/* Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * 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/init.h>
#include <linux/rtc.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <linux/mfd/pm8xxx/core.h>
#include <linux/mfd/pm8xxx/rtc.h>


/* RTC Register offsets from RTC CTRL REG */
#define PM8XXX_ALARM_CTRL_OFFSET	0x01
#define PM8XXX_RTC_WRITE_OFFSET		0x02
#define PM8XXX_RTC_READ_OFFSET		0x06
#define PM8XXX_ALARM_RW_OFFSET		0x0A

/* RTC_CTRL register bit fields */
#define PM8xxx_RTC_ENABLE		BIT(7)
#define PM8xxx_RTC_ALARM_ENABLE		BIT(1)
#define PM8xxx_RTC_ALARM_CLEAR		BIT(0)

#define NUM_8_BIT_RTC_REGS		0x4

/**
 * struct pm8xxx_rtc -  rtc driver internal structure
 * @rtc:		rtc device for this driver.
 * @rtc_alarm_irq:	rtc alarm irq number.
 * @rtc_base:		address of rtc control register.
 * @rtc_read_base:	base address of read registers.
 * @rtc_write_base:	base address of write registers.
 * @alarm_rw_base:	base address of alarm registers.
 * @ctrl_reg:		rtc control register.
 * @rtc_dev:		device structure.
 * @ctrl_reg_lock:	spinlock protecting access to ctrl_reg.
 */
struct pm8xxx_rtc {
	struct rtc_device *rtc;
	int rtc_alarm_irq;
	int rtc_base;
	int rtc_read_base;
	int rtc_write_base;
	int alarm_rw_base;
	u8 ctrl_reg;
	struct device *rtc_dev;
	spinlock_t ctrl_reg_lock;
};

/*
 * The RTC registers need to be read/written one byte at a time. This is a
 * hardware limitation.
 */
static int pm8xxx_read_wrapper(struct pm8xxx_rtc *rtc_dd, u8 *rtc_val,
			       int base, int count)
{
	int i, rc;
	struct device *parent = rtc_dd->rtc_dev->parent;

	for (i = 0; i < count; i++) {
		rc = pm8xxx_readb(parent, base + i, &rtc_val[i]);
		if (rc < 0) {
			dev_err(rtc_dd->rtc_dev, "PMIC read failed\n");
			return rc;
		}
	}

	return 0;
}

static int pm8xxx_write_wrapper(struct pm8xxx_rtc *rtc_dd, u8 *rtc_val,
				int base, int count)
{
	int i, rc;
	struct device *parent = rtc_dd->rtc_dev->parent;

	for (i = 0; i < count; i++) {
		rc = pm8xxx_writeb(parent, base + i, rtc_val[i]);
		if (rc < 0) {
			dev_err(rtc_dd->rtc_dev, "PMIC write failed\n");
			return rc;
		}
	}

	return 0;
}

/*
 * Steps to write the RTC registers.
 * 1. Disable alarm if enabled.
 * 2. Write 0x00 to LSB.
 * 3. Write Byte[1], Byte[2], Byte[3] then Byte[0].
 * 4. Enable alarm if disabled in step 1.
 */
static int pm8xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	int rc, i;
	unsigned long secs, irq_flags;
	u8 value[NUM_8_BIT_RTC_REGS], reg = 0, alarm_enabled = 0, ctrl_reg;
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	rtc_tm_to_time(tm, &secs);

	for (i = 0; i < NUM_8_BIT_RTC_REGS; i++) {
		value[i] = secs & 0xFF;
		secs >>= 8;
	}

	dev_dbg(dev, "Seconds value to be written to RTC = %lu\n", secs);

	spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);
	ctrl_reg = rtc_dd->ctrl_reg;

	if (ctrl_reg & PM8xxx_RTC_ALARM_ENABLE) {
		alarm_enabled = 1;
		ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;
		rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
					  1);
		if (rc < 0) {
			dev_err(dev, "Write to RTC control register failed\n");
			goto rtc_rw_fail;
		}
		rtc_dd->ctrl_reg = ctrl_reg;
	} else {
		spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
	}

	/* Write 0 to Byte[0] */
	reg = 0;
	rc = pm8xxx_write_wrapper(rtc_dd, &reg, rtc_dd->rtc_write_base, 1);
	if (rc < 0) {
		dev_err(dev, "Write to RTC write data register failed\n");
		goto rtc_rw_fail;
	}

	/* Write Byte[1], Byte[2], Byte[3] */
	rc = pm8xxx_write_wrapper(rtc_dd, value + 1,
				  rtc_dd->rtc_write_base + 1, 3);
	if (rc < 0) {
		dev_err(dev, "Write to RTC write data register failed\n");
		goto rtc_rw_fail;
	}

	/* Write Byte[0] */
	rc = pm8xxx_write_wrapper(rtc_dd, value, rtc_dd->rtc_write_base, 1);
	if (rc < 0) {
		dev_err(dev, "Write to RTC write data register failed\n");
		goto rtc_rw_fail;
	}

	if (alarm_enabled) {
		ctrl_reg |= PM8xxx_RTC_ALARM_ENABLE;
		rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
					  1);
		if (rc < 0) {
			dev_err(dev, "Write to RTC control register failed\n");
			goto rtc_rw_fail;
		}
		rtc_dd->ctrl_reg = ctrl_reg;
	}

rtc_rw_fail:
	if (alarm_enabled)
		spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);

	return rc;
}

static int pm8xxx_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	int rc;
	u8 value[NUM_8_BIT_RTC_REGS], reg;
	unsigned long secs;
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	rc = pm8xxx_read_wrapper(rtc_dd, value, rtc_dd->rtc_read_base,
				 NUM_8_BIT_RTC_REGS);
	if (rc < 0) {
		dev_err(dev, "RTC read data register failed\n");
		return rc;
	}

	/*
	 * Read the LSB again and check if there has been a carry over.
	 * If there is, redo the read operation.
	 */
	rc = pm8xxx_read_wrapper(rtc_dd, &reg, rtc_dd->rtc_read_base, 1);
	if (rc < 0) {
		dev_err(dev, "RTC read data register failed\n");
		return rc;
	}

	if (unlikely(reg < value[0])) {
		rc = pm8xxx_read_wrapper(rtc_dd, value,
					 rtc_dd->rtc_read_base,
					 NUM_8_BIT_RTC_REGS);
		if (rc < 0) {
			dev_err(dev, "RTC read data register failed\n");
			return rc;
		}
	}

	secs = value[0] | (value[1] << 8) | (value[2] << 16) | (value[3] << 24);

	rtc_time_to_tm(secs, tm);

	rc = rtc_valid_tm(tm);
	if (rc < 0) {
		dev_err(dev, "Invalid time read from RTC\n");
		return rc;
	}

	dev_dbg(dev, "secs = %lu, h:m:s == %d:%d:%d, d/m/y = %d/%d/%d\n",
		secs, tm->tm_hour, tm->tm_min, tm->tm_sec,
		tm->tm_mday, tm->tm_mon, tm->tm_year);

	return 0;
}

static int pm8xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
	int rc, i;
	u8 value[NUM_8_BIT_RTC_REGS], ctrl_reg;
	unsigned long secs, irq_flags;
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	rtc_tm_to_time(&alarm->time, &secs);

	for (i = 0; i < NUM_8_BIT_RTC_REGS; i++) {
		value[i] = secs & 0xFF;
		secs >>= 8;
	}

	spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);

	rc = pm8xxx_write_wrapper(rtc_dd, value, rtc_dd->alarm_rw_base,
				  NUM_8_BIT_RTC_REGS);
	if (rc < 0) {
		dev_err(dev, "Write to RTC ALARM register failed\n");
		goto rtc_rw_fail;
	}

	ctrl_reg = rtc_dd->ctrl_reg;

	if (alarm->enabled)
		ctrl_reg |= PM8xxx_RTC_ALARM_ENABLE;
	else
		ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;

	rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
	if (rc < 0) {
		dev_err(dev, "Write to RTC control register failed\n");
		goto rtc_rw_fail;
	}

	rtc_dd->ctrl_reg = ctrl_reg;

	dev_dbg(dev, "Alarm Set for h:r:s=%d:%d:%d, d/m/y=%d/%d/%d\n",
		alarm->time.tm_hour, alarm->time.tm_min,
		alarm->time.tm_sec, alarm->time.tm_mday,
		alarm->time.tm_mon, alarm->time.tm_year);
rtc_rw_fail:
	spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
	return rc;
}

static int pm8xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
	int rc;
	u8 value[NUM_8_BIT_RTC_REGS];
	unsigned long secs;
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	rc = pm8xxx_read_wrapper(rtc_dd, value, rtc_dd->alarm_rw_base,
				 NUM_8_BIT_RTC_REGS);
	if (rc < 0) {
		dev_err(dev, "RTC alarm time read failed\n");
		return rc;
	}

	secs = value[0] | (value[1] << 8) | (value[2] << 16) | (value[3] << 24);

	rtc_time_to_tm(secs, &alarm->time);

	rc = rtc_valid_tm(&alarm->time);
	if (rc < 0) {
		dev_err(dev, "Invalid alarm time read from RTC\n");
		return rc;
	}

	dev_dbg(dev, "Alarm set for - h:r:s=%d:%d:%d, d/m/y=%d/%d/%d\n",
		alarm->time.tm_hour, alarm->time.tm_min,
		alarm->time.tm_sec, alarm->time.tm_mday,
		alarm->time.tm_mon, alarm->time.tm_year);

	return 0;
}

static int pm8xxx_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
{
	int rc;
	unsigned long irq_flags;
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);
	u8 ctrl_reg;

	spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);

	ctrl_reg = rtc_dd->ctrl_reg;

	if (enable)
		ctrl_reg |= PM8xxx_RTC_ALARM_ENABLE;
	else
		ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;

	rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
	if (rc < 0) {
		dev_err(dev, "Write to RTC control register failed\n");
		goto rtc_rw_fail;
	}

	rtc_dd->ctrl_reg = ctrl_reg;

rtc_rw_fail:
	spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
	return rc;
}

static struct rtc_class_ops pm8xxx_rtc_ops = {
	.read_time	= pm8xxx_rtc_read_time,
	.set_alarm	= pm8xxx_rtc_set_alarm,
	.read_alarm	= pm8xxx_rtc_read_alarm,
	.alarm_irq_enable = pm8xxx_rtc_alarm_irq_enable,
};

static irqreturn_t pm8xxx_alarm_trigger(int irq, void *dev_id)
{
	struct pm8xxx_rtc *rtc_dd = dev_id;
	u8 ctrl_reg;
	int rc;
	unsigned long irq_flags;

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

	spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);

	/* Clear the alarm enable bit */
	ctrl_reg = rtc_dd->ctrl_reg;
	ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;

	rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
	if (rc < 0) {
		spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
		dev_err(rtc_dd->rtc_dev,
			"Write to RTC control register failed\n");
		goto rtc_alarm_handled;
	}

	rtc_dd->ctrl_reg = ctrl_reg;
	spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);

	/* Clear RTC alarm register */
	rc = pm8xxx_read_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base +
				 PM8XXX_ALARM_CTRL_OFFSET, 1);
	if (rc < 0) {
		dev_err(rtc_dd->rtc_dev,
			"RTC Alarm control register read failed\n");
		goto rtc_alarm_handled;
	}

	ctrl_reg &= ~PM8xxx_RTC_ALARM_CLEAR;
	rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base +
				  PM8XXX_ALARM_CTRL_OFFSET, 1);
	if (rc < 0)
		dev_err(rtc_dd->rtc_dev,
			"Write to RTC Alarm control register failed\n");

rtc_alarm_handled:
	return IRQ_HANDLED;
}

static int pm8xxx_rtc_probe(struct platform_device *pdev)
{
	int rc;
	u8 ctrl_reg;
	bool rtc_write_enable = false;
	struct pm8xxx_rtc *rtc_dd;
	struct resource *rtc_resource;
	const struct pm8xxx_rtc_platform_data *pdata =
						dev_get_platdata(&pdev->dev);

	if (pdata != NULL)
		rtc_write_enable = pdata->rtc_write_enable;

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

	/* Initialise spinlock to protect RTC control register */
	spin_lock_init(&rtc_dd->ctrl_reg_lock);

	rtc_dd->rtc_alarm_irq = platform_get_irq(pdev, 0);
	if (rtc_dd->rtc_alarm_irq < 0) {
		dev_err(&pdev->dev, "Alarm IRQ resource absent!\n");
		return -ENXIO;
	}

	rtc_resource = platform_get_resource_byname(pdev, IORESOURCE_IO,
						    "pmic_rtc_base");
	if (!(rtc_resource && rtc_resource->start)) {
		dev_err(&pdev->dev, "RTC IO resource absent!\n");
		return -ENXIO;
	}

	rtc_dd->rtc_base = rtc_resource->start;

	/* Setup RTC register addresses */
	rtc_dd->rtc_write_base = rtc_dd->rtc_base + PM8XXX_RTC_WRITE_OFFSET;
	rtc_dd->rtc_read_base = rtc_dd->rtc_base + PM8XXX_RTC_READ_OFFSET;
	rtc_dd->alarm_rw_base = rtc_dd->rtc_base + PM8XXX_ALARM_RW_OFFSET;

	rtc_dd->rtc_dev = &pdev->dev;

	/* Check if the RTC is on, else turn it on */
	rc = pm8xxx_read_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
	if (rc < 0) {
		dev_err(&pdev->dev, "RTC control register read failed!\n");
		return rc;
	}

	if (!(ctrl_reg & PM8xxx_RTC_ENABLE)) {
		ctrl_reg |= PM8xxx_RTC_ENABLE;
		rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
									1);
		if (rc < 0) {
			dev_err(&pdev->dev,
				"Write to RTC control register failed\n");
			return rc;
		}
	}

	rtc_dd->ctrl_reg = ctrl_reg;
	if (rtc_write_enable)
		pm8xxx_rtc_ops.set_time = pm8xxx_rtc_set_time;

	platform_set_drvdata(pdev, rtc_dd);

	/* Register the RTC device */
	rtc_dd->rtc = devm_rtc_device_register(&pdev->dev, "pm8xxx_rtc",
					       &pm8xxx_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc_dd->rtc)) {
		dev_err(&pdev->dev, "%s: RTC registration failed (%ld)\n",
			__func__, PTR_ERR(rtc_dd->rtc));
		return PTR_ERR(rtc_dd->rtc);
	}

	/* Request the alarm IRQ */
	rc = request_any_context_irq(rtc_dd->rtc_alarm_irq,
				     pm8xxx_alarm_trigger, IRQF_TRIGGER_RISING,
				     "pm8xxx_rtc_alarm", rtc_dd);
	if (rc < 0) {
		dev_err(&pdev->dev, "Request IRQ failed (%d)\n", rc);
		return rc;
	}

	device_init_wakeup(&pdev->dev, 1);

	dev_dbg(&pdev->dev, "Probe success !!\n");

	return 0;
}

static int pm8xxx_rtc_remove(struct platform_device *pdev)
{
	struct pm8xxx_rtc *rtc_dd = platform_get_drvdata(pdev);

	device_init_wakeup(&pdev->dev, 0);
	free_irq(rtc_dd->rtc_alarm_irq, rtc_dd);

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int pm8xxx_rtc_resume(struct device *dev)
{
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	if (device_may_wakeup(dev))
		disable_irq_wake(rtc_dd->rtc_alarm_irq);

	return 0;
}

static int pm8xxx_rtc_suspend(struct device *dev)
{
	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

	if (device_may_wakeup(dev))
		enable_irq_wake(rtc_dd->rtc_alarm_irq);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(pm8xxx_rtc_pm_ops,
			 pm8xxx_rtc_suspend,
			 pm8xxx_rtc_resume);

static struct platform_driver pm8xxx_rtc_driver = {
	.probe		= pm8xxx_rtc_probe,
	.remove		= pm8xxx_rtc_remove,
	.driver	= {
		.name	= PM8XXX_RTC_DEV_NAME,
		.owner	= THIS_MODULE,
		.pm	= &pm8xxx_rtc_pm_ops,
	},
};

module_platform_driver(pm8xxx_rtc_driver);

MODULE_ALIAS("platform:rtc-pm8xxx");
MODULE_DESCRIPTION("PMIC8xxx RTC driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Anirudh Ghayal <aghayal@codeaurora.org>");