/* drivers/rtc/rtc-goldfish.c
 *
 * Copyright (C) 2007 Google, Inc.
 * Copyright (C) 2017 Imagination Technologies Ltd.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/io.h>

#define TIMER_TIME_LOW		0x00	/* get low bits of current time  */
					/*   and update TIMER_TIME_HIGH  */
#define TIMER_TIME_HIGH	0x04	/* get high bits of time at last */
					/*   TIMER_TIME_LOW read         */
#define TIMER_ALARM_LOW	0x08	/* set low bits of alarm and     */
					/*   activate it                 */
#define TIMER_ALARM_HIGH	0x0c	/* set high bits of next alarm   */
#define TIMER_IRQ_ENABLED	0x10
#define TIMER_CLEAR_ALARM	0x14
#define TIMER_ALARM_STATUS	0x18
#define TIMER_CLEAR_INTERRUPT	0x1c

struct goldfish_rtc {
	void __iomem *base;
	int irq;
	struct rtc_device *rtc;
};

static int goldfish_rtc_read_alarm(struct device *dev,
				   struct rtc_wkalrm *alrm)
{
	u64 rtc_alarm;
	u64 rtc_alarm_low;
	u64 rtc_alarm_high;
	void __iomem *base;
	struct goldfish_rtc *rtcdrv;

	rtcdrv = dev_get_drvdata(dev);
	base = rtcdrv->base;

	rtc_alarm_low = readl(base + TIMER_ALARM_LOW);
	rtc_alarm_high = readl(base + TIMER_ALARM_HIGH);
	rtc_alarm = (rtc_alarm_high << 32) | rtc_alarm_low;

	do_div(rtc_alarm, NSEC_PER_SEC);
	memset(alrm, 0, sizeof(struct rtc_wkalrm));

	rtc_time_to_tm(rtc_alarm, &alrm->time);

	if (readl(base + TIMER_ALARM_STATUS))
		alrm->enabled = 1;
	else
		alrm->enabled = 0;

	return 0;
}

static int goldfish_rtc_set_alarm(struct device *dev,
				  struct rtc_wkalrm *alrm)
{
	struct goldfish_rtc *rtcdrv;
	unsigned long rtc_alarm;
	u64 rtc_alarm64;
	u64 rtc_status_reg;
	void __iomem *base;
	int ret = 0;

	rtcdrv = dev_get_drvdata(dev);
	base = rtcdrv->base;

	if (alrm->enabled) {
		ret = rtc_tm_to_time(&alrm->time, &rtc_alarm);
		if (ret != 0)
			return ret;

		rtc_alarm64 = rtc_alarm * NSEC_PER_SEC;
		writel((rtc_alarm64 >> 32), base + TIMER_ALARM_HIGH);
		writel(rtc_alarm64, base + TIMER_ALARM_LOW);
	} else {
		/*
		 * if this function was called with enabled=0
		 * then it could mean that the application is
		 * trying to cancel an ongoing alarm
		 */
		rtc_status_reg = readl(base + TIMER_ALARM_STATUS);
		if (rtc_status_reg)
			writel(1, base + TIMER_CLEAR_ALARM);
	}

	return ret;
}

static int goldfish_rtc_alarm_irq_enable(struct device *dev,
					 unsigned int enabled)
{
	void __iomem *base;
	struct goldfish_rtc *rtcdrv;

	rtcdrv = dev_get_drvdata(dev);
	base = rtcdrv->base;

	if (enabled)
		writel(1, base + TIMER_IRQ_ENABLED);
	else
		writel(0, base + TIMER_IRQ_ENABLED);

	return 0;
}

static irqreturn_t goldfish_rtc_interrupt(int irq, void *dev_id)
{
	struct goldfish_rtc *rtcdrv = dev_id;
	void __iomem *base = rtcdrv->base;

	writel(1, base + TIMER_CLEAR_INTERRUPT);

	rtc_update_irq(rtcdrv->rtc, 1, RTC_IRQF | RTC_AF);

	return IRQ_HANDLED;
}

static int goldfish_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct goldfish_rtc *rtcdrv;
	void __iomem *base;
	u64 time_high;
	u64 time_low;
	u64 time;

	rtcdrv = dev_get_drvdata(dev);
	base = rtcdrv->base;

	time_low = readl(base + TIMER_TIME_LOW);
	time_high = readl(base + TIMER_TIME_HIGH);
	time = (time_high << 32) | time_low;

	do_div(time, NSEC_PER_SEC);

	rtc_time_to_tm(time, tm);

	return 0;
}

static int goldfish_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct goldfish_rtc *rtcdrv;
	void __iomem *base;
	unsigned long now;
	u64 now64;
	int ret;

	rtcdrv = dev_get_drvdata(dev);
	base = rtcdrv->base;

	ret = rtc_tm_to_time(tm, &now);
	if (ret == 0) {
		now64 = now * NSEC_PER_SEC;
		writel((now64 >> 32), base + TIMER_TIME_HIGH);
		writel(now64, base + TIMER_TIME_LOW);
	}

	return ret;
}

static const struct rtc_class_ops goldfish_rtc_ops = {
	.read_time	= goldfish_rtc_read_time,
	.set_time	= goldfish_rtc_set_time,
	.read_alarm	= goldfish_rtc_read_alarm,
	.set_alarm	= goldfish_rtc_set_alarm,
	.alarm_irq_enable = goldfish_rtc_alarm_irq_enable
};

static int goldfish_rtc_probe(struct platform_device *pdev)
{
	struct goldfish_rtc *rtcdrv;
	struct resource *r;
	int err;

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

	platform_set_drvdata(pdev, rtcdrv);

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!r)
		return -ENODEV;

	rtcdrv->base = devm_ioremap_resource(&pdev->dev, r);
	if (IS_ERR(rtcdrv->base))
		return -ENODEV;

	rtcdrv->irq = platform_get_irq(pdev, 0);
	if (rtcdrv->irq < 0)
		return -ENODEV;

	rtcdrv->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
					       &goldfish_rtc_ops,
					       THIS_MODULE);
	if (IS_ERR(rtcdrv->rtc))
		return PTR_ERR(rtcdrv->rtc);

	err = devm_request_irq(&pdev->dev, rtcdrv->irq,
			       goldfish_rtc_interrupt,
			       0, pdev->name, rtcdrv);
	if (err)
		return err;

	return 0;
}

static const struct of_device_id goldfish_rtc_of_match[] = {
	{ .compatible = "google,goldfish-rtc", },
	{},
};
MODULE_DEVICE_TABLE(of, goldfish_rtc_of_match);

static struct platform_driver goldfish_rtc = {
	.probe = goldfish_rtc_probe,
	.driver = {
		.name = "goldfish_rtc",
		.of_match_table = goldfish_rtc_of_match,
	}
};

module_platform_driver(goldfish_rtc);

MODULE_LICENSE("GPL v2");