LXR linux/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 */
  31static 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
  89static 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 */
 120