Improved biasing of i586 clock by adjusting for hardclock() latency.

I decided to do this for every hardclock() call instead of lazily
in microtime().  The lazy method is simpler but has more overhead
if microtime() is called a lot.

CPU_THISTICKLEN() is now a no-op and should probably go away.
Previously it did nothing directly but had the side effect of
setting i586_last_tick for CPU_CLOCKUPDATE() and i586_avg_tick for
debugging.  CPU_CLOCKUPDATE() now uses a better method and
i586_avg_tick is too much trouble to maintain.

Reduced nesting of #includes in the usual case.

Increased nesting of #includes when CLOCK_HAIR is defined.  This
is a kludge to get typedefs for inline functions only when the
inline functions are used.  Normally only kern_clock.c defines
this.  kern_clock.c can't include the i386 headers directly.

Removed unused LOCORE support.

1 files changed, 62 insertions, 51 deletions

diff --git a/sys/i386/include/clock.h b/sys/i386/include/clock.h
index 9c6646e..f20902f 100644
--- a/sys/i386/include/clock.h
+++ b/sys/i386/include/clock.h
@@ -3,48 +3,24 @@
  * Garrett Wollman, September 1994.
  * This file is in the public domain.
  *
- *	$Id: clock.h,v 1.18 1996/10/10 10:25:26 bde Exp $
+ *	$Id: clock.h,v 1.19 1996/10/17 17:31:25 bde Exp $
  */
 
 #ifndef _MACHINE_CLOCK_H_
 #define	_MACHINE_CLOCK_H_
 
 #if defined(I586_CPU) || defined(I686_CPU)
-
-/*
- * When we update the clock, we also update this bias value which is
- * automatically subtracted in microtime().  We assume that CPU_THISTICKLEN()
- * has been called at some point in the past, so that an appropriate value is
- * set up in i586_last_tick.  (This works even if we are not being called
- * from hardclock because hardclock will have run before and will made the
- * call.)
- */
-#define CPU_CLOCKUPDATE(otime, ntime) \
-	do { \
-	if (i586_ctr_freq != 0) { \
-		disable_intr(); \
-		i586_ctr_bias = i586_last_tick; \
-		*(otime) = *(ntime); \
-		enable_intr(); \
-	} else { \
-		*(otime) = *(ntime); \
-	} \
-	} while(0)
-
-#define	CPU_THISTICKLEN(dflt) cpu_thisticklen(dflt)
+#define CPU_CLOCKUPDATE(otime, ntime)	cpu_clockupdate((otime), (ntime))
 #else
-#define CPU_CLOCKUPDATE(otime, ntime) \
-		(*(otime) = *(ntime))
-#define CPU_THISTICKLEN(dflt) dflt
+#define CPU_CLOCKUPDATE(otime, ntime)	(*(otime) = *(ntime))
 #endif
 
+#define CPU_THISTICKLEN(dflt) dflt
+
 #define	I586_CTR_COMULTIPLIER_SHIFT	20
 #define	I586_CTR_MULTIPLIER_SHIFT	32
 
-#if defined(KERNEL) && !defined(LOCORE)
-#include <sys/cdefs.h>
-#include <machine/frame.h>
-
+#ifdef KERNEL
 /*
  * i386 to clock driver interface.
  * XXX almost all of it is misplaced.  i586 stuff is done in isa/clock.c
@@ -57,8 +33,6 @@ extern u_int	i586_ctr_bias;
 extern u_int	i586_ctr_comultiplier;
 extern u_int	i586_ctr_freq;
 extern u_int	i586_ctr_multiplier;
-extern long long i586_last_tick;
-extern unsigned long i586_avg_tick;
 #endif
 extern int	statclock_disable;
 extern u_int	timer_freq;
@@ -67,27 +41,11 @@ extern u_int	timer0_overflow_threshold;
 extern u_int	timer0_prescaler_count;
 extern int	wall_cmos_clock;
 
-#if defined(I586_CPU) || defined(I686_CPU)
-static __inline u_long 
-cpu_thisticklen(u_long dflt)
-{
-	long long old;
-	long len;
-
-	if (i586_ctr_freq != 0) {
-		old = i586_last_tick;
-		i586_last_tick = rdtsc();
-		len = ((i586_last_tick - old) * i586_ctr_multiplier)
-			>> I586_CTR_MULTIPLIER_SHIFT;
-		i586_avg_tick = i586_avg_tick * 15 / 16 + len / 16;
-	}
-	return dflt;
-}
-#endif
-
 /*
  * Driver to clock driver interface.
  */
+struct clockframe;
+
 void	DELAY __P((int usec));
 int	acquire_timer0 __P((int rate,
 			    void (*function)(struct clockframe *frame)));
@@ -105,6 +63,59 @@ void	rtc_outb __P((int val));
 #endif
 int	sysbeep __P((int pitch, int period));
 
-#endif /* KERNEL && !LOCORE */
+#ifdef CLOCK_HAIR
+
+#include <i386/isa/isa.h>		/* XXX */
+#include <i386/isa/timerreg.h>		/* XXX */
+
+static __inline u_int
+clock_latency(void)
+{
+	u_char high, low;
+
+	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
+	low = inb(TIMER_CNTR0);
+	high = inb(TIMER_CNTR0);
+	return (timer0_prescaler_count + timer0_max_count
+		- ((high << 8) | low));
+}
+
+#if defined(I586_CPU) || defined(I686_CPU)
+/*
+ * When we update `time', on i586's we also update `i586_ctr_bias'
+ * atomically.  `i586_ctr_bias' is the best available approximation to
+ * the value of the i586 counter (mod 2^32) at the time of the i8254
+ * counter transition that caused the clock interrupt that caused the
+ * update.  clock_latency() gives the time between the transition and
+ * the update to within a few usec provided another such transition
+ * hasn't occurred.  We don't bother checking for counter overflow as
+ * in microtime(), since if it occurs then we're close to losing clock
+ * interrupts.
+ */
+static __inline void
+cpu_clockupdate(volatile struct timeval *otime, struct timeval *ntime)
+{
+	if (i586_ctr_freq != 0) {
+		u_int i586_count;	/* truncated */
+		u_int i8254_count;
+
+		disable_intr();
+		i8254_count = clock_latency();
+		i586_count = rdtsc();
+		i586_ctr_bias = i586_count
+				- (u_int)
+				  (((unsigned long long)i586_ctr_comultiplier
+				    * i8254_count)
+				   >> I586_CTR_COMULTIPLIER_SHIFT);
+		*otime = *ntime;
+		enable_intr();
+	} else
+		*otime = *ntime;
+}
+#endif /* I586_CPU || I686_CPU */
+
+#endif /* CLOCK_HAIR */
+
+#endif /* KERNEL */
 
 #endif /* !_MACHINE_CLOCK_H_ */