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

4 files changed, 98 insertions, 20 deletions

diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 23918b1..de15f18 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.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)
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)
diff --git a/sys/sys/time.h b/sys/sys/time.h
index 43821b6..32ea4a0 100644
--- a/sys/sys/time.h
+++ b/sys/sys/time.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.37 1999/03/11 15:09:41 phk Exp $
+ * $Id: time.h,v 1.38 1999/04/25 08:59:55 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -121,11 +121,14 @@ struct timezone {
  * used in a safe way.  Such changes may be adopted with a delay of up to 1/HZ,
  * index one & two are used alternately for the actual timekeeping.
  *
- * `other' points to the opposite "work" timecounter, ie, in index one it
- *      points to index two and vice versa
+ * 'tc_avail' points to the next available (external) timecounter in a
+ *      circular queue.  This is only valid for index 0.
  *
- * `tweak' points to index zero.
+ * `tc_other' points to the next "work" timecounter in a circular queue,
+ *      i.e., for index i > 0 it points to index 1 + (i - 1) % NTIMECOUNTER.
+ *      We also use it to point from index 0 to index 1.
  *
+ * `tc_tweak' points to index 0.
  */
 
 struct timecounter;
@@ -151,6 +154,7 @@ struct timecounter {
 	u_int64_t		tc_offset_nano;
 	struct timeval		tc_microtime;
 	struct timespec		tc_nanotime;
+	struct timecounter	*tc_avail;
 	struct timecounter	*tc_other;
 	struct timecounter	*tc_tweak;
 };
diff --git a/sys/sys/timetc.h b/sys/sys/timetc.h
index 43821b6..32ea4a0 100644
--- a/sys/sys/timetc.h
+++ b/sys/sys/timetc.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.37 1999/03/11 15:09:41 phk Exp $
+ * $Id: time.h,v 1.38 1999/04/25 08:59:55 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -121,11 +121,14 @@ struct timezone {
  * used in a safe way.  Such changes may be adopted with a delay of up to 1/HZ,
  * index one & two are used alternately for the actual timekeeping.
  *
- * `other' points to the opposite "work" timecounter, ie, in index one it
- *      points to index two and vice versa
+ * 'tc_avail' points to the next available (external) timecounter in a
+ *      circular queue.  This is only valid for index 0.
  *
- * `tweak' points to index zero.
+ * `tc_other' points to the next "work" timecounter in a circular queue,
+ *      i.e., for index i > 0 it points to index 1 + (i - 1) % NTIMECOUNTER.
+ *      We also use it to point from index 0 to index 1.
  *
+ * `tc_tweak' points to index 0.
  */
 
 struct timecounter;
@@ -151,6 +154,7 @@ struct timecounter {
 	u_int64_t		tc_offset_nano;
 	struct timeval		tc_microtime;
 	struct timespec		tc_nanotime;
+	struct timecounter	*tc_avail;
 	struct timecounter	*tc_other;
 	struct timecounter	*tc_tweak;
 };