// SPDX-License-Identifier: GPL-2.0-only
/*
 * sl28cpld watchdog driver
 *
 * Copyright 2020 Kontron Europe GmbH
 */

#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

/*
 * Watchdog timer block registers.
 */
#define WDT_CTRL			0x00
#define  WDT_CTRL_EN			BIT(0)
#define  WDT_CTRL_LOCK			BIT(2)
#define  WDT_CTRL_ASSERT_SYS_RESET	BIT(6)
#define  WDT_CTRL_ASSERT_WDT_TIMEOUT	BIT(7)
#define WDT_TIMEOUT			0x01
#define WDT_KICK			0x02
#define  WDT_KICK_VALUE			0x6b
#define WDT_COUNT			0x03

#define WDT_DEFAULT_TIMEOUT		10

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 timeout;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Initial watchdog timeout in seconds");

struct sl28cpld_wdt {
	struct watchdog_device wdd;
	struct regmap *regmap;
	u32 offset;
	bool assert_wdt_timeout;
};

static int sl28cpld_wdt_ping(struct watchdog_device *wdd)
{
	struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);

	return regmap_write(wdt->regmap, wdt->offset + WDT_KICK,
			    WDT_KICK_VALUE);
}

static int sl28cpld_wdt_start(struct watchdog_device *wdd)
{
	struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
	unsigned int val;

	val = WDT_CTRL_EN | WDT_CTRL_ASSERT_SYS_RESET;
	if (wdt->assert_wdt_timeout)
		val |= WDT_CTRL_ASSERT_WDT_TIMEOUT;
	if (nowayout)
		val |= WDT_CTRL_LOCK;

	return regmap_update_bits(wdt->regmap, wdt->offset + WDT_CTRL,
				  val, val);
}

static int sl28cpld_wdt_stop(struct watchdog_device *wdd)
{
	struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);

	return regmap_update_bits(wdt->regmap, wdt->offset + WDT_CTRL,
				  WDT_CTRL_EN, 0);
}

static unsigned int sl28cpld_wdt_get_timeleft(struct watchdog_device *wdd)
{
	struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
	unsigned int val;
	int ret;

	ret = regmap_read(wdt->regmap, wdt->offset + WDT_COUNT, &val);
	if (ret)
		return 0;

	return val;
}

static int sl28cpld_wdt_set_timeout(struct watchdog_device *wdd,
				    unsigned int timeout)
{
	struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
	int ret;

	ret = regmap_write(wdt->regmap, wdt->offset + WDT_TIMEOUT, timeout);
	if (ret)
		return ret;

	wdd->timeout = timeout;

	return 0;
}

static const struct watchdog_info sl28cpld_wdt_info = {
	.options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
	.identity = "sl28cpld watchdog",
};

static const struct watchdog_ops sl28cpld_wdt_ops = {
	.owner = THIS_MODULE,
	.start = sl28cpld_wdt_start,
	.stop = sl28cpld_wdt_stop,
	.ping = sl28cpld_wdt_ping,
	.set_timeout = sl28cpld_wdt_set_timeout,
	.get_timeleft = sl28cpld_wdt_get_timeleft,
};

static int sl28cpld_wdt_probe(struct platform_device *pdev)
{
	struct watchdog_device *wdd;
	struct sl28cpld_wdt *wdt;
	unsigned int status;
	unsigned int val;
	int ret;

	if (!pdev->dev.parent)
		return -ENODEV;

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

	wdt->regmap = dev_get_regmap(pdev->dev.parent, NULL);
	if (!wdt->regmap)
		return -ENODEV;

	ret = device_property_read_u32(&pdev->dev, "reg", &wdt->offset);
	if (ret)
		return -EINVAL;

	wdt->assert_wdt_timeout = device_property_read_bool(&pdev->dev,
							    "kontron,assert-wdt-timeout-pin");

	/* initialize struct watchdog_device */
	wdd = &wdt->wdd;
	wdd->parent = &pdev->dev;
	wdd->info = &sl28cpld_wdt_info;
	wdd->ops = &sl28cpld_wdt_ops;
	wdd->min_timeout = 1;
	wdd->max_timeout = 255;

	watchdog_set_drvdata(wdd, wdt);
	watchdog_stop_on_reboot(wdd);

	/*
	 * Read the status early, in case of an error, we haven't modified the
	 * hardware.
	 */
	ret = regmap_read(wdt->regmap, wdt->offset + WDT_CTRL, &status);
	if (ret)
		return ret;

	/*
	 * Initial timeout value, may be overwritten by device tree or module
	 * parameter in watchdog_init_timeout().
	 *
	 * Reading a zero here means that either the hardware has a default
	 * value of zero (which is very unlikely and definitely a hardware
	 * bug) or the bootloader set it to zero. In any case, we handle
	 * this case gracefully and set out own timeout.
	 */
	ret = regmap_read(wdt->regmap, wdt->offset + WDT_TIMEOUT, &val);
	if (ret)
		return ret;

	if (val)
		wdd->timeout = val;
	else
		wdd->timeout = WDT_DEFAULT_TIMEOUT;

	watchdog_init_timeout(wdd, timeout, &pdev->dev);
	sl28cpld_wdt_set_timeout(wdd, wdd->timeout);

	/* if the watchdog is locked, we set nowayout */
	if (status & WDT_CTRL_LOCK)
		nowayout = true;
	watchdog_set_nowayout(wdd, nowayout);

	/*
	 * If watchdog is already running, keep it enabled, but make
	 * sure its mode is set correctly.
	 */
	if (status & WDT_CTRL_EN) {
		sl28cpld_wdt_start(wdd);
		set_bit(WDOG_HW_RUNNING, &wdd->status);
	}

	ret = devm_watchdog_register_device(&pdev->dev, wdd);
	if (ret < 0)
		return ret;

	dev_info(&pdev->dev, "initial timeout %d sec%s\n",
		 wdd->timeout, nowayout ? ", nowayout" : "");

	return 0;
}

static const struct of_device_id sl28cpld_wdt_of_match[] = {
	{ .compatible = "kontron,sl28cpld-wdt" },
	{}
};
MODULE_DEVICE_TABLE(of, sl28cpld_wdt_of_match);

static struct platform_driver sl28cpld_wdt_driver = {
	.probe = sl28cpld_wdt_probe,
	.driver = {
		.name = "sl28cpld-wdt",
		.of_match_table = sl28cpld_wdt_of_match,
	},
};
module_platform_driver(sl28cpld_wdt_driver);

MODULE_DESCRIPTION("sl28cpld Watchdog Driver");
MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
MODULE_LICENSE("GPL");