diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 95d67c0..bcfdac1 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -839,7 +839,7 @@ cpu_idle(int busy)
 	}
 
 	/* Apply AMD APIC timer C1E workaround. */
-	if (cpu_ident_amdc1e && cpu_disable_deep_sleep) {
+	if (cpu_ident_amdc1e && cpu_disable_c3_sleep) {
 		msr = rdmsr(MSR_AMDK8_IPM);
 		if (msr & AMDK8_CMPHALT)
 			wrmsr(MSR_AMDK8_IPM, msr & ~AMDK8_CMPHALT);
diff --git a/sys/dev/acpica/acpi_cpu.c b/sys/dev/acpica/acpi_cpu.c
index 9350935..794aee2 100644
--- a/sys/dev/acpica/acpi_cpu.c
+++ b/sys/dev/acpica/acpi_cpu.c
@@ -85,6 +85,7 @@ struct acpi_cpu_softc {
     int			 cpu_prev_sleep;/* Last idle sleep duration. */
     int			 cpu_features;	/* Child driver supported features. */
     /* Runtime state. */
+    int			 cpu_non_c2;	/* Index of lowest non-C2 state. */
     int			 cpu_non_c3;	/* Index of lowest non-C3 state. */
     u_int		 cpu_cx_stats[MAX_CX_STATES];/* Cx usage history. */
     /* Values for sysctl. */
@@ -668,8 +669,10 @@ acpi_cpu_generic_cx_probe(struct acpi_cpu_softc *sc)
     cx_ptr->type = ACPI_STATE_C1;
     cx_ptr->trans_lat = 0;
     cx_ptr++;
+    sc->cpu_non_c2 = sc->cpu_cx_count;
     sc->cpu_non_c3 = sc->cpu_cx_count;
     sc->cpu_cx_count++;
+    cpu_deepest_sleep = 1;
 
     /* 
      * The spec says P_BLK must be 6 bytes long.  However, some systems
@@ -695,6 +698,7 @@ acpi_cpu_generic_cx_probe(struct acpi_cpu_softc *sc)
 	    cx_ptr++;
 	    sc->cpu_non_c3 = sc->cpu_cx_count;
 	    sc->cpu_cx_count++;
+	    cpu_deepest_sleep = 2;
 	}
     }
     if (sc->cpu_p_blk_len < 6)
@@ -711,7 +715,7 @@ acpi_cpu_generic_cx_probe(struct acpi_cpu_softc *sc)
 	    cx_ptr->trans_lat = AcpiGbl_FADT.C3Latency;
 	    cx_ptr++;
 	    sc->cpu_cx_count++;
-	    cpu_can_deep_sleep = 1;
+	    cpu_deepest_sleep = 3;
 	}
     }
 }
@@ -757,6 +761,7 @@ acpi_cpu_cx_cst(struct acpi_cpu_softc *sc)
 	count = MAX_CX_STATES;
     }
 
+    sc->cpu_non_c2 = 0;
     sc->cpu_non_c3 = 0;
     sc->cpu_cx_count = 0;
     cx_ptr = sc->cpu_cx_states;
@@ -768,6 +773,7 @@ acpi_cpu_cx_cst(struct acpi_cpu_softc *sc)
     cx_ptr->type = ACPI_STATE_C0;
     cx_ptr++;
     sc->cpu_cx_count++;
+    cpu_deepest_sleep = 1;
 
     /* Set up all valid states. */
     for (i = 0; i < count; i++) {
@@ -788,6 +794,7 @@ acpi_cpu_cx_cst(struct acpi_cpu_softc *sc)
 		/* This is the first C1 state.  Use the reserved slot. */
 		sc->cpu_cx_states[0] = *cx_ptr;
 	    } else {
+		sc->cpu_non_c2 = sc->cpu_cx_count;
 		sc->cpu_non_c3 = sc->cpu_cx_count;
 		cx_ptr++;
 		sc->cpu_cx_count++;
@@ -795,6 +802,8 @@ acpi_cpu_cx_cst(struct acpi_cpu_softc *sc)
 	    continue;
 	case ACPI_STATE_C2:
 	    sc->cpu_non_c3 = sc->cpu_cx_count;
+	    if (cpu_deepest_sleep < 2)
+		    cpu_deepest_sleep = 2;
 	    break;
 	case ACPI_STATE_C3:
 	default:
@@ -804,7 +813,7 @@ acpi_cpu_cx_cst(struct acpi_cpu_softc *sc)
 				 device_get_unit(sc->cpu_dev), i));
 		continue;
 	    } else
-		cpu_can_deep_sleep = 1;
+		cpu_deepest_sleep = 3;
 	    break;
 	}
 
@@ -993,7 +1002,9 @@ acpi_cpu_idle(sbintime_t sbt)
     if (sbt >= 0 && us > (sbt >> 12))
 	us = (sbt >> 12);
     cx_next_idx = 0;
-    if (cpu_disable_deep_sleep)
+    if (cpu_disable_c2_sleep)
+	i = min(sc->cpu_cx_lowest, sc->cpu_non_c2);
+    else if (cpu_disable_c3_sleep)
 	i = min(sc->cpu_cx_lowest, sc->cpu_non_c3);
     else
 	i = sc->cpu_cx_lowest;
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 5ed5c54..4948f20 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -1423,7 +1423,7 @@ cpu_idle(int busy)
 
 #ifndef XEN
 	/* Apply AMD APIC timer C1E workaround. */
-	if (cpu_ident_amdc1e && cpu_disable_deep_sleep) {
+	if (cpu_ident_amdc1e && cpu_disable_c3_sleep) {
 		msr = rdmsr(MSR_AMDK8_IPM);
 		if (msr & AMDK8_CMPHALT)
 			wrmsr(MSR_AMDK8_IPM, msr & ~AMDK8_CMPHALT);
diff --git a/sys/kern/kern_clocksource.c b/sys/kern/kern_clocksource.c
index 092c818..6e50441 100644
--- a/sys/kern/kern_clocksource.c
+++ b/sys/kern/kern_clocksource.c
@@ -59,8 +59,9 @@ __FBSDID("$FreeBSD$");
 cyclic_clock_func_t	cyclic_clock_func = NULL;
 #endif
 
-int			cpu_can_deep_sleep = 0;	/* C3 state is available. */
-int			cpu_disable_deep_sleep = 0; /* Timer dies in C3. */
+int			cpu_deepest_sleep = 0;	/* Deepest Cx state available. */
+int			cpu_disable_c2_sleep = 0; /* Timer dies in C2. */
+int			cpu_disable_c3_sleep = 0; /* Timer dies in C3. */
 
 static void		setuptimer(void);
 static void		loadtimer(sbintime_t now, int first);
@@ -627,7 +628,7 @@ cpu_initclocks_bsp(void)
 	else if (!periodic && (timer->et_flags & ET_FLAGS_ONESHOT) == 0)
 		periodic = 1;
 	if (timer->et_flags & ET_FLAGS_C3STOP)
-		cpu_disable_deep_sleep++;
+		cpu_disable_c3_sleep++;
 
 	/*
 	 * We honor the requested 'hz' value.
@@ -928,9 +929,9 @@ sysctl_kern_eventtimer_timer(SYSCTL_HANDLER_ARGS)
 	configtimer(0);
 	et_free(timer);
 	if (et->et_flags & ET_FLAGS_C3STOP)
-		cpu_disable_deep_sleep++;
+		cpu_disable_c3_sleep++;
 	if (timer->et_flags & ET_FLAGS_C3STOP)
-		cpu_disable_deep_sleep--;
+		cpu_disable_c3_sleep--;
 	periodic = want_periodic;
 	timer = et;
 	et_init(timer, timercb, NULL, NULL);
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 78ceff2..7a6b4e6 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -1330,10 +1330,10 @@ tc_windup(void)
 	/* Now is a good time to change timecounters. */
 	if (th->th_counter != timecounter) {
 #ifndef __arm__
-		if ((timecounter->tc_flags & TC_FLAGS_C3STOP) != 0)
-			cpu_disable_deep_sleep++;
-		if ((th->th_counter->tc_flags & TC_FLAGS_C3STOP) != 0)
-			cpu_disable_deep_sleep--;
+		if ((timecounter->tc_flags & TC_FLAGS_C2STOP) != 0)
+			cpu_disable_c2_sleep++;
+		if ((th->th_counter->tc_flags & TC_FLAGS_C2STOP) != 0)
+			cpu_disable_c2_sleep--;
 #endif
 		th->th_counter = timecounter;
 		th->th_offset_count = ncount;
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index f4eae57..4457414 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -289,8 +289,9 @@ sbintime_t 	cpu_idleclock(void);
 void	cpu_activeclock(void);
 void	cpu_new_callout(int cpu, sbintime_t bt, sbintime_t bt_opt);
 void	cpu_et_frequency(struct eventtimer *et, uint64_t newfreq);
-extern int	cpu_can_deep_sleep;
-extern int	cpu_disable_deep_sleep;
+extern int	cpu_deepest_sleep;
+extern int	cpu_disable_c2_sleep;
+extern int	cpu_disable_c3_sleep;
 
 int	cr_cansee(struct ucred *u1, struct ucred *u2);
 int	cr_canseesocket(struct ucred *cred, struct socket *so);
diff --git a/sys/sys/timetc.h b/sys/sys/timetc.h
index 48b962f..e68e327 100644
--- a/sys/sys/timetc.h
+++ b/sys/sys/timetc.h
@@ -58,7 +58,7 @@ struct timecounter {
 		 * means "only use at explicit request".
 		 */
 	u_int			tc_flags;
-#define	TC_FLAGS_C3STOP		1	/* Timer dies in C3. */
+#define	TC_FLAGS_C2STOP		1	/* Timer dies in C2+. */
 #define	TC_FLAGS_SUSPEND_SAFE	2	/*
 					 * Timer functional across
 					 * suspend/resume.
diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
index b78e3c9..4364df2 100644
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
@@ -581,16 +581,16 @@ init_TSC_tc(void)
 	}
 
 	/*
-	 * We cannot use the TSC if it stops incrementing in deep sleep.
-	 * Currently only Intel CPUs are known for this problem unless
-	 * the invariant TSC bit is set.
+	 * We cannot use the TSC if it stops incrementing while idle.
+	 * Intel CPUs without a C-state invariant TSC can stop the TSC
+	 * in either C2 or C3.
 	 */
-	if (cpu_can_deep_sleep && cpu_vendor_id == CPU_VENDOR_INTEL &&
+	if (cpu_deepest_sleep >= 2 && cpu_vendor_id == CPU_VENDOR_INTEL &&
 	    (amd_pminfo & AMDPM_TSC_INVARIANT) == 0) {
 		tsc_timecounter.tc_quality = -1000;
-		tsc_timecounter.tc_flags |= TC_FLAGS_C3STOP;
+		tsc_timecounter.tc_flags |= TC_FLAGS_C2STOP;
 		if (bootverbose)
-			printf("TSC timecounter disabled: C3 enabled.\n");
+			printf("TSC timecounter disabled: C-states may halt it.\n");
 		goto init;
 	}