// SPDX-License-Identifier: GPL-2.0+
/*
 * Watchdog driver for Marvell Armada 37xx SoCs
 *
 * Author: Marek Behún <kabel@kernel.org>
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/types.h>
#include <linux/watchdog.h>

/*
 * There are four counters that can be used for watchdog on Armada 37xx.
 * The addresses for counter control registers are register base plus ID*0x10,
 * where ID is 0, 1, 2 or 3.
 *
 * In this driver we use IDs 0 and 1. Counter ID 1 is used as watchdog counter,
 * while counter ID 0 is used to implement pinging the watchdog: counter ID 1 is
 * set to restart counting from initial value on counter ID 0 end count event.
 * Pinging is done by forcing immediate end count event on counter ID 0.
 * If only one counter was used, pinging would have to be implemented by
 * disabling and enabling the counter, leaving the system in a vulnerable state
 * for a (really) short period of time.
 *
 * Counters ID 2 and 3 are enabled by default even before U-Boot loads,
 * therefore this driver does not provide a way to use them, eg. by setting a
 * property in device tree.
 */

#define CNTR_ID_RETRIGGER		0
#define CNTR_ID_WDOG			1

/* relative to cpu_misc */
#define WDT_TIMER_SELECT		0x64
#define WDT_TIMER_SELECT_MASK		0xf
#define WDT_TIMER_SELECT_VAL		BIT(CNTR_ID_WDOG)

/* relative to reg */
#define CNTR_CTRL(id)			((id) * 0x10)
#define CNTR_CTRL_ENABLE		0x0001
#define CNTR_CTRL_ACTIVE		0x0002
#define CNTR_CTRL_MODE_MASK		0x000c
#define CNTR_CTRL_MODE_ONESHOT		0x0000
#define CNTR_CTRL_MODE_HWSIG		0x000c
#define CNTR_CTRL_TRIG_SRC_MASK		0x00f0
#define CNTR_CTRL_TRIG_SRC_PREV_CNTR	0x0050
#define CNTR_CTRL_PRESCALE_MASK		0xff00
#define CNTR_CTRL_PRESCALE_MIN		2
#define CNTR_CTRL_PRESCALE_SHIFT	8

#define CNTR_COUNT_LOW(id)		(CNTR_CTRL(id) + 0x4)
#define CNTR_COUNT_HIGH(id)		(CNTR_CTRL(id) + 0x8)

#define WATCHDOG_TIMEOUT		120

static unsigned int timeout;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");

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) ")");

struct armada_37xx_watchdog {
	struct watchdog_device wdt;
	struct regmap *cpu_misc;
	void __iomem *reg;
	u64 timeout; /* in clock ticks */
	unsigned long clk_rate;
	struct clk *clk;
};

static u64 get_counter_value(struct armada_37xx_watchdog *dev, int id)
{
	u64 val;

	/*
	 * when low is read, high is latched into flip-flops so that it can be
	 * read consistently without using software debouncing
	 */
	val = readl(dev->reg + CNTR_COUNT_LOW(id));
	val |= ((u64)readl(dev->reg + CNTR_COUNT_HIGH(id))) << 32;

	return val;
}

static void set_counter_value(struct armada_37xx_watchdog *dev, int id, u64 val)
{
	writel(val & 0xffffffff, dev->reg + CNTR_COUNT_LOW(id));
	writel(val >> 32, dev->reg + CNTR_COUNT_HIGH(id));
}

static void counter_enable(struct armada_37xx_watchdog *dev, int id)
{
	u32 reg;

	reg = readl(dev->reg + CNTR_CTRL(id));
	reg |= CNTR_CTRL_ENABLE;
	writel(reg, dev->reg + CNTR_CTRL(id));
}

static void counter_disable(struct armada_37xx_watchdog *dev, int id)
{
	u32 reg;

	reg = readl(dev->reg + CNTR_CTRL(id));
	reg &= ~CNTR_CTRL_ENABLE;
	writel(reg, dev->reg + CNTR_CTRL(id));
}

static void init_counter(struct armada_37xx_watchdog *dev, int id, u32 mode,
			 u32 trig_src)
{
	u32 reg;

	reg = readl(dev->reg + CNTR_CTRL(id));

	reg &= ~(CNTR_CTRL_MODE_MASK | CNTR_CTRL_PRESCALE_MASK |
		 CNTR_CTRL_TRIG_SRC_MASK);

	/* set mode */
	reg |= mode & CNTR_CTRL_MODE_MASK;

	/* set prescaler to the min value */
	reg |= CNTR_CTRL_PRESCALE_MIN << CNTR_CTRL_PRESCALE_SHIFT;

	/* set trigger source */
	reg |= trig_src & CNTR_CTRL_TRIG_SRC_MASK;

	writel(reg, dev->reg + CNTR_CTRL(id));
}

static int armada_37xx_wdt_ping(struct watchdog_device *wdt)
{
	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

	/* counter 1 is retriggered by forcing end count on counter 0 */
	counter_disable(dev, CNTR_ID_RETRIGGER);
	counter_enable(dev, CNTR_ID_RETRIGGER);

	return 0;
}

static unsigned int armada_37xx_wdt_get_timeleft(struct watchdog_device *wdt)
{
	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
	u64 res;

	res = get_counter_value(dev, CNTR_ID_WDOG) * CNTR_CTRL_PRESCALE_MIN;
	do_div(res, dev->clk_rate);

	return res;
}

static int armada_37xx_wdt_set_timeout(struct watchdog_device *wdt,
				       unsigned int timeout)
{
	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

	wdt->timeout = timeout;

	/*
	 * Compute the timeout in clock rate. We use smallest possible
	 * prescaler, which divides the clock rate by 2
	 * (CNTR_CTRL_PRESCALE_MIN).
	 */
	dev->timeout = (u64)dev->clk_rate * timeout;
	do_div(dev->timeout, CNTR_CTRL_PRESCALE_MIN);

	set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);

	return 0;
}

static bool armada_37xx_wdt_is_running(struct armada_37xx_watchdog *dev)
{
	u32 reg;

	regmap_read(dev->cpu_misc, WDT_TIMER_SELECT, &reg);
	if ((reg & WDT_TIMER_SELECT_MASK) != WDT_TIMER_SELECT_VAL)
		return false;

	reg = readl(dev->reg + CNTR_CTRL(CNTR_ID_WDOG));
	return !!(reg & CNTR_CTRL_ACTIVE);
}

static int armada_37xx_wdt_start(struct watchdog_device *wdt)
{
	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

	/* select counter 1 as watchdog counter */
	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, WDT_TIMER_SELECT_VAL);

	/* init counter 0 as retrigger counter for counter 1 */
	init_counter(dev, CNTR_ID_RETRIGGER, CNTR_CTRL_MODE_ONESHOT, 0);
	set_counter_value(dev, CNTR_ID_RETRIGGER, 0);

	/* init counter 1 to be retriggerable by counter 0 end count */
	init_counter(dev, CNTR_ID_WDOG, CNTR_CTRL_MODE_HWSIG,
		     CNTR_CTRL_TRIG_SRC_PREV_CNTR);
	set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);

	/* enable counter 1 */
	counter_enable(dev, CNTR_ID_WDOG);

	/* start counter 1 by forcing immediate end count on counter 0 */
	counter_enable(dev, CNTR_ID_RETRIGGER);

	return 0;
}

static int armada_37xx_wdt_stop(struct watchdog_device *wdt)
{
	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

	counter_disable(dev, CNTR_ID_WDOG);
	counter_disable(dev, CNTR_ID_RETRIGGER);
	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, 0);

	return 0;
}

static const struct watchdog_info armada_37xx_wdt_info = {
	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
	.identity = "Armada 37xx Watchdog",
};

static const struct watchdog_ops armada_37xx_wdt_ops = {
	.owner = THIS_MODULE,
	.start = armada_37xx_wdt_start,
	.stop = armada_37xx_wdt_stop,
	.ping = armada_37xx_wdt_ping,
	.set_timeout = armada_37xx_wdt_set_timeout,
	.get_timeleft = armada_37xx_wdt_get_timeleft,
};

static int armada_37xx_wdt_probe(struct platform_device *pdev)
{
	struct armada_37xx_watchdog *dev;
	struct resource *res;
	struct regmap *regmap;
	int ret;

	dev = devm_kzalloc(&pdev->dev, sizeof(struct armada_37xx_watchdog),
			   GFP_KERNEL);
	if (!dev)
		return -ENOMEM;

	dev->wdt.info = &armada_37xx_wdt_info;
	dev->wdt.ops = &armada_37xx_wdt_ops;

	regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
						 "marvell,system-controller");
	if (IS_ERR(regmap))
		return PTR_ERR(regmap);
	dev->cpu_misc = regmap;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENODEV;
	dev->reg = devm_ioremap(&pdev->dev, res->start, resource_size(res));
	if (!dev->reg)
		return -ENOMEM;

	/* init clock */
	dev->clk = devm_clk_get_enabled(&pdev->dev, NULL);
	if (IS_ERR(dev->clk))
		return PTR_ERR(dev->clk);

	dev->clk_rate = clk_get_rate(dev->clk);
	if (!dev->clk_rate)
		return -EINVAL;

	/*
	 * Since the timeout in seconds is given as 32 bit unsigned int, and
	 * the counters hold 64 bit values, even after multiplication by clock
	 * rate the counter can hold timeout of UINT_MAX seconds.
	 */
	dev->wdt.min_timeout = 1;
	dev->wdt.max_timeout = UINT_MAX;
	dev->wdt.parent = &pdev->dev;

	/* default value, possibly override by module parameter or dtb */
	dev->wdt.timeout = WATCHDOG_TIMEOUT;
	watchdog_init_timeout(&dev->wdt, timeout, &pdev->dev);

	platform_set_drvdata(pdev, &dev->wdt);
	watchdog_set_drvdata(&dev->wdt, dev);

	armada_37xx_wdt_set_timeout(&dev->wdt, dev->wdt.timeout);

	if (armada_37xx_wdt_is_running(dev))
		set_bit(WDOG_HW_RUNNING, &dev->wdt.status);

	watchdog_set_nowayout(&dev->wdt, nowayout);
	watchdog_stop_on_reboot(&dev->wdt);
	ret = devm_watchdog_register_device(&pdev->dev, &dev->wdt);
	if (ret)
		return ret;

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

	return 0;
}

static int __maybe_unused armada_37xx_wdt_suspend(struct device *dev)
{
	struct watchdog_device *wdt = dev_get_drvdata(dev);

	return armada_37xx_wdt_stop(wdt);
}

static int __maybe_unused armada_37xx_wdt_resume(struct device *dev)
{
	struct watchdog_device *wdt = dev_get_drvdata(dev);

	if (watchdog_active(wdt))
		return armada_37xx_wdt_start(wdt);

	return 0;
}

static const struct dev_pm_ops armada_37xx_wdt_dev_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(armada_37xx_wdt_suspend,
				armada_37xx_wdt_resume)
};

#ifdef CONFIG_OF
static const struct of_device_id armada_37xx_wdt_match[] = {
	{ .compatible = "marvell,armada-3700-wdt", },
	{},
};
MODULE_DEVICE_TABLE(of, armada_37xx_wdt_match);
#endif

static struct platform_driver armada_37xx_wdt_driver = {
	.probe		= armada_37xx_wdt_probe,
	.driver		= {
		.name	= "armada_37xx_wdt",
		.of_match_table = of_match_ptr(armada_37xx_wdt_match),
		.pm = &armada_37xx_wdt_dev_pm_ops,
	},
};

module_platform_driver(armada_37xx_wdt_driver);

MODULE_AUTHOR("Marek Behun <kabel@kernel.org>");
MODULE_DESCRIPTION("Armada 37xx CPU Watchdog");

MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:armada_37xx_wdt");