129 lines
4.1 KiB
C
129 lines
4.1 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Machine dependent access functions for RTC registers.
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*/
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#ifndef __ASM_MC146818_TIME_H
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#define __ASM_MC146818_TIME_H
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#include <linux/bcd.h>
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#include <linux/mc146818rtc.h>
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#include <linux/time.h>
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/*
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* For check timing call set_rtc_mmss() 500ms; used in timer interrupt.
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*/
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#define USEC_AFTER 500000
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#define USEC_BEFORE 500000
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/*
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* In order to set the CMOS clock precisely, set_rtc_mmss has to be
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* called 500 ms after the second nowtime has started, because when
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* nowtime is written into the registers of the CMOS clock, it will
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* jump to the next second precisely 500 ms later. Check the Motorola
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* MC146818A or Dallas DS12887 data sheet for details.
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*
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* BUG: This routine does not handle hour overflow properly; it just
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* sets the minutes. Usually you'll only notice that after reboot!
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*/
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static inline int mc146818_set_rtc_mmss(unsigned long nowtime)
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{
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int real_seconds, real_minutes, cmos_minutes;
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unsigned char save_control, save_freq_select;
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int retval = 0;
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save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
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CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
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save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
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CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
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cmos_minutes = CMOS_READ(RTC_MINUTES);
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
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BCD_TO_BIN(cmos_minutes);
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/*
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* since we're only adjusting minutes and seconds,
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* don't interfere with hour overflow. This avoids
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* messing with unknown time zones but requires your
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* RTC not to be off by more than 15 minutes
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*/
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real_seconds = nowtime % 60;
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real_minutes = nowtime / 60;
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if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
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real_minutes += 30; /* correct for half hour time zone */
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real_minutes %= 60;
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if (abs(real_minutes - cmos_minutes) < 30) {
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
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BIN_TO_BCD(real_seconds);
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BIN_TO_BCD(real_minutes);
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}
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CMOS_WRITE(real_seconds,RTC_SECONDS);
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CMOS_WRITE(real_minutes,RTC_MINUTES);
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} else {
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printk(KERN_WARNING
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"set_rtc_mmss: can't update from %d to %d\n",
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cmos_minutes, real_minutes);
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retval = -1;
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}
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/* The following flags have to be released exactly in this order,
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* otherwise the DS12887 (popular MC146818A clone with integrated
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* battery and quartz) will not reset the oscillator and will not
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* update precisely 500 ms later. You won't find this mentioned in
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* the Dallas Semiconductor data sheets, but who believes data
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* sheets anyway ... -- Markus Kuhn
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*/
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CMOS_WRITE(save_control, RTC_CONTROL);
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CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
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return retval;
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}
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static inline unsigned long mc146818_get_cmos_time(void)
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{
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unsigned int year, mon, day, hour, min, sec;
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int i;
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/*
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* The Linux interpretation of the CMOS clock register contents:
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* When the Update-In-Progress (UIP) flag goes from 1 to 0, the
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* RTC registers show the second which has precisely just started.
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* Let's hope other operating systems interpret the RTC the same way.
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*/
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/* read RTC exactly on falling edge of update flag */
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for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
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if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
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break;
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for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
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if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
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break;
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do { /* Isn't this overkill ? UIP above should guarantee consistency */
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sec = CMOS_READ(RTC_SECONDS);
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min = CMOS_READ(RTC_MINUTES);
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hour = CMOS_READ(RTC_HOURS);
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day = CMOS_READ(RTC_DAY_OF_MONTH);
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mon = CMOS_READ(RTC_MONTH);
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year = CMOS_READ(RTC_YEAR);
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} while (sec != CMOS_READ(RTC_SECONDS));
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if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
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BCD_TO_BIN(sec);
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BCD_TO_BIN(min);
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BCD_TO_BIN(hour);
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BCD_TO_BIN(day);
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BCD_TO_BIN(mon);
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BCD_TO_BIN(year);
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}
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year = mc146818_decode_year(year);
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return mktime(year, mon, day, hour, min, sec);
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}
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#endif /* __ASM_MC146818_TIME_H */
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