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Linux/arch/mips/include/asm/mc146818-time.h

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  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  */
 31 static 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 
 89 static inline unsigned long 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 mktime(year, mon, day, hour, min, sec);
117 }
118 
119 #endif /* __ASM_MC146818_TIME_H */
120 

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