ARK-OS/arkos/kernel/drivers/rtc/rtc-renesas-rtca3.c

// SPDX-License-Identifier: GPL-2.0
/*
 * On-Chip RTC Support available on RZ/G3S SoC
 *
 * Copyright (C) 2024 Renesas Electronics Corp.
 */
#include <linux/bcd.h>
#include <linux/bitfield.h>
#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/iopoll.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/rtc.h>

/* Counter registers. */
#define RTCA3_RSECCNT			0x2
#define RTCA3_RSECCNT_SEC		GENMASK(6, 0)
#define RTCA3_RMINCNT			0x4
#define RTCA3_RMINCNT_MIN		GENMASK(6, 0)
#define RTCA3_RHRCNT			0x6
#define RTCA3_RHRCNT_HR			GENMASK(5, 0)
#define RTCA3_RHRCNT_PM			BIT(6)
#define RTCA3_RWKCNT			0x8
#define RTCA3_RWKCNT_WK			GENMASK(2, 0)
#define RTCA3_RDAYCNT			0xa
#define RTCA3_RDAYCNT_DAY		GENMASK(5, 0)
#define RTCA3_RMONCNT			0xc
#define RTCA3_RMONCNT_MONTH		GENMASK(4, 0)
#define RTCA3_RYRCNT			0xe
#define RTCA3_RYRCNT_YEAR		GENMASK(7, 0)

/* Alarm registers. */
#define RTCA3_RSECAR			0x10
#define RTCA3_RSECAR_SEC		GENMASK(6, 0)
#define RTCA3_RMINAR			0x12
#define RTCA3_RMINAR_MIN		GENMASK(6, 0)
#define RTCA3_RHRAR			0x14
#define RTCA3_RHRAR_HR			GENMASK(5, 0)
#define RTCA3_RHRAR_PM			BIT(6)
#define RTCA3_RWKAR			0x16
#define RTCA3_RWKAR_DAYW		GENMASK(2, 0)
#define RTCA3_RDAYAR			0x18
#define RTCA3_RDAYAR_DATE		GENMASK(5, 0)
#define RTCA3_RMONAR			0x1a
#define RTCA3_RMONAR_MON		GENMASK(4, 0)
#define RTCA3_RYRAR			0x1c
#define RTCA3_RYRAR_YR			GENMASK(7, 0)
#define RTCA3_RYRAREN			0x1e

/* Alarm enable bit (for all alarm registers). */
#define RTCA3_AR_ENB			BIT(7)

/* Control registers. */
#define RTCA3_RCR1			0x22
#define RTCA3_RCR1_AIE			BIT(0)
#define RTCA3_RCR1_CIE			BIT(1)
#define RTCA3_RCR1_PIE			BIT(2)
#define RTCA3_RCR1_PES			GENMASK(7, 4)
#define RTCA3_RCR1_PES_1_64_SEC		0x8
#define RTCA3_RCR2			0x24
#define RTCA3_RCR2_START		BIT(0)
#define RTCA3_RCR2_RESET		BIT(1)
#define RTCA3_RCR2_AADJE		BIT(4)
#define RTCA3_RCR2_ADJP			BIT(5)
#define RTCA3_RCR2_HR24			BIT(6)
#define RTCA3_RCR2_CNTMD		BIT(7)
#define RTCA3_RSR			0x20
#define RTCA3_RSR_AF			BIT(0)
#define RTCA3_RSR_CF			BIT(1)
#define RTCA3_RSR_PF			BIT(2)
#define RTCA3_RADJ			0x2e
#define RTCA3_RADJ_ADJ			GENMASK(5, 0)
#define RTCA3_RADJ_ADJ_MAX		0x3f
#define RTCA3_RADJ_PMADJ		GENMASK(7, 6)
#define RTCA3_RADJ_PMADJ_NONE		0
#define RTCA3_RADJ_PMADJ_ADD		1
#define RTCA3_RADJ_PMADJ_SUB		2

/* Polling operation timeouts. */
#define RTCA3_DEFAULT_TIMEOUT_US	150
#define RTCA3_IRQSET_TIMEOUT_US		5000
#define RTCA3_START_TIMEOUT_US		150000
#define RTCA3_RESET_TIMEOUT_US		200000

/**
 * enum rtca3_alrm_set_step - RTCA3 alarm set steps
 * @RTCA3_ALRM_SSTEP_DONE: alarm setup done step
 * @RTCA3_ALRM_SSTEP_IRQ: two 1/64 periodic IRQs were generated step
 * @RTCA3_ALRM_SSTEP_INIT: alarm setup initialization step
 */
enum rtca3_alrm_set_step {
	RTCA3_ALRM_SSTEP_DONE = 0,
	RTCA3_ALRM_SSTEP_IRQ = 1,
	RTCA3_ALRM_SSTEP_INIT = 3,
};

/**
 * struct rtca3_ppb_per_cycle - PPB per cycle
 * @ten_sec: PPB per cycle in 10 seconds adjutment mode
 * @sixty_sec: PPB per cycle in 60 seconds adjustment mode
 */
struct rtca3_ppb_per_cycle {
	int ten_sec;
	int sixty_sec;
};

/**
 * struct rtca3_priv - RTCA3 private data structure
 * @base: base address
 * @rtc_dev: RTC device
 * @rstc: reset control
 * @set_alarm_completion: alarm setup completion
 * @alrm_sstep: alarm setup step (see enum rtca3_alrm_set_step)
 * @lock: device lock
 * @ppb: ppb per cycle for each the available adjustment modes
 * @wakeup_irq: wakeup IRQ
 */
struct rtca3_priv {
	void __iomem *base;
	struct rtc_device *rtc_dev;
	struct reset_control *rstc;
	struct completion set_alarm_completion;
	atomic_t alrm_sstep;
	spinlock_t lock;
	struct rtca3_ppb_per_cycle ppb;
	int wakeup_irq;
};

static void rtca3_byte_update_bits(struct rtca3_priv *priv, u8 off, u8 mask, u8 val)
{
	u8 tmp;

	tmp = readb(priv->base + off);
	tmp &= ~mask;
	tmp |= (val & mask);
	writeb(tmp, priv->base + off);
}

static u8 rtca3_alarm_handler_helper(struct rtca3_priv *priv)
{
	u8 val, pending;

	val = readb(priv->base + RTCA3_RSR);
	pending = val & RTCA3_RSR_AF;
	writeb(val & ~pending, priv->base + RTCA3_RSR);

	if (pending)
		rtc_update_irq(priv->rtc_dev, 1, RTC_AF | RTC_IRQF);

	return pending;
}

static irqreturn_t rtca3_alarm_handler(int irq, void *dev_id)
{
	struct rtca3_priv *priv = dev_id;
	u8 pending;

	guard(spinlock)(&priv->lock);

	pending = rtca3_alarm_handler_helper(priv);

	return IRQ_RETVAL(pending);
}

static irqreturn_t rtca3_periodic_handler(int irq, void *dev_id)
{
	struct rtca3_priv *priv = dev_id;
	u8 val, pending;

	guard(spinlock)(&priv->lock);

	val = readb(priv->base + RTCA3_RSR);
	pending = val & RTCA3_RSR_PF;

	if (pending) {
		writeb(val & ~pending, priv->base + RTCA3_RSR);

		if (atomic_read(&priv->alrm_sstep) > RTCA3_ALRM_SSTEP_IRQ) {
			/* Alarm setup in progress. */
			atomic_dec(&priv->alrm_sstep);

			if (atomic_read(&priv->alrm_sstep) == RTCA3_ALRM_SSTEP_IRQ) {
				/*
				 * We got 2 * 1/64 periodic interrupts. Disable
				 * interrupt and let alarm setup continue.
				 */
				rtca3_byte_update_bits(priv, RTCA3_RCR1,
						       RTCA3_RCR1_PIE, 0);
				readb_poll_timeout_atomic(priv->base + RTCA3_RCR1, val,
							  !(val & RTCA3_RCR1_PIE),
							  10, RTCA3_DEFAULT_TIMEOUT_US);
				complete(&priv->set_alarm_completion);
			}
		}
	}

	return IRQ_RETVAL(pending);
}

static void rtca3_prepare_cntalrm_regs_for_read(struct rtca3_priv *priv, bool cnt)
{
	/* Offset b/w time and alarm registers. */
	u8 offset = cnt ? 0 : 0xe;

	/*
	 * According to HW manual (section 22.6.4. Notes on writing to and
	 * reading from registers) after writing to count registers, alarm
	 * registers, year alarm enable register, bits RCR2.AADJE, AADJP,
	 * and HR24 register, we need to do 3 empty reads before being
	 * able to fetch the registers content.
	 */
	for (u8 i = 0; i < 3; i++) {
		readb(priv->base + RTCA3_RSECCNT + offset);
		readb(priv->base + RTCA3_RMINCNT + offset);
		readb(priv->base + RTCA3_RHRCNT  + offset);
		readb(priv->base + RTCA3_RWKCNT  + offset);
		readb(priv->base + RTCA3_RDAYCNT + offset);
		readw(priv->base + RTCA3_RYRCNT  + offset);
		if (!cnt)
			readb(priv->base + RTCA3_RYRAREN);
	}
}

static int rtca3_read_time(struct device *dev, struct rtc_time *tm)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	u8 sec, min, hour, wday, mday, month, tmp;
	u8 trials = 0;
	u32 year100;
	u16 year;

	guard(spinlock_irqsave)(&priv->lock);

	tmp = readb(priv->base + RTCA3_RCR2);
	if (!(tmp & RTCA3_RCR2_START))
		return -EINVAL;

	do {
		/* Clear carry interrupt. */
		rtca3_byte_update_bits(priv, RTCA3_RSR, RTCA3_RSR_CF, 0);

		/* Read counters. */
		sec = readb(priv->base + RTCA3_RSECCNT);
		min = readb(priv->base + RTCA3_RMINCNT);
		hour = readb(priv->base + RTCA3_RHRCNT);
		wday = readb(priv->base + RTCA3_RWKCNT);
		mday = readb(priv->base + RTCA3_RDAYCNT);
		month = readb(priv->base + RTCA3_RMONCNT);
		year = readw(priv->base + RTCA3_RYRCNT);

		tmp = readb(priv->base + RTCA3_RSR);

		/*
		 * We cannot generate carries due to reading 64Hz counter as
		 * the driver doesn't implement carry, thus, carries will be
		 * generated once per seconds. Add a timeout of 5 trials here
		 * to avoid infinite loop, if any.
		 */
	} while ((tmp & RTCA3_RSR_CF) && ++trials < 5);

	if (trials >= 5)
		return -ETIMEDOUT;

	tm->tm_sec = bcd2bin(FIELD_GET(RTCA3_RSECCNT_SEC, sec));
	tm->tm_min = bcd2bin(FIELD_GET(RTCA3_RMINCNT_MIN, min));
	tm->tm_hour = bcd2bin(FIELD_GET(RTCA3_RHRCNT_HR, hour));
	tm->tm_wday = bcd2bin(FIELD_GET(RTCA3_RWKCNT_WK, wday));
	tm->tm_mday = bcd2bin(FIELD_GET(RTCA3_RDAYCNT_DAY, mday));
	tm->tm_mon = bcd2bin(FIELD_GET(RTCA3_RMONCNT_MONTH, month)) - 1;
	year = FIELD_GET(RTCA3_RYRCNT_YEAR, year);
	year100 = bcd2bin((year == 0x99) ? 0x19 : 0x20);
	tm->tm_year = (year100 * 100 + bcd2bin(year)) - 1900;

	return 0;
}

static int rtca3_set_time(struct device *dev, struct rtc_time *tm)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	u8 rcr2, tmp;
	int ret;

	guard(spinlock_irqsave)(&priv->lock);

	/* Stop the RTC. */
	rcr2 = readb(priv->base + RTCA3_RCR2);
	writeb(rcr2 & ~RTCA3_RCR2_START, priv->base + RTCA3_RCR2);
	ret = readb_poll_timeout_atomic(priv->base + RTCA3_RCR2, tmp,
					!(tmp & RTCA3_RCR2_START),
					10, RTCA3_DEFAULT_TIMEOUT_US);
	if (ret)
		return ret;

	/* Update time. */
	writeb(bin2bcd(tm->tm_sec), priv->base + RTCA3_RSECCNT);
	writeb(bin2bcd(tm->tm_min), priv->base + RTCA3_RMINCNT);
	writeb(bin2bcd(tm->tm_hour), priv->base + RTCA3_RHRCNT);
	writeb(bin2bcd(tm->tm_wday), priv->base + RTCA3_RWKCNT);
	writeb(bin2bcd(tm->tm_mday), priv->base + RTCA3_RDAYCNT);
	writeb(bin2bcd(tm->tm_mon + 1), priv->base + RTCA3_RMONCNT);
	writew(bin2bcd(tm->tm_year % 100), priv->base + RTCA3_RYRCNT);

	/* Make sure we can read back the counters. */
	rtca3_prepare_cntalrm_regs_for_read(priv, true);

	/* Start RTC. */
	writeb(rcr2 | RTCA3_RCR2_START, priv->base + RTCA3_RCR2);
	return readb_poll_timeout_atomic(priv->base + RTCA3_RCR2, tmp,
					 (tmp & RTCA3_RCR2_START),
					 10, RTCA3_DEFAULT_TIMEOUT_US);
}

static int rtca3_alarm_irq_set_helper(struct rtca3_priv *priv,
				      u8 interrupts,
				      unsigned int enabled)
{
	u8 tmp, val;

	if (enabled) {
		/*
		 * AIE, CIE, PIE bit indexes in RSR corresponds with
		 * those on RCR1. Same interrupts mask can be used.
		 */
		rtca3_byte_update_bits(priv, RTCA3_RSR, interrupts, 0);
		val = interrupts;
	} else {
		val = 0;
	}

	rtca3_byte_update_bits(priv, RTCA3_RCR1, interrupts, val);
	return readb_poll_timeout_atomic(priv->base + RTCA3_RCR1, tmp,
					 ((tmp & interrupts) == val),
					 10, RTCA3_IRQSET_TIMEOUT_US);
}

static int rtca3_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);

	guard(spinlock_irqsave)(&priv->lock);

	return rtca3_alarm_irq_set_helper(priv, RTCA3_RCR1_AIE, enabled);
}

static int rtca3_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	u8 sec, min, hour, wday, mday, month;
	struct rtc_time *tm = &wkalrm->time;
	u32 year100;
	u16 year;

	guard(spinlock_irqsave)(&priv->lock);

	sec = readb(priv->base + RTCA3_RSECAR);
	min = readb(priv->base + RTCA3_RMINAR);
	hour = readb(priv->base + RTCA3_RHRAR);
	wday = readb(priv->base + RTCA3_RWKAR);
	mday = readb(priv->base + RTCA3_RDAYAR);
	month = readb(priv->base + RTCA3_RMONAR);
	year = readw(priv->base + RTCA3_RYRAR);

	tm->tm_sec = bcd2bin(FIELD_GET(RTCA3_RSECAR_SEC, sec));
	tm->tm_min = bcd2bin(FIELD_GET(RTCA3_RMINAR_MIN, min));
	tm->tm_hour = bcd2bin(FIELD_GET(RTCA3_RHRAR_HR, hour));
	tm->tm_wday = bcd2bin(FIELD_GET(RTCA3_RWKAR_DAYW, wday));
	tm->tm_mday = bcd2bin(FIELD_GET(RTCA3_RDAYAR_DATE, mday));
	tm->tm_mon = bcd2bin(FIELD_GET(RTCA3_RMONAR_MON, month)) - 1;
	year = FIELD_GET(RTCA3_RYRAR_YR, year);
	year100 = bcd2bin((year == 0x99) ? 0x19 : 0x20);
	tm->tm_year = (year100 * 100 + bcd2bin(year)) - 1900;

	wkalrm->enabled = !!(readb(priv->base + RTCA3_RCR1) & RTCA3_RCR1_AIE);

	return 0;
}

static int rtca3_set_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	struct rtc_time *tm = &wkalrm->time;
	u8 rcr1, tmp;
	int ret;

	scoped_guard(spinlock_irqsave, &priv->lock) {
		tmp = readb(priv->base + RTCA3_RCR2);
		if (!(tmp & RTCA3_RCR2_START))
			return -EPERM;

		/* Disable AIE to prevent false interrupts. */
		rcr1 = readb(priv->base + RTCA3_RCR1);
		rcr1 &= ~RTCA3_RCR1_AIE;
		writeb(rcr1, priv->base + RTCA3_RCR1);
		ret = readb_poll_timeout_atomic(priv->base + RTCA3_RCR1, tmp,
						!(tmp & RTCA3_RCR1_AIE),
						10, RTCA3_DEFAULT_TIMEOUT_US);
		if (ret)
			return ret;

		/* Set the time and enable the alarm. */
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_sec), priv->base + RTCA3_RSECAR);
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_min), priv->base + RTCA3_RMINAR);
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_hour), priv->base + RTCA3_RHRAR);
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_wday), priv->base + RTCA3_RWKAR);
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_mday), priv->base + RTCA3_RDAYAR);
		writeb(RTCA3_AR_ENB | bin2bcd(tm->tm_mon + 1), priv->base + RTCA3_RMONAR);

		writew(bin2bcd(tm->tm_year % 100), priv->base + RTCA3_RYRAR);
		writeb(RTCA3_AR_ENB, priv->base + RTCA3_RYRAREN);

		/* Make sure we can read back the counters. */
		rtca3_prepare_cntalrm_regs_for_read(priv, false);

		/* Need to wait for 2 * 1/64 periodic interrupts to be generated. */
		atomic_set(&priv->alrm_sstep, RTCA3_ALRM_SSTEP_INIT);
		reinit_completion(&priv->set_alarm_completion);

		/* Enable periodic interrupt. */
		rcr1 |= RTCA3_RCR1_PIE;
		writeb(rcr1, priv->base + RTCA3_RCR1);
		ret = readb_poll_timeout_atomic(priv->base + RTCA3_RCR1, tmp,
						(tmp & RTCA3_RCR1_PIE),
						10, RTCA3_IRQSET_TIMEOUT_US);
	}

	if (ret)
		goto setup_failed;

	/* Wait for the 2 * 1/64 periodic interrupts. */
	ret = wait_for_completion_interruptible_timeout(&priv->set_alarm_completion,
							msecs_to_jiffies(500));
	if (ret <= 0) {
		ret = -ETIMEDOUT;
		goto setup_failed;
	}

	scoped_guard(spinlock_irqsave, &priv->lock) {
		ret = rtca3_alarm_irq_set_helper(priv, RTCA3_RCR1_AIE, wkalrm->enabled);
		atomic_set(&priv->alrm_sstep, RTCA3_ALRM_SSTEP_DONE);
	}

	return ret;

setup_failed:
	scoped_guard(spinlock_irqsave, &priv->lock) {
		/*
		 * Disable PIE to avoid interrupt storm in case HW needed more than
		 * specified timeout for setup.
		 */
		writeb(rcr1 & ~RTCA3_RCR1_PIE, priv->base + RTCA3_RCR1);
		readb_poll_timeout_atomic(priv->base + RTCA3_RCR1, tmp, !(tmp & ~RTCA3_RCR1_PIE),
					  10, RTCA3_DEFAULT_TIMEOUT_US);
		atomic_set(&priv->alrm_sstep, RTCA3_ALRM_SSTEP_DONE);
	}

	return ret;
}

static int rtca3_read_offset(struct device *dev, long *offset)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	u8 val, radj, cycles;
	u32 ppb_per_cycle;

	scoped_guard(spinlock_irqsave, &priv->lock) {
		radj = readb(priv->base + RTCA3_RADJ);
		val = readb(priv->base + RTCA3_RCR2);
	}

	cycles = FIELD_GET(RTCA3_RADJ_ADJ, radj);

	if (!cycles) {
		*offset = 0;
		return 0;
	}

	if (val & RTCA3_RCR2_ADJP)
		ppb_per_cycle = priv->ppb.ten_sec;
	else
		ppb_per_cycle = priv->ppb.sixty_sec;

	*offset = cycles * ppb_per_cycle;
	val = FIELD_GET(RTCA3_RADJ_PMADJ, radj);
	if (val == RTCA3_RADJ_PMADJ_SUB)
		*offset = -(*offset);

	return 0;
}

static int rtca3_set_offset(struct device *dev, long offset)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	int cycles, cycles10, cycles60;
	u8 radj, adjp, tmp;
	int ret;

	/*
	 * Automatic time error adjustment could be set at intervals of 10
	 * or 60 seconds.
	 */
	cycles10 = DIV_ROUND_CLOSEST(offset, priv->ppb.ten_sec);
	cycles60 = DIV_ROUND_CLOSEST(offset, priv->ppb.sixty_sec);

	/* We can set b/w 1 and 63 clock cycles. */
	if (cycles60 >= -RTCA3_RADJ_ADJ_MAX &&
	    cycles60 <= RTCA3_RADJ_ADJ_MAX) {
		cycles = cycles60;
		adjp = 0;
	} else if (cycles10 >= -RTCA3_RADJ_ADJ_MAX &&
		   cycles10 <= RTCA3_RADJ_ADJ_MAX) {
		cycles = cycles10;
		adjp = RTCA3_RCR2_ADJP;
	} else {
		return -ERANGE;
	}

	radj = FIELD_PREP(RTCA3_RADJ_ADJ, abs(cycles));
	if (!cycles)
		radj |= FIELD_PREP(RTCA3_RADJ_PMADJ, RTCA3_RADJ_PMADJ_NONE);
	else if (cycles > 0)
		radj |= FIELD_PREP(RTCA3_RADJ_PMADJ, RTCA3_RADJ_PMADJ_ADD);
	else
		radj |= FIELD_PREP(RTCA3_RADJ_PMADJ, RTCA3_RADJ_PMADJ_SUB);

	guard(spinlock_irqsave)(&priv->lock);

	tmp = readb(priv->base + RTCA3_RCR2);

	if ((tmp & RTCA3_RCR2_ADJP) != adjp) {
		/* RADJ.PMADJ need to be set to zero before setting RCR2.ADJP. */
		writeb(0, priv->base + RTCA3_RADJ);
		ret = readb_poll_timeout_atomic(priv->base + RTCA3_RADJ, tmp, !tmp,
						10, RTCA3_DEFAULT_TIMEOUT_US);
		if (ret)
			return ret;

		rtca3_byte_update_bits(priv, RTCA3_RCR2, RTCA3_RCR2_ADJP, adjp);
		ret = readb_poll_timeout_atomic(priv->base + RTCA3_RCR2, tmp,
						((tmp & RTCA3_RCR2_ADJP) == adjp),
						10, RTCA3_DEFAULT_TIMEOUT_US);
		if (ret)
			return ret;
	}

	writeb(radj, priv->base + RTCA3_RADJ);
	return readb_poll_timeout_atomic(priv->base + RTCA3_RADJ, tmp, (tmp == radj),
					 10, RTCA3_DEFAULT_TIMEOUT_US);
}

static const struct rtc_class_ops rtca3_ops = {
	.read_time = rtca3_read_time,
	.set_time = rtca3_set_time,
	.read_alarm = rtca3_read_alarm,
	.set_alarm = rtca3_set_alarm,
	.alarm_irq_enable = rtca3_alarm_irq_enable,
	.set_offset = rtca3_set_offset,
	.read_offset = rtca3_read_offset,
};

static int rtca3_initial_setup(struct clk *clk, struct rtca3_priv *priv)
{
	unsigned long osc32k_rate;
	u8 val, tmp, mask;
	u32 sleep_us;
	int ret;

	osc32k_rate = clk_get_rate(clk);
	if (!osc32k_rate)
		return -EINVAL;

	sleep_us = DIV_ROUND_UP_ULL(1000000ULL, osc32k_rate) * 6;

	priv->ppb.ten_sec = DIV_ROUND_CLOSEST_ULL(1000000000ULL, (osc32k_rate * 10));
	priv->ppb.sixty_sec = DIV_ROUND_CLOSEST_ULL(1000000000ULL, (osc32k_rate * 60));

	/*
	 * According to HW manual (section 22.4.2. Clock and count mode setting procedure)
	 * we need to wait at least 6 cycles of the 32KHz clock after clock was enabled.
	 */
	usleep_range(sleep_us, sleep_us + 10);

	mask = RTCA3_RCR2_START | RTCA3_RCR2_HR24;
	val = readb(priv->base + RTCA3_RCR2);
	/* Only disable the interrupts if already started in 24 hours and calendar count mode. */
	if ((val & mask) == mask) {
		/* Disable all interrupts. */
		mask = RTCA3_RCR1_AIE | RTCA3_RCR1_CIE | RTCA3_RCR1_PIE;
		return rtca3_alarm_irq_set_helper(priv, mask, 0);
	}

	/* Reconfigure the RTC in 24 hours and calendar count mode. */
	mask = RTCA3_RCR2_START | RTCA3_RCR2_CNTMD;
	writeb(0, priv->base + RTCA3_RCR2);
	ret = readb_poll_timeout(priv->base + RTCA3_RCR2, tmp, !(tmp & mask),
				 10, RTCA3_DEFAULT_TIMEOUT_US);
	if (ret)
		return ret;

	/*
	 * Set 24 hours mode. According to HW manual (section 22.3.19. RTC Control
	 * Register 2) this needs to be done separate from stop operation.
	 */
	mask = RTCA3_RCR2_HR24;
	val = RTCA3_RCR2_HR24;
	writeb(val, priv->base + RTCA3_RCR2);
	ret = readb_poll_timeout(priv->base + RTCA3_RCR2, tmp, (tmp & mask),
				 10, RTCA3_DEFAULT_TIMEOUT_US);
	if (ret)
		return ret;

	/* Execute reset. */
	mask = RTCA3_RCR2_RESET;
	writeb(val | RTCA3_RCR2_RESET, priv->base + RTCA3_RCR2);
	ret = readb_poll_timeout(priv->base + RTCA3_RCR2, tmp, !(tmp & mask),
				 10, RTCA3_RESET_TIMEOUT_US);
	if (ret)
		return ret;

	/*
	 * According to HW manual (section 22.6.3. Notes on writing to and reading
	 * from registers) after reset we need to wait 6 clock cycles before
	 * writing to RTC registers.
	 */
	usleep_range(sleep_us, sleep_us + 10);

	/* Set no adjustment. */
	writeb(0, priv->base + RTCA3_RADJ);
	ret = readb_poll_timeout(priv->base + RTCA3_RADJ, tmp, !tmp, 10,
				 RTCA3_DEFAULT_TIMEOUT_US);

	/* Start the RTC and enable automatic time error adjustment. */
	mask = RTCA3_RCR2_START | RTCA3_RCR2_AADJE;
	val |= RTCA3_RCR2_START | RTCA3_RCR2_AADJE;
	writeb(val, priv->base + RTCA3_RCR2);
	ret = readb_poll_timeout(priv->base + RTCA3_RCR2, tmp, ((tmp & mask) == mask),
				 10, RTCA3_START_TIMEOUT_US);
	if (ret)
		return ret;

	/*
	 * According to HW manual (section 22.6.4. Notes on writing to and reading
	 * from registers) we need to wait 1/128 seconds while the clock is operating
	 * (RCR2.START bit = 1) to be able to read the counters after a return from
	 * reset.
	 */
	usleep_range(8000, 9000);

	/* Set period interrupt to 1/64 seconds. It is necessary for alarm setup. */
	val = FIELD_PREP(RTCA3_RCR1_PES, RTCA3_RCR1_PES_1_64_SEC);
	rtca3_byte_update_bits(priv, RTCA3_RCR1, RTCA3_RCR1_PES, val);
	return readb_poll_timeout(priv->base + RTCA3_RCR1, tmp, ((tmp & RTCA3_RCR1_PES) == val),
				  10, RTCA3_DEFAULT_TIMEOUT_US);
}

static int rtca3_request_irqs(struct platform_device *pdev, struct rtca3_priv *priv)
{
	struct device *dev = &pdev->dev;
	int ret, irq;

	irq = platform_get_irq_byname(pdev, "alarm");
	if (irq < 0)
		return dev_err_probe(dev, irq, "Failed to get alarm IRQ!\n");

	ret = devm_request_irq(dev, irq, rtca3_alarm_handler, 0, "rtca3-alarm", priv);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to request alarm IRQ!\n");
	priv->wakeup_irq = irq;

	irq = platform_get_irq_byname(pdev, "period");
	if (irq < 0)
		return dev_err_probe(dev, irq, "Failed to get period IRQ!\n");

	ret = devm_request_irq(dev, irq, rtca3_periodic_handler, 0, "rtca3-period", priv);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to request period IRQ!\n");

	/*
	 * Driver doesn't implement carry handler. Just get the IRQ here
	 * for backward compatibility, in case carry support will be added later.
	 */
	irq = platform_get_irq_byname(pdev, "carry");
	if (irq < 0)
		return dev_err_probe(dev, irq, "Failed to get carry IRQ!\n");

	return 0;
}

static void rtca3_action(void *data)
{
	struct device *dev = data;
	struct rtca3_priv *priv = dev_get_drvdata(dev);
	int ret;

	ret = reset_control_assert(priv->rstc);
	if (ret)
		dev_err(dev, "Failed to de-assert reset!");

	ret = pm_runtime_put_sync(dev);
	if (ret < 0)
		dev_err(dev, "Failed to runtime suspend!");
}

static int rtca3_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct rtca3_priv *priv;
	struct clk *clk;
	int ret;

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

	priv->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->base))
		return PTR_ERR(priv->base);

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

	priv->rstc = devm_reset_control_array_get_shared(dev);
	if (IS_ERR(priv->rstc))
		return PTR_ERR(priv->rstc);

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

	ret = reset_control_deassert(priv->rstc);
	if (ret) {
		pm_runtime_put_sync(dev);
		return ret;
	}

	dev_set_drvdata(dev, priv);
	ret = devm_add_action_or_reset(dev, rtca3_action, dev);
	if (ret)
		return ret;

	/*
	 * This must be an always-on clock to keep the RTC running even after
	 * driver is unbinded.
	 */
	clk = devm_clk_get_enabled(dev, "counter");
	if (IS_ERR(clk))
		return PTR_ERR(clk);

	spin_lock_init(&priv->lock);
	atomic_set(&priv->alrm_sstep, RTCA3_ALRM_SSTEP_DONE);
	init_completion(&priv->set_alarm_completion);

	ret = rtca3_initial_setup(clk, priv);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to setup the RTC!\n");

	ret = rtca3_request_irqs(pdev, priv);
	if (ret)
		return ret;

	device_init_wakeup(&pdev->dev, true);

	priv->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
	if (IS_ERR(priv->rtc_dev))
		return PTR_ERR(priv->rtc_dev);

	priv->rtc_dev->ops = &rtca3_ops;
	priv->rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
	priv->rtc_dev->range_max = RTC_TIMESTAMP_END_2099;

	return devm_rtc_register_device(priv->rtc_dev);
}

static void rtca3_remove(struct platform_device *pdev)
{
	struct rtca3_priv *priv = platform_get_drvdata(pdev);

	guard(spinlock_irqsave)(&priv->lock);

	/*
	 * Disable alarm, periodic interrupts. The RTC device cannot
	 * power up the system.
	 */
	rtca3_alarm_irq_set_helper(priv, RTCA3_RCR1_AIE | RTCA3_RCR1_PIE, 0);
}

static int rtca3_suspend(struct device *dev)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);

	if (!device_may_wakeup(dev))
		return 0;

	/* Alarm setup in progress. */
	if (atomic_read(&priv->alrm_sstep) != RTCA3_ALRM_SSTEP_DONE)
		return -EBUSY;

	enable_irq_wake(priv->wakeup_irq);

	return 0;
}

static int rtca3_clean_alarm(struct rtca3_priv *priv)
{
	struct rtc_device *rtc_dev = priv->rtc_dev;
	time64_t alarm_time, now;
	struct rtc_wkalrm alarm;
	struct rtc_time tm;
	u8 pending;
	int ret;

	ret = rtc_read_alarm(rtc_dev, &alarm);
	if (ret)
		return ret;

	if (!alarm.enabled)
		return 0;

	ret = rtc_read_time(rtc_dev, &tm);
	if (ret)
		return ret;

	alarm_time = rtc_tm_to_time64(&alarm.time);
	now = rtc_tm_to_time64(&tm);
	if (alarm_time >= now)
		return 0;

	/*
	 * Heuristically, it has been determined that when returning from deep
	 * sleep state the RTCA3_RSR.AF is zero even though the alarm expired.
	 * Call again the rtc_update_irq() if alarm helper detects this.
	 */

	guard(spinlock_irqsave)(&priv->lock);

	pending = rtca3_alarm_handler_helper(priv);
	if (!pending)
		rtc_update_irq(priv->rtc_dev, 1, RTC_AF | RTC_IRQF);

	return 0;
}

static int rtca3_resume(struct device *dev)
{
	struct rtca3_priv *priv = dev_get_drvdata(dev);

	if (!device_may_wakeup(dev))
		return 0;

	disable_irq_wake(priv->wakeup_irq);

	/*
	 * According to the HW manual (section 22.6.4 Notes on writing to
	 * and reading from registers) we need to wait 1/128 seconds while
	 * RCR2.START = 1 to be able to read the counters after a return from low
	 * power consumption state.
	 */
	mdelay(8);

	/*
	 * The alarm cannot wake the system from deep sleep states. In case
	 * we return from deep sleep states and the alarm expired we need
	 * to disable it to avoid failures when setting another alarm.
	 */
	return rtca3_clean_alarm(priv);
}

static DEFINE_SIMPLE_DEV_PM_OPS(rtca3_pm_ops, rtca3_suspend, rtca3_resume);

static const struct of_device_id rtca3_of_match[] = {
	{ .compatible = "renesas,rz-rtca3", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rtca3_of_match);

static struct platform_driver rtca3_platform_driver = {
	.driver = {
		.name = "rtc-rtca3",
		.pm = pm_ptr(&rtca3_pm_ops),
		.of_match_table = rtca3_of_match,
	},
	.probe = rtca3_probe,
	.remove = rtca3_remove,
};
module_platform_driver(rtca3_platform_driver);

MODULE_DESCRIPTION("Renesas RTCA-3 RTC driver");
MODULE_AUTHOR("Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>");
MODULE_LICENSE("GPL");