// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *  Copyright (C) 2000, 2003  Maciej W. Rozycki
 *
 * This file contains the time handling details for PC-style clocks as
 * found in some MIPS systems.
 *
 */
#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/param.h>

#include <asm/cpu-features.h>
#include <asm/ds1287.h>
#include <asm/time.h>
#include <asm/dec/interrupts.h>
#include <asm/dec/ioasic.h>
#include <asm/dec/machtype.h>

void read_persistent_clock64(struct timespec64 *ts)
{
        unsigned int year, mon, day, hour, min, sec, real_year;
        unsigned long flags;

        spin_lock_irqsave(&rtc_lock, flags);

        do {
                sec = CMOS_READ(RTC_SECONDS);
                min = CMOS_READ(RTC_MINUTES);
                hour = CMOS_READ(RTC_HOURS);
                day = CMOS_READ(RTC_DAY_OF_MONTH);
                mon = CMOS_READ(RTC_MONTH);
                year = CMOS_READ(RTC_YEAR);
                /*
                 * The PROM will reset the year to either '72 or '73.
                 * Therefore we store the real year separately, in one
                 * of unused BBU RAM locations.
                 */
                real_year = CMOS_READ(RTC_DEC_YEAR);
        } while (sec != CMOS_READ(RTC_SECONDS));

        spin_unlock_irqrestore(&rtc_lock, flags);

        if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                sec = bcd2bin(sec);
                min = bcd2bin(min);
                hour = bcd2bin(hour);
                day = bcd2bin(day);
                mon = bcd2bin(mon);
                year = bcd2bin(year);
        }

        year += real_year - 72 + 2000;

        ts->tv_sec = mktime64(year, mon, day, hour, min, sec);
        ts->tv_nsec = 0;
}

/*
 * In order to set the CMOS clock precisely, update_persistent_clock64 has to
 * be called 500 ms after the second nowtime has started, because when
 * nowtime is written into the registers of the CMOS clock, it will
 * jump to the next second precisely 500 ms later.  Check the Dallas
 * DS1287 data sheet for details.
 */
int update_persistent_clock64(struct timespec64 now)
{
        time64_t nowtime = now.tv_sec;
        int retval = 0;
        int real_seconds, real_minutes, cmos_minutes;
        unsigned char save_control, save_freq_select;

        /* irq are locally disabled here */
        spin_lock(&rtc_lock);
        /* tell the clock it's being set */
        save_control = CMOS_READ(RTC_CONTROL);
        CMOS_WRITE((save_control | RTC_SET), RTC_CONTROL);

        /* stop and reset prescaler */
        save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
        CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT);

        cmos_minutes = CMOS_READ(RTC_MINUTES);
        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
                cmos_minutes = bcd2bin(cmos_minutes);

        /*
         * since we're only adjusting minutes and seconds,
         * don't interfere with hour overflow. This avoids
         * messing with unknown time zones but requires your
         * RTC not to be off by more than 15 minutes
         */
        real_minutes = div_s64_rem(nowtime, 60, &real_seconds);
        if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
                real_minutes += 30;     /* correct for half hour time zone */
        real_minutes %= 60;

        if (abs(real_minutes - cmos_minutes) < 30) {
                if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                        real_seconds = bin2bcd(real_seconds);
                        real_minutes = bin2bcd(real_minutes);
                }
                CMOS_WRITE(real_seconds, RTC_SECONDS);
                CMOS_WRITE(real_minutes, RTC_MINUTES);
        } else {
                printk_once(KERN_NOTICE
                       "set_rtc_mmss: can't update from %d to %d\n",
                       cmos_minutes, real_minutes);
                retval = -1;
        }

        /* The following flags have to be released exactly in this order,
         * otherwise the DS1287 will not reset the oscillator and will not
         * update precisely 500 ms later.  You won't find this mentioned
         * in the Dallas Semiconductor data sheets, but who believes data
         * sheets anyway ...                           -- Markus Kuhn
         */
        CMOS_WRITE(save_control, RTC_CONTROL);
        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
        spin_unlock(&rtc_lock);

        return retval;
}

void __init plat_time_init(void)
{
        int ioasic_clock = 0;
        u32 start, end;
        int i = HZ / 8;

        /* Set up the rate of periodic DS1287 interrupts. */
        ds1287_set_base_clock(HZ);

        /* On some I/O ASIC systems we have the I/O ASIC's counter.  */
        if (IOASIC)
                ioasic_clock = dec_ioasic_clocksource_init() == 0;
        if (cpu_has_counter) {
                ds1287_timer_state();
                while (!ds1287_timer_state())
                        ;

                start = read_c0_count();

                while (i--)
                        while (!ds1287_timer_state())
                                ;

                end = read_c0_count();

                mips_hpt_frequency = (end - start) * 8;
                printk(KERN_INFO "MIPS counter frequency %dHz\n",
                        mips_hpt_frequency);

                /*
                 * All R4k DECstations suffer from the CP0 Count erratum,
                 * so we can't use the timer as a clock source, and a clock
                 * event both at a time.  An accurate wall clock is more
                 * important than a high-precision interval timer so only
                 * use the timer as a clock source, and not a clock event
                 * if there's no I/O ASIC counter available to serve as a
                 * clock source.
                 */
                if (!ioasic_clock) {
                        init_r4k_clocksource();
                        mips_hpt_frequency = 0;
                }
        }

        ds1287_clockevent_init(dec_interrupt[DEC_IRQ_RTC]);
}