diff --git a/payloads/libpayload/drivers/usb/xhci.c b/payloads/libpayload/drivers/usb/xhci.c
index 0a69c5137b..2f61f8658a 100644
--- a/payloads/libpayload/drivers/usb/xhci.c
+++ b/payloads/libpayload/drivers/usb/xhci.c
@@ -185,26 +185,27 @@ xhci_init (unsigned long physical_bar)
 		goto _free_xhci;
 	}
 
-	xhci->capreg	= phys_to_virt(physical_bar);
-	xhci->opreg	= ((void *)xhci->capreg) + xhci->capreg->caplength;
-	xhci->hcrreg	= ((void *)xhci->capreg) + xhci->capreg->rtsoff;
-	xhci->dbreg	= ((void *)xhci->capreg) + xhci->capreg->dboff;
+	memcpy(&xhci->capreg, phys_to_virt(physical_bar), sizeof(xhci->capreg));
+	xhci->opreg = phys_to_virt(physical_bar) + CAP_GET(CAPLEN, xhci->capreg);
+	xhci->hcrreg = phys_to_virt(physical_bar) + xhci->capreg.rtsoff;
+	xhci->dbreg = phys_to_virt(physical_bar) + xhci->capreg.dboff;
+
 	xhci_debug("regbase: 0x%"PRIx32"\n", physical_bar);
-	xhci_debug("caplen:  0x%"PRIx32"\n", xhci->capreg->caplength);
-	xhci_debug("rtsoff:  0x%"PRIx32"\n", xhci->capreg->rtsoff);
-	xhci_debug("dboff:   0x%"PRIx32"\n", xhci->capreg->dboff);
+	xhci_debug("caplen:  0x%"PRIx32"\n", CAP_GET(CAPLEN, xhci->capreg));
+	xhci_debug("rtsoff:  0x%"PRIx32"\n", xhci->capreg.rtsoff);
+	xhci_debug("dboff:   0x%"PRIx32"\n", xhci->capreg.dboff);
 
 	xhci_debug("hciversion: %"PRIx8".%"PRIx8"\n",
-		   xhci->capreg->hciver_hi, xhci->capreg->hciver_lo);
-	if ((xhci->capreg->hciversion < 0x96) ||
-			(xhci->capreg->hciversion > 0x110)) {
+		   CAP_GET(CAPVER_HI, xhci->capreg), CAP_GET(CAPVER_LO, xhci->capreg));
+	if ((CAP_GET(CAPVER, xhci->capreg) < 0x96) ||
+	    (CAP_GET(CAPVER, xhci->capreg) > 0x110)) {
 		xhci_debug("Unsupported xHCI version\n");
 		goto _free_xhci;
 	}
 
 	xhci_debug("context size: %dB\n", CTXSIZE(xhci));
-	xhci_debug("maxslots: 0x%02lx\n", xhci->capreg->MaxSlots);
-	xhci_debug("maxports: 0x%02lx\n", xhci->capreg->MaxPorts);
+	xhci_debug("maxslots: 0x%02lx\n", CAP_GET(MAXSLOTS, xhci->capreg));
+	xhci_debug("maxports: 0x%02lx\n", CAP_GET(MAXPORTS, xhci->capreg));
 	const unsigned pagesize = xhci->opreg->pagesize << 12;
 	xhci_debug("pagesize: 0x%04x\n", pagesize);
 
@@ -213,7 +214,8 @@ xhci_init (unsigned long physical_bar)
 	 * structures at first and can still chicken out easily if we run out
 	 * of memory.
 	 */
-	xhci->max_slots_en = xhci->capreg->MaxSlots & CONFIG_LP_MASK_MaxSlotsEn;
+	xhci->max_slots_en = CAP_GET(MAXSLOTS, xhci->capreg) &
+		CONFIG_LP_MASK_MaxSlotsEn;
 	xhci->dcbaa = xhci_align(64, (xhci->max_slots_en + 1) * sizeof(u64));
 	xhci->dev = malloc((xhci->max_slots_en + 1) * sizeof(*xhci->dev));
 	if (!xhci->dcbaa || !xhci->dev) {
@@ -227,8 +229,9 @@ xhci_init (unsigned long physical_bar)
 	 * Let dcbaa[0] point to another array of pointers, sp_ptrs.
 	 * The pointers therein point to scratchpad buffers (pages).
 	 */
-	const size_t max_sp_bufs = xhci->capreg->Max_Scratchpad_Bufs_Hi << 5 |
-				   xhci->capreg->Max_Scratchpad_Bufs_Lo;
+	const size_t max_sp_bufs =
+		CAP_GET(MAX_SCRATCH_BUFS_HI, xhci->capreg) << 5 |
+		CAP_GET(MAX_SCRATCH_BUFS_LO, xhci->capreg);
 	xhci_debug("max scratchpad bufs: 0x%zx\n", max_sp_bufs);
 	if (max_sp_bufs) {
 		const size_t sp_ptrs_size = max_sp_bufs * sizeof(u64);
@@ -376,7 +379,8 @@ xhci_reinit (hci_t *controller)
 	xhci_debug("event ring @%p (0x%08x)\n",
 		   xhci->er.ring, virt_to_phys(xhci->er.ring));
 	xhci_debug("ERST Max: 0x%lx ->  0x%lx entries\n",
-		   xhci->capreg->ERST_Max, 1 << xhci->capreg->ERST_Max);
+		   CAP_GET(ERST_MAX, xhci->capreg),
+		   1 << CAP_GET(ERST_MAX, xhci->capreg));
 	memset((void*)xhci->ev_ring_table, 0x00, sizeof(erst_entry_t));
 	xhci->ev_ring_table[0].seg_base_lo = virt_to_phys(xhci->er.ring);
 	xhci->ev_ring_table[0].seg_base_hi = 0;
@@ -432,8 +436,9 @@ xhci_shutdown(hci_t *const controller)
 #endif
 
 	if (xhci->sp_ptrs) {
-		size_t max_sp_bufs = xhci->capreg->Max_Scratchpad_Bufs_Hi << 5 |
-				     xhci->capreg->Max_Scratchpad_Bufs_Lo;
+		const size_t max_sp_bufs =
+			CAP_GET(MAX_SCRATCH_BUFS_HI, xhci->capreg) << 5 |
+			CAP_GET(MAX_SCRATCH_BUFS_LO, xhci->capreg);
 		for (i = 0; i < max_sp_bufs; ++i) {
 			if (xhci->sp_ptrs[i])
 				free(phys_to_virt(xhci->sp_ptrs[i]));
diff --git a/payloads/libpayload/drivers/usb/xhci_private.h b/payloads/libpayload/drivers/usb/xhci_private.h
index ab1dfa98e1..65c3fdd6cc 100644
--- a/payloads/libpayload/drivers/usb/xhci_private.h
+++ b/payloads/libpayload/drivers/usb/xhci_private.h
@@ -274,7 +274,6 @@ typedef volatile struct epctx {
 } epctx_t;
 
 #define NUM_EPS 32
-#define CTXSIZE(xhci) ((xhci)->capreg->csz ? 64 : 32)
 
 typedef union devctx {
 	/* set of pointers, so we can dynamically adjust Slot/EP context size */
@@ -321,66 +320,65 @@ typedef struct erst_entry {
 	u32 rsvd;
 } erst_entry_t;
 
+#define CAP_CAPLEN_FIELD		hciparams
+#define CAP_CAPLEN_START		0
+#define CAP_CAPLEN_LEN			8
+#define CAP_CAPVER_FIELD		hciparams
+#define CAP_CAPVER_START		16
+#define CAP_CAPVER_LEN			16
+#define CAP_CAPVER_HI_FIELD		hciparams
+#define CAP_CAPVER_HI_START		24
+#define CAP_CAPVER_HI_LEN		8
+#define CAP_CAPVER_LO_FIELD		hciparams
+#define CAP_CAPVER_LO_START		16
+#define CAP_CAPVER_LO_LEN		8
+#define CAP_MAXSLOTS_FIELD		hcsparams1
+#define CAP_MAXSLOTS_START		0
+#define CAP_MAXSLOTS_LEN		7
+#define CAP_MAXINTRS_FIELD		hcsparams1
+#define CAP_MAXINTRS_START		7
+#define CAP_MAXINTRS_LEN		11
+#define CAP_MAXPORTS_FIELD		hcsparams1
+#define CAP_MAXPORTS_START		24
+#define CAP_MAXPORTS_LEN		8
+#define CAP_IST_FIELD			hcsparams2
+#define CAP_IST_START			0
+#define CAP_IST_LEN			4
+#define CAP_ERST_MAX_FIELD		hcsparams2
+#define CAP_ERST_MAX_START		4
+#define CAP_ERST_MAX_LEN		4
+#define CAP_MAX_SCRATCH_BUFS_HI_FIELD	hcsparams2
+#define CAP_MAX_SCRATCH_BUFS_HI_START	21
+#define CAP_MAX_SCRATCH_BUFS_HI_LEN	5
+#define CAP_MAX_SCRATCH_BUFS_LO_FIELD	hcsparams2
+#define CAP_MAX_SCRATCH_BUFS_LO_START	27
+#define CAP_MAX_SCRATCH_BUFS_LO_LEN	5
+#define CAP_U1_LATENCY_FIELD		hcsparams3
+#define CAP_U1_LATENCY_START		0
+#define CAP_U1_LATENCY_LEN		8
+#define CAP_U2_LATENCY_FIELD		hcsparams3
+#define CAP_U2_LATENCY_START		16
+#define CAP_U2_LATENCY_LEN		16
+#define CAP_CSZ_FIELD			hccparams
+#define CAP_CSZ_START			2
+#define CAP_CSZ_LEN			1
+
+#define CAP_MASK(tok)		MASK(CAP_##tok##_START, CAP_##tok##_LEN)
+#define CAP_GET(tok, cap)	(((cap).CAP_##tok##_FIELD & CAP_MASK(tok)) \
+				 >> CAP_##tok##_START)
+
+#define CTXSIZE(xhci) (CAP_GET(CSZ, (xhci)->capreg) ? 64 : 32)
+
 typedef struct xhci {
-	/* capreg is read-only, so no need for volatile,
-	   and thus 32bit accesses can be assumed. */
 	struct capreg {
-		u8 caplength; /* 0x00 */
-		u8 res1; /* 0x01 */
-		union { /* 0x02 */
-			u16 hciversion;
-			struct {
-				u8 hciver_lo;
-				u8 hciver_hi;
-			} __packed;
-		} __packed;
-		union { /* 0x04 */
-			u32 hcsparams1;
-			struct {
-				unsigned long MaxSlots:7;
-				unsigned long MaxIntrs:11;
-				unsigned long:6;
-				unsigned long MaxPorts:8;
-			} __packed;
-		} __packed;
-		union { /* 0x08 */
-			u32 hcsparams2;
-			struct {
-				unsigned long IST:4;
-				unsigned long ERST_Max:4;
-				unsigned long:13;
-				unsigned long Max_Scratchpad_Bufs_Hi:5;
-				unsigned long SPR:1;
-				unsigned long Max_Scratchpad_Bufs_Lo:5;
-			} __packed;
-		} __packed;
-		union { /* 0x0C */
-			u32 hcsparams3;
-			struct {
-				unsigned long u1latency:8;
-				unsigned long:8;
-				unsigned long u2latency:16;
-			} __packed;
-		} __packed;
-		union { /* 0x10 */
-			u32 hccparams;
-			struct {
-				unsigned long ac64:1;
-				unsigned long bnc:1;
-				unsigned long csz:1;
-				unsigned long ppc:1;
-				unsigned long pind:1;
-				unsigned long lhrc:1;
-				unsigned long ltc:1;
-				unsigned long nss:1;
-				unsigned long:4;
-				unsigned long MaxPSASize:4;
-				unsigned long xECP:16;
-			} __packed;
-		} __packed;
-		u32 dboff; /* 0x14 */
-		u32 rtsoff; /* 0x18 */
-	} __packed *capreg;
+		u32 hciparams;
+		u32 hcsparams1;
+		u32 hcsparams2;
+		u32 hcsparams3;
+		u32 hccparams;
+		u32 dboff;
+		u32 rtsoff;
+	} __packed capreg;
 
 	/* opreg is R/W is most places, so volatile access is necessary.
 	   volatile means that the compiler seeks byte writes if possible,
diff --git a/payloads/libpayload/drivers/usb/xhci_rh.c b/payloads/libpayload/drivers/usb/xhci_rh.c
index 453fa5b409..865b9ac18b 100644
--- a/payloads/libpayload/drivers/usb/xhci_rh.c
+++ b/payloads/libpayload/drivers/usb/xhci_rh.c
@@ -160,7 +160,7 @@ xhci_rh_init (usbdev_t *dev)
 	dev->port = -1;
 
 	const int num_ports = /* TODO: maybe we need to read extended caps */
-		(XHCI_INST(dev->controller)->capreg->hcsparams1 >> 24) & 0xff;
+		CAP_GET(MAXPORTS, XHCI_INST(dev->controller)->capreg);
 	generic_hub_init(dev, num_ports, &xhci_rh_ops);
 
 	usb_debug("xHCI: root hub init done\n");