/*
   * An RTC driver for Allwinner A10/A20
   *
   * Copyright (c) 2013, Carlo Caione <carlo.caione@gmail.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License along
   * with this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
   */
  
  #include <linux/delay.h>
  #include <linux/err.h>
  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/of_address.h>
  #include <linux/of_device.h>
  #include <linux/platform_device.h>
  #include <linux/rtc.h>
  #include <linux/types.h>
  
  #define SUNXI_LOSC_CTRL				0x0000
  #define SUNXI_LOSC_CTRL_RTC_HMS_ACC		BIT(8)
  #define SUNXI_LOSC_CTRL_RTC_YMD_ACC		BIT(7)
  
  #define SUNXI_RTC_YMD				0x0004
  
  #define SUNXI_RTC_HMS				0x0008
  
  #define SUNXI_ALRM_DHMS				0x000c
  
  #define SUNXI_ALRM_EN				0x0014
  #define SUNXI_ALRM_EN_CNT_EN			BIT(8)
  
  #define SUNXI_ALRM_IRQ_EN			0x0018
  #define SUNXI_ALRM_IRQ_EN_CNT_IRQ_EN		BIT(0)
  
  #define SUNXI_ALRM_IRQ_STA			0x001c
  #define SUNXI_ALRM_IRQ_STA_CNT_IRQ_PEND		BIT(0)
  
  #define SUNXI_MASK_DH				0x0000001f
  #define SUNXI_MASK_SM				0x0000003f
  #define SUNXI_MASK_M				0x0000000f
  #define SUNXI_MASK_LY				0x00000001
  #define SUNXI_MASK_D				0x00000ffe
  #define SUNXI_MASK_M				0x0000000f
  
  #define SUNXI_GET(x, mask, shift)		(((x) & ((mask) << (shift))) \
  							>> (shift))
  
  #define SUNXI_SET(x, mask, shift)		(((x) & (mask)) << (shift))
  
  /*
   * Get date values
   */
  #define SUNXI_DATE_GET_DAY_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_DH, 0)
  #define SUNXI_DATE_GET_MON_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_M, 8)
  #define SUNXI_DATE_GET_YEAR_VALUE(x, mask)	SUNXI_GET(x, mask, 16)
  
  /*
   * Get time values
   */
  #define SUNXI_TIME_GET_SEC_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_SM, 0)
  #define SUNXI_TIME_GET_MIN_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_SM, 8)
  #define SUNXI_TIME_GET_HOUR_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_DH, 16)
  
  /*
   * Get alarm values
   */
  #define SUNXI_ALRM_GET_SEC_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_SM, 0)
  #define SUNXI_ALRM_GET_MIN_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_SM, 8)
  #define SUNXI_ALRM_GET_HOUR_VALUE(x)		SUNXI_GET(x, SUNXI_MASK_DH, 16)
  
  /*
   * Set date values
   */
  #define SUNXI_DATE_SET_DAY_VALUE(x)		SUNXI_DATE_GET_DAY_VALUE(x)
  #define SUNXI_DATE_SET_MON_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_M, 8)
  #define SUNXI_DATE_SET_YEAR_VALUE(x, mask)	SUNXI_SET(x, mask, 16)
  #define SUNXI_LEAP_SET_VALUE(x, shift)		SUNXI_SET(x, SUNXI_MASK_LY, shift)
  
  /*
   * Set time values
   */
  #define SUNXI_TIME_SET_SEC_VALUE(x)		SUNXI_TIME_GET_SEC_VALUE(x)
  #define SUNXI_TIME_SET_MIN_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_SM, 8)
  #define SUNXI_TIME_SET_HOUR_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_DH, 16)
  
  /*
   * Set alarm values
   */
  #define SUNXI_ALRM_SET_SEC_VALUE(x)		SUNXI_ALRM_GET_SEC_VALUE(x)
  #define SUNXI_ALRM_SET_MIN_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_SM, 8)
  #define SUNXI_ALRM_SET_HOUR_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_DH, 16)
  #define SUNXI_ALRM_SET_DAY_VALUE(x)		SUNXI_SET(x, SUNXI_MASK_D, 21)
  
  /*
   * Time unit conversions
   */
  #define SEC_IN_MIN				60
  #define SEC_IN_HOUR				(60 * SEC_IN_MIN)
  #define SEC_IN_DAY				(24 * SEC_IN_HOUR)
  
  /*
   * The year parameter passed to the driver is usually an offset relative to
   * the year 1900. This macro is used to convert this offset to another one
   * relative to the minimum year allowed by the hardware.
   */
  #define SUNXI_YEAR_OFF(x)			((x)->min - 1900)
  
  /*
   * min and max year are arbitrary set considering the limited range of the
   * hardware register field
   */
  struct sunxi_rtc_data_year {
  	unsigned int min;		/* min year allowed */
  	unsigned int max;		/* max year allowed */
  	unsigned int mask;		/* mask for the year field */
  	unsigned char leap_shift;	/* bit shift to get the leap year */
  };
  
  static struct sunxi_rtc_data_year data_year_param[] = {
  	[0] = {
  		.min		= 2010,
  		.max		= 2073,
  		.mask		= 0x3f,
  		.leap_shift	= 22,
  	},
  	[1] = {
  		.min		= 1970,
  		.max		= 2225,
  		.mask		= 0xff,
  		.leap_shift	= 24,
  	},
  };
  
  struct sunxi_rtc_dev {
  	struct rtc_device *rtc;
  	struct device *dev;
  	struct sunxi_rtc_data_year *data_year;
  	void __iomem *base;
  	int irq;
  };
  
  static irqreturn_t sunxi_rtc_alarmirq(int irq, void *id)
  {
  	struct sunxi_rtc_dev *chip = (struct sunxi_rtc_dev *) id;
  	u32 val;
  
  	val = readl(chip->base + SUNXI_ALRM_IRQ_STA);
  
  	if (val & SUNXI_ALRM_IRQ_STA_CNT_IRQ_PEND) {
  		val |= SUNXI_ALRM_IRQ_STA_CNT_IRQ_PEND;
  		writel(val, chip->base + SUNXI_ALRM_IRQ_STA);
  
  		rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);
  
  		return IRQ_HANDLED;
  	}
  
  	return IRQ_NONE;
  }
  
  static void sunxi_rtc_setaie(int to, struct sunxi_rtc_dev *chip)
  {
  	u32 alrm_val = 0;
  	u32 alrm_irq_val = 0;
  
  	if (to) {
  		alrm_val = readl(chip->base + SUNXI_ALRM_EN);
  		alrm_val |= SUNXI_ALRM_EN_CNT_EN;
  
  		alrm_irq_val = readl(chip->base + SUNXI_ALRM_IRQ_EN);
  		alrm_irq_val |= SUNXI_ALRM_IRQ_EN_CNT_IRQ_EN;
  	} else {
  		writel(SUNXI_ALRM_IRQ_STA_CNT_IRQ_PEND,
  				chip->base + SUNXI_ALRM_IRQ_STA);
  	}
  
  	writel(alrm_val, chip->base + SUNXI_ALRM_EN);
  	writel(alrm_irq_val, chip->base + SUNXI_ALRM_IRQ_EN);
  }
  
  static int sunxi_rtc_getalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
  {
  	struct sunxi_rtc_dev *chip = dev_get_drvdata(dev);
  	struct rtc_time *alrm_tm = &wkalrm->time;
  	u32 alrm;
  	u32 alrm_en;
  	u32 date;
  
  	alrm = readl(chip->base + SUNXI_ALRM_DHMS);
  	date = readl(chip->base + SUNXI_RTC_YMD);
  
  	alrm_tm->tm_sec = SUNXI_ALRM_GET_SEC_VALUE(alrm);
  	alrm_tm->tm_min = SUNXI_ALRM_GET_MIN_VALUE(alrm);
  	alrm_tm->tm_hour = SUNXI_ALRM_GET_HOUR_VALUE(alrm);
  
  	alrm_tm->tm_mday = SUNXI_DATE_GET_DAY_VALUE(date);
  	alrm_tm->tm_mon = SUNXI_DATE_GET_MON_VALUE(date);
  	alrm_tm->tm_year = SUNXI_DATE_GET_YEAR_VALUE(date,
  			chip->data_year->mask);
  
  	alrm_tm->tm_mon -= 1;
  
  	/*
  	 * switch from (data_year->min)-relative offset to
  	 * a (1900)-relative one
  	 */
  	alrm_tm->tm_year += SUNXI_YEAR_OFF(chip->data_year);
  
  	alrm_en = readl(chip->base + SUNXI_ALRM_IRQ_EN);
  	if (alrm_en & SUNXI_ALRM_EN_CNT_EN)
  		wkalrm->enabled = 1;
  
  	return 0;
  }
  
  static int sunxi_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
  {
  	struct sunxi_rtc_dev *chip = dev_get_drvdata(dev);
  	u32 date, time;
  
  	/*
  	 * read again in case it changes
  	 */
  	do {
  		date = readl(chip->base + SUNXI_RTC_YMD);
  		time = readl(chip->base + SUNXI_RTC_HMS);
  	} while ((date != readl(chip->base + SUNXI_RTC_YMD)) ||
  		 (time != readl(chip->base + SUNXI_RTC_HMS)));
  
  	rtc_tm->tm_sec  = SUNXI_TIME_GET_SEC_VALUE(time);
  	rtc_tm->tm_min  = SUNXI_TIME_GET_MIN_VALUE(time);
  	rtc_tm->tm_hour = SUNXI_TIME_GET_HOUR_VALUE(time);
  
  	rtc_tm->tm_mday = SUNXI_DATE_GET_DAY_VALUE(date);
  	rtc_tm->tm_mon  = SUNXI_DATE_GET_MON_VALUE(date);
  	rtc_tm->tm_year = SUNXI_DATE_GET_YEAR_VALUE(date,
  					chip->data_year->mask);
  
  	rtc_tm->tm_mon  -= 1;
  
  	/*
  	 * switch from (data_year->min)-relative offset to
  	 * a (1900)-relative one
  	 */
  	rtc_tm->tm_year += SUNXI_YEAR_OFF(chip->data_year);
  
  	return rtc_valid_tm(rtc_tm);
  }
  
  static int sunxi_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
  {
  	struct sunxi_rtc_dev *chip = dev_get_drvdata(dev);
  	struct rtc_time *alrm_tm = &wkalrm->time;
  	struct rtc_time tm_now;
  	u32 alrm = 0;
  	unsigned long time_now = 0;
  	unsigned long time_set = 0;
  	unsigned long time_gap = 0;
  	unsigned long time_gap_day = 0;
  	unsigned long time_gap_hour = 0;
  	unsigned long time_gap_min = 0;
  	int ret = 0;
  
  	ret = sunxi_rtc_gettime(dev, &tm_now);
  	if (ret < 0) {
  		dev_err(dev, "Error in getting time
  ");
  		return -EINVAL;
  	}
  
  	rtc_tm_to_time(alrm_tm, &time_set);
  	rtc_tm_to_time(&tm_now, &time_now);
  	if (time_set <= time_now) {
  		dev_err(dev, "Date to set in the past
  ");
  		return -EINVAL;
  	}
  
  	time_gap = time_set - time_now;
  	time_gap_day = time_gap / SEC_IN_DAY;
  	time_gap -= time_gap_day * SEC_IN_DAY;
  	time_gap_hour = time_gap / SEC_IN_HOUR;
  	time_gap -= time_gap_hour * SEC_IN_HOUR;
  	time_gap_min = time_gap / SEC_IN_MIN;
  	time_gap -= time_gap_min * SEC_IN_MIN;
  
  	if (time_gap_day > 255) {
  		dev_err(dev, "Day must be in the range 0 - 255
  ");
  		return -EINVAL;
  	}
  
  	sunxi_rtc_setaie(0, chip);
  	writel(0, chip->base + SUNXI_ALRM_DHMS);
  	usleep_range(100, 300);
  
  	alrm = SUNXI_ALRM_SET_SEC_VALUE(time_gap) |
  		SUNXI_ALRM_SET_MIN_VALUE(time_gap_min) |
  		SUNXI_ALRM_SET_HOUR_VALUE(time_gap_hour) |
  		SUNXI_ALRM_SET_DAY_VALUE(time_gap_day);
  	writel(alrm, chip->base + SUNXI_ALRM_DHMS);
  
  	writel(0, chip->base + SUNXI_ALRM_IRQ_EN);
  	writel(SUNXI_ALRM_IRQ_EN_CNT_IRQ_EN, chip->base + SUNXI_ALRM_IRQ_EN);
  
  	sunxi_rtc_setaie(wkalrm->enabled, chip);
  
  	return 0;
  }
  
  static int sunxi_rtc_wait(struct sunxi_rtc_dev *chip, int offset,
  			  unsigned int mask, unsigned int ms_timeout)
  {
  	const unsigned long timeout = jiffies + msecs_to_jiffies(ms_timeout);
  	u32 reg;
  
  	do {
  		reg = readl(chip->base + offset);
  		reg &= mask;
  
  		if (reg == mask)
  			return 0;
  
  	} while (time_before(jiffies, timeout));
  
  	return -ETIMEDOUT;
  }
  
  static int sunxi_rtc_settime(struct device *dev, struct rtc_time *rtc_tm)
  {
  	struct sunxi_rtc_dev *chip = dev_get_drvdata(dev);
  	u32 date = 0;
  	u32 time = 0;
  	int year;
  
  	/*
  	 * the input rtc_tm->tm_year is the offset relative to 1900. We use
  	 * the SUNXI_YEAR_OFF macro to rebase it with respect to the min year
  	 * allowed by the hardware
  	 */
  
  	year = rtc_tm->tm_year + 1900;
  	if (year < chip->data_year->min || year > chip->data_year->max) {
  		dev_err(dev, "rtc only supports year in range %d - %d
  ",
  				chip->data_year->min, chip->data_year->max);
  		return -EINVAL;
  	}
  
  	rtc_tm->tm_year -= SUNXI_YEAR_OFF(chip->data_year);
  	rtc_tm->tm_mon += 1;
  
  	date = SUNXI_DATE_SET_DAY_VALUE(rtc_tm->tm_mday) |
  		SUNXI_DATE_SET_MON_VALUE(rtc_tm->tm_mon)  |
  		SUNXI_DATE_SET_YEAR_VALUE(rtc_tm->tm_year,
  				chip->data_year->mask);
  
  	if (is_leap_year(year))
  		date |= SUNXI_LEAP_SET_VALUE(1, chip->data_year->leap_shift);
  
  	time = SUNXI_TIME_SET_SEC_VALUE(rtc_tm->tm_sec)  |
  		SUNXI_TIME_SET_MIN_VALUE(rtc_tm->tm_min)  |
  		SUNXI_TIME_SET_HOUR_VALUE(rtc_tm->tm_hour);
  
  	writel(0, chip->base + SUNXI_RTC_HMS);
  	writel(0, chip->base + SUNXI_RTC_YMD);
  
  	writel(time, chip->base + SUNXI_RTC_HMS);
  
  	/*
  	 * After writing the RTC HH-MM-SS register, the
  	 * SUNXI_LOSC_CTRL_RTC_HMS_ACC bit is set and it will not
  	 * be cleared until the real writing operation is finished
  	 */
  
  	if (sunxi_rtc_wait(chip, SUNXI_LOSC_CTRL,
  				SUNXI_LOSC_CTRL_RTC_HMS_ACC, 50)) {
  		dev_err(dev, "Failed to set rtc time.
  ");
  		return -1;
  	}
  
  	writel(date, chip->base + SUNXI_RTC_YMD);
  
  	/*
  	 * After writing the RTC YY-MM-DD register, the
  	 * SUNXI_LOSC_CTRL_RTC_YMD_ACC bit is set and it will not
  	 * be cleared until the real writing operation is finished
  	 */
  
  	if (sunxi_rtc_wait(chip, SUNXI_LOSC_CTRL,
  				SUNXI_LOSC_CTRL_RTC_YMD_ACC, 50)) {
  		dev_err(dev, "Failed to set rtc time.
  ");
  		return -1;
  	}
  
  	return 0;
  }
  
  static int sunxi_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct sunxi_rtc_dev *chip = dev_get_drvdata(dev);
  
  	if (!enabled)
  		sunxi_rtc_setaie(enabled, chip);
  
  	return 0;
  }
  
  static const struct rtc_class_ops sunxi_rtc_ops = {
  	.read_time		= sunxi_rtc_gettime,
  	.set_time		= sunxi_rtc_settime,
  	.read_alarm		= sunxi_rtc_getalarm,
  	.set_alarm		= sunxi_rtc_setalarm,
  	.alarm_irq_enable	= sunxi_rtc_alarm_irq_enable
  };
  
  static const struct of_device_id sunxi_rtc_dt_ids[] = {
  	{ .compatible = "allwinner,sun4i-rtc", .data = &data_year_param[0] },
  	{ .compatible = "allwinner,sun7i-a20-rtc", .data = &data_year_param[1] },
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, sunxi_rtc_dt_ids);
  
  static int sunxi_rtc_probe(struct platform_device *pdev)
  {
  	struct sunxi_rtc_dev *chip;
  	struct resource *res;
  	const struct of_device_id *of_id;
  	int ret;
  
  	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
  	if (!chip)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, chip);
  	chip->dev = &pdev->dev;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	chip->base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(chip->base))
  		return PTR_ERR(chip->base);
  
  	chip->irq = platform_get_irq(pdev, 0);
  	if (chip->irq < 0) {
  		dev_err(&pdev->dev, "No IRQ resource
  ");
  		return chip->irq;
  	}
  	ret = devm_request_irq(&pdev->dev, chip->irq, sunxi_rtc_alarmirq,
  			0, dev_name(&pdev->dev), chip);
  	if (ret) {
  		dev_err(&pdev->dev, "Could not request IRQ
  ");
  		return ret;
  	}
  
  	of_id = of_match_device(sunxi_rtc_dt_ids, &pdev->dev);
  	if (!of_id) {
  		dev_err(&pdev->dev, "Unable to setup RTC data
  ");
  		return -ENODEV;
  	}
  	chip->data_year = (struct sunxi_rtc_data_year *) of_id->data;
  
  	/* clear the alarm count value */
  	writel(0, chip->base + SUNXI_ALRM_DHMS);
  
  	/* disable alarm, not generate irq pending */
  	writel(0, chip->base + SUNXI_ALRM_EN);
  
  	/* disable alarm week/cnt irq, unset to cpu */
  	writel(0, chip->base + SUNXI_ALRM_IRQ_EN);
  
  	/* clear alarm week/cnt irq pending */
  	writel(SUNXI_ALRM_IRQ_STA_CNT_IRQ_PEND, chip->base +
  			SUNXI_ALRM_IRQ_STA);
  
  	chip->rtc = rtc_device_register("rtc-sunxi", &pdev->dev,
  			&sunxi_rtc_ops, THIS_MODULE);
  	if (IS_ERR(chip->rtc)) {
  		dev_err(&pdev->dev, "unable to register device
  ");
  		return PTR_ERR(chip->rtc);
  	}
  
  	dev_info(&pdev->dev, "RTC enabled
  ");
  
  	return 0;
  }
  
  static int sunxi_rtc_remove(struct platform_device *pdev)
  {
  	struct sunxi_rtc_dev *chip = platform_get_drvdata(pdev);
  
  	rtc_device_unregister(chip->rtc);
  
  	return 0;
  }
  
  static struct platform_driver sunxi_rtc_driver = {
  	.probe		= sunxi_rtc_probe,
  	.remove		= sunxi_rtc_remove,
  	.driver		= {
  		.name		= "sunxi-rtc",
  		.owner		= THIS_MODULE,
  		.of_match_table = sunxi_rtc_dt_ids,
  	},
  };
  
  module_platform_driver(sunxi_rtc_driver);
  
  MODULE_DESCRIPTION("sunxi RTC driver");
  MODULE_AUTHOR("Carlo Caione <carlo.caione@gmail.com>");
  MODULE_LICENSE("GPL");