// SPDX-License-Identifier: GPL-2.0-only
/*
 *      intel-mid_wdt: generic Intel MID SCU watchdog driver
 *
 *      Platforms supported so far:
 *      - Merrifield only
 *
 *      Copyright (C) 2014 Intel Corporation. All rights reserved.
 *      Contact: David Cohen <david.a.cohen@linux.intel.com>
 */

#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/panic.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/watchdog.h>

#include <linux/platform_data/x86/intel-mid_wdt.h>
#include <linux/platform_data/x86/intel_scu_ipc.h>

#define IPC_WATCHDOG 0xf8

#define MID_WDT_PRETIMEOUT              15
#define MID_WDT_TIMEOUT_MIN             (1 + MID_WDT_PRETIMEOUT)
#define MID_WDT_TIMEOUT_MAX             170
#define MID_WDT_DEFAULT_TIMEOUT         90

/* SCU watchdog messages */
enum {
        SCU_WATCHDOG_START = 0,
        SCU_WATCHDOG_STOP,
        SCU_WATCHDOG_KEEPALIVE,
};

struct mid_wdt {
        struct watchdog_device wd;
        struct device *dev;
        struct intel_scu_ipc_dev *scu;
};

static inline int
wdt_command(struct mid_wdt *mid, int sub, const void *in, size_t inlen, size_t size)
{
        struct intel_scu_ipc_dev *scu = mid->scu;

        return intel_scu_ipc_dev_command_with_size(scu, IPC_WATCHDOG, sub, in,
                                                   inlen, size, NULL, 0);
}

static int wdt_start(struct watchdog_device *wd)
{
        struct mid_wdt *mid = watchdog_get_drvdata(wd);
        int ret, in_size;
        int timeout = wd->timeout;
        struct ipc_wd_start {
                u32 pretimeout;
                u32 timeout;
        } ipc_wd_start = { timeout - MID_WDT_PRETIMEOUT, timeout };

        /*
         * SCU expects the input size for watchdog IPC to be 2 which is the
         * size of the structure in dwords. SCU IPC normally takes bytes
         * but this is a special case where we specify size to be different
         * than inlen.
         */
        in_size = DIV_ROUND_UP(sizeof(ipc_wd_start), 4);

        ret = wdt_command(mid, SCU_WATCHDOG_START, &ipc_wd_start,
                          sizeof(ipc_wd_start), in_size);
        if (ret)
                dev_crit(mid->dev, "error starting watchdog: %d\n", ret);

        return ret;
}

static int wdt_ping(struct watchdog_device *wd)
{
        struct mid_wdt *mid = watchdog_get_drvdata(wd);
        int ret;

        ret = wdt_command(mid, SCU_WATCHDOG_KEEPALIVE, NULL, 0, 0);
        if (ret)
                dev_crit(mid->dev, "Error executing keepalive: %d\n", ret);

        return ret;
}

static int wdt_stop(struct watchdog_device *wd)
{
        struct mid_wdt *mid = watchdog_get_drvdata(wd);
        int ret;

        ret = wdt_command(mid, SCU_WATCHDOG_STOP, NULL, 0, 0);
        if (ret)
                dev_crit(mid->dev, "Error stopping watchdog: %d\n", ret);

        return ret;
}

static irqreturn_t mid_wdt_irq(int irq, void *dev_id)
{
        panic("Kernel Watchdog");

        /* This code should not be reached */
        return IRQ_HANDLED;
}

static const struct watchdog_info mid_wdt_info = {
        .identity = "Intel MID SCU watchdog",
        .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
};

static const struct watchdog_ops mid_wdt_ops = {
        .owner = THIS_MODULE,
        .start = wdt_start,
        .stop = wdt_stop,
        .ping = wdt_ping,
};

static int mid_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct watchdog_device *wdt_dev;
        struct intel_mid_wdt_pdata *pdata = dev_get_platdata(dev);
        struct mid_wdt *mid;
        int ret;

        if (!pdata) {
                dev_err(dev, "missing platform data\n");
                return -EINVAL;
        }

        if (pdata->probe) {
                ret = pdata->probe(pdev);
                if (ret)
                        return ret;
        }

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

        mid->dev = dev;
        wdt_dev = &mid->wd;

        wdt_dev->info = &mid_wdt_info;
        wdt_dev->ops = &mid_wdt_ops;
        wdt_dev->min_timeout = MID_WDT_TIMEOUT_MIN;
        wdt_dev->max_timeout = MID_WDT_TIMEOUT_MAX;
        wdt_dev->timeout = MID_WDT_DEFAULT_TIMEOUT;
        wdt_dev->parent = dev;

        watchdog_set_nowayout(wdt_dev, WATCHDOG_NOWAYOUT);
        watchdog_set_drvdata(wdt_dev, mid);

        mid->scu = devm_intel_scu_ipc_dev_get(dev);
        if (!mid->scu)
                return -EPROBE_DEFER;

        ret = devm_request_irq(dev, pdata->irq, mid_wdt_irq,
                               IRQF_SHARED | IRQF_NO_SUSPEND, "watchdog",
                               wdt_dev);
        if (ret) {
                dev_err(dev, "error requesting warning irq %d\n", pdata->irq);
                return ret;
        }

        /*
         * The firmware followed by U-Boot leaves the watchdog running
         * with the default threshold which may vary. When we get here
         * we should make a decision to prevent any side effects before
         * user space daemon will take care of it. The best option,
         * taking into consideration that there is no way to read values
         * back from hardware, is to enforce watchdog being run with
         * deterministic values.
         */
        ret = wdt_start(wdt_dev);
        if (ret)
                return ret;

        /* Make sure the watchdog is serviced */
        set_bit(WDOG_HW_RUNNING, &wdt_dev->status);

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

        dev_info(dev, "Intel MID watchdog device probed\n");

        return 0;
}

static struct platform_driver mid_wdt_driver = {
        .probe          = mid_wdt_probe,
        .driver         = {
                .name   = "intel_mid_wdt",
        },
};

module_platform_driver(mid_wdt_driver);

MODULE_AUTHOR("David Cohen <david.a.cohen@linux.intel.com>");
MODULE_DESCRIPTION("Watchdog Driver for Intel MID platform");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:intel_mid_wdt");