4.1cBSD/a/sys/vax/clock.c

/*	clock.c	4.1	83/02/10	*/

#include "../h/param.h"
#include "../h/time.h"
#include "../h/kernel.h"

#include "../vax/mtpr.h"
#include "../vax/clock.h"

/*
 * Machine-dependent clock routines.
 *
 * Startrtclock restarts the real-time clock, which provides
 * hardclock interrupts to kern_clock.c.
 *
 * Inittodr initializes the time of day hardware which provides
 * date functions.  Its primary function is to use some file
 * system information in case the hardare clock lost state.
 *
 * Resettodr restores the time of day hardware after a time change.
 */

/*
 * Start the real-time clock.
 */
startrtclock()
{

	mtpr(NICR, -1000000/hz);
	mtpr(ICCS, ICCS_RUN+ICCS_IE+ICCS_TRANS+ICCS_INT+ICCS_ERR);
}

/*
 * Initialze the time of day register, based on the time base which is, e.g.
 * from a filesystem.  Base provides the time to within six months,
 * and the time of year clock provides the rest.
 */
inittodr(base)
	time_t base;
{
	register u_int todr = mfpr(TODR);
	long deltat;
	int year = YRREF;

	if (base < 5*SECYR) {
		printf("WARNING: preposterous time in file system");
		time.tv_sec = 6*SECYR + 186*SECDAY + SECDAY/2;
		resettodr();
		goto check;
	}
	/*
	 * TODRZERO is base used by VMS, which runs on local time.
	 */
	if (todr < TODRZERO) {
		printf("WARNING: todr too small");
		time.tv_sec = base;
		/*
		 * Believe the time in the file system for lack of
		 * anything better, resetting the TODR.
		 */
		resettodr();
		goto check;
	}

	/*
	 * Sneak to within 6 month of the time in the filesystem,
	 * by starting with the time of the year suggested by the TODR,
	 * and advancing through succesive years.  Adding the number of
	 * seconds in the current year takes us to the end of the current year
	 * and then around into the next year to the same position.
	 */
	time.tv_sec = (todr-TODRZERO)/100;
	while (time.tv_sec < base-SECYR/2) {
		if (LEAPYEAR(year))
			time.tv_sec += SECDAY;
		year++;
		time.tv_sec += SECYR;
	}

	/*
	 * See if we gained/lost two or more days;
	 * if so, assume something is amiss.
	 */
	deltat = time.tv_sec - base;
	if (deltat < 0)
		deltat = -deltat;
	if (deltat < 2*SECDAY)
		return;
	printf("WARNING: clock %s %d days",
	    time.tv_sec < base ? "lost" : "gained", deltat / SECDAY);
check:
	printf(" -- CHECK AND RESET THE DATE!\n");
}

/*
 * Reset the TODR based on the time value; used when the TODR
 * has a preposterous value and also when the time is reset
 * by the stime system call.  Also called when the TODR goes past
 * TODRZERO + 100*(SECYEAR+2*SECDAY) (e.g. on Jan 2 just after midnight)
 * to wrap the TODR around.
 */
resettodr()
{
	int year = YRREF;
	u_int secyr;
	u_int yrtime = time.tv_sec;

	/*
	 * Whittle the time down to an offset in the current year,
	 * by subtracting off whole years as long as possible.
	 */
	for (;;) {
		secyr = SECYR;
		if (LEAPYEAR(year))
			secyr += SECDAY;
		if (yrtime < secyr)
			break;
		yrtime -= secyr;
		year++;
	}
	mtpr(TODR, TODRZERO + yrtime*100);
}