// SPDX-License-Identifier: GPL-2.0
/*
 *	Airoha Watchdog Driver
 *
 *	Copyright (c) 2024, AIROHA  All rights reserved.
 *
 *	Mayur Kumar <mayur.kumar@airoha.com>
 *	Christian Marangi <ansuelsmth@gmail.com>
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/math.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

/* Base address of timer and watchdog registers */
#define TIMER_CTRL			0x0
#define   WDT_ENABLE			BIT(25)
#define   WDT_TIMER_INTERRUPT		BIT(21)
/* Timer3 is used as Watchdog Timer */
#define   WDT_TIMER_ENABLE		BIT(5)
#define WDT_TIMER_LOAD_VALUE		0x2c
#define WDT_TIMER_CUR_VALUE		0x30
#define  WDT_TIMER_VAL			GENMASK(31, 0)
#define WDT_RELOAD			0x38
#define   WDT_RLD			BIT(0)

/* Airoha watchdog structure description */
struct airoha_wdt_desc {
	struct watchdog_device wdog_dev;
	unsigned int wdt_freq;
	void __iomem *base;
};

#define WDT_HEARTBEAT			24
static int heartbeat = WDT_HEARTBEAT;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. (default="
		 __MODULE_STRING(WDT_HEARTBEAT) ")");

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) ")");

static int airoha_wdt_start(struct watchdog_device *wdog_dev)
{
	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
	u32 val;

	val = readl(airoha_wdt->base + TIMER_CTRL);
	val |= (WDT_TIMER_ENABLE | WDT_ENABLE | WDT_TIMER_INTERRUPT);
	writel(val, airoha_wdt->base + TIMER_CTRL);
	val = wdog_dev->timeout * airoha_wdt->wdt_freq;
	writel(val, airoha_wdt->base + WDT_TIMER_LOAD_VALUE);

	return 0;
}

static int airoha_wdt_stop(struct watchdog_device *wdog_dev)
{
	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
	u32 val;

	val = readl(airoha_wdt->base + TIMER_CTRL);
	val &= (~WDT_ENABLE & ~WDT_TIMER_ENABLE);
	writel(val, airoha_wdt->base + TIMER_CTRL);

	return 0;
}

static int airoha_wdt_ping(struct watchdog_device *wdog_dev)
{
	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
	u32 val;

	val = readl(airoha_wdt->base + WDT_RELOAD);
	val |= WDT_RLD;
	writel(val, airoha_wdt->base + WDT_RELOAD);

	return 0;
}

static int airoha_wdt_set_timeout(struct watchdog_device *wdog_dev, unsigned int timeout)
{
	wdog_dev->timeout = timeout;

	if (watchdog_active(wdog_dev)) {
		airoha_wdt_stop(wdog_dev);
		return airoha_wdt_start(wdog_dev);
	}

	return 0;
}

static unsigned int airoha_wdt_get_timeleft(struct watchdog_device *wdog_dev)
{
	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
	u32 val;

	val = readl(airoha_wdt->base + WDT_TIMER_CUR_VALUE);
	return DIV_ROUND_UP(val, airoha_wdt->wdt_freq);
}

static const struct watchdog_info airoha_wdt_info = {
	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
	.identity = "Airoha Watchdog",
};

static const struct watchdog_ops airoha_wdt_ops = {
	.owner = THIS_MODULE,
	.start = airoha_wdt_start,
	.stop = airoha_wdt_stop,
	.ping = airoha_wdt_ping,
	.set_timeout = airoha_wdt_set_timeout,
	.get_timeleft = airoha_wdt_get_timeleft,
};

static int airoha_wdt_probe(struct platform_device *pdev)
{
	struct airoha_wdt_desc *airoha_wdt;
	struct watchdog_device *wdog_dev;
	struct device *dev = &pdev->dev;
	struct clk *bus_clk;
	int ret;

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

	airoha_wdt->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(airoha_wdt->base))
		return PTR_ERR(airoha_wdt->base);

	bus_clk = devm_clk_get_enabled(dev, "bus");
	if (IS_ERR(bus_clk))
		return dev_err_probe(dev, PTR_ERR(bus_clk),
				     "failed to enable bus clock\n");

	/* Watchdog ticks at half the bus rate */
	airoha_wdt->wdt_freq = clk_get_rate(bus_clk) / 2;

	/* Initialize struct watchdog device */
	wdog_dev = &airoha_wdt->wdog_dev;
	wdog_dev->timeout = heartbeat;
	wdog_dev->info = &airoha_wdt_info;
	wdog_dev->ops = &airoha_wdt_ops;
	/* Bus 300MHz, watchdog 150MHz, 28 seconds */
	wdog_dev->max_timeout = FIELD_MAX(WDT_TIMER_VAL) / airoha_wdt->wdt_freq;
	wdog_dev->parent = dev;

	watchdog_set_drvdata(wdog_dev, airoha_wdt);
	watchdog_set_nowayout(wdog_dev, nowayout);
	watchdog_stop_on_unregister(wdog_dev);

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

	platform_set_drvdata(pdev, airoha_wdt);
	return 0;
}

static int airoha_wdt_suspend(struct device *dev)
{
	struct airoha_wdt_desc *airoha_wdt = dev_get_drvdata(dev);

	if (watchdog_active(&airoha_wdt->wdog_dev))
		airoha_wdt_stop(&airoha_wdt->wdog_dev);

	return 0;
}

static int airoha_wdt_resume(struct device *dev)
{
	struct airoha_wdt_desc *airoha_wdt = dev_get_drvdata(dev);

	if (watchdog_active(&airoha_wdt->wdog_dev)) {
		airoha_wdt_start(&airoha_wdt->wdog_dev);
		airoha_wdt_ping(&airoha_wdt->wdog_dev);
	}
	return 0;
}

static const struct of_device_id airoha_wdt_of_match[] = {
	{ .compatible = "airoha,en7581-wdt", },
	{ },
};

MODULE_DEVICE_TABLE(of, airoha_wdt_of_match);

static DEFINE_SIMPLE_DEV_PM_OPS(airoha_wdt_pm_ops, airoha_wdt_suspend, airoha_wdt_resume);

static struct platform_driver airoha_wdt_driver = {
	.probe = airoha_wdt_probe,
	.driver = {
		.name = "airoha-wdt",
		.pm = pm_sleep_ptr(&airoha_wdt_pm_ops),
		.of_match_table = airoha_wdt_of_match,
	},
};

module_platform_driver(airoha_wdt_driver);

MODULE_AUTHOR("Mayur Kumar <mayur.kumar@airoha.com>");
MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
MODULE_DESCRIPTION("Airoha EN7581 Watchdog Driver");
MODULE_LICENSE("GPL");