LXR linux/arch/mips/dec/time.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
   4 *  Copyright (C) 2000, 2003  Maciej W. Rozycki
   5 *
   6 * This file contains the time handling details for PC-style clocks as
   7 * found in some MIPS systems.
   8 *
   9 */
  10#include <linux/bcd.h>
  11#include <linux/init.h>
  12#include <linux/mc146818rtc.h>
  13#include <linux/param.h>
  14
  15#include <asm/cpu-features.h>
  16#include <asm/ds1287.h>
  17#include <asm/time.h>
  18#include <asm/dec/interrupts.h>
  19#include <asm/dec/ioasic.h>
  20#include <asm/dec/machtype.h>
  21
  22void read_persistent_clock64(struct timespec64 *ts)
  23{
  24        unsigned int year, mon, day, hour, min, sec, real_year;
  25        unsigned long flags;
  26
  27        spin_lock_irqsave(&rtc_lock, flags);
  28
  29        do {
  30                sec = CMOS_READ(RTC_SECONDS);
  31                min = CMOS_READ(RTC_MINUTES);
  32                hour = CMOS_READ(RTC_HOURS);
  33                day = CMOS_READ(RTC_DAY_OF_MONTH);
  34                mon = CMOS_READ(RTC_MONTH);
  35                year = CMOS_READ(RTC_YEAR);
  36                /*
  37                 * The PROM will reset the year to either '72 or '73.
  38                 * Therefore we store the real year separately, in one
  39                 * of unused BBU RAM locations.
  40                 */
  41                real_year = CMOS_READ(RTC_DEC_YEAR);
  42        } while (sec != CMOS_READ(RTC_SECONDS));
  43
  44        spin_unlock_irqrestore(&rtc_lock, flags);
  45
  46        if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  47                sec = bcd2bin(sec);
  48                min = bcd2bin(min);
  49                hour = bcd2bin(hour);
  50                day = bcd2bin(day);
  51                mon = bcd2bin(mon);
  52                year = bcd2bin(year);
  53        }
  54
  55        year += real_year - 72 + 2000;
  56
  57        ts->tv_sec = mktime64(year, mon, day, hour, min, sec);
  58        ts->tv_nsec = 0;
  59}
  60
  61/*
  62 * In order to set the CMOS clock precisely, update_persistent_clock64 has to
  63 * be called 500 ms after the second nowtime has started, because when
  64 * nowtime is written into the registers of the CMOS clock, it will
  65 * jump to the next second precisely 500 ms later.  Check the Dallas
  66 * DS1287 data sheet for details.
  67 */
  68int update_persistent_clock64(struct timespec64 now)
  69{
  70        time64_t nowtime = now.tv_sec;
  71        int retval = 0;
  72        int real_seconds, real_minutes, cmos_minutes;
  73        unsigned char save_control, save_freq_select;
  74
  75        /* irq are locally disabled here */
  76        spin_lock(&rtc_lock);
  77        /* tell the clock it's being set */
  78        save_control = CMOS_READ(RTC_CONTROL);
  79        CMOS_WRITE((save_control | RTC_SET), RTC_CONTROL);
  80
  81        /* stop and reset prescaler */
  82        save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  83        CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT);
  84
  85        cmos_minutes = CMOS_READ(RTC_MINUTES);
  86        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  87                cmos_minutes = bcd2bin(cmos_minutes);
  88
  89        /*
  90         * since we're only adjusting minutes and seconds,
  91         * don't interfere with hour overflow. This avoids
  92         * messing with unknown time zones but requires your
  93         * RTC not to be off by more than 15 minutes
  94         */
  95        real_minutes = div_s64_rem(nowtime, 60, &real_seconds);
  96        if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
  97                real_minutes += 30;     /* correct for half hour time zone */
  98        real_minutes %= 60;
  99
 100        if (abs(real_minutes - cmos_minutes) < 30) {
 101                if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
 102                        real_seconds = bin2bcd(real_seconds);
 103                        real_minutes = bin2bcd(real_minutes);
 104                }
 105                CMOS_WRITE(real_seconds, RTC_SECONDS);
 106                CMOS_WRITE(real_minutes, RTC_MINUTES);
 107        } else {
 108                printk_once(KERN_NOTICE
 109                       "set_rtc_mmss: can't update from %d to %d\n",
 110                       cmos_minutes, real_minutes);
 111                retval = -1;
 112        }
 113
 114        /* The following flags have to be released exactly in this order,
 115         * otherwise the DS1287 will not reset the oscillator and will not
 116         * update precisely 500 ms later.  You won't find this mentioned
 117         * in the Dallas Semiconductor data sheets, but who believes data
 118         * sheets anyway ...                           -- Markus Kuhn
 119         */
 120        CMOS_WRITE(save_control, RTC_CONTROL);
 121        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 122        spin_unlock(&rtc_lock);
 123
 124        return retval;
 125}
 126
 127void __init plat_time_init(void)
 128{
 129        int ioasic_clock = 0;
 130        u32 start, end;
 131        int i = HZ / 8;
 132
 133        /* Set up the rate of periodic DS1287 interrupts. */
 134        ds1287_set_base_clock(HZ);
 135
 136        /* On some I/O ASIC systems we have the I/O ASIC's counter.  */
 137        if (IOASIC)
 138                ioasic_clock = dec_ioasic_clocksource_init() == 0;
 139        if (cpu_has_counter) {
 140                ds1287_timer_state();
 141                while (!ds1287_timer_state())
 142                        ;
 143
 144                start = read_c0_count();
 145
 146                while (i--)
 147                        while (!ds1287_timer_state())
 148                                ;
 149
 150                end = read_c0_count();
 151
 152                mips_hpt_frequency = (end - start) * 8;
 153                printk(KERN_INFO "MIPS counter frequency %dHz\n",
 154                        mips_hpt_frequency);
 155
 156                /*
 157                 * All R4k DECstations suffer from the CP0 Count erratum,
 158                 * so we can't use the timer as a clock source, and a clock
 159                 * event both at a time.  An accurate wall clock is more
 160                 * important than a high-precision interval timer so only
 161                 * use the timer as a clock source, and not a clock event
 162                 * if there's no I/O ASIC counter available to serve as a
 163                 * clock source.
 164                 */
 165                if (!ioasic_clock) {
 166                        init_r4k_clocksource();
 167                        mips_hpt_frequency = 0;
 168                }
 169        }
 170
 171        ds1287_clockevent_init(dec_interrupt[DEC_IRQ_RTC]);
 172}
 173