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/mc146818rtc.h>
  13
  14 #ifndef BCD_TO_BIN
  15 #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
  16 #endif
  17
  18 #ifndef BIN_TO_BCD
  19 #define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
  20 #endif
  21
  22 /* arc/i386/kernel/time.c */
  23 unsigned long get_cmos_time(void)
  24 {
  25         unsigned int year, mon, day, hour, min, sec;
  26         int i;
  27
  28         spin_lock(&rtc_lock);
  29         /* The Linux interpretation of the CMOS clock register contents:
  30          * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
  31          * RTC registers show the second which has precisely just started.
  32          * Let's hope other operating systems interpret the RTC the same way.
  33          */
  34         /* read RTC exactly on falling edge of update flag */
  35         for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
  36                 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
  37                         break;
  38         for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
  39                 if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
  40                         break;
  41         do { /* Isn't this overkill ? UIP above should guarantee consistency */
  42                 sec = CMOS_READ(RTC_SECONDS);
  43                 min = CMOS_READ(RTC_MINUTES);
  44                 hour = CMOS_READ(RTC_HOURS);
  45                 day = CMOS_READ(RTC_DAY_OF_MONTH);
  46                 mon = CMOS_READ(RTC_MONTH);
  47                 year = CMOS_READ(RTC_YEAR);
  48         } while (sec != CMOS_READ(RTC_SECONDS));
  49         if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  50           {
  51             BCD_TO_BIN(sec);
  52             BCD_TO_BIN(min);
  53             BCD_TO_BIN(hour);
  54             BCD_TO_BIN(day);
  55             BCD_TO_BIN(mon);
  56             BCD_TO_BIN(year);
  57           }
  58         spin_unlock(&rtc_lock);
  59         if ((year += 1900) < 1970)
  60                 year += 100;
  61         return mktime(year, mon, day, hour, min, sec);
  62 }
  63
  64 void mpc1211_rtc_gettimeofday(struct timeval *tv)
  65 {
  66
  67         tv->tv_sec = get_cmos_time();
  68         tv->tv_usec = 0;
  69 }
  70
  71 /* arc/i386/kernel/time.c */
  72 /*
  73  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  74  * called 500 ms after the second nowtime has started, because when
  75  * nowtime is written into the registers of the CMOS clock, it will
  76  * jump to the next second precisely 500 ms later. Check the Motorola
  77  * MC146818A or Dallas DS12887 data sheet for details.
  78  *
  79  * BUG: This routine does not handle hour overflow properly; it just
  80  *      sets the minutes. Usually you'll only notice that after reboot!
  81  */
  82 static int set_rtc_mmss(unsigned long nowtime)
  83 {
  84         int retval = 0;
  85         int real_seconds, real_minutes, cmos_minutes;
  86         unsigned char save_control, save_freq_select;
  87
  88         /* gets recalled with irq locally disabled */
  89         spin_lock(&rtc_lock);
  90         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
  91         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  92
  93         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
  94         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  95
  96         cmos_minutes = CMOS_READ(RTC_MINUTES);
  97         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  98                 BCD_TO_BIN(cmos_minutes);
  99
 100         /*
 101          * since we're only adjusting minutes and seconds,
 102          * don't interfere with hour overflow. This avoids
 103          * messing with unknown time zones but requires your
 104          * RTC not to be off by more than 15 minutes
 105          */
 106         real_seconds = nowtime % 60;
 107         real_minutes = nowtime / 60;
 108         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
 109                 real_minutes += 30;             /* correct for half hour time zone */
 110         real_minutes %= 60;
 111
 112         if (abs(real_minutes - cmos_minutes) < 30) {
 113                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
 114                         BIN_TO_BCD(real_seconds);
 115                         BIN_TO_BCD(real_minutes);
 116                 }
 117                 CMOS_WRITE(real_seconds,RTC_SECONDS);
 118                 CMOS_WRITE(real_minutes,RTC_MINUTES);
 119         } else {
 120                 printk(KERN_WARNING
 121                        "set_rtc_mmss: can't update from %d to %d\n",
 122                        cmos_minutes, real_minutes);
 123                 retval = -1;
 124         }
 125
 126         /* The following flags have to be released exactly in this order,
 127          * otherwise the DS12887 (popular MC146818A clone with integrated
 128          * battery and quartz) will not reset the oscillator and will not
 129          * update precisely 500 ms later. You won't find this mentioned in
 130          * the Dallas Semiconductor data sheets, but who believes data
 131          * sheets anyway ...                           -- Markus Kuhn
 132          */
 133         CMOS_WRITE(save_control, RTC_CONTROL);
 134         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 135         spin_unlock(&rtc_lock);
 136
 137         return retval;
 138 }
 139
 140 int mpc1211_rtc_settimeofday(const struct timeval *tv)
 141 {
 142         unsigned long nowtime = tv->tv_sec;
 143
 144         return set_rtc_mmss(nowtime);
 145 }
 146
 147 void mpc1211_time_init(void)
 148 {
 149         rtc_get_time = mpc1211_rtc_gettimeofday;
 150         rtc_set_time = mpc1211_rtc_settimeofday;
 151 }
 152