// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for MediaTek SoC based RTC
 *
 * Copyright (C) 2017 Sean Wang <sean.wang@mediatek.com>
 */

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

#define MTK_RTC_DEV KBUILD_MODNAME

#define MTK_RTC_PWRCHK1         0x4
#define RTC_PWRCHK1_MAGIC       0xc6

#define MTK_RTC_PWRCHK2         0x8
#define RTC_PWRCHK2_MAGIC       0x9a

#define MTK_RTC_KEY             0xc
#define RTC_KEY_MAGIC           0x59

#define MTK_RTC_PROT1           0x10
#define RTC_PROT1_MAGIC         0xa3

#define MTK_RTC_PROT2           0x14
#define RTC_PROT2_MAGIC         0x57

#define MTK_RTC_PROT3           0x18
#define RTC_PROT3_MAGIC         0x67

#define MTK_RTC_PROT4           0x1c
#define RTC_PROT4_MAGIC         0xd2

#define MTK_RTC_CTL             0x20
#define RTC_RC_STOP             BIT(0)

#define MTK_RTC_DEBNCE          0x2c
#define RTC_DEBNCE_MASK         GENMASK(2, 0)

#define MTK_RTC_INT             0x30
#define RTC_INT_AL_STA          BIT(4)

/*
 * Ranges from 0x40 to 0x78 provide RTC time setup for year, month,
 * day of month, day of week, hour, minute and second.
 */
#define MTK_RTC_TREG(_t, _f)    (0x40 + (0x4 * (_f)) + ((_t) * 0x20))

#define MTK_RTC_AL_CTL          0x7c
#define RTC_AL_EN               BIT(0)
#define RTC_AL_ALL              GENMASK(7, 0)

/*
 * The offset is used in the translation for the year between in struct
 * rtc_time and in hardware register MTK_RTC_TREG(x,MTK_YEA)
 */
#define MTK_RTC_TM_YR_OFFSET    100

/*
 * The lowest value for the valid tm_year. RTC hardware would take incorrectly
 * tm_year 100 as not a leap year and thus it is also required being excluded
 * from the valid options.
 */
#define MTK_RTC_TM_YR_L         (MTK_RTC_TM_YR_OFFSET + 1)

/*
 * The most year the RTC can hold is 99 and the next to 99 in year register
 * would be wraparound to 0, for MT7622.
 */
#define MTK_RTC_HW_YR_LIMIT     99

/* The highest value for the valid tm_year */
#define MTK_RTC_TM_YR_H         (MTK_RTC_TM_YR_OFFSET + MTK_RTC_HW_YR_LIMIT)

/* Simple macro helps to check whether the hardware supports the tm_year */
#define MTK_RTC_TM_YR_VALID(_y) ((_y) >= MTK_RTC_TM_YR_L && \
                                 (_y) <= MTK_RTC_TM_YR_H)

/* Types of the function the RTC provides are time counter and alarm. */
enum {
        MTK_TC,
        MTK_AL,
};

/* Indexes are used for the pointer to relevant registers in MTK_RTC_TREG */
enum {
        MTK_YEA,
        MTK_MON,
        MTK_DOM,
        MTK_DOW,
        MTK_HOU,
        MTK_MIN,
        MTK_SEC
};

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

static void mtk_w32(struct mtk_rtc *rtc, u32 reg, u32 val)
{
        writel_relaxed(val, rtc->base + reg);
}

static u32 mtk_r32(struct mtk_rtc *rtc, u32 reg)
{
        return readl_relaxed(rtc->base + reg);
}

static void mtk_rmw(struct mtk_rtc *rtc, u32 reg, u32 mask, u32 set)
{
        u32 val;

        val = mtk_r32(rtc, reg);
        val &= ~mask;
        val |= set;
        mtk_w32(rtc, reg, val);
}

static void mtk_set(struct mtk_rtc *rtc, u32 reg, u32 val)
{
        mtk_rmw(rtc, reg, 0, val);
}

static void mtk_clr(struct mtk_rtc *rtc, u32 reg, u32 val)
{
        mtk_rmw(rtc, reg, val, 0);
}

static void mtk_rtc_hw_init(struct mtk_rtc *hw)
{
        /* The setup of the init sequence is for allowing RTC got to work */
        mtk_w32(hw, MTK_RTC_PWRCHK1, RTC_PWRCHK1_MAGIC);
        mtk_w32(hw, MTK_RTC_PWRCHK2, RTC_PWRCHK2_MAGIC);
        mtk_w32(hw, MTK_RTC_KEY, RTC_KEY_MAGIC);
        mtk_w32(hw, MTK_RTC_PROT1, RTC_PROT1_MAGIC);
        mtk_w32(hw, MTK_RTC_PROT2, RTC_PROT2_MAGIC);
        mtk_w32(hw, MTK_RTC_PROT3, RTC_PROT3_MAGIC);
        mtk_w32(hw, MTK_RTC_PROT4, RTC_PROT4_MAGIC);
        mtk_rmw(hw, MTK_RTC_DEBNCE, RTC_DEBNCE_MASK, 0);
        mtk_clr(hw, MTK_RTC_CTL, RTC_RC_STOP);
}

static void mtk_rtc_get_alarm_or_time(struct mtk_rtc *hw, struct rtc_time *tm,
                                      int time_alarm)
{
        u32 year, mon, mday, wday, hour, min, sec;

        /*
         * Read again until the field of the second is not changed which
         * ensures all fields in the consistent state. Note that MTK_SEC must
         * be read first. In this way, it guarantees the others remain not
         * changed when the results for two MTK_SEC consecutive reads are same.
         */
        do {
                sec = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_SEC));
                min = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_MIN));
                hour = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_HOU));
                wday = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_DOW));
                mday = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_DOM));
                mon = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_MON));
                year = mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_YEA));
        } while (sec != mtk_r32(hw, MTK_RTC_TREG(time_alarm, MTK_SEC)));

        tm->tm_sec  = sec;
        tm->tm_min  = min;
        tm->tm_hour = hour;
        tm->tm_wday = wday;
        tm->tm_mday = mday;
        tm->tm_mon  = mon - 1;

        /* Rebase to the absolute year which userspace queries */
        tm->tm_year = year + MTK_RTC_TM_YR_OFFSET;
}

static void mtk_rtc_set_alarm_or_time(struct mtk_rtc *hw, struct rtc_time *tm,
                                      int time_alarm)
{
        u32 year;

        /* Rebase to the relative year which RTC hardware requires */
        year = tm->tm_year - MTK_RTC_TM_YR_OFFSET;

        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_YEA), year);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_MON), tm->tm_mon + 1);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_DOW), tm->tm_wday);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_DOM), tm->tm_mday);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_HOU), tm->tm_hour);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_MIN), tm->tm_min);
        mtk_w32(hw, MTK_RTC_TREG(time_alarm, MTK_SEC), tm->tm_sec);
}

static irqreturn_t mtk_rtc_alarmirq(int irq, void *id)
{
        struct mtk_rtc *hw = (struct mtk_rtc *)id;
        u32 irq_sta;

        irq_sta = mtk_r32(hw, MTK_RTC_INT);
        if (irq_sta & RTC_INT_AL_STA) {
                /* Stop alarm also implicitly disables the alarm interrupt */
                mtk_w32(hw, MTK_RTC_AL_CTL, 0);
                rtc_update_irq(hw->rtc, 1, RTC_IRQF | RTC_AF);

                /* Ack alarm interrupt status */
                mtk_w32(hw, MTK_RTC_INT, RTC_INT_AL_STA);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static int mtk_rtc_gettime(struct device *dev, struct rtc_time *tm)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);

        mtk_rtc_get_alarm_or_time(hw, tm, MTK_TC);

        return 0;
}

static int mtk_rtc_settime(struct device *dev, struct rtc_time *tm)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);

        if (!MTK_RTC_TM_YR_VALID(tm->tm_year))
                return -EINVAL;

        /* Stop time counter before setting a new one*/
        mtk_set(hw, MTK_RTC_CTL, RTC_RC_STOP);

        mtk_rtc_set_alarm_or_time(hw, tm, MTK_TC);

        /* Restart the time counter */
        mtk_clr(hw, MTK_RTC_CTL, RTC_RC_STOP);

        return 0;
}

static int mtk_rtc_getalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);
        struct rtc_time *alrm_tm = &wkalrm->time;

        mtk_rtc_get_alarm_or_time(hw, alrm_tm, MTK_AL);

        wkalrm->enabled = !!(mtk_r32(hw, MTK_RTC_AL_CTL) & RTC_AL_EN);
        wkalrm->pending = !!(mtk_r32(hw, MTK_RTC_INT) & RTC_INT_AL_STA);

        return 0;
}

static int mtk_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);
        struct rtc_time *alrm_tm = &wkalrm->time;

        if (!MTK_RTC_TM_YR_VALID(alrm_tm->tm_year))
                return -EINVAL;

        /*
         * Stop the alarm also implicitly including disables interrupt before
         * setting a new one.
         */
        mtk_clr(hw, MTK_RTC_AL_CTL, RTC_AL_EN);

        /*
         * Avoid contention between mtk_rtc_setalarm and IRQ handler so that
         * disabling the interrupt and awaiting for pending IRQ handler to
         * complete.
         */
        synchronize_irq(hw->irq);

        mtk_rtc_set_alarm_or_time(hw, alrm_tm, MTK_AL);

        /* Restart the alarm with the new setup */
        mtk_w32(hw, MTK_RTC_AL_CTL, RTC_AL_ALL);

        return 0;
}

static const struct rtc_class_ops mtk_rtc_ops = {
        .read_time              = mtk_rtc_gettime,
        .set_time               = mtk_rtc_settime,
        .read_alarm             = mtk_rtc_getalarm,
        .set_alarm              = mtk_rtc_setalarm,
};

static const struct of_device_id mtk_rtc_match[] = {
        { .compatible = "mediatek,mt7622-rtc" },
        { .compatible = "mediatek,soc-rtc" },
        {},
};
MODULE_DEVICE_TABLE(of, mtk_rtc_match);

static int mtk_rtc_probe(struct platform_device *pdev)
{
        struct mtk_rtc *hw;
        int ret;

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

        platform_set_drvdata(pdev, hw);

        hw->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(hw->base))
                return PTR_ERR(hw->base);

        hw->clk = devm_clk_get(&pdev->dev, "rtc");
        if (IS_ERR(hw->clk)) {
                dev_err(&pdev->dev, "No clock\n");
                return PTR_ERR(hw->clk);
        }

        ret = clk_prepare_enable(hw->clk);
        if (ret)
                return ret;

        hw->irq = platform_get_irq(pdev, 0);
        if (hw->irq < 0) {
                ret = hw->irq;
                goto err;
        }

        ret = devm_request_irq(&pdev->dev, hw->irq, mtk_rtc_alarmirq,
                               0, dev_name(&pdev->dev), hw);
        if (ret) {
                dev_err(&pdev->dev, "Can't request IRQ\n");
                goto err;
        }

        mtk_rtc_hw_init(hw);

        device_init_wakeup(&pdev->dev, true);

        hw->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
                                           &mtk_rtc_ops, THIS_MODULE);
        if (IS_ERR(hw->rtc)) {
                ret = PTR_ERR(hw->rtc);
                dev_err(&pdev->dev, "Unable to register device\n");
                goto err;
        }

        return 0;
err:
        clk_disable_unprepare(hw->clk);

        return ret;
}

static void mtk_rtc_remove(struct platform_device *pdev)
{
        struct mtk_rtc *hw = platform_get_drvdata(pdev);

        clk_disable_unprepare(hw->clk);
}

#ifdef CONFIG_PM_SLEEP
static int mtk_rtc_suspend(struct device *dev)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                enable_irq_wake(hw->irq);

        return 0;
}

static int mtk_rtc_resume(struct device *dev)
{
        struct mtk_rtc *hw = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                disable_irq_wake(hw->irq);

        return 0;
}

static SIMPLE_DEV_PM_OPS(mtk_rtc_pm_ops, mtk_rtc_suspend, mtk_rtc_resume);

#define MTK_RTC_PM_OPS (&mtk_rtc_pm_ops)
#else   /* CONFIG_PM */
#define MTK_RTC_PM_OPS NULL
#endif  /* CONFIG_PM */

static struct platform_driver mtk_rtc_driver = {
        .probe  = mtk_rtc_probe,
        .remove = mtk_rtc_remove,
        .driver = {
                .name = MTK_RTC_DEV,
                .of_match_table = mtk_rtc_match,
                .pm = MTK_RTC_PM_OPS,
        },
};

module_platform_driver(mtk_rtc_driver);

MODULE_DESCRIPTION("MediaTek SoC based RTC Driver");
MODULE_AUTHOR("Sean Wang <sean.wang@mediatek.com>");
MODULE_LICENSE("GPL");