Index: head/sys/dev/ahci/ahci.h
===================================================================
--- head/sys/dev/ahci/ahci.h
+++ head/sys/dev/ahci/ahci.h
@@ -461,6 +461,8 @@
 	struct mtx_padalign	mtx;		/* state lock */
 	STAILQ_HEAD(, ccb_hdr)	doneq;		/* queue of completed CCBs */
 	int			batch;		/* doneq is in use */
+
+	int			disablephy;	/* keep PHY disabled */
 };
 
 struct ahci_enclosure {
Index: head/sys/dev/ahci/ahci.c
===================================================================
--- head/sys/dev/ahci/ahci.c
+++ head/sys/dev/ahci/ahci.c
@@ -39,6 +39,7 @@
 #include <sys/malloc.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/sysctl.h>
 #include <machine/stdarg.h>
 #include <machine/resource.h>
 #include <machine/bus.h>
@@ -80,6 +81,8 @@
 static void ahci_clo(struct ahci_channel *ch);
 static void ahci_start_fr(struct ahci_channel *ch);
 static void ahci_stop_fr(struct ahci_channel *ch);
+static int ahci_phy_check_events(struct ahci_channel *ch, u_int32_t serr);
+static uint32_t ahci_ch_detval(struct ahci_channel *ch, uint32_t val);
 
 static int ahci_sata_connect(struct ahci_channel *ch);
 static int ahci_sata_phy_reset(struct ahci_channel *ch);
@@ -100,6 +103,13 @@
 #define RECOVERY_REQUEST_SENSE	2
 #define recovery_slot		spriv_field1
 
+static uint32_t
+ahci_ch_detval(struct ahci_channel *ch, uint32_t val)
+{
+
+	return ch->disablephy ? ATA_SC_DET_DISABLE : val;
+}
+
 int
 ahci_ctlr_setup(device_t dev)
 {
@@ -665,11 +675,38 @@
 }
 
 static int
+ahci_ch_disablephy_proc(SYSCTL_HANDLER_ARGS)
+{
+	struct ahci_channel *ch;
+	int error, value;
+
+	ch = arg1;
+	value = ch->disablephy;
+	error = sysctl_handle_int(oidp, &value, 0, req);
+	if (error != 0 || req->newptr == NULL || (value != 0 && value != 1))
+		return (error);
+
+	mtx_lock(&ch->mtx);
+	ch->disablephy = value;
+	if (value) {
+		ahci_ch_deinit(ch->dev);
+	} else {
+		ahci_ch_init(ch->dev);
+		ahci_phy_check_events(ch, ATA_SE_PHY_CHANGED | ATA_SE_EXCHANGED);
+	}
+	mtx_unlock(&ch->mtx);
+
+	return (0);
+}
+
+static int
 ahci_ch_attach(device_t dev)
 {
 	struct ahci_controller *ctlr = device_get_softc(device_get_parent(dev));
 	struct ahci_channel *ch = device_get_softc(dev);
 	struct cam_devq *devq;
+	struct sysctl_ctx_list *ctx;
+	struct sysctl_oid *tree;
 	int rid, error, i, sata_rev = 0;
 	u_int32_t version;
 
@@ -787,6 +824,11 @@
 		    ahci_ch_pm, ch);
 	}
 	mtx_unlock(&ch->mtx);
+	ctx = device_get_sysctl_ctx(dev);
+	tree = device_get_sysctl_tree(dev);
+	SYSCTL_ADD_PROC(ctx, SYSCTL_CHILDREN(tree), OID_AUTO, "disable_phy",
+	    CTLFLAG_RW | CTLTYPE_UINT, ch, 0, ahci_ch_disablephy_proc, "IU",
+	    "Disable PHY");
 	return (0);
 
 err3:
@@ -2497,7 +2539,7 @@
 ahci_sata_phy_reset(struct ahci_channel *ch)
 {
 	int sata_rev;
-	uint32_t val;
+	uint32_t val, detval;
 
 	if (ch->listening) {
 		val = ATA_INL(ch->r_mem, AHCI_P_CMD);
@@ -2514,12 +2556,14 @@
 		val = ATA_SC_SPD_SPEED_GEN3;
 	else
 		val = 0;
+	detval = ahci_ch_detval(ch, ATA_SC_DET_RESET);
 	ATA_OUTL(ch->r_mem, AHCI_P_SCTL,
-	    ATA_SC_DET_RESET | val |
+	    detval | val |
 	    ATA_SC_IPM_DIS_PARTIAL | ATA_SC_IPM_DIS_SLUMBER);
 	DELAY(1000);
+	detval = ahci_ch_detval(ch, ATA_SC_DET_IDLE);
 	ATA_OUTL(ch->r_mem, AHCI_P_SCTL,
-	    ATA_SC_DET_IDLE | val | ((ch->pm_level > 0) ? 0 :
+	    detval | val | ((ch->pm_level > 0) ? 0 :
 	    (ATA_SC_IPM_DIS_PARTIAL | ATA_SC_IPM_DIS_SLUMBER)));
 	if (!ahci_sata_connect(ch)) {
 		if (ch->caps & AHCI_CAP_SSS) {