Added a sysctl "kern.timecounter.hardware" for selecting the hardware

used for timecounting.  The possible values are the names of the
physically present harware timecounters ("i8254" and "TSC" on i386's).

Fixed some nearby bitrot in comments in <sys/time.h>.

Reviewed by:	phk

1 files changed, 41 insertions, 6 deletions

diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 23918b1..de15f18 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -37,7 +37,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_clock.c	8.5 (Berkeley) 1/21/94
- * $Id: kern_clock.c,v 1.94 1999/04/25 08:59:59 phk Exp $
+ * $Id: kern_clock.c,v 1.95 1999/07/18 01:35:26 jdp Exp $
  */
 
 #include "opt_ntp.h"
@@ -679,7 +679,14 @@ init_timecounter(struct timecounter *tc)
 	tc->tc_tweak = tc;
 	tco_setscales(tc);
 	tc->tc_offset_count = tc->tc_get_timecount(tc);
+	if (timecounter == &dummy_timecounter)
+		tc->tc_avail = tc;
+	else {
+		tc->tc_avail = timecounter->tc_tweak->tc_avail;
+		timecounter->tc_tweak->tc_avail = tc;
+	}
 	MALLOC(t1, struct timecounter *, sizeof *t1, M_TIMECOUNTER, M_WAITOK);
+	tc->tc_other = t1;
 	*t1 = *tc;
 	t2 = t1;
 	for (i = 1; i < NTIMECOUNTER; i++) {
@@ -720,9 +727,7 @@ set_timecounter(struct timespec *ts)
 	tco_forward(1);
 }
 
-
-#if 0 /* Currently unused */
-void
+static void
 switch_timecounter(struct timecounter *newtc)
 {
 	int s;
@@ -731,19 +736,20 @@ switch_timecounter(struct timecounter *newtc)
 
 	s = splclock();
 	tc = timecounter;
-	if (newtc == tc || newtc == tc->tc_other) {
+	if (newtc->tc_tweak == tc->tc_tweak) {
 		splx(s);
 		return;
 	}
+	newtc = newtc->tc_tweak->tc_other;
 	nanouptime(&ts);
 	newtc->tc_offset_sec = ts.tv_sec;
 	newtc->tc_offset_nano = (u_int64_t)ts.tv_nsec << 32;
 	newtc->tc_offset_micro = ts.tv_nsec / 1000;
 	newtc->tc_offset_count = newtc->tc_get_timecount(newtc);
+	tco_setscales(newtc);
 	timecounter = newtc;
 	splx(s);
 }
-#endif
 
 static struct timecounter *
 sync_other_counter(void)
@@ -825,6 +831,35 @@ SYSCTL_INT(_kern_timecounter, OID_AUTO, method, CTLFLAG_RW, &tco_method, 0,
 
 );
 
+static int
+sysctl_kern_timecounter_hardware SYSCTL_HANDLER_ARGS
+{
+	char newname[32];
+	struct timecounter *newtc, *tc;
+	int error;
+
+	tc = timecounter->tc_tweak;
+	strncpy(newname, tc->tc_name, sizeof(newname));
+	error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
+	if (error == 0 && req->newptr != NULL &&
+	    strcmp(newname, tc->tc_name) != 0) {
+		for (newtc = tc->tc_avail; newtc != tc; newtc = tc->tc_avail) {
+			if (strcmp(newname, newtc->tc_name) == 0) {
+				/* Warm up new timecounter. */
+				(void)newtc->tc_get_timecount(newtc);
+
+				switch_timecounter(newtc);
+				return (0);
+			}
+		}
+		return (EINVAL);
+	}
+	return (error);
+}
+
+SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
+    0, 0, sysctl_kern_timecounter_hardware, "A", "");
+
 
 int
 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)