// SPDX-License-Identifier: GPL-2.0-only
/*
 * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
 *
 * Copyright (C) 2008 Mercury IMC Ltd
 * Written by Mark Jackson <mpfj@mimc.co.uk>
 *
 * NOTE: Currently this driver only supports the bare minimum for read
 * and write the RTC. The extra features provided by the chip family
 * (alarms, trickle charger, different control registers) are unavailable.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#include <linux/slab.h>
#include <linux/of.h>

#define DS1390_REG_100THS               0x00
#define DS1390_REG_SECONDS              0x01
#define DS1390_REG_MINUTES              0x02
#define DS1390_REG_HOURS                0x03
#define DS1390_REG_DAY                  0x04
#define DS1390_REG_DATE                 0x05
#define DS1390_REG_MONTH_CENT           0x06
#define DS1390_REG_YEAR                 0x07

#define DS1390_REG_ALARM_100THS         0x08
#define DS1390_REG_ALARM_SECONDS        0x09
#define DS1390_REG_ALARM_MINUTES        0x0A
#define DS1390_REG_ALARM_HOURS          0x0B
#define DS1390_REG_ALARM_DAY_DATE       0x0C

#define DS1390_REG_CONTROL              0x0D
#define DS1390_REG_STATUS               0x0E
#define DS1390_REG_TRICKLE              0x0F

#define DS1390_TRICKLE_CHARGER_ENABLE   0xA0
#define DS1390_TRICKLE_CHARGER_250_OHM  0x01
#define DS1390_TRICKLE_CHARGER_2K_OHM   0x02
#define DS1390_TRICKLE_CHARGER_4K_OHM   0x03
#define DS1390_TRICKLE_CHARGER_NO_DIODE 0x04
#define DS1390_TRICKLE_CHARGER_DIODE    0x08

struct ds1390 {
        struct rtc_device *rtc;
        u8 txrx_buf[9]; /* cmd + 8 registers */
};

static void ds1390_set_reg(struct device *dev, unsigned char address,
                           unsigned char data)
{
        struct spi_device *spi = to_spi_device(dev);
        unsigned char buf[2];

        /* MSB must be '1' to write */
        buf[0] = address | 0x80;
        buf[1] = data;

        spi_write(spi, buf, 2);
}

static int ds1390_get_reg(struct device *dev, unsigned char address,
                                unsigned char *data)
{
        struct spi_device *spi = to_spi_device(dev);
        struct ds1390 *chip = dev_get_drvdata(dev);
        int status;

        if (!data)
                return -EINVAL;

        /* Clear MSB to indicate read */
        chip->txrx_buf[0] = address & 0x7f;
        /* do the i/o */
        status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
        if (status != 0)
                return status;

        *data = chip->txrx_buf[0];

        return 0;
}

static void ds1390_trickle_of_init(struct spi_device *spi)
{
        u32 ohms = 0;
        u8 value;

        if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
                                 &ohms))
                goto out;

        /* Enable charger */
        value = DS1390_TRICKLE_CHARGER_ENABLE;
        if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
                value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
        else
                value |= DS1390_TRICKLE_CHARGER_DIODE;

        /* Resistor select */
        switch (ohms) {
        case 250:
                value |= DS1390_TRICKLE_CHARGER_250_OHM;
                break;
        case 2000:
                value |= DS1390_TRICKLE_CHARGER_2K_OHM;
                break;
        case 4000:
                value |= DS1390_TRICKLE_CHARGER_4K_OHM;
                break;
        default:
                dev_warn(&spi->dev,
                         "Unsupported ohm value %02ux in dt\n", ohms);
                return;
        }

        ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);

out:
        return;
}

static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
{
        struct spi_device *spi = to_spi_device(dev);
        struct ds1390 *chip = dev_get_drvdata(dev);
        int status;

        /* build the message */
        chip->txrx_buf[0] = DS1390_REG_SECONDS;

        /* do the i/o */
        status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 7);
        if (status != 0)
                return status;

        /* The chip sends data in this order:
         * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
        dt->tm_sec      = bcd2bin(chip->txrx_buf[0]);
        dt->tm_min      = bcd2bin(chip->txrx_buf[1]);
        dt->tm_hour     = bcd2bin(chip->txrx_buf[2]);
        dt->tm_wday     = bcd2bin(chip->txrx_buf[3]);
        dt->tm_mday     = bcd2bin(chip->txrx_buf[4]);
        /* mask off century bit */
        dt->tm_mon      = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
        /* adjust for century bit */
        dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);

        return 0;
}

static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
{
        struct spi_device *spi = to_spi_device(dev);
        struct ds1390 *chip = dev_get_drvdata(dev);

        /* build the message */
        chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
        chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
        chip->txrx_buf[2] = bin2bcd(dt->tm_min);
        chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
        chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
        chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
        chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
                                ((dt->tm_year > 99) ? 0x80 : 0x00);
        chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);

        /* do the i/o */
        return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
}

static const struct rtc_class_ops ds1390_rtc_ops = {
        .read_time      = ds1390_read_time,
        .set_time       = ds1390_set_time,
};

static int ds1390_probe(struct spi_device *spi)
{
        unsigned char tmp;
        struct ds1390 *chip;
        int res;

        spi->mode = SPI_MODE_3;
        spi->bits_per_word = 8;
        spi_setup(spi);

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

        spi_set_drvdata(spi, chip);

        res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
        if (res != 0) {
                dev_err(&spi->dev, "unable to read device\n");
                return res;
        }

        if (spi->dev.of_node)
                ds1390_trickle_of_init(spi);

        chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
                                        &ds1390_rtc_ops, THIS_MODULE);
        if (IS_ERR(chip->rtc)) {
                dev_err(&spi->dev, "unable to register device\n");
                res = PTR_ERR(chip->rtc);
        }

        return res;
}

static const struct of_device_id ds1390_of_match[] __maybe_unused = {
        { .compatible = "dallas,ds1390" },
        {}
};
MODULE_DEVICE_TABLE(of, ds1390_of_match);

static const struct spi_device_id ds1390_spi_ids[] = {
        { .name = "ds1390" },
        {}
};
MODULE_DEVICE_TABLE(spi, ds1390_spi_ids);

static struct spi_driver ds1390_driver = {
        .driver = {
                .name   = "rtc-ds1390",
                .of_match_table = of_match_ptr(ds1390_of_match),
        },
        .probe  = ds1390_probe,
        .id_table = ds1390_spi_ids,
};

module_spi_driver(ds1390_driver);

MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-ds1390");