// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2024 ROHM Semiconductors
 *
 * ROHM BD96801 watchdog driver
 */

#include <linux/bitfield.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/mfd/rohm-bd96801.h>
#include <linux/mfd/rohm-generic.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

static bool nowayout;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
		"Watchdog cannot be stopped once started (default=\"false\")");

#define BD96801_WD_TMO_SHORT_MASK	0x70
#define BD96801_WD_RATIO_MASK		0x3
#define BD96801_WD_TYPE_MASK		0x4
#define BD96801_WD_TYPE_SLOW		0x4
#define BD96801_WD_TYPE_WIN		0x0

#define BD96801_WD_EN_MASK		0x3
#define BD96801_WD_IF_EN		0x1
#define BD96801_WD_QA_EN		0x2
#define BD96801_WD_DISABLE		0x0

#define BD96801_WD_ASSERT_MASK		0x8
#define BD96801_WD_ASSERT_RST		0x8
#define BD96801_WD_ASSERT_IRQ		0x0

#define BD96801_WD_FEED_MASK		0x1
#define BD96801_WD_FEED			0x1

/* 1.1 mS */
#define FASTNG_MIN			11
#define FASTNG_MAX_US			(100 * FASTNG_MIN << 7)
#define SLOWNG_MAX_US			(16 * FASTNG_MAX_US)

#define BD96801_WDT_DEFAULT_MARGIN_MS	1843
/* Unit is seconds */
#define DEFAULT_TIMEOUT 30

/*
 * BD96801 WDG supports window mode so the TMO consists of SHORT and LONG
 * timeout values. SHORT time is meaningful only in window mode where feeding
 * period shorter than SHORT would be an error. LONG time is used to detect if
 * feeding is not occurring within given time limit (SoC SW hangs). The LONG
 * timeout time is a multiple of (2, 4, 8 or 16 times) the SHORT timeout.
 */

struct wdtbd96801 {
	struct device		*dev;
	struct regmap		*regmap;
	struct watchdog_device	wdt;
};

static int bd96801_wdt_ping(struct watchdog_device *wdt)
{
	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);

	return regmap_update_bits(w->regmap, BD96801_REG_WD_FEED,
				  BD96801_WD_FEED_MASK, BD96801_WD_FEED);
}

static int bd96801_wdt_start(struct watchdog_device *wdt)
{
	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);

	return regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
				  BD96801_WD_EN_MASK, BD96801_WD_IF_EN);
}

static int bd96801_wdt_stop(struct watchdog_device *wdt)
{
	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);

	return regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
				  BD96801_WD_EN_MASK, BD96801_WD_DISABLE);
}

static const struct watchdog_info bd96801_wdt_info = {
	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
			  WDIOF_SETTIMEOUT,
	.identity	= "BD96801 Watchdog",
};

static const struct watchdog_ops bd96801_wdt_ops = {
	.start		= bd96801_wdt_start,
	.stop		= bd96801_wdt_stop,
	.ping		= bd96801_wdt_ping,
};

static int find_closest_fast(unsigned int target, int *sel, unsigned int *val)
{
	unsigned int window = FASTNG_MIN;
	int i;

	for (i = 0; i < 8 && window < target; i++)
		window <<= 1;

	if (i == 8)
		return -EINVAL;

	*val = window;
	*sel = i;

	return 0;
}

static int find_closest_slow_by_fast(unsigned int fast_val, unsigned int *target,
				     int *slowsel)
{
	static const int multipliers[] = {2, 4, 8, 16};
	int sel;

	for (sel = 0; sel < ARRAY_SIZE(multipliers) &&
	     multipliers[sel] * fast_val < *target; sel++)
		;

	if (sel == ARRAY_SIZE(multipliers))
		return -EINVAL;

	*slowsel = sel;
	*target = multipliers[sel] * fast_val;

	return 0;
}

static int find_closest_slow(unsigned int *target, int *slow_sel, int *fast_sel)
{
	static const int multipliers[] = {2, 4, 8, 16};
	unsigned int window = FASTNG_MIN;
	unsigned int val = 0;
	int i, j;

	for (i = 0; i < 8; i++) {
		for (j = 0; j < ARRAY_SIZE(multipliers); j++) {
			unsigned int slow;

			slow = window * multipliers[j];
			if (slow >= *target && (!val || slow < val)) {
				val = slow;
				*fast_sel = i;
				*slow_sel = j;
			}
		}
		window <<= 1;
	}
	if (!val)
		return -EINVAL;

	*target = val;

	return 0;
}

static int bd96801_set_wdt_mode(struct wdtbd96801 *w, unsigned int hw_margin,
			       unsigned int hw_margin_min)
{
	int fastng, slowng, type, ret, reg, mask;
	struct device *dev = w->dev;


	if (hw_margin_min * 1000 > FASTNG_MAX_US) {
		dev_err(dev, "Unsupported fast timeout %u uS [max %u]\n",
			hw_margin_min * 1000, FASTNG_MAX_US);

		return -EINVAL;
	}

	if (hw_margin * 1000 > SLOWNG_MAX_US) {
		dev_err(dev, "Unsupported slow timeout %u uS [max %u]\n",
			hw_margin * 1000, SLOWNG_MAX_US);

		return -EINVAL;
	}

	/*
	 * Convert to 100uS to guarantee reasonable timeouts fit in
	 * 32bit maintaining also a decent accuracy.
	 */
	hw_margin *= 10;
	hw_margin_min *= 10;

	if (hw_margin_min) {
		unsigned int min;

		type = BD96801_WD_TYPE_WIN;
		dev_dbg(dev, "Setting type WINDOW 0x%x\n", type);
		ret = find_closest_fast(hw_margin_min, &fastng, &min);
		if (ret)
			return ret;

		ret = find_closest_slow_by_fast(min, &hw_margin, &slowng);
		if (ret) {
			dev_err(dev,
				"can't support slow timeout %u uS using fast %u uS. [max slow %u uS]\n",
				hw_margin * 100, min * 100, min * 100 * 16);

			return ret;
		}
		w->wdt.min_hw_heartbeat_ms = min / 10;
	} else {
		type = BD96801_WD_TYPE_SLOW;
		dev_dbg(dev, "Setting type SLOW 0x%x\n", type);
		ret = find_closest_slow(&hw_margin, &slowng, &fastng);
		if (ret)
			return ret;
	}

	w->wdt.max_hw_heartbeat_ms = hw_margin / 10;

	fastng = FIELD_PREP(BD96801_WD_TMO_SHORT_MASK, fastng);

	reg = slowng | fastng;
	mask = BD96801_WD_RATIO_MASK | BD96801_WD_TMO_SHORT_MASK;
	ret = regmap_update_bits(w->regmap, BD96801_REG_WD_TMO,
				 mask, reg);
	if (ret)
		return ret;

	ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
				 BD96801_WD_TYPE_MASK, type);

	return ret;
}

static int bd96801_set_heartbeat_from_hw(struct wdtbd96801 *w,
					 unsigned int conf_reg)
{
	int ret;
	unsigned int val, sel, fast;

	/*
	 * The BD96801 supports a somewhat peculiar QA-mode, which we do not
	 * support in this driver. If the QA-mode is enabled then we just
	 * warn and bail-out.
	 */
	if ((conf_reg & BD96801_WD_EN_MASK) != BD96801_WD_IF_EN) {
		dev_err(w->dev, "watchdog set to Q&A mode - exiting\n");
		return -EINVAL;
	}

	ret = regmap_read(w->regmap, BD96801_REG_WD_TMO, &val);
	if (ret)
		return ret;

	sel = FIELD_GET(BD96801_WD_TMO_SHORT_MASK, val);
	fast = FASTNG_MIN << sel;

	sel = (val & BD96801_WD_RATIO_MASK) + 1;
	w->wdt.max_hw_heartbeat_ms = (fast << sel) / USEC_PER_MSEC;

	if ((conf_reg & BD96801_WD_TYPE_MASK) == BD96801_WD_TYPE_WIN)
		w->wdt.min_hw_heartbeat_ms = fast / USEC_PER_MSEC;

	return 0;
}

static int init_wdg_hw(struct wdtbd96801 *w)
{
	u32 hw_margin[2];
	int count, ret;
	u32 hw_margin_max = BD96801_WDT_DEFAULT_MARGIN_MS, hw_margin_min = 0;

	count = device_property_count_u32(w->dev->parent, "rohm,hw-timeout-ms");
	if (count < 0 && count != -EINVAL)
		return count;

	if (count > 0) {
		if (count > ARRAY_SIZE(hw_margin))
			return -EINVAL;

		ret = device_property_read_u32_array(w->dev->parent,
						     "rohm,hw-timeout-ms",
						     &hw_margin[0], count);
		if (ret < 0)
			return ret;

		if (count == 1)
			hw_margin_max = hw_margin[0];

		if (count == 2) {
			if (hw_margin[1] > hw_margin[0]) {
				hw_margin_max = hw_margin[1];
				hw_margin_min = hw_margin[0];
			} else {
				hw_margin_max = hw_margin[0];
				hw_margin_min = hw_margin[1];
			}
		}
	}

	ret = bd96801_set_wdt_mode(w, hw_margin_max, hw_margin_min);
	if (ret)
		return ret;

	ret = device_property_match_string(w->dev->parent, "rohm,wdg-action",
					   "prstb");
	if (ret >= 0) {
		ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
				 BD96801_WD_ASSERT_MASK,
				 BD96801_WD_ASSERT_RST);
		return ret;
	}

	ret = device_property_match_string(w->dev->parent, "rohm,wdg-action",
					   "intb-only");
	if (ret >= 0) {
		ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
				 BD96801_WD_ASSERT_MASK,
				 BD96801_WD_ASSERT_IRQ);
		return ret;
	}

	return 0;
}

static irqreturn_t bd96801_irq_hnd(int irq, void *data)
{
	emergency_restart();

	return IRQ_NONE;
}

static int bd96801_wdt_probe(struct platform_device *pdev)
{
	struct wdtbd96801 *w;
	int ret, irq;
	unsigned int val;

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

	w->regmap = dev_get_regmap(pdev->dev.parent, NULL);
	w->dev = &pdev->dev;

	w->wdt.info = &bd96801_wdt_info;
	w->wdt.ops =  &bd96801_wdt_ops;
	w->wdt.parent = pdev->dev.parent;
	w->wdt.timeout = DEFAULT_TIMEOUT;
	watchdog_set_drvdata(&w->wdt, w);

	ret = regmap_read(w->regmap, BD96801_REG_WD_CONF, &val);
	if (ret)
		return dev_err_probe(&pdev->dev, ret,
				     "Failed to get the watchdog state\n");

	/*
	 * If the WDG is already enabled we assume it is configured by boot.
	 * In this case we just update the hw-timeout based on values set to
	 * the timeout / mode registers and leave the hardware configs
	 * untouched.
	 */
	if ((val & BD96801_WD_EN_MASK) != BD96801_WD_DISABLE) {
		dev_dbg(&pdev->dev, "watchdog was running during probe\n");
		ret = bd96801_set_heartbeat_from_hw(w, val);
		if (ret)
			return ret;

		set_bit(WDOG_HW_RUNNING, &w->wdt.status);
	} else {
		/* If WDG is not running so we will initializate it */
		ret = init_wdg_hw(w);
		if (ret)
			return ret;
	}

	dev_dbg(w->dev, "heartbeat set to %u - %u\n",
		w->wdt.min_hw_heartbeat_ms, w->wdt.max_hw_heartbeat_ms);

	watchdog_init_timeout(&w->wdt, 0, pdev->dev.parent);
	watchdog_set_nowayout(&w->wdt, nowayout);
	watchdog_stop_on_reboot(&w->wdt);

	irq = platform_get_irq_byname(pdev, "bd96801-wdg");
	if (irq > 0) {
		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
						bd96801_irq_hnd,
						IRQF_ONESHOT,  "bd96801-wdg",
						NULL);
		if (ret)
			return dev_err_probe(&pdev->dev, ret,
					     "Failed to register IRQ\n");
	}

	return devm_watchdog_register_device(&pdev->dev, &w->wdt);
}

static const struct platform_device_id bd96801_wdt_id[] = {
	{ "bd96801-wdt", },
	{ }
};
MODULE_DEVICE_TABLE(platform, bd96801_wdt_id);

static struct platform_driver bd96801_wdt = {
	.driver = {
		.name = "bd96801-wdt"
	},
	.probe = bd96801_wdt_probe,
	.id_table = bd96801_wdt_id,
};
module_platform_driver(bd96801_wdt);

MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
MODULE_DESCRIPTION("BD96801 watchdog driver");
MODULE_LICENSE("GPL");