/*
 * 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 const 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;
        const 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(unsigned 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;
        time64_t diff;
        unsigned long time_gap;
        unsigned long time_gap_day;
        unsigned long time_gap_hour;
        unsigned long time_gap_min;
        int ret;

        ret = sunxi_rtc_gettime(dev, &tm_now);
        if (ret < 0) {
                dev_err(dev, "Error in getting time\n");
                return -EINVAL;
        }

        diff = rtc_tm_sub(alrm_tm, &tm_now);
        if (diff <= 0) {
                dev_err(dev, "Date to set in the past\n");
                return -EINVAL;
        }

        if (diff > 255 * SEC_IN_DAY) {
                dev_err(dev, "Day must be in the range 0 - 255\n");
                return -EINVAL;
        }

        time_gap = diff;
        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;

        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;
        unsigned 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 %u - %u\n",
                        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.\n");
                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.\n");
                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-a10-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;
        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\n");
                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\n");
                return ret;
        }

        chip->data_year = of_device_get_match_data(&pdev->dev);
        if (!chip->data_year) {
                dev_err(&pdev->dev, "Unable to setup RTC data\n");
                return -ENODEV;
        }

        /* 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\n");
                return PTR_ERR(chip->rtc);
        }

        dev_info(&pdev->dev, "RTC enabled\n");

        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",
                .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");