// SPDX-License-Identifier: GPL-2.0-only
/*
 * RTC Driver for X-Powers AC100
 *
 * Copyright (c) 2016 Chen-Yu Tsai
 *
 * Chen-Yu Tsai <wens@csie.org>
 */

#include <linux/bcd.h>
#include <linux/clk-provider.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/mfd/ac100.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
#include <linux/types.h>

/* Control register */
#define AC100_RTC_CTRL_24HOUR   BIT(0)

/* Clock output register bits */
#define AC100_CLKOUT_PRE_DIV_SHIFT      5
#define AC100_CLKOUT_PRE_DIV_WIDTH      3
#define AC100_CLKOUT_MUX_SHIFT          4
#define AC100_CLKOUT_MUX_WIDTH          1
#define AC100_CLKOUT_DIV_SHIFT          1
#define AC100_CLKOUT_DIV_WIDTH          3
#define AC100_CLKOUT_EN                 BIT(0)

/* RTC */
#define AC100_RTC_SEC_MASK      GENMASK(6, 0)
#define AC100_RTC_MIN_MASK      GENMASK(6, 0)
#define AC100_RTC_HOU_MASK      GENMASK(5, 0)
#define AC100_RTC_WEE_MASK      GENMASK(2, 0)
#define AC100_RTC_DAY_MASK      GENMASK(5, 0)
#define AC100_RTC_MON_MASK      GENMASK(4, 0)
#define AC100_RTC_YEA_MASK      GENMASK(7, 0)
#define AC100_RTC_YEA_LEAP      BIT(15)
#define AC100_RTC_UPD_TRIGGER   BIT(15)

/* Alarm (wall clock) */
#define AC100_ALM_INT_ENABLE    BIT(0)

#define AC100_ALM_SEC_MASK      GENMASK(6, 0)
#define AC100_ALM_MIN_MASK      GENMASK(6, 0)
#define AC100_ALM_HOU_MASK      GENMASK(5, 0)
#define AC100_ALM_WEE_MASK      GENMASK(2, 0)
#define AC100_ALM_DAY_MASK      GENMASK(5, 0)
#define AC100_ALM_MON_MASK      GENMASK(4, 0)
#define AC100_ALM_YEA_MASK      GENMASK(7, 0)
#define AC100_ALM_ENABLE_FLAG   BIT(15)
#define AC100_ALM_UPD_TRIGGER   BIT(15)

/*
 * 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 - 2069. This range is selected to match Allwinner's
 * driver.
 */
#define AC100_YEAR_MIN                          1970
#define AC100_YEAR_MAX                          2069
#define AC100_YEAR_OFF                          (AC100_YEAR_MIN - 1900)

struct ac100_clkout {
        struct clk_hw hw;
        struct regmap *regmap;
        u8 offset;
};

#define to_ac100_clkout(_hw) container_of(_hw, struct ac100_clkout, hw)

#define AC100_RTC_32K_NAME      "ac100-rtc-32k"
#define AC100_RTC_32K_RATE      32768
#define AC100_CLKOUT_NUM        3

static const char * const ac100_clkout_names[AC100_CLKOUT_NUM] = {
        "ac100-cko1-rtc",
        "ac100-cko2-rtc",
        "ac100-cko3-rtc",
};

struct ac100_rtc_dev {
        struct rtc_device *rtc;
        struct device *dev;
        struct regmap *regmap;
        int irq;
        unsigned long alarm;

        struct clk_hw *rtc_32k_clk;
        struct ac100_clkout clks[AC100_CLKOUT_NUM];
        struct clk_hw_onecell_data *clk_data;
};

/**
 * Clock controls for 3 clock output pins
 */

static const struct clk_div_table ac100_clkout_prediv[] = {
        { .val = 0, .div = 1 },
        { .val = 1, .div = 2 },
        { .val = 2, .div = 4 },
        { .val = 3, .div = 8 },
        { .val = 4, .div = 16 },
        { .val = 5, .div = 32 },
        { .val = 6, .div = 64 },
        { .val = 7, .div = 122 },
        { },
};

/* Abuse the fact that one parent is 32768 Hz, and the other is 4 MHz */
static unsigned long ac100_clkout_recalc_rate(struct clk_hw *hw,
                                              unsigned long prate)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);
        unsigned int reg, div;

        regmap_read(clk->regmap, clk->offset, &reg);

        /* Handle pre-divider first */
        if (prate != AC100_RTC_32K_RATE) {
                div = (reg >> AC100_CLKOUT_PRE_DIV_SHIFT) &
                        ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1);
                prate = divider_recalc_rate(hw, prate, div,
                                            ac100_clkout_prediv, 0,
                                            AC100_CLKOUT_PRE_DIV_WIDTH);
        }

        div = (reg >> AC100_CLKOUT_DIV_SHIFT) &
                (BIT(AC100_CLKOUT_DIV_WIDTH) - 1);
        return divider_recalc_rate(hw, prate, div, NULL,
                                   CLK_DIVIDER_POWER_OF_TWO,
                                   AC100_CLKOUT_DIV_WIDTH);
}

static long ac100_clkout_round_rate(struct clk_hw *hw, unsigned long rate,
                                    unsigned long prate)
{
        unsigned long best_rate = 0, tmp_rate, tmp_prate;
        int i;

        if (prate == AC100_RTC_32K_RATE)
                return divider_round_rate(hw, rate, &prate, NULL,
                                          AC100_CLKOUT_DIV_WIDTH,
                                          CLK_DIVIDER_POWER_OF_TWO);

        for (i = 0; ac100_clkout_prediv[i].div; i++) {
                tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[i].val);
                tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
                                              AC100_CLKOUT_DIV_WIDTH,
                                              CLK_DIVIDER_POWER_OF_TWO);

                if (tmp_rate > rate)
                        continue;
                if (rate - tmp_rate < best_rate - tmp_rate)
                        best_rate = tmp_rate;
        }

        return best_rate;
}

static int ac100_clkout_determine_rate(struct clk_hw *hw,
                                       struct clk_rate_request *req)
{
        struct clk_hw *best_parent;
        unsigned long best = 0;
        int i, num_parents = clk_hw_get_num_parents(hw);

        for (i = 0; i < num_parents; i++) {
                struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
                unsigned long tmp, prate;

                /*
                 * The clock has two parents, one is a fixed clock which is
                 * internally registered by the ac100 driver. The other parent
                 * is a clock from the codec side of the chip, which we
                 * properly declare and reference in the devicetree and is
                 * not implemented in any driver right now.
                 * If the clock core looks for the parent of that second
                 * missing clock, it can't find one that is registered and
                 * returns NULL.
                 * So we end up in a situation where clk_hw_get_num_parents
                 * returns the amount of clocks we can be parented to, but
                 * clk_hw_get_parent_by_index will not return the orphan
                 * clocks.
                 * Thus we need to check if the parent exists before
                 * we get the parent rate, so we could use the RTC
                 * without waiting for the codec to be supported.
                 */
                if (!parent)
                        continue;

                prate = clk_hw_get_rate(parent);

                tmp = ac100_clkout_round_rate(hw, req->rate, prate);

                if (tmp > req->rate)
                        continue;
                if (req->rate - tmp < req->rate - best) {
                        best = tmp;
                        best_parent = parent;
                }
        }

        if (!best)
                return -EINVAL;

        req->best_parent_hw = best_parent;
        req->best_parent_rate = best;
        req->rate = best;

        return 0;
}

static int ac100_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
                                 unsigned long prate)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);
        int div = 0, pre_div = 0;

        do {
                div = divider_get_val(rate * ac100_clkout_prediv[pre_div].div,
                                      prate, NULL, AC100_CLKOUT_DIV_WIDTH,
                                      CLK_DIVIDER_POWER_OF_TWO);
                if (div >= 0)
                        break;
        } while (prate != AC100_RTC_32K_RATE &&
                 ac100_clkout_prediv[++pre_div].div);

        if (div < 0)
                return div;

        pre_div = ac100_clkout_prediv[pre_div].val;

        regmap_update_bits(clk->regmap, clk->offset,
                           ((1 << AC100_CLKOUT_DIV_WIDTH) - 1) << AC100_CLKOUT_DIV_SHIFT |
                           ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
                           (div - 1) << AC100_CLKOUT_DIV_SHIFT |
                           (pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);

        return 0;
}

static int ac100_clkout_prepare(struct clk_hw *hw)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);

        return regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN,
                                  AC100_CLKOUT_EN);
}

static void ac100_clkout_unprepare(struct clk_hw *hw)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);

        regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN, 0);
}

static int ac100_clkout_is_prepared(struct clk_hw *hw)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);
        unsigned int reg;

        regmap_read(clk->regmap, clk->offset, &reg);

        return reg & AC100_CLKOUT_EN;
}

static u8 ac100_clkout_get_parent(struct clk_hw *hw)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);
        unsigned int reg;

        regmap_read(clk->regmap, clk->offset, &reg);

        return (reg >> AC100_CLKOUT_MUX_SHIFT) & 0x1;
}

static int ac100_clkout_set_parent(struct clk_hw *hw, u8 index)
{
        struct ac100_clkout *clk = to_ac100_clkout(hw);

        return regmap_update_bits(clk->regmap, clk->offset,
                                  BIT(AC100_CLKOUT_MUX_SHIFT),
                                  index ? BIT(AC100_CLKOUT_MUX_SHIFT) : 0);
}

static const struct clk_ops ac100_clkout_ops = {
        .prepare        = ac100_clkout_prepare,
        .unprepare      = ac100_clkout_unprepare,
        .is_prepared    = ac100_clkout_is_prepared,
        .recalc_rate    = ac100_clkout_recalc_rate,
        .determine_rate = ac100_clkout_determine_rate,
        .get_parent     = ac100_clkout_get_parent,
        .set_parent     = ac100_clkout_set_parent,
        .set_rate       = ac100_clkout_set_rate,
};

static int ac100_rtc_register_clks(struct ac100_rtc_dev *chip)
{
        struct device_node *np = chip->dev->of_node;
        const char *parents[2] = {AC100_RTC_32K_NAME};
        int i, ret;

        chip->clk_data = devm_kzalloc(chip->dev,
                                      struct_size(chip->clk_data, hws,
                                                  AC100_CLKOUT_NUM),
                                      GFP_KERNEL);
        if (!chip->clk_data)
                return -ENOMEM;

        chip->rtc_32k_clk = clk_hw_register_fixed_rate(chip->dev,
                                                       AC100_RTC_32K_NAME,
                                                       NULL, 0,
                                                       AC100_RTC_32K_RATE);
        if (IS_ERR(chip->rtc_32k_clk)) {
                ret = PTR_ERR(chip->rtc_32k_clk);
                dev_err(chip->dev, "Failed to register RTC-32k clock: %d\n",
                        ret);
                return ret;
        }

        parents[1] = of_clk_get_parent_name(np, 0);
        if (!parents[1]) {
                dev_err(chip->dev, "Failed to get ADDA 4M clock\n");
                return -EINVAL;
        }

        for (i = 0; i < AC100_CLKOUT_NUM; i++) {
                struct ac100_clkout *clk = &chip->clks[i];
                struct clk_init_data init = {
                        .name = ac100_clkout_names[i],
                        .ops = &ac100_clkout_ops,
                        .parent_names = parents,
                        .num_parents = ARRAY_SIZE(parents),
                        .flags = 0,
                };

                of_property_read_string_index(np, "clock-output-names",
                                              i, &init.name);
                clk->regmap = chip->regmap;
                clk->offset = AC100_CLKOUT_CTRL1 + i;
                clk->hw.init = &init;

                ret = devm_clk_hw_register(chip->dev, &clk->hw);
                if (ret) {
                        dev_err(chip->dev, "Failed to register clk '%s': %d\n",
                                init.name, ret);
                        goto err_unregister_rtc_32k;
                }

                chip->clk_data->hws[i] = &clk->hw;
        }

        chip->clk_data->num = i;
        ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get, chip->clk_data);
        if (ret)
                goto err_unregister_rtc_32k;

        return 0;

err_unregister_rtc_32k:
        clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);

        return ret;
}

static void ac100_rtc_unregister_clks(struct ac100_rtc_dev *chip)
{
        of_clk_del_provider(chip->dev->of_node);
        clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
}

/**
 * RTC related bits
 */
static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
{
        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
        struct regmap *regmap = chip->regmap;
        u16 reg[7];
        int ret;

        ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
        if (ret)
                return ret;

        rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
        rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
        rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
        rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
        rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
        rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK) - 1;
        rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK) +
                          AC100_YEAR_OFF;

        return 0;
}

static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
{
        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
        struct regmap *regmap = chip->regmap;
        int year;
        u16 reg[8];

        /* our RTC has a limited year range... */
        year = rtc_tm->tm_year - AC100_YEAR_OFF;
        if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
                dev_err(dev, "rtc only supports year in range %d - %d\n",
                        AC100_YEAR_MIN, AC100_YEAR_MAX);
                return -EINVAL;
        }

        /* convert to BCD */
        reg[0] = bin2bcd(rtc_tm->tm_sec)     & AC100_RTC_SEC_MASK;
        reg[1] = bin2bcd(rtc_tm->tm_min)     & AC100_RTC_MIN_MASK;
        reg[2] = bin2bcd(rtc_tm->tm_hour)    & AC100_RTC_HOU_MASK;
        reg[3] = bin2bcd(rtc_tm->tm_wday)    & AC100_RTC_WEE_MASK;
        reg[4] = bin2bcd(rtc_tm->tm_mday)    & AC100_RTC_DAY_MASK;
        reg[5] = bin2bcd(rtc_tm->tm_mon + 1) & AC100_RTC_MON_MASK;
        reg[6] = bin2bcd(year)               & AC100_RTC_YEA_MASK;
        /* trigger write */
        reg[7] = AC100_RTC_UPD_TRIGGER;

        /* Is it a leap year? */
        if (is_leap_year(year + AC100_YEAR_OFF + 1900))
                reg[6] |= AC100_RTC_YEA_LEAP;

        return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
}

static int ac100_rtc_alarm_irq_enable(struct device *dev, unsigned int en)
{
        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
        struct regmap *regmap = chip->regmap;
        unsigned int val;

        val = en ? AC100_ALM_INT_ENABLE : 0;

        return regmap_write(regmap, AC100_ALM_INT_ENA, val);
}

static int ac100_rtc_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
        struct regmap *regmap = chip->regmap;
        struct rtc_time *alrm_tm = &alrm->time;
        u16 reg[7];
        unsigned int val;
        int ret;

        ret = regmap_read(regmap, AC100_ALM_INT_ENA, &val);
        if (ret)
                return ret;

        alrm->enabled = !!(val & AC100_ALM_INT_ENABLE);

        ret = regmap_bulk_read(regmap, AC100_ALM_SEC, reg, 7);
        if (ret)
                return ret;

        alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
        alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
        alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
        alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
        alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
        alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK) - 1;
        alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK) +
                           AC100_YEAR_OFF;

        return 0;
}

static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
        struct regmap *regmap = chip->regmap;
        struct rtc_time *alrm_tm = &alrm->time;
        u16 reg[8];
        int year;
        int ret;

        /* our alarm has a limited year range... */
        year = alrm_tm->tm_year - AC100_YEAR_OFF;
        if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
                dev_err(dev, "alarm only supports year in range %d - %d\n",
                        AC100_YEAR_MIN, AC100_YEAR_MAX);
                return -EINVAL;
        }

        /* convert to BCD */
        reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        /* Do not enable weekday alarm */
        reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
        reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        reg[5] = (bin2bcd(alrm_tm->tm_mon + 1)  & AC100_ALM_MON_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        reg[6] = (bin2bcd(year) & AC100_ALM_YEA_MASK) |
                        AC100_ALM_ENABLE_FLAG;
        /* trigger write */
        reg[7] = AC100_ALM_UPD_TRIGGER;

        ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
        if (ret)
                return ret;

        return ac100_rtc_alarm_irq_enable(dev, alrm->enabled);
}

static irqreturn_t ac100_rtc_irq(int irq, void *data)
{
        struct ac100_rtc_dev *chip = data;
        struct regmap *regmap = chip->regmap;
        unsigned int val = 0;
        int ret;

        rtc_lock(chip->rtc);

        /* read status */
        ret = regmap_read(regmap, AC100_ALM_INT_STA, &val);
        if (ret)
                goto out;

        if (val & AC100_ALM_INT_ENABLE) {
                /* signal rtc framework */
                rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);

                /* clear status */
                ret = regmap_write(regmap, AC100_ALM_INT_STA, val);
                if (ret)
                        goto out;

                /* disable interrupt */
                ret = ac100_rtc_alarm_irq_enable(chip->dev, 0);
                if (ret)
                        goto out;
        }

out:
        rtc_unlock(chip->rtc);
        return IRQ_HANDLED;
}

static const struct rtc_class_ops ac100_rtc_ops = {
        .read_time        = ac100_rtc_get_time,
        .set_time         = ac100_rtc_set_time,
        .read_alarm       = ac100_rtc_get_alarm,
        .set_alarm        = ac100_rtc_set_alarm,
        .alarm_irq_enable = ac100_rtc_alarm_irq_enable,
};

static int ac100_rtc_probe(struct platform_device *pdev)
{
        struct ac100_dev *ac100 = dev_get_drvdata(pdev->dev.parent);
        struct ac100_rtc_dev *chip;
        int ret;

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

        platform_set_drvdata(pdev, chip);
        chip->dev = &pdev->dev;
        chip->regmap = ac100->regmap;

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

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

        chip->rtc->ops = &ac100_rtc_ops;

        ret = devm_request_threaded_irq(&pdev->dev, chip->irq, NULL,
                                        ac100_rtc_irq,
                                        IRQF_SHARED | IRQF_ONESHOT,
                                        dev_name(&pdev->dev), chip);
        if (ret) {
                dev_err(&pdev->dev, "Could not request IRQ\n");
                return ret;
        }

        /* always use 24 hour mode */
        regmap_write_bits(chip->regmap, AC100_RTC_CTRL, AC100_RTC_CTRL_24HOUR,
                          AC100_RTC_CTRL_24HOUR);

        /* disable counter alarm interrupt */
        regmap_write(chip->regmap, AC100_ALM_INT_ENA, 0);

        /* clear counter alarm pending interrupts */
        regmap_write(chip->regmap, AC100_ALM_INT_STA, AC100_ALM_INT_ENABLE);

        ret = ac100_rtc_register_clks(chip);
        if (ret)
                return ret;

        return devm_rtc_register_device(chip->rtc);
}

static int ac100_rtc_remove(struct platform_device *pdev)
{
        struct ac100_rtc_dev *chip = platform_get_drvdata(pdev);

        ac100_rtc_unregister_clks(chip);

        return 0;
}

static const struct of_device_id ac100_rtc_match[] = {
        { .compatible = "x-powers,ac100-rtc" },
        { },
};
MODULE_DEVICE_TABLE(of, ac100_rtc_match);

static struct platform_driver ac100_rtc_driver = {
        .probe          = ac100_rtc_probe,
        .remove         = ac100_rtc_remove,
        .driver         = {
                .name           = "ac100-rtc",
                .of_match_table = of_match_ptr(ac100_rtc_match),
        },
};
module_platform_driver(ac100_rtc_driver);

MODULE_DESCRIPTION("X-Powers AC100 RTC driver");
MODULE_AUTHOR("Chen-Yu Tsai <wens@csie.org>");
MODULE_LICENSE("GPL v2");