linux/drivers/clocksource/timer-tegra186.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
 */

#include <linux/bitfield.h>
#include <linux/clocksource.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/watchdog.h>

/* shared registers */
#define TKETSC0 0x000
#define TKETSC1 0x004
#define TKEUSEC 0x008
#define TKEOSC  0x00c

#define TKEIE(x) (0x100 + ((x) * 4))
#define  TKEIE_WDT_MASK(x, y) ((y) << (16 + 4 * (x)))

/* timer registers */
#define TMRCR 0x000
#define  TMRCR_ENABLE BIT(31)
#define  TMRCR_PERIODIC BIT(30)
#define  TMRCR_PTV(x) ((x) & 0x0fffffff)

#define TMRSR 0x004
#define  TMRSR_INTR_CLR BIT(30)
#define  TMRSR_PCV GENMASK(28, 0)

#define TMRCSSR 0x008
#define  TMRCSSR_SRC_USEC (0 << 0)

/* watchdog registers */
#define WDTCR 0x000
#define  WDTCR_SYSTEM_POR_RESET_ENABLE BIT(16)
#define  WDTCR_SYSTEM_DEBUG_RESET_ENABLE BIT(15)
#define  WDTCR_REMOTE_INT_ENABLE BIT(14)
#define  WDTCR_LOCAL_FIQ_ENABLE BIT(13)
#define  WDTCR_LOCAL_INT_ENABLE BIT(12)
#define  WDTCR_PERIOD_MASK (0xff << 4)
#define  WDTCR_PERIOD(x) (((x) & 0xff) << 4)
#define  WDTCR_TIMER_SOURCE_MASK 0xf
#define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)

#define WDTSR 0x004
#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)

#define WDTCMDR 0x008
#define  WDTCMDR_DISABLE_COUNTER BIT(1)
#define  WDTCMDR_START_COUNTER BIT(0)

#define WDTUR 0x00c
#define  WDTUR_UNLOCK_PATTERN 0x0000c45a

#define TEGRA186_KERNEL_WDT_TIMEOUT 120

/* WDT security configuration registers */
#define WDTSCR(x)		(0xf02c + (x) * 4)
#define  WDTSCR_SEC_WEN		BIT(28)
#define  WDTSCR_SEC_REN		BIT(27)
#define  WDTSCR_SEC_G1W		BIT(9)
#define  WDTSCR_SEC_G1R		BIT(1)

struct tegra186_timer_soc {
	unsigned int num_timers;
	unsigned int num_wdts;
};

struct tegra186_tmr {
	struct tegra186_timer *parent;
	void __iomem *regs;
	unsigned int index;
	unsigned int hwirq;
};

struct tegra186_wdt {
	struct watchdog_device base;

	void __iomem *regs;
	unsigned int index;
	bool locked;
	bool is_kernel_wdt;

	struct tegra186_tmr *tmr;
};

static inline struct tegra186_wdt *to_tegra186_wdt(struct watchdog_device *wdd)
{
	return container_of(wdd, struct tegra186_wdt, base);
}

struct tegra186_timer {
	const struct tegra186_timer_soc *soc;
	struct device *dev;
	void __iomem *regs;

	struct tegra186_wdt **wdts;
	struct clocksource usec;
	struct clocksource tsc;
	struct clocksource osc;
};

static void tmr_writel(struct tegra186_tmr *tmr, u32 value, unsigned int offset)
{
	writel_relaxed(value, tmr->regs + offset);
}

static void wdt_writel(struct tegra186_wdt *wdt, u32 value, unsigned int offset)
{
	writel_relaxed(value, wdt->regs + offset);
}

static u32 wdt_readl(struct tegra186_wdt *wdt, unsigned int offset)
{
	return readl_relaxed(wdt->regs + offset);
}

static struct tegra186_tmr *tegra186_tmr_create(struct tegra186_timer *tegra,
						unsigned int index)
{
	unsigned int offset = 0x10000 + index * 0x10000;
	struct tegra186_tmr *tmr;

	tmr = devm_kzalloc(tegra->dev, sizeof(*tmr), GFP_KERNEL);
	if (!tmr)
		return ERR_PTR(-ENOMEM);

	tmr->parent = tegra;
	tmr->regs = tegra->regs + offset;
	tmr->index = index;
	tmr->hwirq = 0;

	return tmr;
}

static const struct watchdog_info tegra186_wdt_info = {
	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
	.identity = "NVIDIA Tegra186 WDT",
};

static void tegra186_wdt_disable(struct tegra186_wdt *wdt)
{
	/* unlock and disable the watchdog */
	wdt_writel(wdt, WDTUR_UNLOCK_PATTERN, WDTUR);
	wdt_writel(wdt, WDTCMDR_DISABLE_COUNTER, WDTCMDR);

	/* disable timer */
	tmr_writel(wdt->tmr, 0, TMRCR);
}

static void tegra186_wdt_enable(struct tegra186_wdt *wdt)
{
	struct tegra186_timer *tegra = wdt->tmr->parent;
	u32 value;

	/* unmask hardware IRQ, this may have been lost across powergate */
	value = readl(tegra->regs + TKEIE(wdt->tmr->hwirq));
	value |= TKEIE_WDT_MASK(wdt->index, 1);
	writel(value, tegra->regs + TKEIE(wdt->tmr->hwirq));

	/* clear interrupt */
	tmr_writel(wdt->tmr, TMRSR_INTR_CLR, TMRSR);

	/* select microsecond source */
	tmr_writel(wdt->tmr, TMRCSSR_SRC_USEC, TMRCSSR);

	/* configure timer (system reset happens on the fifth expiration) */
	value = TMRCR_PTV(wdt->base.timeout * (USEC_PER_SEC / 5)) |
		TMRCR_PERIODIC | TMRCR_ENABLE;
	tmr_writel(wdt->tmr, value, TMRCR);

	if (!wdt->locked) {
		value = wdt_readl(wdt, WDTCR);

		/* select the proper timer source */
		value &= ~WDTCR_TIMER_SOURCE_MASK;
		value |= WDTCR_TIMER_SOURCE(wdt->tmr->index);

		/* single timer period since that's already configured */
		value &= ~WDTCR_PERIOD_MASK;
		value |= WDTCR_PERIOD(1);

		/* enable local interrupt for kernel watchdog */
		if (wdt->is_kernel_wdt)
			value |= WDTCR_LOCAL_INT_ENABLE;

		/* enable system POR reset */
		value |= WDTCR_SYSTEM_POR_RESET_ENABLE;

		wdt_writel(wdt, value, WDTCR);
	}

	wdt_writel(wdt, WDTCMDR_START_COUNTER, WDTCMDR);
}

static int tegra186_wdt_start(struct watchdog_device *wdd)
{
	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);

	tegra186_wdt_enable(wdt);

	return 0;
}

static int tegra186_wdt_stop(struct watchdog_device *wdd)
{
	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);

	tegra186_wdt_disable(wdt);

	return 0;
}

static int tegra186_wdt_ping(struct watchdog_device *wdd)
{
	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);

	tegra186_wdt_disable(wdt);
	tegra186_wdt_enable(wdt);

	return 0;
}

static irqreturn_t tegra186_wdt_irq(int irq, void *data)
{
	struct tegra186_wdt *wdt = data;

	tegra186_wdt_disable(wdt);
	tegra186_wdt_enable(wdt);

	return IRQ_HANDLED;
}

static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
				    unsigned int timeout)
{
	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);

	if (watchdog_active(&wdt->base))
		tegra186_wdt_disable(wdt);

	wdt->base.timeout = timeout;

	if (watchdog_active(&wdt->base))
		tegra186_wdt_enable(wdt);

	return 0;
}

static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
{
	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
	u32 expiration, val;
	u32 timeleft;

	if (!watchdog_active(&wdt->base)) {
		/* return zero if the watchdog timer is not activated. */
		return 0;
	}

	/*
	 * Reset occurs on the fifth expiration of the
	 * watchdog timer and so when the watchdog timer is configured,
	 * the actual value programmed into the counter is 1/5 of the
	 * timeout value. Once the counter reaches 0, expiration count
	 * will be increased by 1 and the down counter restarts.
	 * Hence to get the time left before system reset we must
	 * combine 2 parts:
	 * 1. value of the current down counter
	 * 2. (number of counter expirations remaining) * (timeout/5)
	 */

	/* Get the current number of counter expirations. Should be a
	 * value between 0 and 4
	 */
	val = readl_relaxed(wdt->regs + WDTSR);
	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
	if (WARN_ON_ONCE(expiration > 4))
		return 0;

	/* Get the current counter value in microsecond. */
	val = readl_relaxed(wdt->tmr->regs + TMRSR);
	timeleft = FIELD_GET(TMRSR_PCV, val);

	/*
	 * Calculate the time remaining by adding the time for the
	 * counter value to the time of the counter expirations that
	 * remain.
	 * Note: Since wdt->base.timeout is bound to 255, the maximum
	 * value added to timeleft is
	 *   255 * (1,000,000 / 5) * 4
	 * = 255 * 200,000 * 4
	 * = 204,000,000
	 * TMRSR_PCV is a 29-bit field.
	 * Its maximum value is 0x1fffffff = 536,870,911.
	 * 204,000,000 + 536,870,911 = 740,870,911 = 0x2C28CAFF.
	 * timeleft can therefore not overflow, and 64-bit calculations
	 * are not necessary.
	 */
	timeleft += (wdt->base.timeout * (USEC_PER_SEC / 5)) * (4 - expiration);

	/*
	 * Convert the current counter value to seconds,
	 * rounding to the nearest second.
	 */
	timeleft = DIV_ROUND_CLOSEST(timeleft, USEC_PER_SEC);

	return timeleft;
}

static const struct watchdog_ops tegra186_wdt_ops = {
	.owner = THIS_MODULE,
	.start = tegra186_wdt_start,
	.stop = tegra186_wdt_stop,
	.ping = tegra186_wdt_ping,
	.set_timeout = tegra186_wdt_set_timeout,
	.get_timeleft = tegra186_wdt_get_timeleft,
};

static bool tegra186_wdt_is_accessible(struct tegra186_timer *tegra, unsigned int index)
{
	u32 value;

	value = readl_relaxed(tegra->regs + WDTSCR(index));

	/* Check OS write access if write blocking is enabled. */
	if ((value & WDTSCR_SEC_WEN) && !(value & WDTSCR_SEC_G1W))
		return false;

	/* Check OS read access if read blocking is enabled. */
	if ((value & WDTSCR_SEC_REN) && !(value & WDTSCR_SEC_G1R))
		return false;

	return true;
}

static struct tegra186_wdt *tegra186_wdt_create(struct tegra186_timer *tegra,
						unsigned int index)
{
	unsigned int offset = 0x10000, source;
	struct tegra186_wdt *wdt;
	u32 value;
	int err;

	offset += tegra->soc->num_timers * 0x10000 + index * 0x10000;

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

	wdt->regs = tegra->regs + offset;
	wdt->index = index;

	/* read the watchdog configuration since it might be locked down */
	value = wdt_readl(wdt, WDTCR);

	if (value & WDTCR_LOCAL_INT_ENABLE)
		wdt->locked = true;

	source = value & WDTCR_TIMER_SOURCE_MASK;

	wdt->tmr = tegra186_tmr_create(tegra, source);
	if (IS_ERR(wdt->tmr))
		return ERR_CAST(wdt->tmr);

	wdt->base.info = &tegra186_wdt_info;
	wdt->base.ops = &tegra186_wdt_ops;
	wdt->base.min_timeout = 1;
	wdt->base.max_timeout = 255;
	wdt->base.parent = tegra->dev;

	err = watchdog_init_timeout(&wdt->base, 5, tegra->dev);
	if (err < 0)
		return ERR_PTR(err);

	return wdt;
}

static u64 tegra186_timer_tsc_read(struct clocksource *cs)
{
	struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
						    tsc);
	u32 hi, lo, ss;

	hi = readl_relaxed(tegra->regs + TKETSC1);

	/*
	 * The 56-bit value of the TSC is spread across two registers that are
	 * not synchronized. In order to read them atomically, ensure that the
	 * high 24 bits match before and after reading the low 32 bits.
	 */
	do {
		/* snapshot the high 24 bits */
		ss = hi;

		lo = readl_relaxed(tegra->regs + TKETSC0);
		hi = readl_relaxed(tegra->regs + TKETSC1);
	} while (hi != ss);

	return (u64)hi << 32 | lo;
}

static int tegra186_timer_tsc_init(struct tegra186_timer *tegra)
{
	tegra->tsc.name = "tsc";
	tegra->tsc.rating = 300;
	tegra->tsc.read = tegra186_timer_tsc_read;
	tegra->tsc.mask = CLOCKSOURCE_MASK(56);
	tegra->tsc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
	tegra->tsc.owner = THIS_MODULE;

	return clocksource_register_hz(&tegra->tsc, 31250000);
}

static u64 tegra186_timer_osc_read(struct clocksource *cs)
{
	struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
						    osc);

	return readl_relaxed(tegra->regs + TKEOSC);
}

static int tegra186_timer_osc_init(struct tegra186_timer *tegra)
{
	tegra->osc.name = "osc";
	tegra->osc.rating = 300;
	tegra->osc.read = tegra186_timer_osc_read;
	tegra->osc.mask = CLOCKSOURCE_MASK(32);
	tegra->osc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
	tegra->osc.owner = THIS_MODULE;

	return clocksource_register_hz(&tegra->osc, 38400000);
}

static u64 tegra186_timer_usec_read(struct clocksource *cs)
{
	struct tegra186_timer *tegra = container_of(cs, struct tegra186_timer,
						    usec);

	return readl_relaxed(tegra->regs + TKEUSEC);
}

static int tegra186_timer_usec_init(struct tegra186_timer *tegra)
{
	tegra->usec.name = "usec";
	tegra->usec.rating = 300;
	tegra->usec.read = tegra186_timer_usec_read;
	tegra->usec.mask = CLOCKSOURCE_MASK(32);
	tegra->usec.flags = CLOCK_SOURCE_IS_CONTINUOUS;
	tegra->usec.owner = THIS_MODULE;

	return clocksource_register_hz(&tegra->usec, USEC_PER_SEC);
}

static int tegra186_timer_probe(struct platform_device *pdev)
{
	struct tegra186_wdt *kernel_wdt = NULL;
	struct device *dev = &pdev->dev;
	struct tegra186_timer *tegra;
	unsigned int i;
	int irq;
	int err;

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

	tegra->soc = of_device_get_match_data(dev);
	dev_set_drvdata(dev, tegra);
	tegra->dev = dev;

	tegra->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(tegra->regs))
		return PTR_ERR(tegra->regs);

	err = platform_get_irq(pdev, 0);
	if (err < 0)
		return err;

	irq = err;

	tegra->wdts = devm_kcalloc(dev, tegra->soc->num_wdts, sizeof(*tegra->wdts), GFP_KERNEL);
	if (!tegra->wdts)
		return -ENOMEM;

	for (i = 0; i < tegra->soc->num_wdts; i++) {
		if (!tegra186_wdt_is_accessible(tegra, i)) {
			dev_warn(dev, "WDT%u is not accessible\n", i);
			continue;
		}

		tegra->wdts[i] = tegra186_wdt_create(tegra, i);
		if (IS_ERR(tegra->wdts[i]))
			return dev_err_probe(dev, PTR_ERR(tegra->wdts[i]),
					     "failed to create WDT%u\n", i);

		/* Reserve the first accessible WDT for the Kernel. */
		if (!kernel_wdt) {
			kernel_wdt = tegra->wdts[i];
			kernel_wdt->is_kernel_wdt = true;
		} else {
			err = devm_watchdog_register_device(dev, &tegra->wdts[i]->base);
			if (err < 0)
				return dev_err_probe(dev, err,
						     "failed to register WDT%u\n", i);
		}
	}

	err = tegra186_timer_tsc_init(tegra);
	if (err < 0) {
		dev_err(dev, "failed to register TSC counter: %d\n", err);
		return err;
	}

	err = tegra186_timer_osc_init(tegra);
	if (err < 0) {
		dev_err(dev, "failed to register OSC counter: %d\n", err);
		goto unregister_tsc;
	}

	err = tegra186_timer_usec_init(tegra);
	if (err < 0) {
		dev_err(dev, "failed to register USEC counter: %d\n", err);
		goto unregister_osc;
	}

	if (kernel_wdt) {
		err = devm_request_irq(dev, irq, tegra186_wdt_irq, 0,
				       dev_name(dev), kernel_wdt);
		if (err < 0) {
			dev_err(dev, "failed to request kernel WDT IRQ: %d\n", err);
			goto unregister_usec;
		}

		tegra186_wdt_set_timeout(&kernel_wdt->base, TEGRA186_KERNEL_WDT_TIMEOUT);
		tegra186_wdt_enable(kernel_wdt);
	}

	return 0;

unregister_usec:
	clocksource_unregister(&tegra->usec);
unregister_osc:
	clocksource_unregister(&tegra->osc);
unregister_tsc:
	clocksource_unregister(&tegra->tsc);
	return err;
}

static void tegra186_timer_remove(struct platform_device *pdev)
{
	struct tegra186_timer *tegra = platform_get_drvdata(pdev);

	clocksource_unregister(&tegra->usec);
	clocksource_unregister(&tegra->osc);
	clocksource_unregister(&tegra->tsc);
}

static int __maybe_unused tegra186_timer_suspend(struct device *dev)
{
	struct tegra186_timer *tegra = dev_get_drvdata(dev);
	unsigned int i;

	for (i = 0; i < tegra->soc->num_wdts; i++) {
		struct tegra186_wdt *wdt = tegra->wdts[i];

		if (wdt && (wdt->is_kernel_wdt || watchdog_active(&wdt->base)))
			tegra186_wdt_disable(wdt);
	}

	return 0;
}

static int __maybe_unused tegra186_timer_resume(struct device *dev)
{
	struct tegra186_timer *tegra = dev_get_drvdata(dev);
	unsigned int i;

	for (i = 0; i < tegra->soc->num_wdts; i++) {
		struct tegra186_wdt *wdt = tegra->wdts[i];

		if (wdt && (wdt->is_kernel_wdt || watchdog_active(&wdt->base)))
			tegra186_wdt_enable(wdt);
	}

	return 0;
}

static SIMPLE_DEV_PM_OPS(tegra186_timer_pm_ops, tegra186_timer_suspend,
			 tegra186_timer_resume);

static const struct tegra186_timer_soc tegra186_timer = {
	.num_timers = 10,
	.num_wdts = 2,
};

static const struct tegra186_timer_soc tegra234_timer = {
	.num_timers = 16,
	.num_wdts = 2,
};

static const struct of_device_id tegra186_timer_of_match[] = {
	{ .compatible = "nvidia,tegra186-timer", .data = &tegra186_timer },
	{ .compatible = "nvidia,tegra234-timer", .data = &tegra234_timer },
	{ }
};
MODULE_DEVICE_TABLE(of, tegra186_timer_of_match);

static struct platform_driver tegra186_wdt_driver = {
	.driver = {
		.name = "tegra186-timer",
		.pm = &tegra186_timer_pm_ops,
		.of_match_table = tegra186_timer_of_match,
	},
	.probe = tegra186_timer_probe,
	.remove = tegra186_timer_remove,
};
module_platform_driver(tegra186_wdt_driver);

MODULE_AUTHOR("Thierry Reding <treding@nvidia.com>");
MODULE_DESCRIPTION("NVIDIA Tegra186 timers driver");