LXR linux/include/asm-x86/mach-default/mach

   1/*
   2 *  include/asm-i386/mach-default/mach_time.h
   3 *
   4 *  Machine specific set RTC function for generic.
   5 *  Split out from time.c by Osamu Tomita <tomita@cinet.co.jp>
   6 */
   7#ifndef _MACH_TIME_H
   8#define _MACH_TIME_H
   9
  10#include <linux/mc146818rtc.h>
  11
  12/* for check timing call set_rtc_mmss() 500ms     */
  13/* used in arch/i386/time.c::do_timer_interrupt() */
  14#define USEC_AFTER      500000
  15#define USEC_BEFORE     500000
  16
  17/*
  18 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  19 * called 500 ms after the second nowtime has started, because when
  20 * nowtime is written into the registers of the CMOS clock, it will
  21 * jump to the next second precisely 500 ms later. Check the Motorola
  22 * MC146818A or Dallas DS12887 data sheet for details.
  23 *
  24 * BUG: This routine does not handle hour overflow properly; it just
  25 *      sets the minutes. Usually you'll only notice that after reboot!
  26 */
  27static inline int mach_set_rtc_mmss(unsigned long nowtime)
  28{
  29        int retval = 0;
  30        int real_seconds, real_minutes, cmos_minutes;
  31        unsigned char save_control, save_freq_select;
  32
  33        save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
  34        CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  35
  36        save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
  37        CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  38
  39        cmos_minutes = CMOS_READ(RTC_MINUTES);
  40        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  41                BCD_TO_BIN(cmos_minutes);
  42
  43        /*
  44         * since we're only adjusting minutes and seconds,
  45         * don't interfere with hour overflow. This avoids
  46         * messing with unknown time zones but requires your
  47         * RTC not to be off by more than 15 minutes
  48         */
  49        real_seconds = nowtime % 60;
  50        real_minutes = nowtime / 60;
  51        if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  52                real_minutes += 30;             /* correct for half hour time zone */
  53        real_minutes %= 60;
  54
  55        if (abs(real_minutes - cmos_minutes) < 30) {
  56                if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  57                        BIN_TO_BCD(real_seconds);
  58                        BIN_TO_BCD(real_minutes);
  59                }
  60                CMOS_WRITE(real_seconds,RTC_SECONDS);
  61                CMOS_WRITE(real_minutes,RTC_MINUTES);
  62        } else {
  63                printk(KERN_WARNING
  64                       "set_rtc_mmss: can't update from %d to %d\n",
  65                       cmos_minutes, real_minutes);
  66                retval = -1;
  67        }
  68
  69        /* The following flags have to be released exactly in this order,
  70         * otherwise the DS12887 (popular MC146818A clone with integrated
  71         * battery and quartz) will not reset the oscillator and will not
  72         * update precisely 500 ms later. You won't find this mentioned in
  73         * the Dallas Semiconductor data sheets, but who believes data
  74         * sheets anyway ...                           -- Markus Kuhn
  75         */
  76        CMOS_WRITE(save_control, RTC_CONTROL);
  77        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  78
  79        return retval;
  80}
  81
  82static inline unsigned long mach_get_cmos_time(void)
  83{
  84        unsigned int year, mon, day, hour, min, sec;
  85
  86        do {
  87                sec = CMOS_READ(RTC_SECONDS);
  88                min = CMOS_READ(RTC_MINUTES);
  89                hour = CMOS_READ(RTC_HOURS);
  90                day = CMOS_READ(RTC_DAY_OF_MONTH);
  91                mon = CMOS_READ(RTC_MONTH);
  92                year = CMOS_READ(RTC_YEAR);
  93        } while (sec != CMOS_READ(RTC_SECONDS));
  94
  95        if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  96                BCD_TO_BIN(sec);
  97                BCD_TO_BIN(min);
  98                BCD_TO_BIN(hour);
  99                BCD_TO_BIN(day);
 100                BCD_TO_BIN(mon);
 101                BCD_TO_BIN(year);
 102        }
 103
 104        year += 1900;
 105        if (year < 1970)
 106                year += 100;
 107
 108        return mktime(year, mon, day, hour, min, sec);
 109}
 110
 111#endif /* !_MACH_TIME_H */
 112