arch/mips/dec/time.c

   1 /*
   2  *  linux/arch/mips/dec/time.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
   5  *  Copyright (C) 2000, 2003  Maciej W. Rozycki
   6  *
   7  * This file contains the time handling details for PC-style clocks as
   8  * found in some MIPS systems.
   9  *
  10  */
  11 #include <linux/bcd.h>
  12 #include <linux/errno.h>
  13 #include <linux/init.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mc146818rtc.h>
  17 #include <linux/mm.h>
  18 #include <linux/module.h>
  19 #include <linux/param.h>
  20 #include <linux/sched.h>
  21 #include <linux/string.h>
  22 #include <linux/time.h>
  23 #include <linux/types.h>
  24
  25 #include <asm/bootinfo.h>
  26 #include <asm/cpu.h>
  27 #include <asm/div64.h>
  28 #include <asm/io.h>
  29 #include <asm/irq.h>
  30 #include <asm/mipsregs.h>
  31 #include <asm/sections.h>
  32 #include <asm/time.h>
  33
  34 #include <asm/dec/interrupts.h>
  35 #include <asm/dec/ioasic.h>
  36 #include <asm/dec/ioasic_addrs.h>
  37 #include <asm/dec/machtype.h>
  38
  39
  40 static unsigned long dec_rtc_get_time(void)
  41 {
  42         unsigned int year, mon, day, hour, min, sec, real_year;
  43         int i;
  44
  45         /* The Linux interpretation of the DS1287 clock register contents:
  46          * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
  47          * RTC registers show the second which has precisely just started.
  48          * Let's hope other operating systems interpret the RTC the same way.
  49          */
  50         /* read RTC exactly on falling edge of update flag */
  51         for (i = 0; i < 1000000; i++)   /* may take up to 1 second... */
  52                 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
  53                         break;
  54         for (i = 0; i < 1000000; i++)   /* must try at least 2.228 ms */
  55                 if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
  56                         break;
  57         /* Isn't this overkill?  UIP above should guarantee consistency */
  58         do {
  59                 sec = CMOS_READ(RTC_SECONDS);
  60                 min = CMOS_READ(RTC_MINUTES);
  61                 hour = CMOS_READ(RTC_HOURS);
  62                 day = CMOS_READ(RTC_DAY_OF_MONTH);
  63                 mon = CMOS_READ(RTC_MONTH);
  64                 year = CMOS_READ(RTC_YEAR);
  65         } while (sec != CMOS_READ(RTC_SECONDS));
  66         if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  67                 sec = BCD2BIN(sec);
  68                 min = BCD2BIN(min);
  69                 hour = BCD2BIN(hour);
  70                 day = BCD2BIN(day);
  71                 mon = BCD2BIN(mon);
  72                 year = BCD2BIN(year);
  73         }
  74         /*
  75          * The PROM will reset the year to either '72 or '73.
  76          * Therefore we store the real year separately, in one
  77          * of unused BBU RAM locations.
  78          */
  79         real_year = CMOS_READ(RTC_DEC_YEAR);
  80         year += real_year - 72 + 2000;
  81
  82         return mktime(year, mon, day, hour, min, sec);
  83 }
  84
  85 /*
  86  * In order to set the CMOS clock precisely, dec_rtc_set_mmss has to
  87  * be called 500 ms after the second nowtime has started, because when
  88  * nowtime is written into the registers of the CMOS clock, it will
  89  * jump to the next second precisely 500 ms later.  Check the Dallas
  90  * DS1287 data sheet for details.
  91  */
  92 static int dec_rtc_set_mmss(unsigned long nowtime)
  93 {
  94         int retval = 0;
  95         int real_seconds, real_minutes, cmos_minutes;
  96         unsigned char save_control, save_freq_select;
  97
  98         /* tell the clock it's being set */
  99         save_control = CMOS_READ(RTC_CONTROL);
 100         CMOS_WRITE((save_control | RTC_SET), RTC_CONTROL);
 101
 102         /* stop and reset prescaler */
 103         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
 104         CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT);
 105
 106         cmos_minutes = CMOS_READ(RTC_MINUTES);
 107         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 108                 cmos_minutes = BCD2BIN(cmos_minutes);
 109
 110         /*
 111          * since we're only adjusting minutes and seconds,
 112          * don't interfere with hour overflow. This avoids
 113          * messing with unknown time zones but requires your
 114          * RTC not to be off by more than 15 minutes
 115          */
 116         real_seconds = nowtime % 60;
 117         real_minutes = nowtime / 60;
 118         if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
 119                 real_minutes += 30;     /* correct for half hour time zone */
 120         real_minutes %= 60;
 121
 122         if (abs(real_minutes - cmos_minutes) < 30) {
 123                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
 124                         real_seconds = BIN2BCD(real_seconds);
 125                         real_minutes = BIN2BCD(real_minutes);
 126                 }
 127                 CMOS_WRITE(real_seconds, RTC_SECONDS);
 128                 CMOS_WRITE(real_minutes, RTC_MINUTES);
 129         } else {
 130                 printk(KERN_WARNING
 131                        "set_rtc_mmss: can't update from %d to %d\n",
 132                        cmos_minutes, real_minutes);
 133                 retval = -1;
 134         }
 135
 136         /* The following flags have to be released exactly in this order,
 137          * otherwise the DS1287 will not reset the oscillator and will not
 138          * update precisely 500 ms later.  You won't find this mentioned
 139          * in the Dallas Semiconductor data sheets, but who believes data
 140          * sheets anyway ...                           -- Markus Kuhn
 141          */
 142         CMOS_WRITE(save_control, RTC_CONTROL);
 143         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 144
 145         return retval;
 146 }
 147
 148
 149 static int dec_timer_state(void)
 150 {
 151         return (CMOS_READ(RTC_REG_C) & RTC_PF) != 0;
 152 }
 153
 154 static void dec_timer_ack(void)
 155 {
 156         CMOS_READ(RTC_REG_C);                   /* Ack the RTC interrupt.  */
 157 }
 158
 159 static unsigned int dec_ioasic_hpt_read(void)
 160 {
 161         /*
 162          * The free-running counter is 32-bit which is good for about
 163          * 2 minutes, 50 seconds at possible count rates of up to 25MHz.
 164          */
 165         return ioasic_read(IO_REG_FCTR);
 166 }
 167
 168 static void dec_ioasic_hpt_init(unsigned int count)
 169 {
 170         ioasic_write(IO_REG_FCTR, ioasic_read(IO_REG_FCTR) - count);
 171 }
 172
 173
 174 void __init dec_time_init(void)
 175 {
 176         rtc_get_time = dec_rtc_get_time;
 177         rtc_set_mmss = dec_rtc_set_mmss;
 178
 179         mips_timer_state = dec_timer_state;
 180         mips_timer_ack = dec_timer_ack;
 181
 182         if (!cpu_has_counter && IOASIC) {
 183                 /* For pre-R4k systems we use the I/O ASIC's counter.  */
 184                 mips_hpt_read = dec_ioasic_hpt_read;
 185                 mips_hpt_init = dec_ioasic_hpt_init;
 186         }
 187
 188         /* Set up the rate of periodic DS1287 interrupts.  */
 189         CMOS_WRITE(RTC_REF_CLCK_32KHZ | (16 - LOG_2_HZ), RTC_REG_A);
 190 }
 191
 192 EXPORT_SYMBOL(do_settimeofday);
 193
 194 void __init dec_timer_setup(struct irqaction *irq)
 195 {
 196         setup_irq(dec_interrupt[DEC_IRQ_RTC], irq);
 197
 198         /* Enable periodic DS1287 interrupts.  */
 199         CMOS_WRITE(CMOS_READ(RTC_REG_B) | RTC_PIE, RTC_REG_B);
 200 }