// SPDX-License-Identifier: GPL-2.0-only
/*
 * A RTC driver for the Simtek STK17TA8
 *
 * By Thomas Hommel <thomas.hommel@ge.com>
 *
 * Based on the DS1553 driver from
 * Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 */

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

#define RTC_REG_SIZE            0x20000
#define RTC_OFFSET              0x1fff0

#define RTC_FLAGS               (RTC_OFFSET + 0)
#define RTC_CENTURY             (RTC_OFFSET + 1)
#define RTC_SECONDS_ALARM       (RTC_OFFSET + 2)
#define RTC_MINUTES_ALARM       (RTC_OFFSET + 3)
#define RTC_HOURS_ALARM         (RTC_OFFSET + 4)
#define RTC_DATE_ALARM          (RTC_OFFSET + 5)
#define RTC_INTERRUPTS          (RTC_OFFSET + 6)
#define RTC_WATCHDOG            (RTC_OFFSET + 7)
#define RTC_CALIBRATION         (RTC_OFFSET + 8)
#define RTC_SECONDS             (RTC_OFFSET + 9)
#define RTC_MINUTES             (RTC_OFFSET + 10)
#define RTC_HOURS               (RTC_OFFSET + 11)
#define RTC_DAY                 (RTC_OFFSET + 12)
#define RTC_DATE                (RTC_OFFSET + 13)
#define RTC_MONTH               (RTC_OFFSET + 14)
#define RTC_YEAR                (RTC_OFFSET + 15)

#define RTC_SECONDS_MASK        0x7f
#define RTC_DAY_MASK            0x07
#define RTC_CAL_MASK            0x3f

/* Bits in the Calibration register */
#define RTC_STOP                0x80

/* Bits in the Flags register */
#define RTC_FLAGS_AF            0x40
#define RTC_FLAGS_PF            0x20
#define RTC_WRITE               0x02
#define RTC_READ                0x01

/* Bits in the Interrupts register */
#define RTC_INTS_AIE            0x40

struct rtc_plat_data {
        struct rtc_device *rtc;
        void __iomem *ioaddr;
        unsigned long last_jiffies;
        int irq;
        unsigned int irqen;
        int alrm_sec;
        int alrm_min;
        int alrm_hour;
        int alrm_mday;
        spinlock_t lock;
};

static int stk17ta8_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr;
        u8 flags;

        flags = readb(pdata->ioaddr + RTC_FLAGS);
        writeb(flags | RTC_WRITE, pdata->ioaddr + RTC_FLAGS);

        writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
        writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
        writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
        writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
        writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
        writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
        writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
        writeb(bin2bcd((tm->tm_year + 1900) / 100), ioaddr + RTC_CENTURY);

        writeb(flags & ~RTC_WRITE, pdata->ioaddr + RTC_FLAGS);
        return 0;
}

static int stk17ta8_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned int year, month, day, hour, minute, second, week;
        unsigned int century;
        u8 flags;

        /* give enough time to update RTC in case of continuous read */
        if (pdata->last_jiffies == jiffies)
                msleep(1);
        pdata->last_jiffies = jiffies;

        flags = readb(pdata->ioaddr + RTC_FLAGS);
        writeb(flags | RTC_READ, ioaddr + RTC_FLAGS);
        second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
        minute = readb(ioaddr + RTC_MINUTES);
        hour = readb(ioaddr + RTC_HOURS);
        day = readb(ioaddr + RTC_DATE);
        week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
        month = readb(ioaddr + RTC_MONTH);
        year = readb(ioaddr + RTC_YEAR);
        century = readb(ioaddr + RTC_CENTURY);
        writeb(flags & ~RTC_READ, ioaddr + RTC_FLAGS);
        tm->tm_sec = bcd2bin(second);
        tm->tm_min = bcd2bin(minute);
        tm->tm_hour = bcd2bin(hour);
        tm->tm_mday = bcd2bin(day);
        tm->tm_wday = bcd2bin(week);
        tm->tm_mon = bcd2bin(month) - 1;
        /* year is 1900 + tm->tm_year */
        tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;

        return 0;
}

static void stk17ta8_rtc_update_alarm(struct rtc_plat_data *pdata)
{
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned long irqflags;
        u8 flags;

        spin_lock_irqsave(&pdata->lock, irqflags);

        flags = readb(ioaddr + RTC_FLAGS);
        writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);

        writeb(pdata->alrm_mday < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_mday),
               ioaddr + RTC_DATE_ALARM);
        writeb(pdata->alrm_hour < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_hour),
               ioaddr + RTC_HOURS_ALARM);
        writeb(pdata->alrm_min < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_min),
               ioaddr + RTC_MINUTES_ALARM);
        writeb(pdata->alrm_sec < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_sec),
               ioaddr + RTC_SECONDS_ALARM);
        writeb(pdata->irqen ? RTC_INTS_AIE : 0, ioaddr + RTC_INTERRUPTS);
        readb(ioaddr + RTC_FLAGS);      /* clear interrupts */
        writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
        spin_unlock_irqrestore(&pdata->lock, irqflags);
}

static int stk17ta8_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        pdata->alrm_mday = alrm->time.tm_mday;
        pdata->alrm_hour = alrm->time.tm_hour;
        pdata->alrm_min = alrm->time.tm_min;
        pdata->alrm_sec = alrm->time.tm_sec;
        if (alrm->enabled)
                pdata->irqen |= RTC_AF;
        stk17ta8_rtc_update_alarm(pdata);
        return 0;
}

static int stk17ta8_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
        alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
        alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
        alrm->time.tm_sec = pdata->alrm_sec < 0 ? 0 : pdata->alrm_sec;
        alrm->enabled = (pdata->irqen & RTC_AF) ? 1 : 0;
        return 0;
}

static irqreturn_t stk17ta8_rtc_interrupt(int irq, void *dev_id)
{
        struct platform_device *pdev = dev_id;
        struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned long events = 0;

        spin_lock(&pdata->lock);
        /* read and clear interrupt */
        if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_AF) {
                events = RTC_IRQF;
                if (readb(ioaddr + RTC_SECONDS_ALARM) & 0x80)
                        events |= RTC_UF;
                else
                        events |= RTC_AF;
                rtc_update_irq(pdata->rtc, 1, events);
        }
        spin_unlock(&pdata->lock);
        return events ? IRQ_HANDLED : IRQ_NONE;
}

static int stk17ta8_rtc_alarm_irq_enable(struct device *dev,
        unsigned int enabled)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        if (enabled)
                pdata->irqen |= RTC_AF;
        else
                pdata->irqen &= ~RTC_AF;
        stk17ta8_rtc_update_alarm(pdata);
        return 0;
}

static const struct rtc_class_ops stk17ta8_rtc_ops = {
        .read_time              = stk17ta8_rtc_read_time,
        .set_time               = stk17ta8_rtc_set_time,
        .read_alarm             = stk17ta8_rtc_read_alarm,
        .set_alarm              = stk17ta8_rtc_set_alarm,
        .alarm_irq_enable       = stk17ta8_rtc_alarm_irq_enable,
};

static int stk17ta8_nvram_read(void *priv, unsigned int pos, void *val,
                               size_t bytes)
{
        struct rtc_plat_data *pdata = priv;
        void __iomem *ioaddr = pdata->ioaddr;
        u8 *buf = val;

        for (; bytes; bytes--)
                *buf++ = readb(ioaddr + pos++);
        return 0;
}

static int stk17ta8_nvram_write(void *priv, unsigned int pos, void *val,
                                size_t bytes)
{
        struct rtc_plat_data *pdata = priv;
        void __iomem *ioaddr = pdata->ioaddr;
        u8 *buf = val;

        for (; bytes; bytes--)
                writeb(*buf++, ioaddr + pos++);
        return 0;
}

static int stk17ta8_rtc_probe(struct platform_device *pdev)
{
        unsigned int cal;
        unsigned int flags;
        struct rtc_plat_data *pdata;
        void __iomem *ioaddr;
        int ret = 0;
        struct nvmem_config nvmem_cfg = {
                .name = "stk17ta8_nvram",
                .word_size = 1,
                .stride = 1,
                .size = RTC_OFFSET,
                .reg_read = stk17ta8_nvram_read,
                .reg_write = stk17ta8_nvram_write,
        };

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

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

        /* turn RTC on if it was not on */
        cal = readb(ioaddr + RTC_CALIBRATION);
        if (cal & RTC_STOP) {
                cal &= RTC_CAL_MASK;
                flags = readb(ioaddr + RTC_FLAGS);
                writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);
                writeb(cal, ioaddr + RTC_CALIBRATION);
                writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
        }
        if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_PF)
                dev_warn(&pdev->dev, "voltage-low detected.\n");

        spin_lock_init(&pdata->lock);
        pdata->last_jiffies = jiffies;
        platform_set_drvdata(pdev, pdata);
        if (pdata->irq > 0) {
                writeb(0, ioaddr + RTC_INTERRUPTS);
                if (devm_request_irq(&pdev->dev, pdata->irq,
                                stk17ta8_rtc_interrupt,
                                IRQF_SHARED,
                                pdev->name, pdev) < 0) {
                        dev_warn(&pdev->dev, "interrupt not available.\n");
                        pdata->irq = 0;
                }
        }

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

        pdata->rtc->ops = &stk17ta8_rtc_ops;

        nvmem_cfg.priv = pdata;
        ret = devm_rtc_nvmem_register(pdata->rtc, &nvmem_cfg);
        if (ret)
                return ret;

        return devm_rtc_register_device(pdata->rtc);
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:stk17ta8");

static struct platform_driver stk17ta8_rtc_driver = {
        .probe          = stk17ta8_rtc_probe,
        .driver         = {
                .name   = "stk17ta8",
        },
};

module_platform_driver(stk17ta8_rtc_driver);

MODULE_AUTHOR("Thomas Hommel <thomas.hommel@ge.com>");
MODULE_DESCRIPTION("Simtek STK17TA8 RTC driver");
MODULE_LICENSE("GPL");