BSD 4_2 release

[unix-history] / usr / src / sys / vax / clock.c

/*      clock.c 6.1     83/07/29        */

#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);
}