alpha/kernel/time.c

6  * This file contains the PC-specific time handling details:
8  * 1994-07-02    Alan Modra
9  *	fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
10  * 1995-03-26    Markus Kuhn
11  *      fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
12  *      precision CMOS clock update
13  * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
15  * 1997-01-09    Adrian Sun
17  * 1997-10-29    John Bowman (bowman@math.ualberta.ca)
18  *      fixed tick loss calculation in timer_interrupt
19  *      (round system clock to nearest tick instead of truncating)
20  *      fixed algorithm in time_init for getting time from CMOS clock
21  * 1999-04-16	Thorsten Kranzkowski (dl8bcu@gmx.net)
22  *	fixed algorithm in do_gettimeofday() for calculating the precise time
24  * 2000-08-13	Jan-Benedict Glaw <jbglaw@lug-owl.de>
25  * 	Fixed time_init to be aware of epoches != 1900. This prevents
27  * 2003-06-03	R. Scott Bailey <scott.bailey@eds.com>
69  * for large CPU clock rates.
138 	/* PC-like is standard; used for year >= 70 */  in read_persistent_clock()
154 	ts->tv_sec = mktime(year, mon, day, hour, min, sec);  in read_persistent_clock()
155 	ts->tv_nsec = 0;  in read_persistent_clock()
161  * timer_interrupt() needs to keep up the real-time clock,
181 	delta = now - state.last_time;  in timer_interrupt()
184 	state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);   in timer_interrupt()
196 	while (nticks--)  in timer_interrupt()
250    timing hardware for any one method to work everywhere.  :-(
272 		/* None of the following are shipping as of 2001-11-01.  */  in validate_cc_value()
285 	cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);  in validate_cc_value()
286 	index = cpu->type & 0xffffffff;  in validate_cc_value()
296 	if (cc < cpu_hz[index].min - deviation  in validate_cc_value()
305  * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
335 	cc = rpcc() - cc;  in calibrate_cc_with_pit()
344 /* The Linux interpretation of the CMOS clock register contents:
345    When the Update-In-Progress (UIP) flag goes from 1 to 0, the
392 	/* Calibrate CPU clock -- attempt #1.  */  in time_init()
398 	/* Calibrate CPU clock -- attempt #2.  */  in time_init()
402 		est_cycle_freq = validate_cc_value(cc2 - cc1);  in time_init()
406 	cycle_freq = hwrpb->cycle_freq;  in time_init()
411 		diff = cycle_freq - est_cycle_freq;  in time_init()
413 			diff = -diff;  in time_init()
427 	   to settle, as the Update-In-Progress bit going low isn't good  in time_init()
450  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
452  * nowtime is written into the registers of the CMOS clock, it will
470 	/* Tell the clock it's being set */  in set_rtc_mmss()
490 	if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) {  in set_rtc_mmss()
496 	if (abs(real_minutes - cmos_minutes) < 30) {  in set_rtc_mmss()
507  		retval = -1;  in set_rtc_mmss()
515 	 * sheets anyway ...                           -- Markus Kuhn  in set_rtc_mmss()