- Don't enable periodic interrupts from the RTC by default in rtc_statusb.

  Instead, explicitly enable them when we setup the interrupt handler.
  Also, move the setting of stathz and profhz down to the same place so
  that the code flow is simpler and easier to follow.
- Don't setup an interrupt handler for IRQ0 if we are using the lapic timer
  as it doesn't do anything productive in that case.

1 files changed, 26 insertions, 22 deletions

diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index c90d018..3664483 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -122,7 +122,7 @@ static	int	(*i8254_pending)(struct intsrc *);
 static	int	i8254_ticked;
 static	int	using_lapic_timer;
 static	u_char	rtc_statusa = RTCSA_DIVIDER | RTCSA_NOPROF;
-static	u_char	rtc_statusb = RTCSB_24HR | RTCSB_PINTR;
+static	u_char	rtc_statusb = RTCSB_24HR;
 
 /* Values for timerX_state: */
 #define	RELEASED	0
@@ -779,37 +779,41 @@ cpu_initclocks()
 #ifdef DEV_APIC
 	using_lapic_timer = lapic_setup_clock();
 #endif
-	if (statclock_disable || using_lapic_timer) {
-		/*
-		 * The stat interrupt mask is different without the
-		 * statistics clock.  Also, don't set the interrupt
-		 * flag which would normally cause the RTC to generate
-		 * interrupts.
-		 */
-		rtc_statusb = RTCSB_24HR;
-	} else {
-	        /* Setting stathz to nonzero early helps avoid races. */
-		stathz = RTC_NOPROFRATE;
-		profhz = RTC_PROFRATE;
-        }
-
-	/* Finish initializing 8254 timer 0. */
-	intr_add_handler("clk", 0, (driver_intr_t *)clkintr, NULL,
-	    INTR_TYPE_CLK | INTR_FAST, NULL);
-	i8254_intsrc = intr_lookup_source(0);
-	if (i8254_intsrc != NULL)
-		i8254_pending = i8254_intsrc->is_pic->pic_source_pending;
+	/*
+	 * If we aren't using the local APIC timer to drive the kernel
+	 * clocks, setup the interrupt handler for the 8254 timer 0 so
+	 * that it can drive hardclock().
+	 */
+	if (!using_lapic_timer) {
+		intr_add_handler("clk", 0, (driver_intr_t *)clkintr, NULL,
+		    INTR_TYPE_CLK | INTR_FAST, NULL);
+		i8254_intsrc = intr_lookup_source(0);
+		if (i8254_intsrc != NULL)
+			i8254_pending =
+			    i8254_intsrc->is_pic->pic_source_pending;
+	}
 
 	/* Initialize RTC. */
 	writertc(RTC_STATUSA, rtc_statusa);
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
-	/* Don't bother enabling the statistics clock. */
+	/*
+	 * If the separate statistics clock hasn't been explicility disabled
+	 * and we aren't already using the local APIC timer to drive the
+	 * kernel clocks, then setup the RTC to periodically interrupt to
+	 * drive statclock() and profclock().
+	 */
 	if (!statclock_disable && !using_lapic_timer) {
 		diag = rtcin(RTC_DIAG);
 		if (diag != 0)
 			printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
 
+	        /* Setting stathz to nonzero early helps avoid races. */
+		stathz = RTC_NOPROFRATE;
+		profhz = RTC_PROFRATE;
+
+		/* Enable periodic interrupts from the RTC. */
+		rtc_statusb |= RTCSB_PINTR;
 		intr_add_handler("rtc", 8, (driver_intr_t *)rtcintr, NULL,
 		    INTR_TYPE_CLK | INTR_FAST, NULL);