diff --git a/sys/dev/ahci.c b/sys/dev/ahci.c
index 91afb21..33fb999 100644
--- a/sys/dev/ahci.c
+++ b/sys/dev/ahci.c
@@ -48,16 +48,105 @@ typedef struct AHCIPort
     uint32_t	_rsvd2;		// *Reserved*
 } AHCIPort;
 
+#define AHCIPORT_CMD_ICCMASK	0xF0000000 /* Interface Communication Control */
+#define AHCIPORT_CMD_ICCSLUMBER	0x60000000 /* ICC Slumber */
+#define AHCIPORT_CMD_ICCPARTIAL	0x20000000 /* ICC Partial */
+#define AHCIPORT_CMD_ICCACTIVE	0x10000000 /* ICC Active */
+#define AHCIPORT_CMD_ICCIDLE	0x00000000 /* ICC Idle */
+#define AHCIPORT_CMD_ASP	0x08000000 /* Aggressive Slumber/Partial */
+#define AHCIPORT_CMD_ALPE	0x04000000 /* Aggressive Link PM Enable */
+#define AHCIPORT_CMD_DLAE	0x02000000 /* Drive LED on ATAPI Enable */
+#define AHCIPORT_CMD_ATAPI	0x01000000 /* Device is ATAPI */
+#define AHCIPORT_CMD_CPD	0x00100000 /* Cold Presence Detection */
+#define AHCIPORT_CMD_ISP	0x00080000 /* Interlock Switch Attached */
+#define AHCIPORT_CMD_HPCP	0x00040000 /* Hot Plug Capable Port */
+#define AHCIPORT_CMD_PMA	0x00020000 /* Port Multiplier Attached */
+#define AHCIPORT_CMD_CPS	0x00010000 /* Cold Presence State */
+#define AHCIPORT_CMD_CR		0x00008000 /* Command List Running */
+#define AHCIPORT_CMD_FR		0x00004000 /* FIS Receive Running */
+#define AHCIPORT_CMD_ISS	0x00002000 /* Interlock Switch State */
+#define AHCIPORT_CMD_FRE	0x00000010 /* FIS Receive Enable */
+#define AHCIPORT_CMD_CLO	0x00000008 /* Command List Override */
+#define AHCIPORT_CMD_POD	0x00000004 /* Power On Device */
+#define AHCIPORT_CMD_SUD	0x00000002 /* Spin-Up Device */
+#define AHCIPORT_CMD_ST		0x00000001 /* Start */
+
 #define AHCI_ABAR		5
 #define AHCI_PORT_OFFSET	0x100
 #define AHCI_PORT_LENGTH	0x80
 #define AHCI_MAX_PORTS		32
+#define AHCI_MAX_CMDS		32
 
+/*
+ * Request Structures
+ */
+
+typedef struct AHCICommandHeader
+{
+    uint32_t		descInfo;
+    uint32_t		cmdStatus;
+    uint64_t		ctba;
+    uint64_t		_rsvd[2];
+} AHCICommandHeader;
+
+typedef struct AHCICommandList
+{
+    AHCICommandHeader	cmds[AHCI_MAX_CMDS];
+} AHCICommandList;
+
+/*
+ * AHCIPRDT - Physical Region Descriptor Table
+ */
+typedef struct AHCIPRDT
+{
+    uint64_t		dba;		// Data Base Address
+    uint32_t		_rsvd;
+    uint32_t		descInfo;	// Description Information
+} AHCIPRDT;
+
+/*
+ * AHCICommandTable
+ * 	This structure is exactly one machine page in size, we fill up the page 
+ * 	with PRDT entries.  AHCI supports up to 64K PRDT entries but on x86 we 
+ * 	limit this to 248.
+ */
+typedef struct AHCICommandTable
+{
+    uint8_t		cfis[64];	// Command FIS
+    uint8_t		acmd[32];	// ATAPI Command
+    uint8_t		_rsvd[32];
+    AHCIPRDT		prdt[248];	// Physical Region Descriptor Table
+} AHCICommandTable;
+
+/*
+ * Response Structures
+ */
+
+typedef struct AHCIRecvFIS
+{
+    uint8_t		dsfis[0x1c];
+    uint8_t		_rsvd0[0x4];
+    uint8_t		psfis[0x14];
+    uint8_t		_rsvd1[0xc];
+    uint8_t		rfis[0x14];
+    uint8_t		_rsvd2[0x4];
+    uint8_t		sdbfis[0x8];
+    uint8_t		ufis[0x40];
+    uint8_t		_rsvd3[0x60];
+} AHCIRecvFIS;
+
+/*
+ * AHCI
+ * 	Exceeds a single page need to use heap
+ */
 typedef struct AHCI
 {
     PCIDevice		dev;
     AHCIHostControl	*hc;
     AHCIPort		*port[AHCI_MAX_PORTS];
+    AHCICommandList	*clst[AHCI_MAX_PORTS];
+    AHCICommandTable	*ctbl[AHCI_MAX_PORTS][AHCI_MAX_CMDS];
+    AHCIRecvFIS		*rfis[AHCI_MAX_PORTS];
 } AHCI;
 
 void AHCI_Configure(PCIDevice dev);
@@ -97,6 +186,29 @@ AHCI_Init(uint32_t bus, uint32_t slot, uint32_t func)
 void
 AHCI_ResetPort(AHCI *ahci, int port)
 {
+    volatile AHCIPort *p = ahci->port[port];
+    uint32_t cmd = p->cmd;
+    uint32_t cmd_mask = AHCIPORT_CMD_ST | AHCIPORT_CMD_CR |
+			AHCIPORT_CMD_FRE | AHCIPORT_CMD_FR;
+
+    // Wait for controller to be idle
+    if (cmd & cmd_mask != 0) {
+	int tries;
+	for (tries = 0; tries < 2; tries++) {
+	    cmd = cmd & ~(AHCIPORT_CMD_ST | AHCIPORT_CMD_FRE);
+	    p->cmd = cmd;
+	    // sleep 500ms
+	    cmd = p->cmd;
+	    if (cmd & cmd_mask != 0) {
+		kprintf("AHCI: failed to reset port %d\n", port);
+	    }
+	}
+    }
+
+    // Reset error
+    p->serr = 0xFFFFFFFF;
+
+    // 
 }
 
 void