// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * An RTC driver for Allwinner A31/A23
 *
 * Copyright (c) 2014, Chen-Yu Tsai <wens@csie.org>
 *
 * based on rtc-sunxi.c
 *
 * An RTC driver for Allwinner A10/A20
 *
 * Copyright (c) 2013, Carlo Caione <carlo.caione@gmail.com>
 */

#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/clk/sunxi-ng.h>
#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/platform_device.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/types.h>

/* Control register */
#define SUN6I_LOSC_CTRL                         0x0000
#define SUN6I_LOSC_CTRL_KEY                     (0x16aa << 16)
#define SUN6I_LOSC_CTRL_AUTO_SWT_BYPASS         BIT(15)
#define SUN6I_LOSC_CTRL_ALM_DHMS_ACC            BIT(9)
#define SUN6I_LOSC_CTRL_RTC_HMS_ACC             BIT(8)
#define SUN6I_LOSC_CTRL_RTC_YMD_ACC             BIT(7)
#define SUN6I_LOSC_CTRL_EXT_LOSC_EN             BIT(4)
#define SUN6I_LOSC_CTRL_EXT_OSC                 BIT(0)
#define SUN6I_LOSC_CTRL_ACC_MASK                GENMASK(9, 7)

#define SUN6I_LOSC_CLK_PRESCAL                  0x0008

/* RTC */
#define SUN6I_RTC_YMD                           0x0010
#define SUN6I_RTC_HMS                           0x0014

/* Alarm 0 (counter) */
#define SUN6I_ALRM_COUNTER                      0x0020
/* This holds the remaining alarm seconds on older SoCs (current value) */
#define SUN6I_ALRM_COUNTER_HMS                  0x0024
#define SUN6I_ALRM_EN                           0x0028
#define SUN6I_ALRM_EN_CNT_EN                    BIT(0)
#define SUN6I_ALRM_IRQ_EN                       0x002c
#define SUN6I_ALRM_IRQ_EN_CNT_IRQ_EN            BIT(0)
#define SUN6I_ALRM_IRQ_STA                      0x0030
#define SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND         BIT(0)

/* Alarm 1 (wall clock) */
#define SUN6I_ALRM1_EN                          0x0044
#define SUN6I_ALRM1_IRQ_EN                      0x0048
#define SUN6I_ALRM1_IRQ_STA                     0x004c
#define SUN6I_ALRM1_IRQ_STA_WEEK_IRQ_PEND       BIT(0)

/* Alarm config */
#define SUN6I_ALARM_CONFIG                      0x0050
#define SUN6I_ALARM_CONFIG_WAKEUP               BIT(0)

#define SUN6I_LOSC_OUT_GATING                   0x0060
#define SUN6I_LOSC_OUT_GATING_EN_OFFSET         0

/* General-purpose data */
#define SUN6I_GP_DATA                           0x0100
#define SUN6I_GP_DATA_SIZE                      0x20

/*
 * Get date values
 */
#define SUN6I_DATE_GET_DAY_VALUE(x)             ((x)  & 0x0000001f)
#define SUN6I_DATE_GET_MON_VALUE(x)             (((x) & 0x00000f00) >> 8)
#define SUN6I_DATE_GET_YEAR_VALUE(x)            (((x) & 0x003f0000) >> 16)
#define SUN6I_LEAP_GET_VALUE(x)                 (((x) & 0x00400000) >> 22)

/*
 * Get time values
 */
#define SUN6I_TIME_GET_SEC_VALUE(x)             ((x)  & 0x0000003f)
#define SUN6I_TIME_GET_MIN_VALUE(x)             (((x) & 0x00003f00) >> 8)
#define SUN6I_TIME_GET_HOUR_VALUE(x)            (((x) & 0x001f0000) >> 16)

/*
 * Set date values
 */
#define SUN6I_DATE_SET_DAY_VALUE(x)             ((x)       & 0x0000001f)
#define SUN6I_DATE_SET_MON_VALUE(x)             ((x) <<  8 & 0x00000f00)
#define SUN6I_DATE_SET_YEAR_VALUE(x)            ((x) << 16 & 0x003f0000)
#define SUN6I_LEAP_SET_VALUE(x)                 ((x) << 22 & 0x00400000)

/*
 * Set time values
 */
#define SUN6I_TIME_SET_SEC_VALUE(x)             ((x)       & 0x0000003f)
#define SUN6I_TIME_SET_MIN_VALUE(x)             ((x) <<  8 & 0x00003f00)
#define SUN6I_TIME_SET_HOUR_VALUE(x)            ((x) << 16 & 0x001f0000)

/*
 * 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.
 *
 * The year range is 1970 - 2033. This range is selected to match Allwinner's
 * driver, even though it is somewhat limited.
 */
#define SUN6I_YEAR_MIN                          1970
#define SUN6I_YEAR_OFF                          (SUN6I_YEAR_MIN - 1900)

#define SECS_PER_DAY                            (24 * 3600ULL)

/*
 * There are other differences between models, including:
 *
 *   - number of GPIO pins that can be configured to hold a certain level
 *   - crypto-key related registers (H5, H6)
 *   - boot process related (super standby, secondary processor entry address)
 *     registers (R40, H6)
 *   - SYS power domain controls (R40)
 *   - DCXO controls (H6)
 *   - RC oscillator calibration (H6)
 *
 * These functions are not covered by this driver.
 */
struct sun6i_rtc_clk_data {
        unsigned long rc_osc_rate;
        unsigned int fixed_prescaler : 16;
        unsigned int has_prescaler : 1;
        unsigned int has_out_clk : 1;
        unsigned int has_losc_en : 1;
        unsigned int has_auto_swt : 1;
};

#define RTC_LINEAR_DAY  BIT(0)

struct sun6i_rtc_dev {
        struct rtc_device *rtc;
        const struct sun6i_rtc_clk_data *data;
        void __iomem *base;
        int irq;
        time64_t alarm;
        unsigned long flags;

        struct clk_hw hw;
        struct clk_hw *int_osc;
        struct clk *losc;
        struct clk *ext_losc;

        spinlock_t lock;
};

static struct sun6i_rtc_dev *sun6i_rtc;

static unsigned long sun6i_rtc_osc_recalc_rate(struct clk_hw *hw,
                                               unsigned long parent_rate)
{
        struct sun6i_rtc_dev *rtc = container_of(hw, struct sun6i_rtc_dev, hw);
        u32 val = 0;

        val = readl(rtc->base + SUN6I_LOSC_CTRL);
        if (val & SUN6I_LOSC_CTRL_EXT_OSC)
                return parent_rate;

        if (rtc->data->fixed_prescaler)
                parent_rate /= rtc->data->fixed_prescaler;

        if (rtc->data->has_prescaler) {
                val = readl(rtc->base + SUN6I_LOSC_CLK_PRESCAL);
                val &= GENMASK(4, 0);
        }

        return parent_rate / (val + 1);
}

static u8 sun6i_rtc_osc_get_parent(struct clk_hw *hw)
{
        struct sun6i_rtc_dev *rtc = container_of(hw, struct sun6i_rtc_dev, hw);

        return readl(rtc->base + SUN6I_LOSC_CTRL) & SUN6I_LOSC_CTRL_EXT_OSC;
}

static int sun6i_rtc_osc_set_parent(struct clk_hw *hw, u8 index)
{
        struct sun6i_rtc_dev *rtc = container_of(hw, struct sun6i_rtc_dev, hw);
        unsigned long flags;
        u32 val;

        if (index > 1)
                return -EINVAL;

        spin_lock_irqsave(&rtc->lock, flags);
        val = readl(rtc->base + SUN6I_LOSC_CTRL);
        val &= ~SUN6I_LOSC_CTRL_EXT_OSC;
        val |= SUN6I_LOSC_CTRL_KEY;
        val |= index ? SUN6I_LOSC_CTRL_EXT_OSC : 0;
        if (rtc->data->has_losc_en) {
                val &= ~SUN6I_LOSC_CTRL_EXT_LOSC_EN;
                val |= index ? SUN6I_LOSC_CTRL_EXT_LOSC_EN : 0;
        }
        writel(val, rtc->base + SUN6I_LOSC_CTRL);
        spin_unlock_irqrestore(&rtc->lock, flags);

        return 0;
}

static const struct clk_ops sun6i_rtc_osc_ops = {
        .recalc_rate    = sun6i_rtc_osc_recalc_rate,
        .determine_rate = clk_hw_determine_rate_no_reparent,

        .get_parent     = sun6i_rtc_osc_get_parent,
        .set_parent     = sun6i_rtc_osc_set_parent,
};

static void __init sun6i_rtc_clk_init(struct device_node *node,
                                      const struct sun6i_rtc_clk_data *data)
{
        struct clk_hw_onecell_data *clk_data;
        struct sun6i_rtc_dev *rtc;
        struct clk_init_data init = {
                .ops            = &sun6i_rtc_osc_ops,
                .name           = "losc",
        };
        const char *iosc_name = "rtc-int-osc";
        const char *clkout_name = "osc32k-out";
        const char *parents[2];
        u32 reg;

        rtc = kzalloc_obj(*rtc);
        if (!rtc)
                return;

        rtc->data = data;
        clk_data = kzalloc_flex(*clk_data, hws, 3);
        if (!clk_data) {
                kfree(rtc);
                return;
        }

        spin_lock_init(&rtc->lock);

        rtc->base = of_io_request_and_map(node, 0, of_node_full_name(node));
        if (IS_ERR(rtc->base)) {
                pr_crit("Can't map RTC registers");
                goto err;
        }

        reg = SUN6I_LOSC_CTRL_KEY;
        if (rtc->data->has_auto_swt) {
                /* Bypass auto-switch to int osc, on ext losc failure */
                reg |= SUN6I_LOSC_CTRL_AUTO_SWT_BYPASS;
                writel(reg, rtc->base + SUN6I_LOSC_CTRL);
        }

        /* Switch to the external, more precise, oscillator, if present */
        if (of_property_present(node, "clocks")) {
                reg |= SUN6I_LOSC_CTRL_EXT_OSC;
                if (rtc->data->has_losc_en)
                        reg |= SUN6I_LOSC_CTRL_EXT_LOSC_EN;
        }
        writel(reg, rtc->base + SUN6I_LOSC_CTRL);

        /* Yes, I know, this is ugly. */
        sun6i_rtc = rtc;

        of_property_read_string_index(node, "clock-output-names", 2,
                                      &iosc_name);

        rtc->int_osc = clk_hw_register_fixed_rate_with_accuracy(NULL,
                                                                iosc_name,
                                                                NULL, 0,
                                                                rtc->data->rc_osc_rate,
                                                                300000000);
        if (IS_ERR(rtc->int_osc)) {
                pr_crit("Couldn't register the internal oscillator\n");
                goto err;
        }

        parents[0] = clk_hw_get_name(rtc->int_osc);
        /* If there is no external oscillator, this will be NULL and ... */
        parents[1] = of_clk_get_parent_name(node, 0);

        rtc->hw.init = &init;

        init.parent_names = parents;
        /* ... number of clock parents will be 1. */
        init.num_parents = of_clk_get_parent_count(node) + 1;
        of_property_read_string_index(node, "clock-output-names", 0,
                                      &init.name);

        rtc->losc = clk_register(NULL, &rtc->hw);
        if (IS_ERR(rtc->losc)) {
                pr_crit("Couldn't register the LOSC clock\n");
                goto err_register;
        }

        of_property_read_string_index(node, "clock-output-names", 1,
                                      &clkout_name);
        rtc->ext_losc = clk_register_gate(NULL, clkout_name, init.name,
                                          0, rtc->base + SUN6I_LOSC_OUT_GATING,
                                          SUN6I_LOSC_OUT_GATING_EN_OFFSET, 0,
                                          &rtc->lock);
        if (IS_ERR(rtc->ext_losc)) {
                pr_crit("Couldn't register the LOSC external gate\n");
                goto err_register;
        }

        clk_data->num = 3;
        clk_data->hws[0] = &rtc->hw;
        clk_data->hws[1] = __clk_get_hw(rtc->ext_losc);
        clk_data->hws[2] = rtc->int_osc;
        of_clk_add_hw_provider(node, of_clk_hw_onecell_get, clk_data);
        return;

err_register:
        clk_hw_unregister_fixed_rate(rtc->int_osc);
err:
        kfree(clk_data);
}

static const struct sun6i_rtc_clk_data sun6i_a31_rtc_data = {
        .rc_osc_rate = 667000, /* datasheet says 600 ~ 700 KHz */
        .has_prescaler = 1,
};

static void __init sun6i_a31_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun6i_a31_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun6i_a31_rtc_clk, "allwinner,sun6i-a31-rtc",
                      sun6i_a31_rtc_clk_init);

static const struct sun6i_rtc_clk_data sun8i_a23_rtc_data = {
        .rc_osc_rate = 667000, /* datasheet says 600 ~ 700 KHz */
        .has_prescaler = 1,
        .has_out_clk = 1,
};

static void __init sun8i_a23_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun8i_a23_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun8i_a23_rtc_clk, "allwinner,sun8i-a23-rtc",
                      sun8i_a23_rtc_clk_init);

static const struct sun6i_rtc_clk_data sun8i_h3_rtc_data = {
        .rc_osc_rate = 16000000,
        .fixed_prescaler = 32,
        .has_prescaler = 1,
        .has_out_clk = 1,
};

static void __init sun8i_h3_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun8i_h3_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun8i_h3_rtc_clk, "allwinner,sun8i-h3-rtc",
                      sun8i_h3_rtc_clk_init);
/* As far as we are concerned, clocks for H5 are the same as H3 */
CLK_OF_DECLARE_DRIVER(sun50i_h5_rtc_clk, "allwinner,sun50i-h5-rtc",
                      sun8i_h3_rtc_clk_init);

static const struct sun6i_rtc_clk_data sun50i_h6_rtc_data = {
        .rc_osc_rate = 16000000,
        .fixed_prescaler = 32,
        .has_prescaler = 1,
        .has_out_clk = 1,
        .has_losc_en = 1,
        .has_auto_swt = 1,
};

static void __init sun50i_h6_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun50i_h6_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun50i_h6_rtc_clk, "allwinner,sun50i-h6-rtc",
                      sun50i_h6_rtc_clk_init);

/*
 * The R40 user manual is self-conflicting on whether the prescaler is
 * fixed or configurable. The clock diagram shows it as fixed, but there
 * is also a configurable divider in the RTC block.
 */
static const struct sun6i_rtc_clk_data sun8i_r40_rtc_data = {
        .rc_osc_rate = 16000000,
        .fixed_prescaler = 512,
};
static void __init sun8i_r40_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun8i_r40_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun8i_r40_rtc_clk, "allwinner,sun8i-r40-rtc",
                      sun8i_r40_rtc_clk_init);

static const struct sun6i_rtc_clk_data sun8i_v3_rtc_data = {
        .rc_osc_rate = 32000,
        .has_out_clk = 1,
        .has_auto_swt = 1,
};

static void __init sun8i_v3_rtc_clk_init(struct device_node *node)
{
        sun6i_rtc_clk_init(node, &sun8i_v3_rtc_data);
}
CLK_OF_DECLARE_DRIVER(sun8i_v3_rtc_clk, "allwinner,sun8i-v3-rtc",
                      sun8i_v3_rtc_clk_init);

static irqreturn_t sun6i_rtc_alarmirq(int irq, void *id)
{
        struct sun6i_rtc_dev *chip = (struct sun6i_rtc_dev *) id;
        irqreturn_t ret = IRQ_NONE;
        u32 val;

        spin_lock(&chip->lock);
        val = readl(chip->base + SUN6I_ALRM_IRQ_STA);

        if (val & SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND) {
                val |= SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND;
                writel(val, chip->base + SUN6I_ALRM_IRQ_STA);

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

                ret = IRQ_HANDLED;
        }
        spin_unlock(&chip->lock);

        return ret;
}

static void sun6i_rtc_setaie(int to, struct sun6i_rtc_dev *chip)
{
        u32 alrm_val = 0;
        u32 alrm_irq_val = 0;
        u32 alrm_wake_val = 0;
        unsigned long flags;

        if (to) {
                alrm_val = SUN6I_ALRM_EN_CNT_EN;
                alrm_irq_val = SUN6I_ALRM_IRQ_EN_CNT_IRQ_EN;
                alrm_wake_val = SUN6I_ALARM_CONFIG_WAKEUP;
        } else {
                writel(SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND,
                       chip->base + SUN6I_ALRM_IRQ_STA);
        }

        spin_lock_irqsave(&chip->lock, flags);
        writel(alrm_val, chip->base + SUN6I_ALRM_EN);
        writel(alrm_irq_val, chip->base + SUN6I_ALRM_IRQ_EN);
        writel(alrm_wake_val, chip->base + SUN6I_ALARM_CONFIG);
        spin_unlock_irqrestore(&chip->lock, flags);
}

static int sun6i_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
        u32 date, time;

        /*
         * read again in case it changes
         */
        do {
                date = readl(chip->base + SUN6I_RTC_YMD);
                time = readl(chip->base + SUN6I_RTC_HMS);
        } while ((date != readl(chip->base + SUN6I_RTC_YMD)) ||
                 (time != readl(chip->base + SUN6I_RTC_HMS)));

        if (chip->flags & RTC_LINEAR_DAY) {
                /*
                 * Newer chips store a linear day number, the manual
                 * does not mandate any epoch base. The BSP driver uses
                 * the UNIX epoch, let's just copy that, as it's the
                 * easiest anyway.
                 */
                rtc_time64_to_tm((date & 0xffff) * SECS_PER_DAY, rtc_tm);
        } else {
                rtc_tm->tm_mday = SUN6I_DATE_GET_DAY_VALUE(date);
                rtc_tm->tm_mon  = SUN6I_DATE_GET_MON_VALUE(date) - 1;
                rtc_tm->tm_year = SUN6I_DATE_GET_YEAR_VALUE(date);

                /*
                 * switch from (data_year->min)-relative offset to
                 * a (1900)-relative one
                 */
                rtc_tm->tm_year += SUN6I_YEAR_OFF;
        }

        rtc_tm->tm_sec  = SUN6I_TIME_GET_SEC_VALUE(time);
        rtc_tm->tm_min  = SUN6I_TIME_GET_MIN_VALUE(time);
        rtc_tm->tm_hour = SUN6I_TIME_GET_HOUR_VALUE(time);

        return 0;
}

static int sun6i_rtc_getalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
        unsigned long flags;
        u32 alrm_st;
        u32 alrm_en;

        spin_lock_irqsave(&chip->lock, flags);
        alrm_en = readl(chip->base + SUN6I_ALRM_IRQ_EN);
        alrm_st = readl(chip->base + SUN6I_ALRM_IRQ_STA);
        spin_unlock_irqrestore(&chip->lock, flags);

        wkalrm->enabled = !!(alrm_en & SUN6I_ALRM_EN_CNT_EN);
        wkalrm->pending = !!(alrm_st & SUN6I_ALRM_EN_CNT_EN);
        rtc_time64_to_tm(chip->alarm, &wkalrm->time);

        return 0;
}

static int sun6i_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
        struct rtc_time *alrm_tm = &wkalrm->time;
        struct rtc_time tm_now;
        time64_t time_set;
        u32 counter_val, counter_val_hms;
        int ret;

        time_set = rtc_tm_to_time64(alrm_tm);

        if (chip->flags & RTC_LINEAR_DAY) {
                /*
                 * The alarm registers hold the actual alarm time, encoded
                 * in the same way (linear day + HMS) as the current time.
                 */
                counter_val_hms = SUN6I_TIME_SET_SEC_VALUE(alrm_tm->tm_sec)  |
                                  SUN6I_TIME_SET_MIN_VALUE(alrm_tm->tm_min)  |
                                  SUN6I_TIME_SET_HOUR_VALUE(alrm_tm->tm_hour);
                /* The division will cut off the H:M:S part of alrm_tm. */
                counter_val = div_u64(rtc_tm_to_time64(alrm_tm), SECS_PER_DAY);
        } else {
                /* The alarm register holds the number of seconds left. */
                time64_t time_now;

                ret = sun6i_rtc_gettime(dev, &tm_now);
                if (ret < 0) {
                        dev_err(dev, "Error in getting time\n");
                        return -EINVAL;
                }

                time_now = rtc_tm_to_time64(&tm_now);
                if (time_set <= time_now) {
                        dev_err(dev, "Date to set in the past\n");
                        return -EINVAL;
                }
                if ((time_set - time_now) > U32_MAX) {
                        dev_err(dev, "Date too far in the future\n");
                        return -EINVAL;
                }

                counter_val = time_set - time_now;
        }

        sun6i_rtc_setaie(0, chip);
        writel(0, chip->base + SUN6I_ALRM_COUNTER);
        if (chip->flags & RTC_LINEAR_DAY)
                writel(0, chip->base + SUN6I_ALRM_COUNTER_HMS);
        usleep_range(100, 300);

        writel(counter_val, chip->base + SUN6I_ALRM_COUNTER);
        if (chip->flags & RTC_LINEAR_DAY)
                writel(counter_val_hms, chip->base + SUN6I_ALRM_COUNTER_HMS);
        chip->alarm = time_set;

        sun6i_rtc_setaie(wkalrm->enabled, chip);

        return 0;
}

static int sun6i_rtc_wait(struct sun6i_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)
                        return 0;

        } while (time_before(jiffies, timeout));

        return -ETIMEDOUT;
}

static int sun6i_rtc_settime(struct device *dev, struct rtc_time *rtc_tm)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
        u32 date = 0;
        u32 time = 0;

        time = SUN6I_TIME_SET_SEC_VALUE(rtc_tm->tm_sec)  |
                SUN6I_TIME_SET_MIN_VALUE(rtc_tm->tm_min)  |
                SUN6I_TIME_SET_HOUR_VALUE(rtc_tm->tm_hour);

        if (chip->flags & RTC_LINEAR_DAY) {
                /* The division will cut off the H:M:S part of rtc_tm. */
                date = div_u64(rtc_tm_to_time64(rtc_tm), SECS_PER_DAY);
        } else {
                rtc_tm->tm_year -= SUN6I_YEAR_OFF;
                rtc_tm->tm_mon += 1;

                date = SUN6I_DATE_SET_DAY_VALUE(rtc_tm->tm_mday) |
                        SUN6I_DATE_SET_MON_VALUE(rtc_tm->tm_mon)  |
                        SUN6I_DATE_SET_YEAR_VALUE(rtc_tm->tm_year);

                if (is_leap_year(rtc_tm->tm_year + SUN6I_YEAR_MIN))
                        date |= SUN6I_LEAP_SET_VALUE(1);
        }

        /* Check whether registers are writable */
        if (sun6i_rtc_wait(chip, SUN6I_LOSC_CTRL,
                           SUN6I_LOSC_CTRL_ACC_MASK, 50)) {
                dev_err(dev, "rtc is still busy.\n");
                return -EBUSY;
        }

        writel(time, chip->base + SUN6I_RTC_HMS);

        /*
         * After writing the RTC HH-MM-SS register, the
         * SUN6I_LOSC_CTRL_RTC_HMS_ACC bit is set and it will not
         * be cleared until the real writing operation is finished
         */

        if (sun6i_rtc_wait(chip, SUN6I_LOSC_CTRL,
                           SUN6I_LOSC_CTRL_RTC_HMS_ACC, 50)) {
                dev_err(dev, "Failed to set rtc time.\n");
                return -ETIMEDOUT;
        }

        writel(date, chip->base + SUN6I_RTC_YMD);

        /*
         * After writing the RTC YY-MM-DD register, the
         * SUN6I_LOSC_CTRL_RTC_YMD_ACC bit is set and it will not
         * be cleared until the real writing operation is finished
         */

        if (sun6i_rtc_wait(chip, SUN6I_LOSC_CTRL,
                           SUN6I_LOSC_CTRL_RTC_YMD_ACC, 50)) {
                dev_err(dev, "Failed to set rtc time.\n");
                return -ETIMEDOUT;
        }

        return 0;
}

static int sun6i_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);

        if (!enabled)
                sun6i_rtc_setaie(enabled, chip);

        return 0;
}

static const struct rtc_class_ops sun6i_rtc_ops = {
        .read_time              = sun6i_rtc_gettime,
        .set_time               = sun6i_rtc_settime,
        .read_alarm             = sun6i_rtc_getalarm,
        .set_alarm              = sun6i_rtc_setalarm,
        .alarm_irq_enable       = sun6i_rtc_alarm_irq_enable
};

static int sun6i_rtc_nvmem_read(void *priv, unsigned int offset, void *_val, size_t bytes)
{
        struct sun6i_rtc_dev *chip = priv;
        u32 *val = _val;
        int i;

        for (i = 0; i < bytes / 4; ++i)
                val[i] = readl(chip->base + SUN6I_GP_DATA + offset + 4 * i);

        return 0;
}

static int sun6i_rtc_nvmem_write(void *priv, unsigned int offset, void *_val, size_t bytes)
{
        struct sun6i_rtc_dev *chip = priv;
        u32 *val = _val;
        int i;

        for (i = 0; i < bytes / 4; ++i)
                writel(val[i], chip->base + SUN6I_GP_DATA + offset + 4 * i);

        return 0;
}

static struct nvmem_config sun6i_rtc_nvmem_cfg = {
        .type           = NVMEM_TYPE_BATTERY_BACKED,
        .reg_read       = sun6i_rtc_nvmem_read,
        .reg_write      = sun6i_rtc_nvmem_write,
        .size           = SUN6I_GP_DATA_SIZE,
        .word_size      = 4,
        .stride         = 4,
};

#ifdef CONFIG_PM_SLEEP
/* Enable IRQ wake on suspend, to wake up from RTC. */
static int sun6i_rtc_suspend(struct device *dev)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);

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

        return 0;
}

/* Disable IRQ wake on resume. */
static int sun6i_rtc_resume(struct device *dev)
{
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);

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

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(sun6i_rtc_pm_ops,
        sun6i_rtc_suspend, sun6i_rtc_resume);

static void sun6i_rtc_bus_clk_cleanup(void *data)
{
        struct clk *bus_clk = data;

        clk_disable_unprepare(bus_clk);
}

static int sun6i_rtc_probe(struct platform_device *pdev)
{
        struct sun6i_rtc_dev *chip = sun6i_rtc;
        struct device *dev = &pdev->dev;
        struct clk *bus_clk;
        int ret;

        bus_clk = devm_clk_get_optional(dev, "bus");
        if (IS_ERR(bus_clk))
                return PTR_ERR(bus_clk);

        if (bus_clk) {
                ret = clk_prepare_enable(bus_clk);
                if (ret)
                        return ret;

                ret = devm_add_action_or_reset(dev, sun6i_rtc_bus_clk_cleanup,
                                               bus_clk);
                if (ret)
                        return ret;
        }

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

                spin_lock_init(&chip->lock);

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

                if (IS_REACHABLE(CONFIG_SUN6I_RTC_CCU)) {
                        ret = sun6i_rtc_ccu_probe(dev, chip->base);
                        if (ret)
                                return ret;
                }
        }

        platform_set_drvdata(pdev, chip);

        chip->flags = (unsigned long)of_device_get_match_data(&pdev->dev);

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

        ret = devm_request_irq(&pdev->dev, chip->irq, sun6i_rtc_alarmirq,
                               0, dev_name(&pdev->dev), chip);
        if (ret) {
                dev_err(&pdev->dev, "Could not request IRQ\n");
                return ret;
        }

        /* clear the alarm counter value */
        writel(0, chip->base + SUN6I_ALRM_COUNTER);

        /* disable counter alarm */
        writel(0, chip->base + SUN6I_ALRM_EN);

        /* disable counter alarm interrupt */
        writel(0, chip->base + SUN6I_ALRM_IRQ_EN);

        /* disable week alarm */
        writel(0, chip->base + SUN6I_ALRM1_EN);

        /* disable week alarm interrupt */
        writel(0, chip->base + SUN6I_ALRM1_IRQ_EN);

        /* clear counter alarm pending interrupts */
        writel(SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND,
               chip->base + SUN6I_ALRM_IRQ_STA);

        /* clear week alarm pending interrupts */
        writel(SUN6I_ALRM1_IRQ_STA_WEEK_IRQ_PEND,
               chip->base + SUN6I_ALRM1_IRQ_STA);

        /* disable alarm wakeup */
        writel(0, chip->base + SUN6I_ALARM_CONFIG);

        clk_prepare_enable(chip->losc);

        device_init_wakeup(&pdev->dev, true);

        chip->rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(chip->rtc))
                return PTR_ERR(chip->rtc);

        chip->rtc->ops = &sun6i_rtc_ops;
        if (chip->flags & RTC_LINEAR_DAY)
                chip->rtc->range_max = (65536 * SECS_PER_DAY) - 1;
        else
                chip->rtc->range_max = 2019686399LL; /* 2033-12-31 23:59:59 */

        ret = devm_rtc_register_device(chip->rtc);
        if (ret)
                return ret;

        sun6i_rtc_nvmem_cfg.priv = chip;
        ret = devm_rtc_nvmem_register(chip->rtc, &sun6i_rtc_nvmem_cfg);
        if (ret)
                return ret;

        return 0;
}

/*
 * As far as RTC functionality goes, all models are the same. The
 * datasheets claim that different models have different number of
 * registers available for non-volatile storage, but experiments show
 * that all SoCs have 16 registers available for this purpose.
 */
static const struct of_device_id sun6i_rtc_dt_ids[] = {
        { .compatible = "allwinner,sun6i-a31-rtc" },
        { .compatible = "allwinner,sun8i-a23-rtc" },
        { .compatible = "allwinner,sun8i-h3-rtc" },
        { .compatible = "allwinner,sun8i-r40-rtc" },
        { .compatible = "allwinner,sun8i-v3-rtc" },
        { .compatible = "allwinner,sun50i-h5-rtc" },
        { .compatible = "allwinner,sun50i-h6-rtc" },
        { .compatible = "allwinner,sun50i-h616-rtc",
                .data = (void *)RTC_LINEAR_DAY },
        { .compatible = "allwinner,sun50i-r329-rtc",
                .data = (void *)RTC_LINEAR_DAY },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, sun6i_rtc_dt_ids);

static struct platform_driver sun6i_rtc_driver = {
        .probe          = sun6i_rtc_probe,
        .driver         = {
                .name           = "sun6i-rtc",
                .of_match_table = sun6i_rtc_dt_ids,
                .pm = &sun6i_rtc_pm_ops,
        },
};
builtin_platform_driver(sun6i_rtc_driver);