// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Epson RTC-9701JE
 *
 * Copyright (C) 2008 Magnus Damm
 *
 * Based on rtc-max6902.c
 *
 * Copyright (C) 2006 8D Technologies inc.
 * Copyright (C) 2004 Compulab Ltd.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/bitops.h>

#define RSECCNT 0x00    /* Second Counter */
#define RMINCNT 0x01    /* Minute Counter */
#define RHRCNT  0x02    /* Hour Counter */
#define RWKCNT  0x03    /* Week Counter */
#define RDAYCNT 0x04    /* Day Counter */
#define RMONCNT 0x05    /* Month Counter */
#define RYRCNT  0x06    /* Year Counter */
#define R100CNT 0x07    /* Y100 Counter */
#define RMINAR  0x08    /* Minute Alarm */
#define RHRAR   0x09    /* Hour Alarm */
#define RWKAR   0x0a    /* Week/Day Alarm */
#define RTIMCNT 0x0c    /* Interval Timer */
#define REXT    0x0d    /* Extension Register */
#define RFLAG   0x0e    /* RTC Flag Register */
#define RCR     0x0f    /* RTC Control Register */

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

        buf[0] = address & 0x7f;
        buf[1] = data;

        return spi_write(spi, buf, ARRAY_SIZE(buf));
}

static int read_regs(struct device *dev, unsigned char *regs, int no_regs)
{
        struct spi_device *spi = to_spi_device(dev);
        u8 txbuf[1], rxbuf[1];
        int k, ret;

        ret = 0;

        for (k = 0; ret == 0 && k < no_regs; k++) {
                txbuf[0] = 0x80 | regs[k];
                ret = spi_write_then_read(spi, txbuf, 1, rxbuf, 1);
                regs[k] = rxbuf[0];
        }

        return ret;
}

static int r9701_get_datetime(struct device *dev, struct rtc_time *dt)
{
        int ret;
        unsigned char buf[] = { RSECCNT, RMINCNT, RHRCNT,
                                RDAYCNT, RMONCNT, RYRCNT };

        ret = read_regs(dev, buf, ARRAY_SIZE(buf));
        if (ret)
                return ret;

        dt->tm_sec = bcd2bin(buf[0]); /* RSECCNT */
        dt->tm_min = bcd2bin(buf[1]); /* RMINCNT */
        dt->tm_hour = bcd2bin(buf[2]); /* RHRCNT */

        dt->tm_mday = bcd2bin(buf[3]); /* RDAYCNT */
        dt->tm_mon = bcd2bin(buf[4]) - 1; /* RMONCNT */
        dt->tm_year = bcd2bin(buf[5]) + 100; /* RYRCNT */

        return 0;
}

static int r9701_set_datetime(struct device *dev, struct rtc_time *dt)
{
        int ret;

        ret = write_reg(dev, RHRCNT, bin2bcd(dt->tm_hour));
        ret = ret ? ret : write_reg(dev, RMINCNT, bin2bcd(dt->tm_min));
        ret = ret ? ret : write_reg(dev, RSECCNT, bin2bcd(dt->tm_sec));
        ret = ret ? ret : write_reg(dev, RDAYCNT, bin2bcd(dt->tm_mday));
        ret = ret ? ret : write_reg(dev, RMONCNT, bin2bcd(dt->tm_mon + 1));
        ret = ret ? ret : write_reg(dev, RYRCNT, bin2bcd(dt->tm_year - 100));

        return ret;
}

static const struct rtc_class_ops r9701_rtc_ops = {
        .read_time      = r9701_get_datetime,
        .set_time       = r9701_set_datetime,
};

static int r9701_probe(struct spi_device *spi)
{
        struct rtc_device *rtc;
        unsigned char tmp;
        int res;

        tmp = R100CNT;
        res = read_regs(&spi->dev, &tmp, 1);
        if (res || tmp != 0x20) {
                dev_err(&spi->dev, "cannot read RTC register\n");
                return -ENODEV;
        }

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

        spi_set_drvdata(spi, rtc);
        rtc->ops = &r9701_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->range_max = RTC_TIMESTAMP_END_2099;

        return devm_rtc_register_device(rtc);
}

static struct spi_driver r9701_driver = {
        .driver = {
                .name   = "rtc-r9701",
        },
        .probe  = r9701_probe,
};

module_spi_driver(r9701_driver);

MODULE_DESCRIPTION("r9701 spi RTC driver");
MODULE_AUTHOR("Magnus Damm <damm@opensource.se>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-r9701");