Index: sys/cam/ata/ata_da.c
===================================================================
--- sys/cam/ata/ata_da.c	(revision 217032)
+++ sys/cam/ata/ata_da.c	(working copy)
@@ -169,6 +169,7 @@ static void		adagetparams(struct cam_periph *perip
 				struct ccb_getdev *cgd);
 static timeout_t	adasendorderedtag;
 static void		adashutdown(void *arg, int howto);
+static void		adasuspend(void *arg);
 
 #ifndef ADA_DEFAULT_TIMEOUT
 #define ADA_DEFAULT_TIMEOUT 30	/* Timeout in seconds */
@@ -186,6 +187,10 @@ static void		adashutdown(void *arg, int howto);
 #define	ADA_DEFAULT_SPINDOWN_SHUTDOWN	1
 #endif
 
+#ifndef	ADA_DEFAULT_SPINDOWN_SUSPEND
+#define	ADA_DEFAULT_SPINDOWN_SUSPEND	1
+#endif
+
 /*
  * Most platforms map firmware geometry to actual, but some don't.  If
  * not overridden, default to nothing.
@@ -198,6 +203,7 @@ static int ada_retry_count = ADA_DEFAULT_RETRY;
 static int ada_default_timeout = ADA_DEFAULT_TIMEOUT;
 static int ada_send_ordered = ADA_DEFAULT_SEND_ORDERED;
 static int ada_spindown_shutdown = ADA_DEFAULT_SPINDOWN_SHUTDOWN;
+static int ada_spindown_suspend = ADA_DEFAULT_SPINDOWN_SUSPEND;
 
 SYSCTL_NODE(_kern_cam, OID_AUTO, ada, CTLFLAG_RD, 0,
             "CAM Direct Access Disk driver");
@@ -213,6 +219,9 @@ TUNABLE_INT("kern.cam.ada.ada_send_ordered", &ada_
 SYSCTL_INT(_kern_cam_ada, OID_AUTO, spindown_shutdown, CTLFLAG_RW,
            &ada_spindown_shutdown, 0, "Spin down upon shutdown");
 TUNABLE_INT("kern.cam.ada.spindown_shutdown", &ada_spindown_shutdown);
+SYSCTL_INT(_kern_cam_ada, OID_AUTO, spindown_suspend, CTLFLAG_RW,
+           &ada_spindown_suspend, 0, "Spin down upon suspend");
+TUNABLE_INT("kern.cam.ada.spindown_suspend", &ada_spindown_suspend);
 
 /*
  * ADA_ORDEREDTAG_INTERVAL determines how often, relative
@@ -506,8 +515,11 @@ adainit(void)
 		       "due to status 0x%x!\n", status);
 	} else if (ada_send_ordered) {
 
-		/* Register our shutdown event handler */
-		if ((EVENTHANDLER_REGISTER(shutdown_post_sync, adashutdown, 
+		/* Register our event handlers */
+		if ((EVENTHANDLER_REGISTER(power_suspend, adasuspend,
+					   NULL, EVENTHANDLER_PRI_LAST)) == NULL)
+		    printf("adainit: power event registration failed!\n");
+		if ((EVENTHANDLER_REGISTER(shutdown_post_sync, adashutdown,
 					   NULL, SHUTDOWN_PRI_DEFAULT)) == NULL)
 		    printf("adainit: shutdown event registration failed!\n");
 	}
@@ -1187,7 +1199,7 @@ adasendorderedtag(void *arg)
  * sync the disk cache to physical media.
  */
 static void
-adashutdown(void * arg, int howto)
+adaflush(void)
 {
 	struct cam_periph *periph;
 	struct ada_softc *softc;
@@ -1239,10 +1251,13 @@ static void
 					 /*getcount_only*/0);
 		cam_periph_unlock(periph);
 	}
+}
 
-	if (ada_spindown_shutdown == 0 ||
-	    (howto & (RB_HALT | RB_POWEROFF)) == 0)
-		return;
+static void
+adaspindown(uint8_t cmd)
+{
+	struct cam_periph *periph;
+	struct ada_softc *softc;
 
 	TAILQ_FOREACH(periph, &adadriver.units, unit_links) {
 		union ccb ccb;
@@ -1275,7 +1290,7 @@ static void
 				    0,
 				    ada_default_timeout*1000);
 
-		ata_28bit_cmd(&ccb.ataio, ATA_STANDBY_IMMEDIATE, 0, 0, 0);
+		ata_28bit_cmd(&ccb.ataio, cmd, 0, 0, 0);
 		xpt_polled_action(&ccb);
 
 		if ((ccb.ccb_h.status & CAM_STATUS_MASK) != CAM_REQ_CMP)
@@ -1291,4 +1306,23 @@ static void
 	}
 }
 
+static void
+adashutdown(void *arg, int howto)
+{
+
+	adaflush();
+	if (ada_spindown_shutdown != 0 &&
+	    (howto & (RB_HALT | RB_POWEROFF)) != 0)
+		adaspindown(ATA_STANDBY_IMMEDIATE);
+}
+
+static void
+adasuspend(void *arg)
+{
+
+	adaflush();
+	if (ada_spindown_suspend != 0)
+		adaspindown(ATA_SLEEP);
+}
+
 #endif /* _KERNEL */
Index: sys/dev/acpica/acpi.c
===================================================================
--- sys/dev/acpica/acpi.c	(revision 217032)
+++ sys/dev/acpica/acpi.c	(working copy)
@@ -2609,6 +2609,8 @@ acpi_EnterSleepState(struct acpi_softc *sc, int st
 	return_ACPI_STATUS (AE_OK);
     }
 
+    EVENTHANDLER_INVOKE(power_suspend);
+
     if (smp_started) {
 	thread_lock(curthread);
 	sched_bind(curthread, 0);
@@ -2700,6 +2702,8 @@ backout:
 	thread_unlock(curthread);
     }
 
+    EVENTHANDLER_INVOKE(power_resume);
+
     /* Allow another sleep request after a while. */
     timeout(acpi_sleep_enable, sc, hz * ACPI_MINIMUM_AWAKETIME);
 
Index: sys/dev/siis/siis.c
===================================================================
--- sys/dev/siis/siis.c	(revision 217032)
+++ sys/dev/siis/siis.c	(working copy)
@@ -589,8 +589,6 @@ siis_ch_suspend(device_t dev)
 
 	mtx_lock(&ch->mtx);
 	xpt_freeze_simq(ch->sim, 1);
-	while (ch->oslots)
-		msleep(ch, &ch->mtx, PRIBIO, "siissusp", hz/100);
 	siis_ch_deinit(dev);
 	mtx_unlock(&ch->mtx);
 	return (0);
Index: sys/dev/ahci/ahci.c
===================================================================
--- sys/dev/ahci/ahci.c	(revision 217032)
+++ sys/dev/ahci/ahci.c	(working copy)
@@ -1056,8 +1056,6 @@ ahci_ch_suspend(device_t dev)
 
 	mtx_lock(&ch->mtx);
 	xpt_freeze_simq(ch->sim, 1);
-	while (ch->oslots)
-		msleep(ch, &ch->mtx, PRIBIO, "ahcisusp", hz/100);
 	ahci_ch_deinit(dev);
 	mtx_unlock(&ch->mtx);
 	return (0);
Index: sys/dev/mvs/mvs.c
===================================================================
--- sys/dev/mvs/mvs.c	(revision 217032)
+++ sys/dev/mvs/mvs.c	(working copy)
@@ -276,8 +276,6 @@ mvs_ch_suspend(device_t dev)
 
 	mtx_lock(&ch->mtx);
 	xpt_freeze_simq(ch->sim, 1);
-	while (ch->oslots)
-		msleep(ch, &ch->mtx, PRIBIO, "mvssusp", hz/100);
 	mvs_ch_deinit(dev);
 	mtx_unlock(&ch->mtx);
 	return (0);
Index: sys/dev/ata/ata-all.c
===================================================================
--- sys/dev/ata/ata-all.c	(revision 217032)
+++ sys/dev/ata/ata-all.c	(working copy)
@@ -472,8 +472,6 @@ ata_suspend(device_t dev)
 #ifdef ATA_CAM
 	mtx_lock(&ch->state_mtx);
 	xpt_freeze_simq(ch->sim, 1);
-	while (ch->state != ATA_IDLE)
-		msleep(ch, &ch->state_mtx, PRIBIO, "atasusp", hz/100);
 	mtx_unlock(&ch->state_mtx);
 #else
     /* wait for the channel to be IDLE or detached before suspending */
Index: sys/sys/eventhandler.h
===================================================================
--- sys/sys/eventhandler.h	(revision 217032)
+++ sys/sys/eventhandler.h	(working copy)
@@ -178,6 +178,11 @@ EVENTHANDLER_DECLARE(shutdown_pre_sync, shutdown_f
 EVENTHANDLER_DECLARE(shutdown_post_sync, shutdown_fn);	/* after fs sync */
 EVENTHANDLER_DECLARE(shutdown_final, shutdown_fn);
 
+/* Power state change events */
+typedef void (*power_change_fn)(void *);
+EVENTHANDLER_DECLARE(power_resume, power_change_fn);
+EVENTHANDLER_DECLARE(power_suspend, power_change_fn);
+
 /* Low memory event */
 typedef void (*vm_lowmem_handler_t)(void *, int);
 #define	LOWMEM_PRI_DEFAULT	EVENTHANDLER_PRI_FIRST