diff options
Diffstat (limited to 'arch/x86/kernel/rtc.c')
| -rw-r--r-- | arch/x86/kernel/rtc.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c new file mode 100644 index 000000000000..45bf54d9f4c5 --- /dev/null +++ b/arch/x86/kernel/rtc.c @@ -0,0 +1,166 @@ +/* + * RTC related functions + */ +#include <linux/bcd.h> +#include <linux/mc146818rtc.h> + +#include <asm/time.h> + +/* + * 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! + */ +int mach_set_rtc_mmss(unsigned long nowtime) +{ + int retval = 0; + int real_seconds, real_minutes, cmos_minutes; + unsigned char save_control, save_freq_select; + + 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; +} + +unsigned long mach_get_cmos_time(void) +{ + unsigned int year, mon, day, hour, min, sec; + + do { + 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 += 1900; + if (year < 1970) + year += 100; + + return mktime(year, mon, day, hour, min, sec); +} + +DEFINE_SPINLOCK(rtc_lock); +EXPORT_SYMBOL(rtc_lock); + +/* + * This is a special lock that is owned by the CPU and holds the index + * register we are working with. It is required for NMI access to the + * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details. + */ +volatile unsigned long cmos_lock = 0; +EXPORT_SYMBOL(cmos_lock); + +/* Routines for accessing the CMOS RAM/RTC. */ +unsigned char rtc_cmos_read(unsigned char addr) +{ + unsigned char val; + + lock_cmos_prefix(addr); + outb_p(addr, RTC_PORT(0)); + val = inb_p(RTC_PORT(1)); + lock_cmos_suffix(addr); + return val; +} +EXPORT_SYMBOL(rtc_cmos_read); + +void rtc_cmos_write(unsigned char val, unsigned char addr) +{ + lock_cmos_prefix(addr); + outb_p(addr, RTC_PORT(0)); + outb_p(val, RTC_PORT(1)); + lock_cmos_suffix(addr); +} +EXPORT_SYMBOL(rtc_cmos_write); + +static int set_rtc_mmss(unsigned long nowtime) +{ + int retval; + unsigned long flags; + + /* gets recalled with irq locally disabled */ + /* XXX - does irqsave resolve this? -johnstul */ + spin_lock_irqsave(&rtc_lock, flags); + retval = set_wallclock(nowtime); + spin_unlock_irqrestore(&rtc_lock, flags); + + return retval; +} + +/* not static: needed by APM */ +unsigned long read_persistent_clock(void) +{ + unsigned long retval; + unsigned long flags; + + spin_lock_irqsave(&rtc_lock, flags); + retval = get_wallclock(); + spin_unlock_irqrestore(&rtc_lock, flags); + + return retval; +} + +int update_persistent_clock(struct timespec now) +{ + return set_rtc_mmss(now.tv_sec); +} |