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Diffstat (limited to 'include/asm-mips/mc146818-time.h')
| -rw-r--r-- | include/asm-mips/mc146818-time.h | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/include/asm-mips/mc146818-time.h b/include/asm-mips/mc146818-time.h new file mode 100644 index 000000000000..a2c2d2c24303 --- /dev/null +++ b/include/asm-mips/mc146818-time.h @@ -0,0 +1,128 @@ +/* + * 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; + + 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); + + return retval; +} + +static inline unsigned long mc146818_get_cmos_time(void) +{ + unsigned int year, mon, day, hour, min, sec; + int i; + + /* + * 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 (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) + break; + for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */ + if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)) + break; + + 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); + } + year = mc146818_decode_year(year); + + return mktime(year, mon, day, hour, min, sec); +} + +#endif /* __ASM_MC146818_TIME_H */ |