// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2008-2009 Nuvoton technology corporation.
 *
 * Wan ZongShun <mcuos.com@gmail.com>
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/bcd.h>

/* RTC Control Registers */
#define REG_RTC_INIR		0x00
#define REG_RTC_AER		0x04
#define REG_RTC_FCR		0x08
#define REG_RTC_TLR		0x0C
#define REG_RTC_CLR		0x10
#define REG_RTC_TSSR		0x14
#define REG_RTC_DWR		0x18
#define REG_RTC_TAR		0x1C
#define REG_RTC_CAR		0x20
#define REG_RTC_LIR		0x24
#define REG_RTC_RIER		0x28
#define REG_RTC_RIIR		0x2C
#define REG_RTC_TTR		0x30

#define RTCSET			0x01
#define AERRWENB		0x10000
#define INIRRESET		0xa5eb1357
#define AERPOWERON		0xA965
#define AERPOWEROFF		0x0000
#define LEAPYEAR		0x0001
#define TICKENB			0x80
#define TICKINTENB		0x0002
#define ALARMINTENB		0x0001
#define MODE24			0x0001

struct nuc900_rtc {
	int			irq_num;
	void __iomem		*rtc_reg;
	struct rtc_device	*rtcdev;
};

struct nuc900_bcd_time {
	int bcd_sec;
	int bcd_min;
	int bcd_hour;
	int bcd_mday;
	int bcd_mon;
	int bcd_year;
};

static irqreturn_t nuc900_rtc_interrupt(int irq, void *_rtc)
{
	struct nuc900_rtc *rtc = _rtc;
	unsigned long events = 0, rtc_irq;

	rtc_irq = __raw_readl(rtc->rtc_reg + REG_RTC_RIIR);

	if (rtc_irq & ALARMINTENB) {
		rtc_irq &= ~ALARMINTENB;
		__raw_writel(rtc_irq, rtc->rtc_reg + REG_RTC_RIIR);
		events |= RTC_AF | RTC_IRQF;
	}

	if (rtc_irq & TICKINTENB) {
		rtc_irq &= ~TICKINTENB;
		__raw_writel(rtc_irq, rtc->rtc_reg + REG_RTC_RIIR);
		events |= RTC_UF | RTC_IRQF;
	}

	rtc_update_irq(rtc->rtcdev, 1, events);

	return IRQ_HANDLED;
}

static int *check_rtc_access_enable(struct nuc900_rtc *nuc900_rtc)
{
	unsigned int timeout = 0x1000;
	__raw_writel(INIRRESET, nuc900_rtc->rtc_reg + REG_RTC_INIR);

	mdelay(10);

	__raw_writel(AERPOWERON, nuc900_rtc->rtc_reg + REG_RTC_AER);

	while (!(__raw_readl(nuc900_rtc->rtc_reg + REG_RTC_AER) & AERRWENB)
								&& --timeout)
		mdelay(1);

	if (!timeout)
		return ERR_PTR(-EPERM);

	return NULL;
}

static void nuc900_rtc_bcd2bin(unsigned int timereg,
			       unsigned int calreg, struct rtc_time *tm)
{
	tm->tm_mday	= bcd2bin(calreg >> 0);
	tm->tm_mon	= bcd2bin(calreg >> 8);
	tm->tm_year	= bcd2bin(calreg >> 16) + 100;

	tm->tm_sec	= bcd2bin(timereg >> 0);
	tm->tm_min	= bcd2bin(timereg >> 8);
	tm->tm_hour	= bcd2bin(timereg >> 16);
}

static void nuc900_rtc_bin2bcd(struct device *dev, struct rtc_time *settm,
						struct nuc900_bcd_time *gettm)
{
	gettm->bcd_mday = bin2bcd(settm->tm_mday) << 0;
	gettm->bcd_mon  = bin2bcd(settm->tm_mon) << 8;

	if (settm->tm_year < 100) {
		dev_warn(dev, "The year will be between 1970-1999, right?\n");
		gettm->bcd_year = bin2bcd(settm->tm_year) << 16;
	} else {
		gettm->bcd_year = bin2bcd(settm->tm_year - 100) << 16;
	}

	gettm->bcd_sec  = bin2bcd(settm->tm_sec) << 0;
	gettm->bcd_min  = bin2bcd(settm->tm_min) << 8;
	gettm->bcd_hour = bin2bcd(settm->tm_hour) << 16;
}

static int nuc900_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct nuc900_rtc *rtc = dev_get_drvdata(dev);

	if (enabled)
		__raw_writel(__raw_readl(rtc->rtc_reg + REG_RTC_RIER)|
				(ALARMINTENB), rtc->rtc_reg + REG_RTC_RIER);
	else
		__raw_writel(__raw_readl(rtc->rtc_reg + REG_RTC_RIER)&
				(~ALARMINTENB), rtc->rtc_reg + REG_RTC_RIER);

	return 0;
}

static int nuc900_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct nuc900_rtc *rtc = dev_get_drvdata(dev);
	unsigned int timeval, clrval;

	timeval = __raw_readl(rtc->rtc_reg + REG_RTC_TLR);
	clrval	= __raw_readl(rtc->rtc_reg + REG_RTC_CLR);

	nuc900_rtc_bcd2bin(timeval, clrval, tm);

	return 0;
}

static int nuc900_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct nuc900_rtc *rtc = dev_get_drvdata(dev);
	struct nuc900_bcd_time gettm;
	unsigned long val;
	int *err;

	nuc900_rtc_bin2bcd(dev, tm, &gettm);

	err = check_rtc_access_enable(rtc);
	if (IS_ERR(err))
		return PTR_ERR(err);

	val = gettm.bcd_mday | gettm.bcd_mon | gettm.bcd_year;
	__raw_writel(val, rtc->rtc_reg + REG_RTC_CLR);

	val = gettm.bcd_sec | gettm.bcd_min | gettm.bcd_hour;
	__raw_writel(val, rtc->rtc_reg + REG_RTC_TLR);

	return 0;
}

static int nuc900_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct nuc900_rtc *rtc = dev_get_drvdata(dev);
	unsigned int timeval, carval;

	timeval = __raw_readl(rtc->rtc_reg + REG_RTC_TAR);
	carval	= __raw_readl(rtc->rtc_reg + REG_RTC_CAR);

	nuc900_rtc_bcd2bin(timeval, carval, &alrm->time);

	return rtc_valid_tm(&alrm->time);
}

static int nuc900_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct nuc900_rtc *rtc = dev_get_drvdata(dev);
	struct nuc900_bcd_time tm;
	unsigned long val;
	int *err;

	nuc900_rtc_bin2bcd(dev, &alrm->time, &tm);

	err = check_rtc_access_enable(rtc);
	if (IS_ERR(err))
		return PTR_ERR(err);

	val = tm.bcd_mday | tm.bcd_mon | tm.bcd_year;
	__raw_writel(val, rtc->rtc_reg + REG_RTC_CAR);

	val = tm.bcd_sec | tm.bcd_min | tm.bcd_hour;
	__raw_writel(val, rtc->rtc_reg + REG_RTC_TAR);

	return 0;
}

static const struct rtc_class_ops nuc900_rtc_ops = {
	.read_time = nuc900_rtc_read_time,
	.set_time = nuc900_rtc_set_time,
	.read_alarm = nuc900_rtc_read_alarm,
	.set_alarm = nuc900_rtc_set_alarm,
	.alarm_irq_enable = nuc900_alarm_irq_enable,
};

static int __init nuc900_rtc_probe(struct platform_device *pdev)
{
	struct resource *res;
	struct nuc900_rtc *nuc900_rtc;

	nuc900_rtc = devm_kzalloc(&pdev->dev, sizeof(struct nuc900_rtc),
				GFP_KERNEL);
	if (!nuc900_rtc)
		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	nuc900_rtc->rtc_reg = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(nuc900_rtc->rtc_reg))
		return PTR_ERR(nuc900_rtc->rtc_reg);

	platform_set_drvdata(pdev, nuc900_rtc);

	nuc900_rtc->rtcdev = devm_rtc_device_register(&pdev->dev, pdev->name,
						&nuc900_rtc_ops, THIS_MODULE);
	if (IS_ERR(nuc900_rtc->rtcdev)) {
		dev_err(&pdev->dev, "rtc device register failed\n");
		return PTR_ERR(nuc900_rtc->rtcdev);
	}

	__raw_writel(__raw_readl(nuc900_rtc->rtc_reg + REG_RTC_TSSR) | MODE24,
					nuc900_rtc->rtc_reg + REG_RTC_TSSR);

	nuc900_rtc->irq_num = platform_get_irq(pdev, 0);
	if (devm_request_irq(&pdev->dev, nuc900_rtc->irq_num,
			nuc900_rtc_interrupt, 0, "nuc900rtc", nuc900_rtc)) {
		dev_err(&pdev->dev, "NUC900 RTC request irq failed\n");
		return -EBUSY;
	}

	return 0;
}

static struct platform_driver nuc900_rtc_driver = {
	.driver		= {
		.name	= "nuc900-rtc",
	},
};

module_platform_driver_probe(nuc900_rtc_driver, nuc900_rtc_probe);

MODULE_AUTHOR("Wan ZongShun <mcuos.com@gmail.com>");
MODULE_DESCRIPTION("nuc910/nuc920 RTC driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:nuc900-rtc");