diff --git a/drivers/infiniband/hw/ipath/ipath_wc_x86_64.c b/drivers/infiniband/hw/ipath/ipath_wc_x86_64.c
index 04696e62da8..9f409fd928f 100644
--- a/drivers/infiniband/hw/ipath/ipath_wc_x86_64.c
+++ b/drivers/infiniband/hw/ipath/ipath_wc_x86_64.c
@@ -63,12 +63,29 @@ int ipath_enable_wc(struct ipath_devdata *dd)
 	 * of 2 address matching the length (which has to be a power of 2).
 	 * For rev1, that means the base address, for rev2, it will be just
 	 * the PIO buffers themselves.
+	 * For chips with two sets of buffers, the calculations are
+	 * somewhat more complicated; we need to sum, and the piobufbase
+	 * register has both offsets, 2K in low 32 bits, 4K in high 32 bits.
+	 * The buffers are still packed, so a single range covers both.
 	 */
-	pioaddr = addr + dd->ipath_piobufbase;
-	piolen = (dd->ipath_piobcnt2k +
-		  dd->ipath_piobcnt4k) *
-		ALIGN(dd->ipath_piobcnt2k +
-		      dd->ipath_piobcnt4k, dd->ipath_palign);
+	if (dd->ipath_piobcnt2k && dd->ipath_piobcnt4k) { /* 2 sizes */
+		unsigned long pio2kbase, pio4kbase;
+		pio2kbase = dd->ipath_piobufbase & 0xffffffffUL;
+		pio4kbase = (dd->ipath_piobufbase >> 32) & 0xffffffffUL;
+		if (pio2kbase < pio4kbase) { /* all, for now */
+			pioaddr = addr + pio2kbase;
+			piolen = pio4kbase - pio2kbase +
+				dd->ipath_piobcnt4k * dd->ipath_4kalign;
+		} else {
+			pioaddr = addr + pio4kbase;
+			piolen = pio2kbase - pio4kbase +
+				dd->ipath_piobcnt2k * dd->ipath_palign;
+		}
+	} else {  /* single buffer size (2K, currently) */
+		pioaddr = addr + dd->ipath_piobufbase;
+		piolen = dd->ipath_piobcnt2k * dd->ipath_palign +
+			dd->ipath_piobcnt4k * dd->ipath_4kalign;
+	}
 
 	for (bits = 0; !(piolen & (1ULL << bits)); bits++)
 		/* do nothing */ ;