Rename statclock_disable variable to atrtcclock_disable that it actually is,

and hide it inside of atrtc driver. Add new tunable hint.atrtc.0.clock
controlling it. Setting it to 0 disables using RTC clock as stat-/
profclock sources.

Teach i386 and amd64 SMP platforms to emulate stat-/profclocks using i8254
hardclock, when LAPIC and RTC clocks are disabled.

This allows to reduce global interrupt rate of idle system down to about
100 interrupts per core, permitting C3 and deeper C-states provide maximum
CPU power efficiency.

2 files changed, 28 insertions, 0 deletions

diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index 990c1ee..777c720 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -49,6 +49,8 @@ __FBSDID("$FreeBSD$");
 #define	RTC_LOCK	mtx_lock_spin(&clock_lock)
 #define	RTC_UNLOCK	mtx_unlock_spin(&clock_lock)
 
+int	atrtcclock_disable = 0;
+
 static	int	rtc_reg = -1;
 static	u_char	rtc_statusa = RTCSA_DIVIDER | RTCSA_NOPROF;
 static	u_char	rtc_statusb = RTCSB_24HR;
@@ -133,6 +135,27 @@ atrtc_restore(void)
 	rtcin(RTC_INTR);
 }
 
+int
+atrtc_setup_clock(void)
+{
+	int diag;
+
+	if (atrtcclock_disable)
+		return (0);
+
+	diag = rtcin(RTC_DIAG);
+	if (diag != 0) {
+		printf("RTC BIOS diagnostic error %b\n",
+		    diag, RTCDG_BITS);
+		return (0);
+	}
+
+	stathz = RTC_NOPROFRATE;
+	profhz = RTC_PROFRATE;
+
+	return (1);
+}
+
 /**********************************************************************
  * RTC driver for subr_rtc
  */
@@ -173,6 +196,7 @@ static int
 atrtc_attach(device_t dev)
 {
 	struct atrtc_softc *sc;
+	int i;
 
 	/*
 	 * Not that we need them or anything, but grab our resources
@@ -187,6 +211,8 @@ atrtc_attach(device_t dev)
 	    &sc->intr_rid, 8, 8, 1, RF_ACTIVE)))
 		device_printf(dev,"Warning: Couldn't map Interrupt.\n");
 	clock_register(dev, 1000000);
+	if (resource_int_value("atrtc", 0, "clock", &i) == 0 && i == 0)
+		atrtcclock_disable = 1;
 	return(0);
 }
 
diff --git a/sys/isa/rtc.h b/sys/isa/rtc.h
index c802b0b..018a4ed 100644
--- a/sys/isa/rtc.h
+++ b/sys/isa/rtc.h
@@ -113,6 +113,8 @@
 
 #ifdef _KERNEL
 extern  struct mtx clock_lock;
+extern	int atrtcclock_disable;
+int	atrtc_setup_clock(void);
 int	rtcin(int reg);
 void	atrtc_start(void);
 void	atrtc_rate(unsigned rate);