The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/include/clock.h

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    1 /*
    2  * Kernel interface to machine-dependent clock driver.
    3  * Garrett Wollman, September 1994.
    4  * This file is in the public domain.
    5  *
    6  * $FreeBSD: src/sys/i386/include/clock.h,v 1.21.2.2 1999/09/05 08:11:41 peter Exp $
    7  */
    8 
    9 #ifndef _MACHINE_CLOCK_H_
   10 #define _MACHINE_CLOCK_H_
   11 
   12 #if defined(I586_CPU) || defined(I686_CPU)
   13 #define CPU_CLOCKUPDATE(otime, ntime)   cpu_clockupdate((otime), (ntime))
   14 #else
   15 #define CPU_CLOCKUPDATE(otime, ntime)   (*(otime) = *(ntime))
   16 #endif
   17 
   18 #define CPU_THISTICKLEN(dflt) dflt
   19 
   20 #define I586_CTR_COMULTIPLIER_SHIFT     20
   21 #define I586_CTR_MULTIPLIER_SHIFT       32
   22 
   23 #ifdef KERNEL
   24 /*
   25  * i386 to clock driver interface.
   26  * XXX almost all of it is misplaced.  i586 stuff is done in isa/clock.c
   27  * and isa stuff is done in i386/microtime.s and i386/support.s.
   28  */
   29 extern int      adjkerntz;
   30 extern int      disable_rtc_set;
   31 #if defined(I586_CPU) || defined(I686_CPU)
   32 extern u_int    i586_ctr_bias;
   33 extern u_int    i586_ctr_comultiplier;
   34 extern u_int    i586_ctr_freq;
   35 extern u_int    i586_ctr_multiplier;
   36 #endif
   37 extern int      statclock_disable;
   38 extern u_int    timer_freq;
   39 extern int      timer0_max_count;
   40 extern u_int    timer0_overflow_threshold;
   41 extern u_int    timer0_prescaler_count;
   42 extern int      wall_cmos_clock;
   43 
   44 /*
   45  * Driver to clock driver interface.
   46  */
   47 struct clockframe;
   48 
   49 void    DELAY __P((int usec));
   50 int     acquire_timer0 __P((int rate,
   51                             void (*function)(struct clockframe *frame)));
   52 int     acquire_timer2 __P((int mode));
   53 int     release_timer0 __P((void));
   54 int     release_timer2 __P((void));
   55 #ifndef PC98
   56 int     rtcin __P((int val));
   57 #else
   58 int     acquire_timer1 __P((int mode));
   59 int     release_timer1 __P((void));
   60 #endif
   61 int     sysbeep __P((int pitch, int period));
   62 
   63 #ifdef CLOCK_HAIR
   64 
   65 #ifdef PC98
   66 #include <pc98/pc98/pc98.h>             /* XXX */
   67 #else
   68 #include <i386/isa/isa.h>               /* XXX */
   69 #endif
   70 #include <i386/isa/timerreg.h>          /* XXX */
   71 
   72 static __inline u_int
   73 clock_latency(void)
   74 {
   75         u_char high, low;
   76 
   77         outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
   78         low = inb(TIMER_CNTR0);
   79         high = inb(TIMER_CNTR0);
   80         return (timer0_prescaler_count + timer0_max_count
   81                 - ((high << 8) | low));
   82 }
   83 
   84 #if defined(I586_CPU) || defined(I686_CPU)
   85 /*
   86  * When we update `time', on i586's we also update `i586_ctr_bias'
   87  * atomically.  `i586_ctr_bias' is the best available approximation to
   88  * the value of the i586 counter (mod 2^32) at the time of the i8254
   89  * counter transition that caused the clock interrupt that caused the
   90  * update.  clock_latency() gives the time between the transition and
   91  * the update to within a few usec provided another such transition
   92  * hasn't occurred.  We don't bother checking for counter overflow as
   93  * in microtime(), since if it occurs then we're close to losing clock
   94  * interrupts.
   95  */
   96 static __inline void
   97 cpu_clockupdate(volatile struct timeval *otime, struct timeval *ntime)
   98 {
   99         if (i586_ctr_freq != 0) {
  100                 u_int i586_count;       /* truncated */
  101                 u_int i8254_count;
  102 
  103                 disable_intr();
  104                 i8254_count = clock_latency();
  105                 i586_count = rdtsc();
  106                 i586_ctr_bias = i586_count
  107                                 - (u_int)
  108                                   (((unsigned long long)i586_ctr_comultiplier
  109                                     * i8254_count)
  110                                    >> I586_CTR_COMULTIPLIER_SHIFT);
  111                 *otime = *ntime;
  112                 enable_intr();
  113         } else
  114                 *otime = *ntime;
  115 }
  116 #endif /* I586_CPU || I686_CPU */
  117 
  118 #endif /* CLOCK_HAIR */
  119 
  120 #endif /* KERNEL */
  121 
  122 #endif /* !_MACHINE_CLOCK_H_ */

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