// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/arch/alpha/kernel/rtc.c
 *
 *  Copyright (C) 1991, 1992, 1995, 1999, 2000  Linus Torvalds
 *
 * This file contains date handling.
 */
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mc146818rtc.h>
#include <linux/bcd.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>

#include "proto.h"


/*
 * Support for the RTC device.
 *
 * We don't want to use the rtc-cmos driver, because we don't want to support
 * alarms, as that would be indistinguishable from timer interrupts.
 *
 * Further, generic code is really, really tied to a 1900 epoch.  This is
 * true in __get_rtc_time as well as the users of struct rtc_time e.g.
 * rtc_tm_to_time.  Thankfully all of the other epochs in use are later
 * than 1900, and so it's easy to adjust.
 */

static unsigned long rtc_epoch;

static int __init
specifiy_epoch(char *str)
{
        unsigned long epoch = simple_strtoul(str, NULL, 0);
        if (epoch < 1900)
                printk("Ignoring invalid user specified epoch %lu\n", epoch);
        else
                rtc_epoch = epoch;
        return 1;
}
__setup("epoch=", specifiy_epoch);

static void __init
init_rtc_epoch(void)
{
        int epoch, year, ctrl;

        if (rtc_epoch != 0) {
                /* The epoch was specified on the command-line.  */
                return;
        }

        /* Detect the epoch in use on this computer.  */
        ctrl = CMOS_READ(RTC_CONTROL);
        year = CMOS_READ(RTC_YEAR);
        if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
                year = bcd2bin(year);

        /* PC-like is standard; used for year >= 70 */
        epoch = 1900;
        if (year < 20) {
                epoch = 2000;
        } else if (year >= 20 && year < 48) {
                /* NT epoch */
                epoch = 1980;
        } else if (year >= 48 && year < 70) {
                /* Digital UNIX epoch */
                epoch = 1952;
        }
        rtc_epoch = epoch;

        printk(KERN_INFO "Using epoch %d for rtc year %d\n", epoch, year);
}

static int
alpha_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        int ret = mc146818_get_time(tm, 10);

        if (ret < 0) {
                dev_err_ratelimited(dev, "unable to read current time\n");
                return ret;
        }

        /* Adjust for non-default epochs.  It's easier to depend on the
           generic __get_rtc_time and adjust the epoch here than create
           a copy of __get_rtc_time with the edits we need.  */
        if (rtc_epoch != 1900) {
                int year = tm->tm_year;
                /* Undo the century adjustment made in __get_rtc_time.  */
                if (year >= 100)
                        year -= 100;
                year += rtc_epoch - 1900;
                /* Redo the century adjustment with the epoch in place.  */
                if (year <= 69)
                        year += 100;
                tm->tm_year = year;
        }

        return 0;
}

static int
alpha_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_time xtm;

        if (rtc_epoch != 1900) {
                xtm = *tm;
                xtm.tm_year -= rtc_epoch - 1900;
                tm = &xtm;
        }

        return mc146818_set_time(tm);
}

static int
alpha_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
        switch (cmd) {
        case RTC_EPOCH_READ:
                return put_user(rtc_epoch, (unsigned long __user *)arg);
        case RTC_EPOCH_SET:
                if (arg < 1900)
                        return -EINVAL;
                rtc_epoch = arg;
                return 0;
        default:
                return -ENOIOCTLCMD;
        }
}

static const struct rtc_class_ops alpha_rtc_ops = {
        .read_time = alpha_rtc_read_time,
        .set_time = alpha_rtc_set_time,
        .ioctl = alpha_rtc_ioctl,
};

/*
 * Similarly, except do the actual CMOS access on the boot cpu only.
 * This requires marshalling the data across an interprocessor call.
 */

#if defined(CONFIG_SMP) && \
    (defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_MARVEL))
# define HAVE_REMOTE_RTC 1

union remote_data {
        struct rtc_time *tm;
        long retval;
};

static void
do_remote_read(void *data)
{
        union remote_data *x = data;
        x->retval = alpha_rtc_read_time(NULL, x->tm);
}

static int
remote_read_time(struct device *dev, struct rtc_time *tm)
{
        union remote_data x;
        if (smp_processor_id() != boot_cpuid) {
                x.tm = tm;
                smp_call_function_single(boot_cpuid, do_remote_read, &x, 1);
                return x.retval;
        }
        return alpha_rtc_read_time(NULL, tm);
}

static void
do_remote_set(void *data)
{
        union remote_data *x = data;
        x->retval = alpha_rtc_set_time(NULL, x->tm);
}

static int
remote_set_time(struct device *dev, struct rtc_time *tm)
{
        union remote_data x;
        if (smp_processor_id() != boot_cpuid) {
                x.tm = tm;
                smp_call_function_single(boot_cpuid, do_remote_set, &x, 1);
                return x.retval;
        }
        return alpha_rtc_set_time(NULL, tm);
}

static const struct rtc_class_ops remote_rtc_ops = {
        .read_time = remote_read_time,
        .set_time = remote_set_time,
        .ioctl = alpha_rtc_ioctl,
};
#endif

static int __init
alpha_rtc_init(void)
{
        struct platform_device *pdev;
        struct rtc_device *rtc;

        init_rtc_epoch();

        pdev = platform_device_register_simple("rtc-alpha", -1, NULL, 0);
        rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        platform_set_drvdata(pdev, rtc);
        rtc->ops = &alpha_rtc_ops;

#ifdef HAVE_REMOTE_RTC
        if (alpha_mv.rtc_boot_cpu_only)
                rtc->ops = &remote_rtc_ops;
#endif

        return devm_rtc_register_device(rtc);
}
device_initcall(alpha_rtc_init);