Index: sys/dev/ahci/ahci.h
===================================================================
--- sys/dev/ahci/ahci.h
+++ sys/dev/ahci/ahci.h
@@ -624,6 +624,7 @@
 #define AHCI_Q_MRVL_SR_DEL	0x00200000
 #define AHCI_Q_NOCCS		0x00400000
 #define AHCI_Q_NOAUX		0x00800000
+#define AHCI_Q_IOMMU_BUSWIDE	0x01000000
 
 #define AHCI_Q_BIT_STRING	\
 	"\020"			\
@@ -650,7 +651,8 @@
 	"\025NOMSIX"		\
 	"\026MRVL_SR_DEL"	\
 	"\027NOCCS"		\
-	"\030NOAUX"
+	"\030NOAUX"		\
+	"\031IOMMU_BUSWIDE"
 
 int ahci_attach(device_t dev);
 int ahci_detach(device_t dev);
Index: sys/dev/ahci/ahci_pci.c
===================================================================
--- sys/dev/ahci/ahci_pci.c
+++ sys/dev/ahci/ahci_pci.c
@@ -37,12 +37,16 @@
 #include <sys/malloc.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/sysctl.h>
+#include <sys/taskqueue.h>
+#include <sys/tree.h>
 #include <machine/stdarg.h>
 #include <machine/resource.h>
 #include <machine/bus.h>
 #include <sys/rman.h>
 #include <dev/pci/pcivar.h>
 #include <dev/pci/pcireg.h>
+#include <dev/iommu/iommu.h>
 #include "ahci.h"
 
 static int force_ahci = 1;
@@ -263,6 +267,7 @@
 	{0x91251b4b, 0x00, "Marvell 88SE9125",	0},
 	{0x91281b4b, 0x00, "Marvell 88SE9128",	AHCI_Q_ALTSIG},
 	{0x91301b4b, 0x00, "Marvell 88SE9130",  AHCI_Q_ALTSIG},
+	{0x91701b4b, 0x00, "Marvell 88SE9170",	AHCI_Q_IOMMU_BUSWIDE},
 	{0x91721b4b, 0x00, "Marvell 88SE9172",	0},
 	{0x91821b4b, 0x00, "Marvell 88SE9182",	0},
 	{0x91831b4b, 0x00, "Marvell 88SS9183",	0},
@@ -482,6 +487,16 @@
 	     ahci_ids[i].rev > revid))
 		i++;
 	ctlr->quirks = ahci_ids[i].quirks;
+
+	if (ctlr->quirks & AHCI_Q_IOMMU_BUSWIDE) {
+		/*
+		 * The controller issues DMA requests from PCI function 1,
+		 * but the device is not multifunction.
+		 * Ref: https://bugzilla.kernel.org/show_bug.cgi?id=42679
+		 */
+		bus_dma_iommu_set_buswide(dev);
+	}
+
 	/* Limit speed for my onboard JMicron external port.
 	 * It is not eSATA really, limit to SATA 1 */
 	if (pci_get_devid(dev) == 0x2363197b &&