/*
 * RTC class driver for "CMOS RTC":  PCs, ACPI, etc
 *
 * Copyright (C) 1996 Paul Gortmaker (drivers/char/rtc.c)
 * Copyright (C) 2006 David Brownell (convert to new framework)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

/*
 * The original "cmos clock" chip was an MC146818 chip, now obsolete.
 * That defined the register interface now provided by all PCs, some
 * non-PC systems, and incorporated into ACPI.  Modern PC chipsets
 * integrate an MC146818 clone in their southbridge, and boards use
 * that instead of discrete clones like the DS12887 or M48T86.  There
 * are also clones that connect using the LPC bus.
 *
 * That register API is also used directly by various other drivers
 * (notably for integrated NVRAM), infrastructure (x86 has code to
 * bypass the RTC framework, directly reading the RTC during boot
 * and updating minutes/seconds for systems using NTP synch) and
 * utilities (like userspace 'hwclock', if no /dev node exists).
 *
 * So **ALL** calls to CMOS_READ and CMOS_WRITE must be done with
 * interrupts disabled, holding the global rtc_lock, to exclude those
 * other drivers and utilities on correctly configured systems.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/platform_device.h>
#include <linux/log2.h>
#include <linux/pm.h>
#include <linux/of.h>
#include <linux/of_platform.h>

/* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
#include <linux/mc146818rtc.h>

struct cmos_rtc {
        struct rtc_device       *rtc;
        struct device           *dev;
        int                     irq;
        struct resource         *iomem;
        time64_t                alarm_expires;

        void                    (*wake_on)(struct device *);
        void                    (*wake_off)(struct device *);

        u8                      enabled_wake;
        u8                      suspend_ctrl;

        /* newer hardware extends the original register set */
        u8                      day_alrm;
        u8                      mon_alrm;
        u8                      century;

        struct rtc_wkalrm       saved_wkalrm;
};

/* both platform and pnp busses use negative numbers for invalid irqs */
#define is_valid_irq(n)         ((n) > 0)

static const char driver_name[] = "rtc_cmos";

/* The RTC_INTR register may have e.g. RTC_PF set even if RTC_PIE is clear;
 * always mask it against the irq enable bits in RTC_CONTROL.  Bit values
 * are the same: PF==PIE, AF=AIE, UF=UIE; so RTC_IRQMASK works with both.
 */
#define RTC_IRQMASK     (RTC_PF | RTC_AF | RTC_UF)

static inline int is_intr(u8 rtc_intr)
{
        if (!(rtc_intr & RTC_IRQF))
                return 0;
        return rtc_intr & RTC_IRQMASK;
}

/*----------------------------------------------------------------*/

/* Much modern x86 hardware has HPETs (10+ MHz timers) which, because
 * many BIOS programmers don't set up "sane mode" IRQ routing, are mostly
 * used in a broken "legacy replacement" mode.  The breakage includes
 * HPET #1 hijacking the IRQ for this RTC, and being unavailable for
 * other (better) use.
 *
 * When that broken mode is in use, platform glue provides a partial
 * emulation of hardware RTC IRQ facilities using HPET #1.  We don't
 * want to use HPET for anything except those IRQs though...
 */
#ifdef CONFIG_HPET_EMULATE_RTC
#include <asm/hpet.h>
#else

static inline int is_hpet_enabled(void)
{
        return 0;
}

static inline int hpet_mask_rtc_irq_bit(unsigned long mask)
{
        return 0;
}

static inline int hpet_set_rtc_irq_bit(unsigned long mask)
{
        return 0;
}

static inline int
hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned char sec)
{
        return 0;
}

static inline int hpet_set_periodic_freq(unsigned long freq)
{
        return 0;
}

static inline int hpet_rtc_dropped_irq(void)
{
        return 0;
}

static inline int hpet_rtc_timer_init(void)
{
        return 0;
}

extern irq_handler_t hpet_rtc_interrupt;

static inline int hpet_register_irq_handler(irq_handler_t handler)
{
        return 0;
}

static inline int hpet_unregister_irq_handler(irq_handler_t handler)
{
        return 0;
}

#endif

/*----------------------------------------------------------------*/

#ifdef RTC_PORT

/* Most newer x86 systems have two register banks, the first used
 * for RTC and NVRAM and the second only for NVRAM.  Caller must
 * own rtc_lock ... and we won't worry about access during NMI.
 */
#define can_bank2       true

static inline unsigned char cmos_read_bank2(unsigned char addr)
{
        outb(addr, RTC_PORT(2));
        return inb(RTC_PORT(3));
}

static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
{
        outb(addr, RTC_PORT(2));
        outb(val, RTC_PORT(3));
}

#else

#define can_bank2       false

static inline unsigned char cmos_read_bank2(unsigned char addr)
{
        return 0;
}

static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
{
}

#endif

/*----------------------------------------------------------------*/

static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
        /* REVISIT:  if the clock has a "century" register, use
         * that instead of the heuristic in mc146818_get_time().
         * That'll make Y3K compatility (year > 2070) easy!
         */
        mc146818_get_time(t);
        return 0;
}

static int cmos_set_time(struct device *dev, struct rtc_time *t)
{
        /* REVISIT:  set the "century" register if available
         *
         * NOTE: this ignores the issue whereby updating the seconds
         * takes effect exactly 500ms after we write the register.
         * (Also queueing and other delays before we get this far.)
         */
        return mc146818_set_time(t);
}

static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char   rtc_control;

        if (!is_valid_irq(cmos->irq))
                return -EIO;

        /* Basic alarms only support hour, minute, and seconds fields.
         * Some also support day and month, for alarms up to a year in
         * the future.
         */

        spin_lock_irq(&rtc_lock);
        t->time.tm_sec = CMOS_READ(RTC_SECONDS_ALARM);
        t->time.tm_min = CMOS_READ(RTC_MINUTES_ALARM);
        t->time.tm_hour = CMOS_READ(RTC_HOURS_ALARM);

        if (cmos->day_alrm) {
                /* ignore upper bits on readback per ACPI spec */
                t->time.tm_mday = CMOS_READ(cmos->day_alrm) & 0x3f;
                if (!t->time.tm_mday)
                        t->time.tm_mday = -1;

                if (cmos->mon_alrm) {
                        t->time.tm_mon = CMOS_READ(cmos->mon_alrm);
                        if (!t->time.tm_mon)
                                t->time.tm_mon = -1;
                }
        }

        rtc_control = CMOS_READ(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                if (((unsigned)t->time.tm_sec) < 0x60)
                        t->time.tm_sec = bcd2bin(t->time.tm_sec);
                else
                        t->time.tm_sec = -1;
                if (((unsigned)t->time.tm_min) < 0x60)
                        t->time.tm_min = bcd2bin(t->time.tm_min);
                else
                        t->time.tm_min = -1;
                if (((unsigned)t->time.tm_hour) < 0x24)
                        t->time.tm_hour = bcd2bin(t->time.tm_hour);
                else
                        t->time.tm_hour = -1;

                if (cmos->day_alrm) {
                        if (((unsigned)t->time.tm_mday) <= 0x31)
                                t->time.tm_mday = bcd2bin(t->time.tm_mday);
                        else
                                t->time.tm_mday = -1;

                        if (cmos->mon_alrm) {
                                if (((unsigned)t->time.tm_mon) <= 0x12)
                                        t->time.tm_mon = bcd2bin(t->time.tm_mon)-1;
                                else
                                        t->time.tm_mon = -1;
                        }
                }
        }

        t->enabled = !!(rtc_control & RTC_AIE);
        t->pending = 0;

        return 0;
}

static void cmos_checkintr(struct cmos_rtc *cmos, unsigned char rtc_control)
{
        unsigned char   rtc_intr;

        /* NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
         * allegedly some older rtcs need that to handle irqs properly
         */
        rtc_intr = CMOS_READ(RTC_INTR_FLAGS);

        if (is_hpet_enabled())
                return;

        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
        if (is_intr(rtc_intr))
                rtc_update_irq(cmos->rtc, 1, rtc_intr);
}

static void cmos_irq_enable(struct cmos_rtc *cmos, unsigned char mask)
{
        unsigned char   rtc_control;

        /* flush any pending IRQ status, notably for update irqs,
         * before we enable new IRQs
         */
        rtc_control = CMOS_READ(RTC_CONTROL);
        cmos_checkintr(cmos, rtc_control);

        rtc_control |= mask;
        CMOS_WRITE(rtc_control, RTC_CONTROL);
        hpet_set_rtc_irq_bit(mask);

        cmos_checkintr(cmos, rtc_control);
}

static void cmos_irq_disable(struct cmos_rtc *cmos, unsigned char mask)
{
        unsigned char   rtc_control;

        rtc_control = CMOS_READ(RTC_CONTROL);
        rtc_control &= ~mask;
        CMOS_WRITE(rtc_control, RTC_CONTROL);
        hpet_mask_rtc_irq_bit(mask);

        cmos_checkintr(cmos, rtc_control);
}

static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char mon, mday, hrs, min, sec, rtc_control;

        if (!is_valid_irq(cmos->irq))
                return -EIO;

        mon = t->time.tm_mon + 1;
        mday = t->time.tm_mday;
        hrs = t->time.tm_hour;
        min = t->time.tm_min;
        sec = t->time.tm_sec;

        rtc_control = CMOS_READ(RTC_CONTROL);
        if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                /* Writing 0xff means "don't care" or "match all".  */
                mon = (mon <= 12) ? bin2bcd(mon) : 0xff;
                mday = (mday >= 1 && mday <= 31) ? bin2bcd(mday) : 0xff;
                hrs = (hrs < 24) ? bin2bcd(hrs) : 0xff;
                min = (min < 60) ? bin2bcd(min) : 0xff;
                sec = (sec < 60) ? bin2bcd(sec) : 0xff;
        }

        spin_lock_irq(&rtc_lock);

        /* next rtc irq must not be from previous alarm setting */
        cmos_irq_disable(cmos, RTC_AIE);

        /* update alarm */
        CMOS_WRITE(hrs, RTC_HOURS_ALARM);
        CMOS_WRITE(min, RTC_MINUTES_ALARM);
        CMOS_WRITE(sec, RTC_SECONDS_ALARM);

        /* the system may support an "enhanced" alarm */
        if (cmos->day_alrm) {
                CMOS_WRITE(mday, cmos->day_alrm);
                if (cmos->mon_alrm)
                        CMOS_WRITE(mon, cmos->mon_alrm);
        }

        /* FIXME the HPET alarm glue currently ignores day_alrm
         * and mon_alrm ...
         */
        hpet_set_alarm_time(t->time.tm_hour, t->time.tm_min, t->time.tm_sec);

        if (t->enabled)
                cmos_irq_enable(cmos, RTC_AIE);

        spin_unlock_irq(&rtc_lock);

        cmos->alarm_expires = rtc_tm_to_time64(&t->time);

        return 0;
}

static int cmos_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned long   flags;

        if (!is_valid_irq(cmos->irq))
                return -EINVAL;

        spin_lock_irqsave(&rtc_lock, flags);

        if (enabled)
                cmos_irq_enable(cmos, RTC_AIE);
        else
                cmos_irq_disable(cmos, RTC_AIE);

        spin_unlock_irqrestore(&rtc_lock, flags);
        return 0;
}

#if IS_ENABLED(CONFIG_RTC_INTF_PROC)

static int cmos_procfs(struct device *dev, struct seq_file *seq)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char   rtc_control, valid;

        spin_lock_irq(&rtc_lock);
        rtc_control = CMOS_READ(RTC_CONTROL);
        valid = CMOS_READ(RTC_VALID);
        spin_unlock_irq(&rtc_lock);

        /* NOTE:  at least ICH6 reports battery status using a different
         * (non-RTC) bit; and SQWE is ignored on many current systems.
         */
        seq_printf(seq,
                   "periodic_IRQ\t: %s\n"
                   "update_IRQ\t: %s\n"
                   "HPET_emulated\t: %s\n"
                   // "square_wave\t: %s\n"
                   "BCD\t\t: %s\n"
                   "DST_enable\t: %s\n"
                   "periodic_freq\t: %d\n"
                   "batt_status\t: %s\n",
                   (rtc_control & RTC_PIE) ? "yes" : "no",
                   (rtc_control & RTC_UIE) ? "yes" : "no",
                   is_hpet_enabled() ? "yes" : "no",
                   // (rtc_control & RTC_SQWE) ? "yes" : "no",
                   (rtc_control & RTC_DM_BINARY) ? "no" : "yes",
                   (rtc_control & RTC_DST_EN) ? "yes" : "no",
                   cmos->rtc->irq_freq,
                   (valid & RTC_VRT) ? "okay" : "dead");

        return 0;
}

#else
#define cmos_procfs     NULL
#endif

static const struct rtc_class_ops cmos_rtc_ops = {
        .read_time              = cmos_read_time,
        .set_time               = cmos_set_time,
        .read_alarm             = cmos_read_alarm,
        .set_alarm              = cmos_set_alarm,
        .proc                   = cmos_procfs,
        .alarm_irq_enable       = cmos_alarm_irq_enable,
};

/*----------------------------------------------------------------*/

/*
 * All these chips have at least 64 bytes of address space, shared by
 * RTC registers and NVRAM.  Most of those bytes of NVRAM are used
 * by boot firmware.  Modern chips have 128 or 256 bytes.
 */

#define NVRAM_OFFSET    (RTC_REG_D + 1)

static ssize_t
cmos_nvram_read(struct file *filp, struct kobject *kobj,
                struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        int     retval;

        off += NVRAM_OFFSET;
        spin_lock_irq(&rtc_lock);
        for (retval = 0; count; count--, off++, retval++) {
                if (off < 128)
                        *buf++ = CMOS_READ(off);
                else if (can_bank2)
                        *buf++ = cmos_read_bank2(off);
                else
                        break;
        }
        spin_unlock_irq(&rtc_lock);

        return retval;
}

static ssize_t
cmos_nvram_write(struct file *filp, struct kobject *kobj,
                struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        struct cmos_rtc *cmos;
        int             retval;

        cmos = dev_get_drvdata(container_of(kobj, struct device, kobj));

        /* NOTE:  on at least PCs and Ataris, the boot firmware uses a
         * checksum on part of the NVRAM data.  That's currently ignored
         * here.  If userspace is smart enough to know what fields of
         * NVRAM to update, updating checksums is also part of its job.
         */
        off += NVRAM_OFFSET;
        spin_lock_irq(&rtc_lock);
        for (retval = 0; count; count--, off++, retval++) {
                /* don't trash RTC registers */
                if (off == cmos->day_alrm
                                || off == cmos->mon_alrm
                                || off == cmos->century)
                        buf++;
                else if (off < 128)
                        CMOS_WRITE(*buf++, off);
                else if (can_bank2)
                        cmos_write_bank2(*buf++, off);
                else
                        break;
        }
        spin_unlock_irq(&rtc_lock);

        return retval;
}

static struct bin_attribute nvram = {
        .attr = {
                .name   = "nvram",
                .mode   = S_IRUGO | S_IWUSR,
        },

        .read   = cmos_nvram_read,
        .write  = cmos_nvram_write,
        /* size gets set up later */
};

/*----------------------------------------------------------------*/

static struct cmos_rtc  cmos_rtc;

static irqreturn_t cmos_interrupt(int irq, void *p)
{
        u8              irqstat;
        u8              rtc_control;

        spin_lock(&rtc_lock);

        /* When the HPET interrupt handler calls us, the interrupt
         * status is passed as arg1 instead of the irq number.  But
         * always clear irq status, even when HPET is in the way.
         *
         * Note that HPET and RTC are almost certainly out of phase,
         * giving different IRQ status ...
         */
        irqstat = CMOS_READ(RTC_INTR_FLAGS);
        rtc_control = CMOS_READ(RTC_CONTROL);
        if (is_hpet_enabled())
                irqstat = (unsigned long)irq & 0xF0;

        /* If we were suspended, RTC_CONTROL may not be accurate since the
         * bios may have cleared it.
         */
        if (!cmos_rtc.suspend_ctrl)
                irqstat &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
        else
                irqstat &= (cmos_rtc.suspend_ctrl & RTC_IRQMASK) | RTC_IRQF;

        /* All Linux RTC alarms should be treated as if they were oneshot.
         * Similar code may be needed in system wakeup paths, in case the
         * alarm woke the system.
         */
        if (irqstat & RTC_AIE) {
                cmos_rtc.suspend_ctrl &= ~RTC_AIE;
                rtc_control &= ~RTC_AIE;
                CMOS_WRITE(rtc_control, RTC_CONTROL);
                hpet_mask_rtc_irq_bit(RTC_AIE);
                CMOS_READ(RTC_INTR_FLAGS);
        }
        spin_unlock(&rtc_lock);

        if (is_intr(irqstat)) {
                rtc_update_irq(p, 1, irqstat);
                return IRQ_HANDLED;
        } else
                return IRQ_NONE;
}

#ifdef  CONFIG_PNP
#define INITSECTION

#else
#define INITSECTION     __init
#endif

static int INITSECTION
cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
{
        struct cmos_rtc_board_info      *info = dev_get_platdata(dev);
        int                             retval = 0;
        unsigned char                   rtc_control;
        unsigned                        address_space;
        u32                             flags = 0;

        /* there can be only one ... */
        if (cmos_rtc.dev)
                return -EBUSY;

        if (!ports)
                return -ENODEV;

        /* Claim I/O ports ASAP, minimizing conflict with legacy driver.
         *
         * REVISIT non-x86 systems may instead use memory space resources
         * (needing ioremap etc), not i/o space resources like this ...
         */
        if (RTC_IOMAPPED)
                ports = request_region(ports->start, resource_size(ports),
                                       driver_name);
        else
                ports = request_mem_region(ports->start, resource_size(ports),
                                           driver_name);
        if (!ports) {
                dev_dbg(dev, "i/o registers already in use\n");
                return -EBUSY;
        }

        cmos_rtc.irq = rtc_irq;
        cmos_rtc.iomem = ports;

        /* Heuristic to deduce NVRAM size ... do what the legacy NVRAM
         * driver did, but don't reject unknown configs.   Old hardware
         * won't address 128 bytes.  Newer chips have multiple banks,
         * though they may not be listed in one I/O resource.
         */
#if     defined(CONFIG_ATARI)
        address_space = 64;
#elif defined(__i386__) || defined(__x86_64__) || defined(__arm__) \
                        || defined(__sparc__) || defined(__mips__) \
                        || defined(__powerpc__) || defined(CONFIG_MN10300)
        address_space = 128;
#else
#warning Assuming 128 bytes of RTC+NVRAM address space, not 64 bytes.
        address_space = 128;
#endif
        if (can_bank2 && ports->end > (ports->start + 1))
                address_space = 256;

        /* For ACPI systems extension info comes from the FADT.  On others,
         * board specific setup provides it as appropriate.  Systems where
         * the alarm IRQ isn't automatically a wakeup IRQ (like ACPI, and
         * some almost-clones) can provide hooks to make that behave.
         *
         * Note that ACPI doesn't preclude putting these registers into
         * "extended" areas of the chip, including some that we won't yet
         * expect CMOS_READ and friends to handle.
         */
        if (info) {
                if (info->flags)
                        flags = info->flags;
                if (info->address_space)
                        address_space = info->address_space;

                if (info->rtc_day_alarm && info->rtc_day_alarm < 128)
                        cmos_rtc.day_alrm = info->rtc_day_alarm;
                if (info->rtc_mon_alarm && info->rtc_mon_alarm < 128)
                        cmos_rtc.mon_alrm = info->rtc_mon_alarm;
                if (info->rtc_century && info->rtc_century < 128)
                        cmos_rtc.century = info->rtc_century;

                if (info->wake_on && info->wake_off) {
                        cmos_rtc.wake_on = info->wake_on;
                        cmos_rtc.wake_off = info->wake_off;
                }
        }

        cmos_rtc.dev = dev;
        dev_set_drvdata(dev, &cmos_rtc);

        cmos_rtc.rtc = rtc_device_register(driver_name, dev,
                                &cmos_rtc_ops, THIS_MODULE);
        if (IS_ERR(cmos_rtc.rtc)) {
                retval = PTR_ERR(cmos_rtc.rtc);
                goto cleanup0;
        }

        rename_region(ports, dev_name(&cmos_rtc.rtc->dev));

        spin_lock_irq(&rtc_lock);

        if (!(flags & CMOS_RTC_FLAGS_NOFREQ)) {
                /* force periodic irq to CMOS reset default of 1024Hz;
                 *
                 * REVISIT it's been reported that at least one x86_64 ALI
                 * mobo doesn't use 32KHz here ... for portability we might
                 * need to do something about other clock frequencies.
                 */
                cmos_rtc.rtc->irq_freq = 1024;
                hpet_set_periodic_freq(cmos_rtc.rtc->irq_freq);
                CMOS_WRITE(RTC_REF_CLCK_32KHZ | 0x06, RTC_FREQ_SELECT);
        }

        /* disable irqs */
        if (is_valid_irq(rtc_irq))
                cmos_irq_disable(&cmos_rtc, RTC_PIE | RTC_AIE | RTC_UIE);

        rtc_control = CMOS_READ(RTC_CONTROL);

        spin_unlock_irq(&rtc_lock);

        /* FIXME:
         * <asm-generic/rtc.h> doesn't know 12-hour mode either.
         */
        if (is_valid_irq(rtc_irq) && !(rtc_control & RTC_24H)) {
                dev_warn(dev, "only 24-hr supported\n");
                retval = -ENXIO;
                goto cleanup1;
        }

        hpet_rtc_timer_init();

        if (is_valid_irq(rtc_irq)) {
                irq_handler_t rtc_cmos_int_handler;

                if (is_hpet_enabled()) {
                        rtc_cmos_int_handler = hpet_rtc_interrupt;
                        retval = hpet_register_irq_handler(cmos_interrupt);
                        if (retval) {
                                hpet_mask_rtc_irq_bit(RTC_IRQMASK);
                                dev_warn(dev, "hpet_register_irq_handler "
                                                " failed in rtc_init().");
                                goto cleanup1;
                        }
                } else
                        rtc_cmos_int_handler = cmos_interrupt;

                retval = request_irq(rtc_irq, rtc_cmos_int_handler,
                                IRQF_SHARED, dev_name(&cmos_rtc.rtc->dev),
                                cmos_rtc.rtc);
                if (retval < 0) {
                        dev_dbg(dev, "IRQ %d is already in use\n", rtc_irq);
                        goto cleanup1;
                }
        }

        /* export at least the first block of NVRAM */
        nvram.size = address_space - NVRAM_OFFSET;
        retval = sysfs_create_bin_file(&dev->kobj, &nvram);
        if (retval < 0) {
                dev_dbg(dev, "can't create nvram file? %d\n", retval);
                goto cleanup2;
        }

        dev_info(dev, "%s%s, %zd bytes nvram%s\n",
                !is_valid_irq(rtc_irq) ? "no alarms" :
                        cmos_rtc.mon_alrm ? "alarms up to one year" :
                        cmos_rtc.day_alrm ? "alarms up to one month" :
                        "alarms up to one day",
                cmos_rtc.century ? ", y3k" : "",
                nvram.size,
                is_hpet_enabled() ? ", hpet irqs" : "");

        return 0;

cleanup2:
        if (is_valid_irq(rtc_irq))
                free_irq(rtc_irq, cmos_rtc.rtc);
cleanup1:
        cmos_rtc.dev = NULL;
        rtc_device_unregister(cmos_rtc.rtc);
cleanup0:
        if (RTC_IOMAPPED)
                release_region(ports->start, resource_size(ports));
        else
                release_mem_region(ports->start, resource_size(ports));
        return retval;
}

static void cmos_do_shutdown(int rtc_irq)
{
        spin_lock_irq(&rtc_lock);
        if (is_valid_irq(rtc_irq))
                cmos_irq_disable(&cmos_rtc, RTC_IRQMASK);
        spin_unlock_irq(&rtc_lock);
}

static void cmos_do_remove(struct device *dev)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        struct resource *ports;

        cmos_do_shutdown(cmos->irq);

        sysfs_remove_bin_file(&dev->kobj, &nvram);

        if (is_valid_irq(cmos->irq)) {
                free_irq(cmos->irq, cmos->rtc);
                hpet_unregister_irq_handler(cmos_interrupt);
        }

        rtc_device_unregister(cmos->rtc);
        cmos->rtc = NULL;

        ports = cmos->iomem;
        if (RTC_IOMAPPED)
                release_region(ports->start, resource_size(ports));
        else
                release_mem_region(ports->start, resource_size(ports));
        cmos->iomem = NULL;

        cmos->dev = NULL;
}

static int cmos_aie_poweroff(struct device *dev)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        struct rtc_time now;
        time64_t t_now;
        int retval = 0;
        unsigned char rtc_control;

        if (!cmos->alarm_expires)
                return -EINVAL;

        spin_lock_irq(&rtc_lock);
        rtc_control = CMOS_READ(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        /* We only care about the situation where AIE is disabled. */
        if (rtc_control & RTC_AIE)
                return -EBUSY;

        cmos_read_time(dev, &now);
        t_now = rtc_tm_to_time64(&now);

        /*
         * When enabling "RTC wake-up" in BIOS setup, the machine reboots
         * automatically right after shutdown on some buggy boxes.
         * This automatic rebooting issue won't happen when the alarm
         * time is larger than now+1 seconds.
         *
         * If the alarm time is equal to now+1 seconds, the issue can be
         * prevented by cancelling the alarm.
         */
        if (cmos->alarm_expires == t_now + 1) {
                struct rtc_wkalrm alarm;

                /* Cancel the AIE timer by configuring the past time. */
                rtc_time64_to_tm(t_now - 1, &alarm.time);
                alarm.enabled = 0;
                retval = cmos_set_alarm(dev, &alarm);
        } else if (cmos->alarm_expires > t_now + 1) {
                retval = -EBUSY;
        }

        return retval;
}

static int cmos_suspend(struct device *dev)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char   tmp;

        /* only the alarm might be a wakeup event source */
        spin_lock_irq(&rtc_lock);
        cmos->suspend_ctrl = tmp = CMOS_READ(RTC_CONTROL);
        if (tmp & (RTC_PIE|RTC_AIE|RTC_UIE)) {
                unsigned char   mask;

                if (device_may_wakeup(dev))
                        mask = RTC_IRQMASK & ~RTC_AIE;
                else
                        mask = RTC_IRQMASK;
                tmp &= ~mask;
                CMOS_WRITE(tmp, RTC_CONTROL);
                hpet_mask_rtc_irq_bit(mask);

                cmos_checkintr(cmos, tmp);
        }
        spin_unlock_irq(&rtc_lock);

        if (tmp & RTC_AIE) {
                cmos->enabled_wake = 1;
                if (cmos->wake_on)
                        cmos->wake_on(dev);
                else
                        enable_irq_wake(cmos->irq);
        }

        cmos_read_alarm(dev, &cmos->saved_wkalrm);

        dev_dbg(dev, "suspend%s, ctrl %02x\n",
                        (tmp & RTC_AIE) ? ", alarm may wake" : "",
                        tmp);

        return 0;
}

/* We want RTC alarms to wake us from e.g. ACPI G2/S5 "soft off", even
 * after a detour through G3 "mechanical off", although the ACPI spec
 * says wakeup should only work from G1/S4 "hibernate".  To most users,
 * distinctions between S4 and S5 are pointless.  So when the hardware
 * allows, don't draw that distinction.
 */
static inline int cmos_poweroff(struct device *dev)
{
        if (!IS_ENABLED(CONFIG_PM))
                return -ENOSYS;

        return cmos_suspend(dev);
}

static void cmos_check_wkalrm(struct device *dev)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        struct rtc_wkalrm current_alarm;
        time64_t t_current_expires;
        time64_t t_saved_expires;

        cmos_read_alarm(dev, &current_alarm);
        t_current_expires = rtc_tm_to_time64(&current_alarm.time);
        t_saved_expires = rtc_tm_to_time64(&cmos->saved_wkalrm.time);
        if (t_current_expires != t_saved_expires ||
            cmos->saved_wkalrm.enabled != current_alarm.enabled) {
                cmos_set_alarm(dev, &cmos->saved_wkalrm);
        }
}

static void cmos_check_acpi_rtc_status(struct device *dev,
                                       unsigned char *rtc_control);

static int __maybe_unused cmos_resume(struct device *dev)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char tmp;

        if (cmos->enabled_wake) {
                if (cmos->wake_off)
                        cmos->wake_off(dev);
                else
                        disable_irq_wake(cmos->irq);
                cmos->enabled_wake = 0;
        }

        /* The BIOS might have changed the alarm, restore it */
        cmos_check_wkalrm(dev);

        spin_lock_irq(&rtc_lock);
        tmp = cmos->suspend_ctrl;
        cmos->suspend_ctrl = 0;
        /* re-enable any irqs previously active */
        if (tmp & RTC_IRQMASK) {
                unsigned char   mask;

                if (device_may_wakeup(dev))
                        hpet_rtc_timer_init();

                do {
                        CMOS_WRITE(tmp, RTC_CONTROL);
                        hpet_set_rtc_irq_bit(tmp & RTC_IRQMASK);

                        mask = CMOS_READ(RTC_INTR_FLAGS);
                        mask &= (tmp & RTC_IRQMASK) | RTC_IRQF;
                        if (!is_hpet_enabled() || !is_intr(mask))
                                break;

                        /* force one-shot behavior if HPET blocked
                         * the wake alarm's irq
                         */
                        rtc_update_irq(cmos->rtc, 1, mask);
                        tmp &= ~RTC_AIE;
                        hpet_mask_rtc_irq_bit(RTC_AIE);
                } while (mask & RTC_AIE);

                if (tmp & RTC_AIE)
                        cmos_check_acpi_rtc_status(dev, &tmp);
        }
        spin_unlock_irq(&rtc_lock);

        dev_dbg(dev, "resume, ctrl %02x\n", tmp);

        return 0;
}

static SIMPLE_DEV_PM_OPS(cmos_pm_ops, cmos_suspend, cmos_resume);

/*----------------------------------------------------------------*/

/* On non-x86 systems, a "CMOS" RTC lives most naturally on platform_bus.
 * ACPI systems always list these as PNPACPI devices, and pre-ACPI PCs
 * probably list them in similar PNPBIOS tables; so PNP is more common.
 *
 * We don't use legacy "poke at the hardware" probing.  Ancient PCs that
 * predate even PNPBIOS should set up platform_bus devices.
 */

#ifdef  CONFIG_ACPI

#include <linux/acpi.h>

static u32 rtc_handler(void *context)
{
        struct device *dev = context;
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        unsigned char rtc_control = 0;
        unsigned char rtc_intr;
        unsigned long flags;

        spin_lock_irqsave(&rtc_lock, flags);
        if (cmos_rtc.suspend_ctrl)
                rtc_control = CMOS_READ(RTC_CONTROL);
        if (rtc_control & RTC_AIE) {
                cmos_rtc.suspend_ctrl &= ~RTC_AIE;
                CMOS_WRITE(rtc_control, RTC_CONTROL);
                rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
                rtc_update_irq(cmos->rtc, 1, rtc_intr);
        }
        spin_unlock_irqrestore(&rtc_lock, flags);

        pm_wakeup_event(dev, 0);
        acpi_clear_event(ACPI_EVENT_RTC);
        acpi_disable_event(ACPI_EVENT_RTC, 0);
        return ACPI_INTERRUPT_HANDLED;
}

static inline void rtc_wake_setup(struct device *dev)
{
        acpi_install_fixed_event_handler(ACPI_EVENT_RTC, rtc_handler, dev);
        /*
         * After the RTC handler is installed, the Fixed_RTC event should
         * be disabled. Only when the RTC alarm is set will it be enabled.
         */
        acpi_clear_event(ACPI_EVENT_RTC);
        acpi_disable_event(ACPI_EVENT_RTC, 0);
}

static void rtc_wake_on(struct device *dev)
{
        acpi_clear_event(ACPI_EVENT_RTC);
        acpi_enable_event(ACPI_EVENT_RTC, 0);
}

static void rtc_wake_off(struct device *dev)
{
        acpi_disable_event(ACPI_EVENT_RTC, 0);
}

/* Every ACPI platform has a mc146818 compatible "cmos rtc".  Here we find
 * its device node and pass extra config data.  This helps its driver use
 * capabilities that the now-obsolete mc146818 didn't have, and informs it
 * that this board's RTC is wakeup-capable (per ACPI spec).
 */
static struct cmos_rtc_board_info acpi_rtc_info;

static void cmos_wake_setup(struct device *dev)
{
        if (acpi_disabled)
                return;

        rtc_wake_setup(dev);
        acpi_rtc_info.wake_on = rtc_wake_on;
        acpi_rtc_info.wake_off = rtc_wake_off;

        /* workaround bug in some ACPI tables */
        if (acpi_gbl_FADT.month_alarm && !acpi_gbl_FADT.day_alarm) {
                dev_dbg(dev, "bogus FADT month_alarm (%d)\n",
                        acpi_gbl_FADT.month_alarm);
                acpi_gbl_FADT.month_alarm = 0;
        }

        acpi_rtc_info.rtc_day_alarm = acpi_gbl_FADT.day_alarm;
        acpi_rtc_info.rtc_mon_alarm = acpi_gbl_FADT.month_alarm;
        acpi_rtc_info.rtc_century = acpi_gbl_FADT.century;

        /* NOTE:  S4_RTC_WAKE is NOT currently useful to Linux */
        if (acpi_gbl_FADT.flags & ACPI_FADT_S4_RTC_WAKE)
                dev_info(dev, "RTC can wake from S4\n");

        dev->platform_data = &acpi_rtc_info;

        /* RTC always wakes from S1/S2/S3, and often S4/STD */
        device_init_wakeup(dev, 1);
}

static void cmos_check_acpi_rtc_status(struct device *dev,
                                       unsigned char *rtc_control)
{
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
        acpi_event_status rtc_status;
        acpi_status status;

        if (acpi_gbl_FADT.flags & ACPI_FADT_FIXED_RTC)
                return;

        status = acpi_get_event_status(ACPI_EVENT_RTC, &rtc_status);
        if (ACPI_FAILURE(status)) {
                dev_err(dev, "Could not get RTC status\n");
        } else if (rtc_status & ACPI_EVENT_FLAG_SET) {
                unsigned char mask;
                *rtc_control &= ~RTC_AIE;
                CMOS_WRITE(*rtc_control, RTC_CONTROL);
                mask = CMOS_READ(RTC_INTR_FLAGS);
                rtc_update_irq(cmos->rtc, 1, mask);
        }
}

#else

static void cmos_wake_setup(struct device *dev)
{
}

static void cmos_check_acpi_rtc_status(struct device *dev,
                                       unsigned char *rtc_control)
{
}

#endif

#ifdef  CONFIG_PNP

#include <linux/pnp.h>

static int cmos_pnp_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
{
        cmos_wake_setup(&pnp->dev);

        if (pnp_port_start(pnp, 0) == 0x70 && !pnp_irq_valid(pnp, 0))
                /* Some machines contain a PNP entry for the RTC, but
                 * don't define the IRQ. It should always be safe to
                 * hardcode it in these cases
                 */
                return cmos_do_probe(&pnp->dev,
                                pnp_get_resource(pnp, IORESOURCE_IO, 0), 8);
        else
                return cmos_do_probe(&pnp->dev,
                                pnp_get_resource(pnp, IORESOURCE_IO, 0),
                                pnp_irq(pnp, 0));
}

static void cmos_pnp_remove(struct pnp_dev *pnp)
{
        cmos_do_remove(&pnp->dev);
}

static void cmos_pnp_shutdown(struct pnp_dev *pnp)
{
        struct device *dev = &pnp->dev;
        struct cmos_rtc *cmos = dev_get_drvdata(dev);

        if (system_state == SYSTEM_POWER_OFF) {
                int retval = cmos_poweroff(dev);

                if (cmos_aie_poweroff(dev) < 0 && !retval)
                        return;
        }

        cmos_do_shutdown(cmos->irq);
}

static const struct pnp_device_id rtc_ids[] = {
        { .id = "PNP0b00", },
        { .id = "PNP0b01", },
        { .id = "PNP0b02", },
        { },
};
MODULE_DEVICE_TABLE(pnp, rtc_ids);

static struct pnp_driver cmos_pnp_driver = {
        .name           = (char *) driver_name,
        .id_table       = rtc_ids,
        .probe          = cmos_pnp_probe,
        .remove         = cmos_pnp_remove,
        .shutdown       = cmos_pnp_shutdown,

        /* flag ensures resume() gets called, and stops syslog spam */
        .flags          = PNP_DRIVER_RES_DO_NOT_CHANGE,
        .driver         = {
                        .pm = &cmos_pm_ops,
        },
};

#endif  /* CONFIG_PNP */

#ifdef CONFIG_OF
static const struct of_device_id of_cmos_match[] = {
        {
                .compatible = "motorola,mc146818",
        },
        { },
};
MODULE_DEVICE_TABLE(of, of_cmos_match);

static __init void cmos_of_init(struct platform_device *pdev)
{
        struct device_node *node = pdev->dev.of_node;
        struct rtc_time time;
        int ret;
        const __be32 *val;

        if (!node)
                return;

        val = of_get_property(node, "ctrl-reg", NULL);
        if (val)
                CMOS_WRITE(be32_to_cpup(val), RTC_CONTROL);

        val = of_get_property(node, "freq-reg", NULL);
        if (val)
                CMOS_WRITE(be32_to_cpup(val), RTC_FREQ_SELECT);

        cmos_read_time(&pdev->dev, &time);
        ret = rtc_valid_tm(&time);
        if (ret) {
                struct rtc_time def_time = {
                        .tm_year = 1,
                        .tm_mday = 1,
                };
                cmos_set_time(&pdev->dev, &def_time);
        }
}
#else
static inline void cmos_of_init(struct platform_device *pdev) {}
#endif
/*----------------------------------------------------------------*/

/* Platform setup should have set up an RTC device, when PNP is
 * unavailable ... this could happen even on (older) PCs.
 */

static int __init cmos_platform_probe(struct platform_device *pdev)
{
        struct resource *resource;
        int irq;

        cmos_of_init(pdev);
        cmos_wake_setup(&pdev->dev);

        if (RTC_IOMAPPED)
                resource = platform_get_resource(pdev, IORESOURCE_IO, 0);
        else
                resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                irq = -1;

        return cmos_do_probe(&pdev->dev, resource, irq);
}

static int cmos_platform_remove(struct platform_device *pdev)
{
        cmos_do_remove(&pdev->dev);
        return 0;
}

static void cmos_platform_shutdown(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct cmos_rtc *cmos = dev_get_drvdata(dev);

        if (system_state == SYSTEM_POWER_OFF) {
                int retval = cmos_poweroff(dev);

                if (cmos_aie_poweroff(dev) < 0 && !retval)
                        return;
        }

        cmos_do_shutdown(cmos->irq);
}

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

static struct platform_driver cmos_platform_driver = {
        .remove         = cmos_platform_remove,
        .shutdown       = cmos_platform_shutdown,
        .driver = {
                .name           = driver_name,
                .pm             = &cmos_pm_ops,
                .of_match_table = of_match_ptr(of_cmos_match),
        }
};

#ifdef CONFIG_PNP
static bool pnp_driver_registered;
#endif
static bool platform_driver_registered;

static int __init cmos_init(void)
{
        int retval = 0;

#ifdef  CONFIG_PNP
        retval = pnp_register_driver(&cmos_pnp_driver);
        if (retval == 0)
                pnp_driver_registered = true;
#endif

        if (!cmos_rtc.dev) {
                retval = platform_driver_probe(&cmos_platform_driver,
                                               cmos_platform_probe);
                if (retval == 0)
                        platform_driver_registered = true;
        }

        if (retval == 0)
                return 0;

#ifdef  CONFIG_PNP
        if (pnp_driver_registered)
                pnp_unregister_driver(&cmos_pnp_driver);
#endif
        return retval;
}
module_init(cmos_init);

static void __exit cmos_exit(void)
{
#ifdef  CONFIG_PNP
        if (pnp_driver_registered)
                pnp_unregister_driver(&cmos_pnp_driver);
#endif
        if (platform_driver_registered)
                platform_driver_unregister(&cmos_platform_driver);
}
module_exit(cmos_exit);


MODULE_AUTHOR("David Brownell");
MODULE_DESCRIPTION("Driver for PC-style 'CMOS' RTCs");
MODULE_LICENSE("GPL");