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