// SPDX-License-Identifier: GPL-2.0
/*
 * RTC driver for tps6594 PMIC
 *
 * Copyright (C) 2023 BayLibre Incorporated - https://www.baylibre.com/
 */

#include <linux/bcd.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/limits.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/mod_devicetable.h>
#include <linux/property.h>
#include <linux/rtc.h>
#include <linux/types.h>
#include <linux/units.h>

#include <linux/mfd/tps6594.h>

// Total number of RTC registers needed to set time
#define NUM_TIME_REGS (TPS6594_REG_RTC_WEEKS - TPS6594_REG_RTC_SECONDS + 1)

// Total number of RTC alarm registers
#define NUM_TIME_ALARM_REGS (NUM_TIME_REGS - 1)

/*
 * Min and max values supported by 'offset' interface (swapped sign).
 * After conversion, the values do not exceed the range [-32767, 33767]
 * which COMP_REG must conform to.
 */
#define MIN_OFFSET (-277774)
#define MAX_OFFSET (277774)

// Number of ticks per hour
#define TICKS_PER_HOUR (32768 * 3600LL)

// Multiplier for ppb conversions
#define PPB_MULT NANO

struct tps6594_rtc {
        struct rtc_device *rtc_dev;
        int irq;
};

static int tps6594_rtc_alarm_irq_enable(struct device *dev,
                                        unsigned int enabled)
{
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        u8 val;

        val = enabled ? TPS6594_BIT_IT_ALARM : 0;

        return regmap_update_bits(tps->regmap, TPS6594_REG_RTC_INTERRUPTS,
                                  TPS6594_BIT_IT_ALARM, val);
}

/* Pulse GET_TIME field of RTC_CTRL_1 to store a timestamp in shadow registers. */
static int tps6594_rtc_shadow_timestamp(struct device *dev, struct tps6594 *tps)
{
        int ret;

        /*
         * Set GET_TIME to 0. Next time we set GET_TIME to 1 we will be sure to store
         * an up-to-date timestamp.
         */
        ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                                TPS6594_BIT_GET_TIME);
        if (ret < 0)
                return ret;

        /*
         * Copy content of RTC registers to shadow registers or latches to read
         * a coherent timestamp.
         */
        return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                               TPS6594_BIT_GET_TIME);
}

static int tps6594_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        unsigned char rtc_data[NUM_TIME_REGS];
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        int ret;

        // Check if RTC is running.
        ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
                               TPS6594_BIT_RUN);
        if (ret < 0)
                return ret;
        if (ret == 0)
                return -EINVAL;

        ret = tps6594_rtc_shadow_timestamp(dev, tps);
        if (ret < 0)
                return ret;

        // Read shadowed RTC registers.
        ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
                               NUM_TIME_REGS);
        if (ret < 0)
                return ret;

        tm->tm_sec = bcd2bin(rtc_data[0]);
        tm->tm_min = bcd2bin(rtc_data[1]);
        tm->tm_hour = bcd2bin(rtc_data[2]);
        tm->tm_mday = bcd2bin(rtc_data[3]);
        tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
        tm->tm_year = bcd2bin(rtc_data[5]) + 100;
        tm->tm_wday = bcd2bin(rtc_data[6]);

        return 0;
}

static int tps6594_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        unsigned char rtc_data[NUM_TIME_REGS];
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        int ret;

        rtc_data[0] = bin2bcd(tm->tm_sec);
        rtc_data[1] = bin2bcd(tm->tm_min);
        rtc_data[2] = bin2bcd(tm->tm_hour);
        rtc_data[3] = bin2bcd(tm->tm_mday);
        rtc_data[4] = bin2bcd(tm->tm_mon + 1);
        rtc_data[5] = bin2bcd(tm->tm_year - 100);
        rtc_data[6] = bin2bcd(tm->tm_wday);

        // Stop RTC while updating the RTC time registers.
        ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                                TPS6594_BIT_STOP_RTC);
        if (ret < 0)
                return ret;

        // Update all the time registers in one shot.
        ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
                                NUM_TIME_REGS);
        if (ret < 0)
                return ret;

        // Start back RTC.
        return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                               TPS6594_BIT_STOP_RTC);
}

static int tps6594_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        unsigned char alarm_data[NUM_TIME_ALARM_REGS];
        u32 int_val;
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        int ret;

        ret = regmap_bulk_read(tps->regmap, TPS6594_REG_ALARM_SECONDS,
                               alarm_data, NUM_TIME_ALARM_REGS);
        if (ret < 0)
                return ret;

        alm->time.tm_sec = bcd2bin(alarm_data[0]);
        alm->time.tm_min = bcd2bin(alarm_data[1]);
        alm->time.tm_hour = bcd2bin(alarm_data[2]);
        alm->time.tm_mday = bcd2bin(alarm_data[3]);
        alm->time.tm_mon = bcd2bin(alarm_data[4]) - 1;
        alm->time.tm_year = bcd2bin(alarm_data[5]) + 100;

        ret = regmap_read(tps->regmap, TPS6594_REG_RTC_INTERRUPTS, &int_val);
        if (ret < 0)
                return ret;

        alm->enabled = int_val & TPS6594_BIT_IT_ALARM;

        return 0;
}

static int tps6594_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        unsigned char alarm_data[NUM_TIME_ALARM_REGS];
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        int ret;

        // Disable alarm irq before changing the alarm timestamp.
        ret = tps6594_rtc_alarm_irq_enable(dev, 0);
        if (ret)
                return ret;

        alarm_data[0] = bin2bcd(alm->time.tm_sec);
        alarm_data[1] = bin2bcd(alm->time.tm_min);
        alarm_data[2] = bin2bcd(alm->time.tm_hour);
        alarm_data[3] = bin2bcd(alm->time.tm_mday);
        alarm_data[4] = bin2bcd(alm->time.tm_mon + 1);
        alarm_data[5] = bin2bcd(alm->time.tm_year - 100);

        // Update all the alarm registers in one shot.
        ret = regmap_bulk_write(tps->regmap, TPS6594_REG_ALARM_SECONDS,
                                alarm_data, NUM_TIME_ALARM_REGS);
        if (ret < 0)
                return ret;

        if (alm->enabled)
                ret = tps6594_rtc_alarm_irq_enable(dev, 1);

        return ret;
}

static int tps6594_rtc_set_calibration(struct device *dev, int calibration)
{
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        __le16 value;
        int ret;

        /*
         * TPS6594 uses two's complement 16 bit value for compensation of RTC
         * crystal inaccuracies. One time every hour when seconds counter
         * increments from 0 to 1 compensation value will be added to internal
         * RTC counter value.
         *
         * Valid range for compensation value: [-32767 .. 32767].
         */
        if (calibration < S16_MIN + 1 || calibration > S16_MAX)
                return -ERANGE;

        value = cpu_to_le16(calibration);

        // Update all the compensation registers in one shot.
        ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
                                sizeof(value));
        if (ret < 0)
                return ret;

        // Enable automatic compensation.
        return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                               TPS6594_BIT_AUTO_COMP);
}

static int tps6594_rtc_get_calibration(struct device *dev, int *calibration)
{
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        unsigned int ctrl;
        __le16 value;
        int ret;

        ret = regmap_read(tps->regmap, TPS6594_REG_RTC_CTRL_1, &ctrl);
        if (ret < 0)
                return ret;

        // If automatic compensation is not enabled report back zero.
        if (!(ctrl & TPS6594_BIT_AUTO_COMP)) {
                *calibration = 0;
                return 0;
        }

        ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
                               sizeof(value));
        if (ret < 0)
                return ret;

        *calibration = le16_to_cpu(value);

        return 0;
}

static int tps6594_rtc_read_offset(struct device *dev, long *offset)
{
        int calibration;
        s64 tmp;
        int ret;

        ret = tps6594_rtc_get_calibration(dev, &calibration);
        if (ret < 0)
                return ret;

        // Convert from RTC calibration register format to ppb format.
        tmp = calibration * PPB_MULT;

        if (tmp < 0)
                tmp -= TICKS_PER_HOUR / 2LL;
        else
                tmp += TICKS_PER_HOUR / 2LL;
        tmp = div_s64(tmp, TICKS_PER_HOUR);

        /*
         * SAFETY:
         * Computatiion is the reverse operation of the one done in
         * `tps6594_rtc_set_offset`. The safety remarks applie here too.
         */

        /*
         * Offset value operates in negative way, so swap sign.
         * See 8.3.10.5, (32768 - COMP_REG).
         */
        *offset = (long)-tmp;

        return 0;
}

static int tps6594_rtc_set_offset(struct device *dev, long offset)
{
        int calibration;
        s64 tmp;

        // Make sure offset value is within supported range.
        if (offset < MIN_OFFSET || offset > MAX_OFFSET)
                return -ERANGE;

        // Convert from ppb format to RTC calibration register format.

        tmp = offset * TICKS_PER_HOUR;
        if (tmp < 0)
                tmp -= PPB_MULT / 2LL;
        else
                tmp += PPB_MULT / 2LL;
        tmp = div_s64(tmp, PPB_MULT);

        /*
         * SAFETY:
         * - tmp = offset * TICK_PER_HOUR :
         *      `offset` can't be more than 277774, so `tmp` can't exceed 277774000000000
         *      which is lower than the maximum value in an `s64` (2^63-1). No overflow here.
         *
         * - tmp += TICK_PER_HOUR / 2LL :
         *      tmp will have a maximum value of 277774117964800 which is still inferior to 2^63-1.
         */

        // Offset value operates in negative way, so swap sign.
        calibration = (int)-tmp;

        return tps6594_rtc_set_calibration(dev, calibration);
}

static irqreturn_t tps6594_rtc_interrupt(int irq, void *data)
{
        struct device *dev = data;
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        struct tps6594_rtc *rtc = dev_get_drvdata(dev);
        int ret;
        u32 rtc_reg;

        ret = regmap_read(tps->regmap, TPS6594_REG_RTC_STATUS, &rtc_reg);
        if (ret)
                return IRQ_NONE;

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

        return IRQ_HANDLED;
}

static const struct rtc_class_ops tps6594_rtc_ops = {
        .read_time = tps6594_rtc_read_time,
        .set_time = tps6594_rtc_set_time,
        .read_alarm = tps6594_rtc_read_alarm,
        .set_alarm = tps6594_rtc_set_alarm,
        .alarm_irq_enable = tps6594_rtc_alarm_irq_enable,
        .read_offset = tps6594_rtc_read_offset,
        .set_offset = tps6594_rtc_set_offset,
};

static int tps6594_rtc_probe(struct platform_device *pdev)
{
        struct tps6594 *tps = dev_get_drvdata(pdev->dev.parent);
        struct device *dev = &pdev->dev;
        struct tps6594_rtc *rtc;
        int irq;
        int ret;

        rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL);
        if (!rtc)
                return -ENOMEM;

        rtc->rtc_dev = devm_rtc_allocate_device(dev);
        if (IS_ERR(rtc->rtc_dev))
                return PTR_ERR(rtc->rtc_dev);

        // Enable crystal oscillator.
        ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_2,
                              TPS6594_BIT_XTAL_EN);
        if (ret < 0)
                return ret;

        ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
                               TPS6594_BIT_RUN);
        if (ret < 0)
                return ret;
        // RTC not running.
        if (ret == 0) {
                ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                                      TPS6594_BIT_STOP_RTC);
                if (ret < 0)
                        return ret;

                /*
                 * On some boards, a 40 ms delay is needed before BIT_RUN is set.
                 * 80 ms should provide sufficient margin.
                 */
                mdelay(80);

                /*
                 * RTC should be running now. Check if this is the case.
                 * If not it might be a missing oscillator.
                 */
                ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
                                       TPS6594_BIT_RUN);
                if (ret < 0)
                        return ret;
                if (ret == 0)
                        return -ENODEV;

                // Stop RTC until first call to `tps6594_rtc_set_time`.
                ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
                                        TPS6594_BIT_STOP_RTC);
                if (ret < 0)
                        return ret;
        }

        platform_set_drvdata(pdev, rtc);

        irq = platform_get_irq_byname(pdev, TPS6594_IRQ_NAME_ALARM);
        if (irq < 0)
                return dev_err_probe(dev, irq, "Failed to get irq\n");

        rtc->irq = irq;

        ret = devm_request_threaded_irq(dev, irq, NULL, tps6594_rtc_interrupt,
                                        IRQF_ONESHOT, TPS6594_IRQ_NAME_ALARM,
                                        dev);
        if (ret < 0)
                return dev_err_probe(dev, ret,
                                     "Failed to request_threaded_irq\n");

        ret = device_init_wakeup(dev, true);
        if (ret < 0)
                return dev_err_probe(dev, ret,
                                     "Failed to init rtc as wakeup source\n");

        rtc->rtc_dev->ops = &tps6594_rtc_ops;
        rtc->rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->rtc_dev->range_max = RTC_TIMESTAMP_END_2099;

        return devm_rtc_register_device(rtc->rtc_dev);
}

static int tps6594_rtc_resume(struct device *dev)
{
        struct tps6594 *tps = dev_get_drvdata(dev->parent);
        struct tps6594_rtc *rtc = dev_get_drvdata(dev);
        int ret;

        ret = regmap_test_bits(tps->regmap, TPS6594_REG_INT_STARTUP,
                               TPS6594_BIT_RTC_INT);
        if (ret < 0) {
                dev_err(dev, "failed to read REG_INT_STARTUP: %d\n", ret);
                goto out;
        }

        if (ret > 0) {
                /*
                 * If the alarm bit is set, it means that the IRQ has been
                 * fired. But, the kernel may not have woke up yet when it
                 * happened. So, we have to clear it.
                 */
                ret = regmap_write(tps->regmap, TPS6594_REG_RTC_STATUS,
                                   TPS6594_BIT_ALARM);
                if (ret < 0)
                        dev_err(dev, "error clearing alarm bit: %d", ret);

                rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);
        }
out:
        disable_irq_wake(rtc->irq);

        return 0;
}

static int tps6594_rtc_suspend(struct device *dev)
{
        struct tps6594_rtc *rtc = dev_get_drvdata(dev);

        enable_irq_wake(rtc->irq);

        return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(tps6594_rtc_pm_ops, tps6594_rtc_suspend, tps6594_rtc_resume);

static const struct platform_device_id tps6594_rtc_id_table[] = {
        { "tps6594-rtc", },
        {}
};
MODULE_DEVICE_TABLE(platform, tps6594_rtc_id_table);

static struct platform_driver tps6594_rtc_driver = {
        .probe          = tps6594_rtc_probe,
        .driver         = {
                .name   = "tps6594-rtc",
                .pm = pm_sleep_ptr(&tps6594_rtc_pm_ops),
        },
        .id_table = tps6594_rtc_id_table,
};

module_platform_driver(tps6594_rtc_driver);
MODULE_AUTHOR("Esteban Blanc <eblanc@baylibre.com>");
MODULE_DESCRIPTION("TPS6594 RTC driver");
MODULE_LICENSE("GPL");