/*
 * Watchdog driver for TS-4800 based boards
 *
 * Copyright (c) 2015 - Savoir-faire Linux
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

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) ")");

/* possible feed values */
#define TS4800_WDT_FEED_2S       0x1
#define TS4800_WDT_FEED_10S      0x2
#define TS4800_WDT_DISABLE       0x3

struct ts4800_wdt {
        struct watchdog_device  wdd;
        struct regmap           *regmap;
        u32                     feed_offset;
        u32                     feed_val;
};

/*
 * TS-4800 supports the following timeout values:
 *
 *   value desc
 *   ---------------------
 *     0    feed for 338ms
 *     1    feed for 2.706s
 *     2    feed for 10.824s
 *     3    disable watchdog
 *
 * Keep the regmap/timeout map ordered by timeout
 */
static const struct {
        const int timeout;
        const int regval;
} ts4800_wdt_map[] = {
        { 2,  TS4800_WDT_FEED_2S },
        { 10, TS4800_WDT_FEED_10S },
};

#define MAX_TIMEOUT_INDEX       (ARRAY_SIZE(ts4800_wdt_map) - 1)

static void ts4800_write_feed(struct ts4800_wdt *wdt, u32 val)
{
        regmap_write(wdt->regmap, wdt->feed_offset, val);
}

static int ts4800_wdt_start(struct watchdog_device *wdd)
{
        struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);

        ts4800_write_feed(wdt, wdt->feed_val);
        return 0;
}

static int ts4800_wdt_stop(struct watchdog_device *wdd)
{
        struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);

        ts4800_write_feed(wdt, TS4800_WDT_DISABLE);
        return 0;
}

static int ts4800_wdt_set_timeout(struct watchdog_device *wdd,
                                  unsigned int timeout)
{
        struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
        int i;

        for (i = 0; i < MAX_TIMEOUT_INDEX; i++) {
                if (ts4800_wdt_map[i].timeout >= timeout)
                        break;
        }

        wdd->timeout = ts4800_wdt_map[i].timeout;
        wdt->feed_val = ts4800_wdt_map[i].regval;

        return 0;
}

static const struct watchdog_ops ts4800_wdt_ops = {
        .owner = THIS_MODULE,
        .start = ts4800_wdt_start,
        .stop = ts4800_wdt_stop,
        .set_timeout = ts4800_wdt_set_timeout,
};

static const struct watchdog_info ts4800_wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
        .identity = "TS-4800 Watchdog",
};

static int ts4800_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *np = dev->of_node;
        struct device_node *syscon_np;
        struct watchdog_device *wdd;
        struct ts4800_wdt *wdt;
        u32 reg;
        int ret;

        syscon_np = of_parse_phandle(np, "syscon", 0);
        if (!syscon_np) {
                dev_err(dev, "no syscon property\n");
                return -ENODEV;
        }

        ret = of_property_read_u32_index(np, "syscon", 1, &reg);
        if (ret < 0) {
                dev_err(dev, "no offset in syscon\n");
                return ret;
        }

        /* allocate memory for watchdog struct */
        wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        /* set regmap and offset to know where to write */
        wdt->feed_offset = reg;
        wdt->regmap = syscon_node_to_regmap(syscon_np);
        of_node_put(syscon_np);
        if (IS_ERR(wdt->regmap)) {
                dev_err(dev, "cannot get parent's regmap\n");
                return PTR_ERR(wdt->regmap);
        }

        /* Initialize struct watchdog_device */
        wdd = &wdt->wdd;
        wdd->parent = dev;
        wdd->info = &ts4800_wdt_info;
        wdd->ops = &ts4800_wdt_ops;
        wdd->min_timeout = ts4800_wdt_map[0].timeout;
        wdd->max_timeout = ts4800_wdt_map[MAX_TIMEOUT_INDEX].timeout;

        watchdog_set_drvdata(wdd, wdt);
        watchdog_set_nowayout(wdd, nowayout);
        watchdog_init_timeout(wdd, 0, dev);

        /*
         * As this watchdog supports only a few values, ts4800_wdt_set_timeout
         * must be called to initialize timeout and feed_val with valid values.
         * Default to maximum timeout if none, or an invalid one, is provided in
         * device tree.
         */
        if (!wdd->timeout)
                wdd->timeout = wdd->max_timeout;
        ts4800_wdt_set_timeout(wdd, wdd->timeout);

        /*
         * The feed register is write-only, so it is not possible to determine
         * watchdog's state. Disable it to be in a known state.
         */
        ts4800_wdt_stop(wdd);

        ret = devm_watchdog_register_device(dev, wdd);
        if (ret)
                return ret;

        platform_set_drvdata(pdev, wdt);

        dev_info(dev, "initialized (timeout = %d sec, nowayout = %d)\n",
                 wdd->timeout, nowayout);

        return 0;
}

static const struct of_device_id ts4800_wdt_of_match[] = {
        { .compatible = "technologic,ts4800-wdt", },
        { },
};
MODULE_DEVICE_TABLE(of, ts4800_wdt_of_match);

static struct platform_driver ts4800_wdt_driver = {
        .probe          = ts4800_wdt_probe,
        .driver         = {
                .name   = "ts4800_wdt",
                .of_match_table = ts4800_wdt_of_match,
        },
};

module_platform_driver(ts4800_wdt_driver);

MODULE_AUTHOR("Damien Riegel <damien.riegel@savoirfairelinux.com>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:ts4800_wdt");