diff --git a/arch/mips/sgi-ip27/ip27-hubio.c b/arch/mips/sgi-ip27/ip27-hubio.c
new file mode 100644
index 0000000..524b371
--- /dev/null
+++ b/arch/mips/sgi-ip27/ip27-hubio.c
@@ -0,0 +1,186 @@
+/*
+ * Copyright (C) 1992-1997, 2000-2003 Silicon Graphics, Inc.
+ * Copyright (C) 2004 Christoph Hellwig.
+ *	Released under GPL v2.
+ *
+ * Support functions for the HUB ASIC - mostly PIO mapping related.
+ */
+
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/mmzone.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/arch.h>
+#include <asm/sn/hub.h>
+
+
+static int force_fire_and_forget = 1;
+
+/**
+ * hub_pio_map  -  establish a HUB PIO mapping
+ *
+ * @hub:	hub to perform PIO mapping on
+ * @widget:	widget ID to perform PIO mapping for
+ * @xtalk_addr:	xtalk_address that needs to be mapped
+ * @size:	size of the PIO mapping
+ *
+ **/
+unsigned long hub_pio_map(cnodeid_t cnode, xwidgetnum_t widget,
+			  unsigned long xtalk_addr, size_t size)
+{
+	nasid_t nasid = COMPACT_TO_NASID_NODEID(cnode);
+	volatile hubreg_t junk;
+	unsigned i;
+
+	/* use small-window mapping if possible */
+	if ((xtalk_addr % SWIN_SIZE) + size <= SWIN_SIZE)
+		return NODE_SWIN_BASE(nasid, widget) + (xtalk_addr % SWIN_SIZE);
+
+	if ((xtalk_addr % BWIN_SIZE) + size > BWIN_SIZE) {
+		printk(KERN_WARNING "PIO mapping at hub %d widget %d addr 0x%lx"
+				" too big (%ld)\n",
+				nasid, widget, xtalk_addr, size);
+		return 0;
+	}
+
+	xtalk_addr &= ~(BWIN_SIZE-1);
+	for (i = 0; i < HUB_NUM_BIG_WINDOW; i++) {
+		if (test_and_set_bit(i, hub_data(cnode)->h_bigwin_used))
+			continue;
+
+		/*
+		 * The code below does a PIO write to setup an ITTE entry.
+		 *
+		 * We need to prevent other CPUs from seeing our updated
+		 * memory shadow of the ITTE (in the piomap) until the ITTE
+		 * entry is actually set up; otherwise, another CPU might
+		 * attempt a PIO prematurely.
+		 *
+		 * Also, the only way we can know that an entry has been
+		 * received  by the hub and can be used by future PIO reads/
+		 * writes is by reading back the ITTE entry after writing it.
+		 *
+		 * For these two reasons, we PIO read back the ITTE entry
+		 * after we write it.
+		 */
+		IIO_ITTE_PUT(nasid, i, HUB_PIO_MAP_TO_MEM, widget, xtalk_addr);
+		junk = HUB_L(IIO_ITTE_GET(nasid, i));
+
+		return NODE_BWIN_BASE(nasid, widget) + (xtalk_addr % BWIN_SIZE);
+	}
+
+	printk(KERN_WARNING "unable to establish PIO mapping for at"
+			" hub %d widget %d addr 0x%lx\n",
+			nasid, widget, xtalk_addr);
+	return 0;
+}
+
+
+/*
+ * hub_setup_prb(nasid, prbnum, credits, conveyor)
+ *
+ * 	Put a PRB into fire-and-forget mode if conveyor isn't set.  Otherwise,
+ * 	put it into conveyor belt mode with the specified number of credits.
+ */
+static void hub_setup_prb(nasid_t nasid, int prbnum, int credits)
+{
+	iprb_t prb;
+	int prb_offset;
+
+	/*
+	 * Get the current register value.
+	 */
+	prb_offset = IIO_IOPRB(prbnum);
+	prb.iprb_regval = REMOTE_HUB_L(nasid, prb_offset);
+
+	/*
+	 * Clear out some fields.
+	 */
+	prb.iprb_ovflow = 1;
+	prb.iprb_bnakctr = 0;
+	prb.iprb_anakctr = 0;
+
+	/*
+	 * Enable or disable fire-and-forget mode.
+	 */
+	prb.iprb_ff = force_fire_and_forget ? 1 : 0;
+
+	/*
+	 * Set the appropriate number of PIO cresits for the widget.
+	 */
+	prb.iprb_xtalkctr = credits;
+
+	/*
+	 * Store the new value to the register.
+	 */
+	REMOTE_HUB_S(nasid, prb_offset, prb.iprb_regval);
+}
+
+/**
+ * hub_set_piomode  -  set pio mode for a given hub
+ *
+ * @nasid:	physical node ID for the hub in question
+ *
+ * Put the hub into either "PIO conveyor belt" mode or "fire-and-forget" mode.
+ * To do this, we have to make absolutely sure that no PIOs are in progress
+ * so we turn off access to all widgets for the duration of the function.
+ *
+ * XXX - This code should really check what kind of widget we're talking
+ * to.  Bridges can only handle three requests, but XG will do more.
+ * How many can crossbow handle to widget 0?  We're assuming 1.
+ *
+ * XXX - There is a bug in the crossbow that link reset PIOs do not
+ * return write responses.  The easiest solution to this problem is to
+ * leave widget 0 (xbow) in fire-and-forget mode at all times.  This
+ * only affects pio's to xbow registers, which should be rare.
+ **/
+static void hub_set_piomode(nasid_t nasid)
+{
+	hubreg_t ii_iowa;
+	hubii_wcr_t ii_wcr;
+	unsigned i;
+
+	ii_iowa = REMOTE_HUB_L(nasid, IIO_OUTWIDGET_ACCESS);
+	REMOTE_HUB_S(nasid, IIO_OUTWIDGET_ACCESS, 0);
+
+	ii_wcr.wcr_reg_value = REMOTE_HUB_L(nasid, IIO_WCR);
+
+	if (ii_wcr.iwcr_dir_con) {
+		/*
+		 * Assume a bridge here.
+		 */
+		hub_setup_prb(nasid, 0, 3);
+	} else {
+		/*
+		 * Assume a crossbow here.
+		 */
+		hub_setup_prb(nasid, 0, 1);
+	}
+
+	/*
+	 * XXX - Here's where we should take the widget type into
+	 * when account assigning credits.
+	 */
+	for (i = HUB_WIDGET_ID_MIN; i <= HUB_WIDGET_ID_MAX; i++)
+		hub_setup_prb(nasid, i, 3);
+
+	REMOTE_HUB_S(nasid, IIO_OUTWIDGET_ACCESS, ii_iowa);
+}
+
+/*
+ * hub_pio_init  -  PIO-related hub initalization
+ *
+ * @hub:	hubinfo structure for our hub
+ */
+void hub_pio_init(cnodeid_t cnode)
+{
+	nasid_t nasid = COMPACT_TO_NASID_NODEID(cnode);
+	unsigned i;
+
+	/* initialize big window piomaps for this hub */
+	bitmap_zero(hub_data(cnode)->h_bigwin_used, HUB_NUM_BIG_WINDOW);
+	for (i = 0; i < HUB_NUM_BIG_WINDOW; i++)
+		IIO_ITTE_DISABLE(nasid, i);
+
+	hub_set_piomode(nasid);
+}