// SPDX-License-Identifier: GPL-2.0
/*
 * Starfive Watchdog driver
 *
 * Copyright (C) 2022 StarFive Technology Co., Ltd.
 */

#include <linux/clk.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/watchdog.h>

/* JH7100 Watchdog register define */
#define STARFIVE_WDT_JH7100_INTSTAUS	0x000
#define STARFIVE_WDT_JH7100_CONTROL	0x104
#define STARFIVE_WDT_JH7100_LOAD	0x108
#define STARFIVE_WDT_JH7100_EN		0x110
#define STARFIVE_WDT_JH7100_RELOAD	0x114	/* Write 0 or 1 to reload preset value */
#define STARFIVE_WDT_JH7100_VALUE	0x118
#define STARFIVE_WDT_JH7100_INTCLR	0x120	/*
						 * [0]: Write 1 to clear interrupt
						 * [1]: 1 mean clearing and 0 mean complete
						 * [31:2]: reserved.
						 */
#define STARFIVE_WDT_JH7100_LOCK	0x13c	/* write 0x378f0765 to unlock */

/* JH7110 Watchdog register define */
#define STARFIVE_WDT_JH7110_LOAD	0x000
#define STARFIVE_WDT_JH7110_VALUE	0x004
#define STARFIVE_WDT_JH7110_CONTROL	0x008	/*
						 * [0]: reset enable;
						 * [1]: interrupt enable && watchdog enable
						 * [31:2]: reserved.
						 */
#define STARFIVE_WDT_JH7110_INTCLR	0x00c	/* clear intterupt and reload the counter */
#define STARFIVE_WDT_JH7110_IMS		0x014
#define STARFIVE_WDT_JH7110_LOCK	0xc00	/* write 0x1ACCE551 to unlock */

/* WDOGCONTROL */
#define STARFIVE_WDT_ENABLE			0x1
#define STARFIVE_WDT_EN_SHIFT			0
#define STARFIVE_WDT_RESET_EN			0x1
#define STARFIVE_WDT_JH7100_RST_EN_SHIFT	0
#define STARFIVE_WDT_JH7110_RST_EN_SHIFT	1

/* WDOGLOCK */
#define STARFIVE_WDT_JH7100_UNLOCK_KEY		0x378f0765
#define STARFIVE_WDT_JH7110_UNLOCK_KEY		0x1acce551

/* WDOGINTCLR */
#define STARFIVE_WDT_INTCLR			0x1
#define STARFIVE_WDT_JH7100_INTCLR_AVA_SHIFT	1	/* Watchdog can clear interrupt when 0 */

#define STARFIVE_WDT_MAXCNT			0xffffffff
#define STARFIVE_WDT_DEFAULT_TIME		(15)
#define STARFIVE_WDT_DELAY_US			0
#define STARFIVE_WDT_TIMEOUT_US			10000

/* module parameter */
#define STARFIVE_WDT_EARLY_ENA			0

static bool nowayout = WATCHDOG_NOWAYOUT;
static int heartbeat;
static bool early_enable = STARFIVE_WDT_EARLY_ENA;

module_param(heartbeat, int, 0);
module_param(early_enable, bool, 0);
module_param(nowayout, bool, 0);

MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (default="
		 __MODULE_STRING(STARFIVE_WDT_DEFAULT_TIME) ")");
MODULE_PARM_DESC(early_enable,
		 "Watchdog is started at boot time if set to 1, default="
		 __MODULE_STRING(STARFIVE_WDT_EARLY_ENA));
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

struct starfive_wdt_variant {
	unsigned int control;		/* Watchdog Control Resgister for reset enable */
	unsigned int load;		/* Watchdog Load register */
	unsigned int reload;		/* Watchdog Reload Control register */
	unsigned int enable;		/* Watchdog Enable Register */
	unsigned int value;		/* Watchdog Counter Value Register */
	unsigned int int_clr;		/* Watchdog Interrupt Clear Register */
	unsigned int unlock;		/* Watchdog Lock Register */
	unsigned int int_status;	/* Watchdog Interrupt Status Register */

	u32 unlock_key;
	char enrst_shift;
	char en_shift;
	bool intclr_check;		/*  whether need to check it before clearing interrupt */
	char intclr_ava_shift;
	bool double_timeout;		/* The watchdog need twice timeout to reboot */
};

struct starfive_wdt {
	struct watchdog_device wdd;
	spinlock_t lock;		/* spinlock for register handling */
	void __iomem *base;
	struct clk *core_clk;
	struct clk *apb_clk;
	const struct starfive_wdt_variant *variant;
	unsigned long freq;
	u32 count;			/* count of timeout */
	u32 reload;			/* restore the count */
};

/* Register layout and configuration for the JH7100 */
static const struct starfive_wdt_variant starfive_wdt_jh7100_variant = {
	.control = STARFIVE_WDT_JH7100_CONTROL,
	.load = STARFIVE_WDT_JH7100_LOAD,
	.reload = STARFIVE_WDT_JH7100_RELOAD,
	.enable = STARFIVE_WDT_JH7100_EN,
	.value = STARFIVE_WDT_JH7100_VALUE,
	.int_clr = STARFIVE_WDT_JH7100_INTCLR,
	.unlock = STARFIVE_WDT_JH7100_LOCK,
	.unlock_key = STARFIVE_WDT_JH7100_UNLOCK_KEY,
	.int_status = STARFIVE_WDT_JH7100_INTSTAUS,
	.enrst_shift = STARFIVE_WDT_JH7100_RST_EN_SHIFT,
	.en_shift = STARFIVE_WDT_EN_SHIFT,
	.intclr_check = true,
	.intclr_ava_shift = STARFIVE_WDT_JH7100_INTCLR_AVA_SHIFT,
	.double_timeout = false,
};

/* Register layout and configuration for the JH7110 */
static const struct starfive_wdt_variant starfive_wdt_jh7110_variant = {
	.control = STARFIVE_WDT_JH7110_CONTROL,
	.load = STARFIVE_WDT_JH7110_LOAD,
	.enable = STARFIVE_WDT_JH7110_CONTROL,
	.value = STARFIVE_WDT_JH7110_VALUE,
	.int_clr = STARFIVE_WDT_JH7110_INTCLR,
	.unlock = STARFIVE_WDT_JH7110_LOCK,
	.unlock_key = STARFIVE_WDT_JH7110_UNLOCK_KEY,
	.int_status = STARFIVE_WDT_JH7110_IMS,
	.enrst_shift = STARFIVE_WDT_JH7110_RST_EN_SHIFT,
	.en_shift = STARFIVE_WDT_EN_SHIFT,
	.intclr_check = false,
	.double_timeout = true,
};

static int starfive_wdt_enable_clock(struct starfive_wdt *wdt)
{
	int ret;

	ret = clk_prepare_enable(wdt->apb_clk);
	if (ret)
		return dev_err_probe(wdt->wdd.parent, ret, "failed to enable apb clock\n");

	ret = clk_prepare_enable(wdt->core_clk);
	if (ret)
		return dev_err_probe(wdt->wdd.parent, ret, "failed to enable core clock\n");

	return 0;
}

static void starfive_wdt_disable_clock(struct starfive_wdt *wdt)
{
	clk_disable_unprepare(wdt->core_clk);
	clk_disable_unprepare(wdt->apb_clk);
}

static inline int starfive_wdt_get_clock(struct starfive_wdt *wdt)
{
	struct device *dev = wdt->wdd.parent;

	wdt->apb_clk = devm_clk_get(dev, "apb");
	if (IS_ERR(wdt->apb_clk))
		return dev_err_probe(dev, PTR_ERR(wdt->apb_clk), "failed to get apb clock\n");

	wdt->core_clk = devm_clk_get(dev, "core");
	if (IS_ERR(wdt->core_clk))
		return dev_err_probe(dev, PTR_ERR(wdt->core_clk), "failed to get core clock\n");

	return 0;
}

static inline int starfive_wdt_reset_init(struct device *dev)
{
	struct reset_control *rsts;
	int ret;

	rsts = devm_reset_control_array_get_exclusive(dev);
	if (IS_ERR(rsts))
		return dev_err_probe(dev, PTR_ERR(rsts), "failed to get resets\n");

	ret = reset_control_deassert(rsts);
	if (ret)
		return dev_err_probe(dev, ret, "failed to deassert resets\n");

	return 0;
}

static u32 starfive_wdt_ticks_to_sec(struct starfive_wdt *wdt, u32 ticks)
{
	return DIV_ROUND_CLOSEST(ticks, wdt->freq);
}

/* Write unlock-key to unlock. Write other value to lock. */
static void starfive_wdt_unlock(struct starfive_wdt *wdt)
	__acquires(&wdt->lock)
{
	spin_lock(&wdt->lock);
	writel(wdt->variant->unlock_key, wdt->base + wdt->variant->unlock);
}

static void starfive_wdt_lock(struct starfive_wdt *wdt)
	__releases(&wdt->lock)
{
	writel(~wdt->variant->unlock_key, wdt->base + wdt->variant->unlock);
	spin_unlock(&wdt->lock);
}

/* enable watchdog interrupt to reset/reboot */
static void starfive_wdt_enable_reset(struct starfive_wdt *wdt)
{
	u32 val;

	val = readl(wdt->base + wdt->variant->control);
	val |= STARFIVE_WDT_RESET_EN << wdt->variant->enrst_shift;
	writel(val, wdt->base + wdt->variant->control);
}

/* interrupt status whether has been raised from the counter */
static bool starfive_wdt_raise_irq_status(struct starfive_wdt *wdt)
{
	return !!readl(wdt->base + wdt->variant->int_status);
}

/* waiting interrupt can be free to clear */
static int starfive_wdt_wait_int_free(struct starfive_wdt *wdt)
{
	u32 value;

	return readl_poll_timeout_atomic(wdt->base + wdt->variant->int_clr, value,
					 !(value & BIT(wdt->variant->intclr_ava_shift)),
					 STARFIVE_WDT_DELAY_US, STARFIVE_WDT_TIMEOUT_US);
}

/* clear interrupt signal before initialization or reload */
static int starfive_wdt_int_clr(struct starfive_wdt *wdt)
{
	int ret;

	if (wdt->variant->intclr_check) {
		ret = starfive_wdt_wait_int_free(wdt);
		if (ret)
			return dev_err_probe(wdt->wdd.parent, ret,
					     "watchdog is not ready to clear interrupt.\n");
	}
	writel(STARFIVE_WDT_INTCLR, wdt->base + wdt->variant->int_clr);

	return 0;
}

static inline void starfive_wdt_set_count(struct starfive_wdt *wdt, u32 val)
{
	writel(val, wdt->base + wdt->variant->load);
}

static inline u32 starfive_wdt_get_count(struct starfive_wdt *wdt)
{
	return readl(wdt->base + wdt->variant->value);
}

/* enable watchdog */
static inline void starfive_wdt_enable(struct starfive_wdt *wdt)
{
	u32 val;

	val = readl(wdt->base + wdt->variant->enable);
	val |= STARFIVE_WDT_ENABLE << wdt->variant->en_shift;
	writel(val, wdt->base + wdt->variant->enable);
}

/* disable watchdog */
static inline void starfive_wdt_disable(struct starfive_wdt *wdt)
{
	u32 val;

	val = readl(wdt->base + wdt->variant->enable);
	val &= ~(STARFIVE_WDT_ENABLE << wdt->variant->en_shift);
	writel(val, wdt->base + wdt->variant->enable);
}

static inline void starfive_wdt_set_reload_count(struct starfive_wdt *wdt, u32 count)
{
	starfive_wdt_set_count(wdt, count);

	/* 7100 need set any value to reload register and could reload value to counter */
	if (wdt->variant->reload)
		writel(0x1, wdt->base + wdt->variant->reload);
}

static unsigned int starfive_wdt_max_timeout(struct starfive_wdt *wdt)
{
	if (wdt->variant->double_timeout)
		return DIV_ROUND_UP(STARFIVE_WDT_MAXCNT, (wdt->freq / 2)) - 1;

	return DIV_ROUND_UP(STARFIVE_WDT_MAXCNT, wdt->freq) - 1;
}

static unsigned int starfive_wdt_get_timeleft(struct watchdog_device *wdd)
{
	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
	u32 count;

	/*
	 * If the watchdog takes twice timeout and set half count value,
	 * timeleft value should add the count value before first timeout.
	 */
	count = starfive_wdt_get_count(wdt);
	if (wdt->variant->double_timeout && !starfive_wdt_raise_irq_status(wdt))
		count += wdt->count;

	return starfive_wdt_ticks_to_sec(wdt, count);
}

static int starfive_wdt_keepalive(struct watchdog_device *wdd)
{
	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
	int ret;

	starfive_wdt_unlock(wdt);
	ret = starfive_wdt_int_clr(wdt);
	if (ret)
		goto exit;

	starfive_wdt_set_reload_count(wdt, wdt->count);

exit:
	/* exit with releasing spinlock and locking registers */
	starfive_wdt_lock(wdt);
	return ret;
}

static int starfive_wdt_start(struct starfive_wdt *wdt)
{
	int ret;

	starfive_wdt_unlock(wdt);
	/* disable watchdog, to be safe */
	starfive_wdt_disable(wdt);

	starfive_wdt_enable_reset(wdt);
	ret = starfive_wdt_int_clr(wdt);
	if (ret)
		goto exit;

	starfive_wdt_set_count(wdt, wdt->count);
	starfive_wdt_enable(wdt);

exit:
	starfive_wdt_lock(wdt);
	return ret;
}

static void starfive_wdt_stop(struct starfive_wdt *wdt)
{
	starfive_wdt_unlock(wdt);
	starfive_wdt_disable(wdt);
	starfive_wdt_lock(wdt);
}

static int starfive_wdt_pm_start(struct watchdog_device *wdd)
{
	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
	int ret = pm_runtime_get_sync(wdd->parent);

	if (ret < 0)
		return ret;

	return starfive_wdt_start(wdt);
}

static int starfive_wdt_pm_stop(struct watchdog_device *wdd)
{
	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);

	starfive_wdt_stop(wdt);
	return pm_runtime_put_sync(wdd->parent);
}

static int starfive_wdt_set_timeout(struct watchdog_device *wdd,
				    unsigned int timeout)
{
	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
	unsigned long count = timeout * wdt->freq;

	/* some watchdogs take two timeouts to reset */
	if (wdt->variant->double_timeout)
		count /= 2;

	wdt->count = count;
	wdd->timeout = timeout;

	starfive_wdt_unlock(wdt);
	starfive_wdt_disable(wdt);
	starfive_wdt_set_reload_count(wdt, wdt->count);
	starfive_wdt_enable(wdt);
	starfive_wdt_lock(wdt);

	return 0;
}

#define STARFIVE_WDT_OPTIONS (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE)

static const struct watchdog_info starfive_wdt_info = {
	.options = STARFIVE_WDT_OPTIONS,
	.identity = "StarFive Watchdog",
};

static const struct watchdog_ops starfive_wdt_ops = {
	.owner = THIS_MODULE,
	.start = starfive_wdt_pm_start,
	.stop = starfive_wdt_pm_stop,
	.ping = starfive_wdt_keepalive,
	.set_timeout = starfive_wdt_set_timeout,
	.get_timeleft = starfive_wdt_get_timeleft,
};

static int starfive_wdt_probe(struct platform_device *pdev)
{
	struct starfive_wdt *wdt;
	int ret;

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

	wdt->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(wdt->base))
		return dev_err_probe(&pdev->dev, PTR_ERR(wdt->base), "error mapping registers\n");

	wdt->wdd.parent = &pdev->dev;
	ret = starfive_wdt_get_clock(wdt);
	if (ret)
		return ret;

	platform_set_drvdata(pdev, wdt);
	pm_runtime_enable(&pdev->dev);
	if (pm_runtime_enabled(&pdev->dev)) {
		ret = pm_runtime_get_sync(&pdev->dev);
		if (ret < 0)
			return ret;
	} else {
		/* runtime PM is disabled but clocks need to be enabled */
		ret = starfive_wdt_enable_clock(wdt);
		if (ret)
			return ret;
	}

	ret = starfive_wdt_reset_init(&pdev->dev);
	if (ret)
		goto err_exit;

	watchdog_set_drvdata(&wdt->wdd, wdt);
	wdt->wdd.info = &starfive_wdt_info;
	wdt->wdd.ops = &starfive_wdt_ops;
	wdt->variant = of_device_get_match_data(&pdev->dev);
	spin_lock_init(&wdt->lock);

	wdt->freq = clk_get_rate(wdt->core_clk);
	if (!wdt->freq) {
		dev_err(&pdev->dev, "get clock rate failed.\n");
		ret = -EINVAL;
		goto err_exit;
	}

	wdt->wdd.min_timeout = 1;
	wdt->wdd.max_timeout = starfive_wdt_max_timeout(wdt);
	wdt->wdd.timeout = STARFIVE_WDT_DEFAULT_TIME;
	watchdog_init_timeout(&wdt->wdd, heartbeat, &pdev->dev);
	starfive_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout);

	watchdog_set_nowayout(&wdt->wdd, nowayout);
	watchdog_stop_on_reboot(&wdt->wdd);
	watchdog_stop_on_unregister(&wdt->wdd);

	if (early_enable) {
		ret = starfive_wdt_start(wdt);
		if (ret)
			goto err_exit;
		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
	} else {
		starfive_wdt_stop(wdt);
	}

	ret = watchdog_register_device(&wdt->wdd);
	if (ret)
		goto err_exit;

	if (!early_enable)
		pm_runtime_put_sync(&pdev->dev);

	return 0;

err_exit:
	starfive_wdt_disable_clock(wdt);
	pm_runtime_disable(&pdev->dev);

	return ret;
}

static void starfive_wdt_remove(struct platform_device *pdev)
{
	struct starfive_wdt *wdt = platform_get_drvdata(pdev);

	starfive_wdt_stop(wdt);
	watchdog_unregister_device(&wdt->wdd);

	if (pm_runtime_enabled(&pdev->dev))
		pm_runtime_disable(&pdev->dev);
	else
		/* disable clock without PM */
		starfive_wdt_disable_clock(wdt);
}

static void starfive_wdt_shutdown(struct platform_device *pdev)
{
	struct starfive_wdt *wdt = platform_get_drvdata(pdev);

	starfive_wdt_pm_stop(&wdt->wdd);
}

static int starfive_wdt_suspend(struct device *dev)
{
	struct starfive_wdt *wdt = dev_get_drvdata(dev);

	/* Save watchdog state, and turn it off. */
	wdt->reload = starfive_wdt_get_count(wdt);

	/* Note that WTCNT doesn't need to be saved. */
	starfive_wdt_stop(wdt);

	return pm_runtime_force_suspend(dev);
}

static int starfive_wdt_resume(struct device *dev)
{
	struct starfive_wdt *wdt = dev_get_drvdata(dev);
	int ret;

	ret = pm_runtime_force_resume(dev);
	if (ret)
		return ret;

	starfive_wdt_unlock(wdt);
	/* Restore watchdog state. */
	starfive_wdt_set_reload_count(wdt, wdt->reload);
	starfive_wdt_lock(wdt);

	return starfive_wdt_start(wdt);
}

static int starfive_wdt_runtime_suspend(struct device *dev)
{
	struct starfive_wdt *wdt = dev_get_drvdata(dev);

	starfive_wdt_disable_clock(wdt);

	return 0;
}

static int starfive_wdt_runtime_resume(struct device *dev)
{
	struct starfive_wdt *wdt = dev_get_drvdata(dev);

	return starfive_wdt_enable_clock(wdt);
}

static const struct dev_pm_ops starfive_wdt_pm_ops = {
	RUNTIME_PM_OPS(starfive_wdt_runtime_suspend, starfive_wdt_runtime_resume, NULL)
	SYSTEM_SLEEP_PM_OPS(starfive_wdt_suspend, starfive_wdt_resume)
};

static const struct of_device_id starfive_wdt_match[] = {
	{ .compatible = "starfive,jh7100-wdt", .data = &starfive_wdt_jh7100_variant },
	{ .compatible = "starfive,jh7110-wdt", .data = &starfive_wdt_jh7110_variant },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, starfive_wdt_match);

static struct platform_driver starfive_wdt_driver = {
	.probe = starfive_wdt_probe,
	.remove_new = starfive_wdt_remove,
	.shutdown = starfive_wdt_shutdown,
	.driver = {
		.name = "starfive-wdt",
		.pm = pm_ptr(&starfive_wdt_pm_ops),
		.of_match_table = starfive_wdt_match,
	},
};
module_platform_driver(starfive_wdt_driver);

MODULE_AUTHOR("Xingyu Wu <xingyu.wu@starfivetech.com>");
MODULE_AUTHOR("Samin Guo <samin.guo@starfivetech.com>");
MODULE_DESCRIPTION("StarFive Watchdog Device Driver");
MODULE_LICENSE("GPL");