Add a tunable "machdep.disable_tsc" to turn off TSC. Specifically, it turns

off boot-time CPU frequency calibration, DELAY(9) with TSC, and using TSC as
a CPU ticker.  Note tsc_present does not change by this tunable.

1 files changed, 15 insertions, 8 deletions

diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index 07b3b84..c1d065c 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -77,6 +77,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/reboot.h>
 #include <sys/sched.h>
 #include <sys/signalvar.h>
+#ifdef SMP
+#include <sys/smp.h>
+#endif
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
 #include <sys/sysent.h>
@@ -1077,16 +1080,18 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate)
 		return (EOPNOTSUPP);
 
 	/* If we're booting, trust the rate calibrated moments ago. */
-	if (cold) {
+	if (cold && tsc_freq != 0) {
 		*rate = tsc_freq;
 		return (0);
 	}
 
 #ifdef SMP
-	/* Schedule ourselves on the indicated cpu. */
-	thread_lock(curthread);
-	sched_bind(curthread, cpu_id);
-	thread_unlock(curthread);
+	if (smp_cpus > 1) {
+		/* Schedule ourselves on the indicated cpu. */
+		thread_lock(curthread);
+		sched_bind(curthread, cpu_id);
+		thread_unlock(curthread);
+	}
 #endif
 
 	/* Calibrate by measuring a short delay. */
@@ -1097,9 +1102,11 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate)
 	intr_restore(reg);
 
 #ifdef SMP
-	thread_lock(curthread);
-	sched_unbind(curthread);
-	thread_unlock(curthread);
+	if (smp_cpus > 1) {
+		thread_lock(curthread);
+		sched_unbind(curthread);
+		thread_unlock(curthread);
+	}
 #endif
 
 	tsc2 -= tsc1;