Index: sys/dev/ahci/ahci.h
===================================================================
--- sys/dev/ahci/ahci.h
+++ sys/dev/ahci/ahci.h
@@ -574,6 +574,8 @@
 #define AHCI_Q_SATA1_UNIT0	0x00008000	/* need better method for this */
 #define AHCI_Q_ABAR0		0x00010000
 #define AHCI_Q_1MSI		0x00020000
+#define AHCI_Q_FORCE_PI		0x00040000
+#define AHCI_Q_RESTORE_CAP	0x00080000
 
 #define AHCI_Q_BIT_STRING	\
 	"\021"			\
@@ -594,7 +596,9 @@
 	"\017MAXIO_64K"		\
 	"\020SATA1_UNIT0"	\
 	"\021ABAR0"		\
-	"\0221MSI"
+	"\0221MSI"              \
+	"\022FORCE_PI"          \
+	"\023RESTORE_CAP"
 
 int ahci_attach(device_t dev);
 int ahci_detach(device_t dev);
Index: sys/dev/ahci/ahci.c
===================================================================
--- sys/dev/ahci/ahci.c
+++ sys/dev/ahci/ahci.c
@@ -146,6 +146,18 @@
 	}
 	/* Reenable AHCI mode */
 	ATA_OUTL(ctlr->r_mem, AHCI_GHC, AHCI_GHC_AE);
+
+	if (ctlr->quirks & AHCI_Q_RESTORE_CAP) {
+		/*
+		 * Restore capability field.
+		 * This is write to a read-only register to restore its state.
+		 * On fully standard-compliant hardware this is not needed and
+		 * this operation shall not take place. See ahci_pci.c for
+		 * platforms using this quirk.
+		 */
+		ATA_OUTL(ctlr->r_mem, AHCI_CAP, ctlr->caps);
+	}
+
 	return (0);
 }
 
@@ -185,6 +197,22 @@
 		ctlr->caps2 = ATA_INL(ctlr->r_mem, AHCI_CAP2);
 	if (ctlr->caps & AHCI_CAP_EMS)
 		ctlr->capsem = ATA_INL(ctlr->r_mem, AHCI_EM_CTL);
+
+	if (ctlr->quirks & AHCI_Q_FORCE_PI) {
+		/*
+		 * Enable ports. 
+		 * The spec says that BIOS sets up bits corresponding to
+		 * available ports. On platforms where this information
+		 * is missing, the driver can define available ports on its own.
+		 */
+		int nports = (ctlr->caps & AHCI_CAP_NPMASK) + 1;
+		int nmask = (1 << nports) - 1;
+
+		ATA_OUTL(ctlr->r_mem, AHCI_PI, nmask);
+		device_printf(dev, "Forcing PI to %d ports (mask = %x)\n",
+		    nports, nmask);
+	}
+
 	ctlr->ichannels = ATA_INL(ctlr->r_mem, AHCI_PI);
 
 	/* Identify and set separate quirks for HBA and RAID f/w Marvells. */
Index: sys/dev/ahci/ahci_pci.c
===================================================================
--- sys/dev/ahci/ahci_pci.c
+++ sys/dev/ahci/ahci_pci.c
@@ -293,6 +293,7 @@
 	{0x11851039, 0x00, "SiS 968",		0},
 	{0x01861039, 0x00, "SiS 968",		0},
 	{0xa01c177d, 0x00, "ThunderX",		AHCI_Q_ABAR0|AHCI_Q_1MSI},
+	{0x00311c36, 0x00, "Annapurna",		AHCI_Q_FORCE_PI|AHCI_Q_RESTORE_CAP},
 	{0x00000000, 0x00, NULL,		0}
 };