// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Congatec Board Controller watchdog driver
 *
 * Copyright (C) 2024 Bootlin
 * Author: Thomas Richard <thomas.richard@bootlin.com>
 */

#include <linux/build_bug.h>
#include <linux/device.h>
#include <linux/limits.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

#include <linux/mfd/cgbc.h>

#define CGBC_WDT_CMD_TRIGGER    0x27
#define CGBC_WDT_CMD_INIT       0x28
#define CGBC_WDT_DISABLE        0x00

#define CGBC_WDT_MODE_SINGLE_EVENT 0x02

#define CGBC_WDT_MIN_TIMEOUT    1
#define CGBC_WDT_MAX_TIMEOUT    ((U32_MAX >> 8) / 1000)

#define CGBC_WDT_DEFAULT_TIMEOUT        30
#define CGBC_WDT_DEFAULT_PRETIMEOUT     0

enum action {
        ACTION_INT = 0,
        ACTION_SMI,
        ACTION_RESET,
        ACTION_BUTTON,
};

static unsigned int timeout;
module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout,
                 "Watchdog timeout in seconds. (>=0, default="
                 __MODULE_STRING(CGBC_WDT_DEFAULT_TIMEOUT) ")");

static unsigned int pretimeout = CGBC_WDT_DEFAULT_PRETIMEOUT;
module_param(pretimeout, uint, 0);
MODULE_PARM_DESC(pretimeout,
                 "Watchdog pretimeout in seconds. (>=0, default="
                 __MODULE_STRING(CGBC_WDT_DEFAULT_PRETIMEOUT) ")");

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) ")");

struct cgbc_wdt_data {
        struct cgbc_device_data *cgbc;
        struct watchdog_device  wdd;
};

struct cgbc_wdt_cmd_cfg {
        u8 cmd;
        u8 mode;
        u8 action;
        u8 timeout1[3];
        u8 timeout2[3];
        u8 reserved[3];
        u8 delay[3];
} __packed;

static_assert(sizeof(struct cgbc_wdt_cmd_cfg) == 15);

static int cgbc_wdt_start(struct watchdog_device *wdd)
{
        struct cgbc_wdt_data *wdt_data = watchdog_get_drvdata(wdd);
        struct cgbc_device_data *cgbc = wdt_data->cgbc;
        unsigned int timeout1 = (wdd->timeout - wdd->pretimeout) * 1000;
        unsigned int timeout2 = wdd->pretimeout * 1000;
        u8 action;

        struct cgbc_wdt_cmd_cfg cmd_start = {
                .cmd = CGBC_WDT_CMD_INIT,
                .mode = CGBC_WDT_MODE_SINGLE_EVENT,
                .timeout1[0] = (u8)timeout1,
                .timeout1[1] = (u8)(timeout1 >> 8),
                .timeout1[2] = (u8)(timeout1 >> 16),
                .timeout2[0] = (u8)timeout2,
                .timeout2[1] = (u8)(timeout2 >> 8),
                .timeout2[2] = (u8)(timeout2 >> 16),
        };

        if (wdd->pretimeout) {
                action = 2;
                action |= ACTION_SMI << 2;
                action |= ACTION_RESET << 4;
        } else {
                action = 1;
                action |= ACTION_RESET << 2;
        }

        cmd_start.action = action;

        return cgbc_command(cgbc, &cmd_start, sizeof(cmd_start), NULL, 0, NULL);
}

static int cgbc_wdt_stop(struct watchdog_device *wdd)
{
        struct cgbc_wdt_data *wdt_data = watchdog_get_drvdata(wdd);
        struct cgbc_device_data *cgbc = wdt_data->cgbc;
        struct cgbc_wdt_cmd_cfg cmd_stop = {
                .cmd = CGBC_WDT_CMD_INIT,
                .mode = CGBC_WDT_DISABLE,
        };

        return cgbc_command(cgbc, &cmd_stop, sizeof(cmd_stop), NULL, 0, NULL);
}

static int cgbc_wdt_keepalive(struct watchdog_device *wdd)
{
        struct cgbc_wdt_data *wdt_data = watchdog_get_drvdata(wdd);
        struct cgbc_device_data *cgbc = wdt_data->cgbc;
        u8 cmd_ping = CGBC_WDT_CMD_TRIGGER;

        return cgbc_command(cgbc, &cmd_ping, sizeof(cmd_ping), NULL, 0, NULL);
}

static int cgbc_wdt_set_pretimeout(struct watchdog_device *wdd,
                                   unsigned int pretimeout)
{
        wdd->pretimeout = pretimeout;

        if (watchdog_active(wdd))
                return cgbc_wdt_start(wdd);

        return 0;
}

static int cgbc_wdt_set_timeout(struct watchdog_device *wdd,
                                unsigned int timeout)
{
        if (timeout < wdd->pretimeout)
                wdd->pretimeout = 0;

        wdd->timeout = timeout;

        if (watchdog_active(wdd))
                return cgbc_wdt_start(wdd);

        return 0;
}

static const struct watchdog_info cgbc_wdt_info = {
        .identity       = "CGBC Watchdog",
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                WDIOF_MAGICCLOSE | WDIOF_PRETIMEOUT
};

static const struct watchdog_ops cgbc_wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = cgbc_wdt_start,
        .stop           = cgbc_wdt_stop,
        .ping           = cgbc_wdt_keepalive,
        .set_timeout    = cgbc_wdt_set_timeout,
        .set_pretimeout = cgbc_wdt_set_pretimeout,
};

static int cgbc_wdt_probe(struct platform_device *pdev)
{
        struct cgbc_device_data *cgbc = dev_get_drvdata(pdev->dev.parent);
        struct device *dev = &pdev->dev;
        struct cgbc_wdt_data *wdt_data;
        struct watchdog_device *wdd;

        wdt_data = devm_kzalloc(dev, sizeof(*wdt_data), GFP_KERNEL);
        if (!wdt_data)
                return -ENOMEM;

        wdt_data->cgbc = cgbc;
        wdd = &wdt_data->wdd;
        wdd->parent = dev;

        wdd->info = &cgbc_wdt_info;
        wdd->ops = &cgbc_wdt_ops;
        wdd->max_timeout = CGBC_WDT_MAX_TIMEOUT;
        wdd->min_timeout = CGBC_WDT_MIN_TIMEOUT;

        watchdog_set_drvdata(wdd, wdt_data);
        watchdog_set_nowayout(wdd, nowayout);

        wdd->timeout = CGBC_WDT_DEFAULT_TIMEOUT;
        watchdog_init_timeout(wdd, timeout, dev);
        cgbc_wdt_set_pretimeout(wdd, pretimeout);

        platform_set_drvdata(pdev, wdt_data);
        watchdog_stop_on_reboot(wdd);
        watchdog_stop_on_unregister(wdd);

        return devm_watchdog_register_device(dev, wdd);
}

static struct platform_driver cgbc_wdt_driver = {
        .driver         = {
                .name   = "cgbc-wdt",
        },
        .probe          = cgbc_wdt_probe,
};

module_platform_driver(cgbc_wdt_driver);

MODULE_DESCRIPTION("Congatec Board Controller Watchdog Driver");
MODULE_AUTHOR("Thomas Richard <thomas.richard@bootlin.com>");
MODULE_LICENSE("GPL");