root/arch/mips/dec/time.c

DEFINITIONS

1. read_persistent_clock64
2. update_persistent_clock64
3. plat_time_init

   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 
  22 void 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  */
  68 int 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 
 127 void __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 }