// SPDX-License-Identifier: GPL-2.0-only
/*
 * An rtc driver for the Dallas DS1511
 *
 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 * Copyright (C) 2007 Andrew Sharp <andy.sharp@lsi.com>
 *
 * Real time clock driver for the Dallas 1511 chip, which also
 * contains a watchdog timer.  There is a tiny amount of code that
 * platform code could use to mess with the watchdog device a little
 * bit, but not a full watchdog driver.
 */

#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/module.h>

#define DS1511_SEC              0x0
#define DS1511_MIN              0x1
#define DS1511_HOUR             0x2
#define DS1511_DOW              0x3
#define DS1511_DOM              0x4
#define DS1511_MONTH            0x5
#define DS1511_YEAR             0x6
#define DS1511_CENTURY          0x7
#define DS1511_AM1_SEC          0x8
#define DS1511_AM2_MIN          0x9
#define DS1511_AM3_HOUR         0xa
#define DS1511_AM4_DATE         0xb
#define DS1511_WD_MSEC          0xc
#define DS1511_WD_SEC           0xd
#define DS1511_CONTROL_A        0xe
#define DS1511_CONTROL_B        0xf
#define DS1511_RAMADDR_LSB      0x10
#define DS1511_RAMDATA          0x13

#define DS1511_BLF1     0x80
#define DS1511_BLF2     0x40
#define DS1511_PRS      0x20
#define DS1511_PAB      0x10
#define DS1511_TDF      0x08
#define DS1511_KSF      0x04
#define DS1511_WDF      0x02
#define DS1511_IRQF     0x01
#define DS1511_TE       0x80
#define DS1511_CS       0x40
#define DS1511_BME      0x20
#define DS1511_TPE      0x10
#define DS1511_TIE      0x08
#define DS1511_KIE      0x04
#define DS1511_WDE      0x02
#define DS1511_WDS      0x01
#define DS1511_RAM_MAX  0x100

struct ds1511_data {
        struct rtc_device *rtc;
        void __iomem *ioaddr;           /* virtual base address */
        int irq;
        spinlock_t lock;
};

static DEFINE_SPINLOCK(ds1511_lock);

static __iomem char *ds1511_base;
static u32 reg_spacing = 1;

static void rtc_write(uint8_t val, uint32_t reg)
{
        writeb(val, ds1511_base + (reg * reg_spacing));
}

static uint8_t rtc_read(uint32_t reg)
{
        return readb(ds1511_base + (reg * reg_spacing));
}

static void rtc_disable_update(void)
{
        rtc_write((rtc_read(DS1511_CONTROL_B) & ~DS1511_TE), DS1511_CONTROL_B);
}

static void rtc_enable_update(void)
{
        rtc_write((rtc_read(DS1511_CONTROL_B) | DS1511_TE), DS1511_CONTROL_B);
}

static int ds1511_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
{
        u8 mon, day, dow, hrs, min, sec, yrs, cen;
        unsigned long flags;

        yrs = rtc_tm->tm_year % 100;
        cen = 19 + rtc_tm->tm_year / 100;
        mon = rtc_tm->tm_mon + 1;   /* tm_mon starts at zero */
        day = rtc_tm->tm_mday;
        dow = rtc_tm->tm_wday & 0x7; /* automatic BCD */
        hrs = rtc_tm->tm_hour;
        min = rtc_tm->tm_min;
        sec = rtc_tm->tm_sec;

        /*
         * each register is a different number of valid bits
         */
        sec = bin2bcd(sec) & 0x7f;
        min = bin2bcd(min) & 0x7f;
        hrs = bin2bcd(hrs) & 0x3f;
        day = bin2bcd(day) & 0x3f;
        mon = bin2bcd(mon) & 0x1f;
        yrs = bin2bcd(yrs) & 0xff;
        cen = bin2bcd(cen) & 0xff;

        spin_lock_irqsave(&ds1511_lock, flags);
        rtc_disable_update();
        rtc_write(cen, DS1511_CENTURY);
        rtc_write(yrs, DS1511_YEAR);
        rtc_write((rtc_read(DS1511_MONTH) & 0xe0) | mon, DS1511_MONTH);
        rtc_write(day, DS1511_DOM);
        rtc_write(hrs, DS1511_HOUR);
        rtc_write(min, DS1511_MIN);
        rtc_write(sec, DS1511_SEC);
        rtc_write(dow, DS1511_DOW);
        rtc_enable_update();
        spin_unlock_irqrestore(&ds1511_lock, flags);

        return 0;
}

static int ds1511_rtc_read_time(struct device *dev, struct rtc_time *rtc_tm)
{
        unsigned int century;
        unsigned long flags;

        spin_lock_irqsave(&ds1511_lock, flags);
        rtc_disable_update();

        rtc_tm->tm_sec = rtc_read(DS1511_SEC) & 0x7f;
        rtc_tm->tm_min = rtc_read(DS1511_MIN) & 0x7f;
        rtc_tm->tm_hour = rtc_read(DS1511_HOUR) & 0x3f;
        rtc_tm->tm_mday = rtc_read(DS1511_DOM) & 0x3f;
        rtc_tm->tm_wday = rtc_read(DS1511_DOW) & 0x7;
        rtc_tm->tm_mon = rtc_read(DS1511_MONTH) & 0x1f;
        rtc_tm->tm_year = rtc_read(DS1511_YEAR) & 0x7f;
        century = rtc_read(DS1511_CENTURY);

        rtc_enable_update();
        spin_unlock_irqrestore(&ds1511_lock, flags);

        rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
        rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
        rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
        rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
        rtc_tm->tm_wday = bcd2bin(rtc_tm->tm_wday);
        rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
        rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
        century = bcd2bin(century) * 100;

        /*
         * Account for differences between how the RTC uses the values
         * and how they are defined in a struct rtc_time;
         */
        century += rtc_tm->tm_year;
        rtc_tm->tm_year = century - 1900;

        rtc_tm->tm_mon--;

        return 0;
}

static void ds1511_rtc_alarm_enable(unsigned int enabled)
{
        rtc_write(rtc_read(DS1511_CONTROL_B) | (enabled ? DS1511_TIE : 0), DS1511_CONTROL_B);
}

static int ds1511_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct ds1511_data *ds1511 = dev_get_drvdata(dev);
        unsigned long flags;

        spin_lock_irqsave(&ds1511->lock, flags);
        rtc_write(bin2bcd(alrm->time.tm_mday) & 0x3f, DS1511_AM4_DATE);
        rtc_write(bin2bcd(alrm->time.tm_hour) & 0x3f, DS1511_AM3_HOUR);
        rtc_write(bin2bcd(alrm->time.tm_min) & 0x7f, DS1511_AM2_MIN);
        rtc_write(bin2bcd(alrm->time.tm_sec) & 0x7f, DS1511_AM1_SEC);
        ds1511_rtc_alarm_enable(alrm->enabled);

        rtc_read(DS1511_CONTROL_A);     /* clear interrupts */
        spin_unlock_irqrestore(&ds1511->lock, flags);

        return 0;
}

static int ds1511_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        alrm->time.tm_mday = bcd2bin(rtc_read(DS1511_AM4_DATE) & 0x3f);
        alrm->time.tm_hour = bcd2bin(rtc_read(DS1511_AM3_HOUR) & 0x3f);
        alrm->time.tm_min = bcd2bin(rtc_read(DS1511_AM2_MIN) & 0x7f);
        alrm->time.tm_sec = bcd2bin(rtc_read(DS1511_AM1_SEC) & 0x7f);
        alrm->enabled = !!(rtc_read(DS1511_CONTROL_B) & DS1511_TIE);

        return 0;
}

static irqreturn_t ds1511_interrupt(int irq, void *dev_id)
{
        struct platform_device *pdev = dev_id;
        struct ds1511_data *ds1511 = platform_get_drvdata(pdev);
        unsigned long events = 0;

        spin_lock(&ds1511->lock);
        /*
         * read and clear interrupt
         */
        if (rtc_read(DS1511_CONTROL_A) & DS1511_IRQF) {
                events = RTC_IRQF | RTC_AF;
                rtc_update_irq(ds1511->rtc, 1, events);
        }
        spin_unlock(&ds1511->lock);
        return events ? IRQ_HANDLED : IRQ_NONE;
}

static int ds1511_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct ds1511_data *ds1511 = dev_get_drvdata(dev);
        unsigned long flags;

        spin_lock_irqsave(&ds1511->lock, flags);
        ds1511_rtc_alarm_enable(enabled);
        spin_unlock_irqrestore(&ds1511->lock, flags);

        return 0;
}

static const struct rtc_class_ops ds1511_rtc_ops = {
        .read_time              = ds1511_rtc_read_time,
        .set_time               = ds1511_rtc_set_time,
        .read_alarm             = ds1511_rtc_read_alarm,
        .set_alarm              = ds1511_rtc_set_alarm,
        .alarm_irq_enable       = ds1511_rtc_alarm_irq_enable,
};

static int ds1511_nvram_read(void *priv, unsigned int pos, void *buf,
                             size_t size)
{
        int i;

        rtc_write(pos, DS1511_RAMADDR_LSB);
        for (i = 0; i < size; i++)
                *(char *)buf++ = rtc_read(DS1511_RAMDATA);

        return 0;
}

static int ds1511_nvram_write(void *priv, unsigned int pos, void *buf,
                              size_t size)
{
        int i;

        rtc_write(pos, DS1511_RAMADDR_LSB);
        for (i = 0; i < size; i++)
                rtc_write(*(char *)buf++, DS1511_RAMDATA);

        return 0;
}

static int ds1511_rtc_probe(struct platform_device *pdev)
{
        struct ds1511_data *ds1511;
        int ret = 0;
        struct nvmem_config ds1511_nvmem_cfg = {
                .name = "ds1511_nvram",
                .word_size = 1,
                .stride = 1,
                .size = DS1511_RAM_MAX,
                .reg_read = ds1511_nvram_read,
                .reg_write = ds1511_nvram_write,
                .priv = &pdev->dev,
        };

        ds1511 = devm_kzalloc(&pdev->dev, sizeof(*ds1511), GFP_KERNEL);
        if (!ds1511)
                return -ENOMEM;

        ds1511_base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(ds1511_base))
                return PTR_ERR(ds1511_base);
        ds1511->ioaddr = ds1511_base;
        ds1511->irq = platform_get_irq(pdev, 0);

        /*
         * turn on the clock and the crystal, etc.
         */
        rtc_write(DS1511_BME, DS1511_CONTROL_B);
        rtc_write(0, DS1511_CONTROL_A);
        /*
         * clear the wdog counter
         */
        rtc_write(0, DS1511_WD_MSEC);
        rtc_write(0, DS1511_WD_SEC);
        /*
         * start the clock
         */
        rtc_enable_update();

        /*
         * check for a dying bat-tree
         */
        if (rtc_read(DS1511_CONTROL_A) & DS1511_BLF1)
                dev_warn(&pdev->dev, "voltage-low detected.\n");

        spin_lock_init(&ds1511->lock);
        platform_set_drvdata(pdev, ds1511);

        ds1511->rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(ds1511->rtc))
                return PTR_ERR(ds1511->rtc);

        ds1511->rtc->ops = &ds1511_rtc_ops;
        ds1511->rtc->range_max = RTC_TIMESTAMP_END_2099;
        ds1511->rtc->alarm_offset_max = 28 * 24 * 60 * 60 - 1;

        /*
         * if the platform has an interrupt in mind for this device,
         * then by all means, set it
         */
        if (ds1511->irq > 0) {
                rtc_read(DS1511_CONTROL_A);
                if (devm_request_irq(&pdev->dev, ds1511->irq, ds1511_interrupt,
                        IRQF_SHARED, pdev->name, pdev) < 0) {

                        dev_warn(&pdev->dev, "interrupt not available.\n");
                        ds1511->irq = 0;
                }
        }

        if (ds1511->irq == 0)
                clear_bit(RTC_FEATURE_ALARM, ds1511->rtc->features);

        ret = devm_rtc_register_device(ds1511->rtc);
        if (ret)
                return ret;

        devm_rtc_nvmem_register(ds1511->rtc, &ds1511_nvmem_cfg);

        return 0;
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:ds1511");

static struct platform_driver ds1511_rtc_driver = {
        .probe          = ds1511_rtc_probe,
        .driver         = {
                .name   = "ds1511",
        },
};

module_platform_driver(ds1511_rtc_driver);

MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
MODULE_DESCRIPTION("Dallas DS1511 RTC driver");
MODULE_LICENSE("GPL");