// SPDX-License-Identifier: GPL-2.0-only
/*
 * ARM Secure Monitor Call watchdog driver
 *
 * Copyright 2020 Google LLC.
 * Julius Werner <jwerner@chromium.org>
 * Based on mtk_wdt.c
 */

#include <linux/arm-smccc.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <uapi/linux/psci.h>

#define DRV_NAME                "arm_smc_wdt"
#define DRV_VERSION             "1.0"

enum smcwd_call {
        SMCWD_INIT              = 0,
        SMCWD_SET_TIMEOUT       = 1,
        SMCWD_ENABLE            = 2,
        SMCWD_PET               = 3,
        SMCWD_GET_TIMELEFT      = 4,
};

static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned int timeout;

static int smcwd_call(struct watchdog_device *wdd, enum smcwd_call call,
                      unsigned long arg, struct arm_smccc_res *res)
{
        struct arm_smccc_res local_res;

        if (!res)
                res = &local_res;

        arm_smccc_smc((u32)(uintptr_t)watchdog_get_drvdata(wdd), call, arg, 0,
                      0, 0, 0, 0, res);

        if (res->a0 == PSCI_RET_NOT_SUPPORTED)
                return -ENODEV;
        if (res->a0 == PSCI_RET_INVALID_PARAMS)
                return -EINVAL;
        if (res->a0 == PSCI_RET_DISABLED)
                return -ENODATA;
        if (res->a0 != PSCI_RET_SUCCESS)
                return -EIO;
        return 0;
}

static int smcwd_ping(struct watchdog_device *wdd)
{
        return smcwd_call(wdd, SMCWD_PET, 0, NULL);
}

static unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
{
        struct arm_smccc_res res;

        smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, &res);
        if (res.a0)
                return 0;
        return res.a1;
}

static int smcwd_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
{
        int res;

        res = smcwd_call(wdd, SMCWD_SET_TIMEOUT, timeout, NULL);
        if (!res)
                wdd->timeout = timeout;
        return res;
}

static int smcwd_stop(struct watchdog_device *wdd)
{
        return smcwd_call(wdd, SMCWD_ENABLE, 0, NULL);
}

static int smcwd_start(struct watchdog_device *wdd)
{
        return smcwd_call(wdd, SMCWD_ENABLE, 1, NULL);
}

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

static const struct watchdog_ops smcwd_ops = {
        .start          = smcwd_start,
        .stop           = smcwd_stop,
        .ping           = smcwd_ping,
        .set_timeout    = smcwd_set_timeout,
};

static const struct watchdog_ops smcwd_timeleft_ops = {
        .start          = smcwd_start,
        .stop           = smcwd_stop,
        .ping           = smcwd_ping,
        .set_timeout    = smcwd_set_timeout,
        .get_timeleft   = smcwd_get_timeleft,
};

static int smcwd_probe(struct platform_device *pdev)
{
        struct watchdog_device *wdd;
        int err;
        struct arm_smccc_res res;
        u32 smc_func_id;

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

        if (of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
                                 &smc_func_id))
                smc_func_id = 0x82003D06;
        watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);

        err = smcwd_call(wdd, SMCWD_INIT, 0, &res);
        if (err < 0)
                return err;

        wdd->info = &smcwd_info;
        /* get_timeleft is optional */
        err = smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, NULL);
        switch (err) {
        case 0:
                set_bit(WDOG_HW_RUNNING, &wdd->status);
                fallthrough;
        case -ENODATA:
                wdd->ops = &smcwd_timeleft_ops;
                break;
        default:
                wdd->ops = &smcwd_ops;
                break;
        }

        wdd->timeout = res.a2;
        wdd->max_timeout = res.a2;
        wdd->min_timeout = res.a1;
        wdd->parent = &pdev->dev;

        watchdog_stop_on_reboot(wdd);
        watchdog_stop_on_unregister(wdd);
        watchdog_set_nowayout(wdd, nowayout);
        watchdog_init_timeout(wdd, timeout, &pdev->dev);
        err = smcwd_set_timeout(wdd, wdd->timeout);
        if (err)
                return err;

        err = devm_watchdog_register_device(&pdev->dev, wdd);
        if (err)
                return err;

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

        return 0;
}

static const struct of_device_id smcwd_dt_ids[] = {
        { .compatible = "arm,smc-wdt" },
        {}
};
MODULE_DEVICE_TABLE(of, smcwd_dt_ids);

static struct platform_driver smcwd_driver = {
        .probe          = smcwd_probe,
        .driver         = {
                .name           = DRV_NAME,
                .of_match_table = smcwd_dt_ids,
        },
};

module_platform_driver(smcwd_driver);

module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
                        __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
MODULE_VERSION(DRV_VERSION);