt_enable(&wdt->wdd);

        return 0;
}

static SIMPLE_DEV_PM_OPS(sp805_wdt_dev_pm_ops, sp805_wdt_suspend,
                sp805_wdt_resume);

static struct amba_id sp805_wdt_ids[] = {
        {
                .id     = 0x00141805,
                .mask   = 0x00ffffff,
        },
        { 0, 0 },
};

MODULE_DEVICE_TABLE(amba, sp805_wdt_ids);

static struct amba_driver sp805_wdt_driver = {
        .drv = {
                .name   = MODULE_NAME,
                .pm     = &sp805_wdt_dev_pm_ops,
        },
        .id_table       = sp805_wdt_ids,
        .probe          = sp805_wdt_probe,
        .remove = sp805_wdt_remove,
};

module_amba_driver(sp805_wdt_driver);

MODULE_AUTHOR("Viresh Kumar <viresh.linux@gmail.com>");
MODULE_DESCRIPTION("ARM SP805 Watchdog Driver");
MODULE_LICENSE("GPL");