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linux-2.6/include/asm-i386/mach-default/mach_time.h

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/*
* include/asm-i386/mach-default/mach_time.h
*
* Machine specific set RTC function for generic.
* Split out from time.c by Osamu Tomita <tomita@cinet.co.jp>
*/
#ifndef _MACH_TIME_H
#define _MACH_TIME_H
#include <linux/mc146818rtc.h>
/* for check timing call set_rtc_mmss() 500ms */
/* used in arch/i386/time.c::do_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 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;
}
static inline unsigned long mach_get_cmos_time(void)
{
unsigned int year, mon, day, hour, min, sec;
[PATCH] RTC: Remove RTC UIP synchronization on x86 Reading the CMOS clock on x86 and some other arches currently takes up to one second because it synchronizes with the CMOS second tick-over. This delay shows up at boot time as well a resume time. This is the currently the most substantial boot time delay for machines that are working towards instant-on capability. Also, a quick back of the envelope calculation (.5sec * 2M users * 1 boot a day * 10 years) suggests it has cost Linux users in the neighborhood of a million man-hours. An earlier thread on this topic is here: http://groups.google.com/group/linux.kernel/browse_frm/thread/8a24255215ff6151/2aa97e66a977653d?hl=en&lr=&ie=UTF-8&rnum=1&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26selm%3D1To2R-2S7-11%40gated-at.bofh.it#2aa97e66a977653d ..from which the consensus seems to be that it's no longer desirable. In my view, there are basically four cases to consider: 1) networked, need precise walltime: use NTP 2) networked, don't need precise walltime: use NTP anyway 3) not networked, don't need sub-second precision walltime: don't care 4) not networked, need sub-second precision walltime: get a network or a radio time source because RTC isn't good enough anyway So this patch series simply removes the synchronization in favor of a simple seqlock-like approach using the seconds value. Note that for purposes of timer accuracy on wakeup, this patch will cause us to fire timers up to one second late. But as the current timer resume code will already sync once (or more!), it's no worse for short timers. Signed-off-by: Matt Mackall <mpm@selenic.com> Cc: Andi Kleen <ak@muc.de> Cc: "David S. Miller" <davem@davemloft.net> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp> Cc: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-28 09:55:58 +00:00
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));
[PATCH] RTC: Remove RTC UIP synchronization on x86 Reading the CMOS clock on x86 and some other arches currently takes up to one second because it synchronizes with the CMOS second tick-over. This delay shows up at boot time as well a resume time. This is the currently the most substantial boot time delay for machines that are working towards instant-on capability. Also, a quick back of the envelope calculation (.5sec * 2M users * 1 boot a day * 10 years) suggests it has cost Linux users in the neighborhood of a million man-hours. An earlier thread on this topic is here: http://groups.google.com/group/linux.kernel/browse_frm/thread/8a24255215ff6151/2aa97e66a977653d?hl=en&lr=&ie=UTF-8&rnum=1&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26selm%3D1To2R-2S7-11%40gated-at.bofh.it#2aa97e66a977653d ..from which the consensus seems to be that it's no longer desirable. In my view, there are basically four cases to consider: 1) networked, need precise walltime: use NTP 2) networked, don't need precise walltime: use NTP anyway 3) not networked, don't need sub-second precision walltime: don't care 4) not networked, need sub-second precision walltime: get a network or a radio time source because RTC isn't good enough anyway So this patch series simply removes the synchronization in favor of a simple seqlock-like approach using the seconds value. Note that for purposes of timer accuracy on wakeup, this patch will cause us to fire timers up to one second late. But as the current timer resume code will already sync once (or more!), it's no worse for short timers. Signed-off-by: Matt Mackall <mpm@selenic.com> Cc: Andi Kleen <ak@muc.de> Cc: "David S. Miller" <davem@davemloft.net> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp> Cc: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-28 09:55:58 +00:00
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);
}
if ((year += 1900) < 1970)
year += 100;
return mktime(year, mon, day, hour, min, sec);
}
#endif /* !_MACH_TIME_H */