arch/sh/boards/mpc1211/rtc.c

   1 /*
   2  * linux/arch/sh/kernel/rtc-mpc1211.c -- MPC-1211 on-chip RTC support
   3  *
   4  *  Copyright (C) 2002  Saito.K & Jeanne
   5  *
   6  */
   7
   8 #include <linux/init.h>
   9 #include <linux/kernel.h>
  10 #include <linux/sched.h>
  11 #include <linux/time.h>
  12 #include <linux/bcd.h>
  13 #include <linux/mc146818rtc.h>
  14
  15 unsigned long get_cmos_time(void)
  16 {
  17         unsigned int year, mon, day, hour, min, sec;
  18
  19         spin_lock(&rtc_lock);
  20
  21         do {
  22                 sec = CMOS_READ(RTC_SECONDS);
  23                 min = CMOS_READ(RTC_MINUTES);
  24                 hour = CMOS_READ(RTC_HOURS);
  25                 day = CMOS_READ(RTC_DAY_OF_MONTH);
  26                 mon = CMOS_READ(RTC_MONTH);
  27                 year = CMOS_READ(RTC_YEAR);
  28         } while (sec != CMOS_READ(RTC_SECONDS));
  29
  30         if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  31                 BCD_TO_BIN(sec);
  32                 BCD_TO_BIN(min);
  33                 BCD_TO_BIN(hour);
  34                 BCD_TO_BIN(day);
  35                 BCD_TO_BIN(mon);
  36                 BCD_TO_BIN(year);
  37         }
  38
  39         spin_unlock(&rtc_lock);
  40
  41         year += 1900;
  42         if (year < 1970)
  43                 year += 100;
  44
  45         return mktime(year, mon, day, hour, min, sec);
  46 }
  47
  48 void mpc1211_rtc_gettimeofday(struct timeval *tv)
  49 {
  50
  51         tv->tv_sec = get_cmos_time();
  52         tv->tv_usec = 0;
  53 }
  54
  55 /* arc/i386/kernel/time.c */
  56 /*
  57  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  58  * called 500 ms after the second nowtime has started, because when
  59  * nowtime is written into the registers of the CMOS clock, it will
  60  * jump to the next second precisely 500 ms later. Check the Motorola
  61  * MC146818A or Dallas DS12887 data sheet for details.
  62  *
  63  * BUG: This routine does not handle hour overflow properly; it just
  64  *      sets the minutes. Usually you'll only notice that after reboot!
  65  */
  66 static int set_rtc_mmss(unsigned long nowtime)
  67 {
  68         int retval = 0;
  69         int real_seconds, real_minutes, cmos_minutes;
  70         unsigned char save_control, save_freq_select;
  71
  72         /* gets recalled with irq locally disabled */
  73         spin_lock(&rtc_lock);
  74         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
  75         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  76
  77         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
  78         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  79
  80         cmos_minutes = CMOS_READ(RTC_MINUTES);
  81         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  82                 BCD_TO_BIN(cmos_minutes);
  83
  84         /*
  85          * since we're only adjusting minutes and seconds,
  86          * don't interfere with hour overflow. This avoids
  87          * messing with unknown time zones but requires your
  88          * RTC not to be off by more than 15 minutes
  89          */
  90         real_seconds = nowtime % 60;
  91         real_minutes = nowtime / 60;
  92         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  93                 real_minutes += 30;             /* correct for half hour time zone */
  94         real_minutes %= 60;
  95
  96         if (abs(real_minutes - cmos_minutes) < 30) {
  97                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  98                         BIN_TO_BCD(real_seconds);
  99                         BIN_TO_BCD(real_minutes);
 100                 }
 101                 CMOS_WRITE(real_seconds,RTC_SECONDS);
 102                 CMOS_WRITE(real_minutes,RTC_MINUTES);
 103         } else {
 104                 printk(KERN_WARNING
 105                        "set_rtc_mmss: can't update from %d to %d\n",
 106                        cmos_minutes, real_minutes);
 107                 retval = -1;
 108         }
 109
 110         /* The following flags have to be released exactly in this order,
 111          * otherwise the DS12887 (popular MC146818A clone with integrated
 112          * battery and quartz) will not reset the oscillator and will not
 113          * update precisely 500 ms later. You won't find this mentioned in
 114          * the Dallas Semiconductor data sheets, but who believes data
 115          * sheets anyway ...                           -- Markus Kuhn
 116          */
 117         CMOS_WRITE(save_control, RTC_CONTROL);
 118         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 119         spin_unlock(&rtc_lock);
 120
 121         return retval;
 122 }
 123
 124 int mpc1211_rtc_settimeofday(const struct timeval *tv)
 125 {
 126         unsigned long nowtime = tv->tv_sec;
 127
 128         return set_rtc_mmss(nowtime);
 129 }
 130
 131 void mpc1211_time_init(void)
 132 {
 133         rtc_sh_get_time = mpc1211_rtc_gettimeofday;
 134         rtc_sh_set_time = mpc1211_rtc_settimeofday;
 135 }
 136