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119 lines
3.7 KiB
119 lines
3.7 KiB
/* |
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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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unsigned long flags; |
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spin_lock_irqsave(&rtc_lock, flags); |
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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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cmos_minutes = bcd2bin(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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real_seconds = bin2bcd(real_seconds); |
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real_minutes = bin2bcd(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_once(KERN_NOTICE |
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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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spin_unlock_irqrestore(&rtc_lock, flags); |
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return retval; |
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} |
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static inline time64_t 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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unsigned long flags; |
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spin_lock_irqsave(&rtc_lock, flags); |
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do { |
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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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sec = bcd2bin(sec); |
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min = bcd2bin(min); |
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hour = bcd2bin(hour); |
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day = bcd2bin(day); |
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mon = bcd2bin(mon); |
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year = bcd2bin(year); |
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} |
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spin_unlock_irqrestore(&rtc_lock, flags); |
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year = mc146818_decode_year(year); |
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return mktime64(year, mon, day, hour, min, sec); |
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} |
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#endif /* __ASM_MC146818_TIME_H */
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