arch/mips/include/asm/mc146818-time.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Machine dependent access functions for RTC registers.
   7  */
   8 #ifndef __ASM_MC146818_TIME_H
   9 #define __ASM_MC146818_TIME_H
  10
  11 #include <linux/bcd.h>
  12 #include <linux/mc146818rtc.h>
  13 #include <linux/time.h>
  14
  15 /*
  16  * For check timing call set_rtc_mmss() 500ms; used in timer interrupt.
  17  */
  18 #define USEC_AFTER      500000
  19 #define USEC_BEFORE     500000
  20
  21 /*
  22  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  23  * called 500 ms after the second nowtime has started, because when
  24  * nowtime is written into the registers of the CMOS clock, it will
  25  * jump to the next second precisely 500 ms later. Check the Motorola
  26  * MC146818A or Dallas DS12887 data sheet for details.
  27  *
  28  * BUG: This routine does not handle hour overflow properly; it just
  29  *      sets the minutes. Usually you'll only notice that after reboot!
  30  */
  31 static inline int mc146818_set_rtc_mmss(unsigned long nowtime)
  32 {
  33         int real_seconds, real_minutes, cmos_minutes;
  34         unsigned char save_control, save_freq_select;
  35         int retval = 0;
  36         unsigned long flags;
  37
  38         spin_lock_irqsave(&rtc_lock, flags);
  39         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
  40         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  41
  42         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
  43         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  44
  45         cmos_minutes = CMOS_READ(RTC_MINUTES);
  46         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  47                 cmos_minutes = bcd2bin(cmos_minutes);
  48
  49         /*
  50          * since we're only adjusting minutes and seconds,
  51          * don't interfere with hour overflow. This avoids
  52          * messing with unknown time zones but requires your
  53          * RTC not to be off by more than 15 minutes
  54          */
  55         real_seconds = nowtime % 60;
  56         real_minutes = nowtime / 60;
  57         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  58                 real_minutes += 30;             /* correct for half hour time zone */
  59         real_minutes %= 60;
  60
  61         if (abs(real_minutes - cmos_minutes) < 30) {
  62                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  63                         real_seconds = bin2bcd(real_seconds);
  64                         real_minutes = bin2bcd(real_minutes);
  65                 }
  66                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  67                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  68         } else {
  69                 printk_once(KERN_NOTICE
  70                        "set_rtc_mmss: can't update from %d to %d\n",
  71                        cmos_minutes, real_minutes);
  72                 retval = -1;
  73         }
  74
  75         /* The following flags have to be released exactly in this order,
  76          * otherwise the DS12887 (popular MC146818A clone with integrated
  77          * battery and quartz) will not reset the oscillator and will not
  78          * update precisely 500 ms later. You won't find this mentioned in
  79          * the Dallas Semiconductor data sheets, but who believes data
  80          * sheets anyway ...                           -- Markus Kuhn
  81          */
  82         CMOS_WRITE(save_control, RTC_CONTROL);
  83         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  84         spin_unlock_irqrestore(&rtc_lock, flags);
  85
  86         return retval;
  87 }
  88
  89 static inline time64_t mc146818_get_cmos_time(void)
  90 {
  91         unsigned int year, mon, day, hour, min, sec;
  92         unsigned long flags;
  93
  94         spin_lock_irqsave(&rtc_lock, flags);
  95
  96         do {
  97                 sec = CMOS_READ(RTC_SECONDS);
  98                 min = CMOS_READ(RTC_MINUTES);
  99                 hour = CMOS_READ(RTC_HOURS);
 100                 day = CMOS_READ(RTC_DAY_OF_MONTH);
 101                 mon = CMOS_READ(RTC_MONTH);
 102                 year = CMOS_READ(RTC_YEAR);
 103         } while (sec != CMOS_READ(RTC_SECONDS));
 104
 105         if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
 106                 sec = bcd2bin(sec);
 107                 min = bcd2bin(min);
 108                 hour = bcd2bin(hour);
 109                 day = bcd2bin(day);
 110                 mon = bcd2bin(mon);
 111                 year = bcd2bin(year);
 112         }
 113         spin_unlock_irqrestore(&rtc_lock, flags);
 114         year = mc146818_decode_year(year);
 115
 116         return mktime64(year, mon, day, hour, min, sec);
 117 }
 118
 119 #endif /* __ASM_MC146818_TIME_H */