diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 4ebc52a..15eb278 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -51,6 +51,11 @@
 	depends on DEBUG_KERNEL
 	default n
 
+config MSI_BITMAP_SELFTEST
+	bool "Run self-tests of the MSI bitmap code."
+	depends on DEBUG_KERNEL
+	default n
+
 config XMON
 	bool "Include xmon kernel debugger"
 	depends on DEBUG_KERNEL
diff --git a/arch/powerpc/include/asm/msi_bitmap.h b/arch/powerpc/include/asm/msi_bitmap.h
new file mode 100644
index 0000000..97ac3f4
--- /dev/null
+++ b/arch/powerpc/include/asm/msi_bitmap.h
@@ -0,0 +1,35 @@
+#ifndef _POWERPC_SYSDEV_MSI_BITMAP_H
+#define _POWERPC_SYSDEV_MSI_BITMAP_H
+
+/*
+ * Copyright 2008, Michael Ellerman, IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2 of the
+ * License.
+ *
+ */
+
+#include <linux/of.h>
+#include <asm/irq.h>
+
+struct msi_bitmap {
+	struct device_node	*of_node;
+	unsigned long		*bitmap;
+	spinlock_t		lock;
+	unsigned int		irq_count;
+};
+
+int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num);
+void msi_bitmap_free_hwirqs(struct msi_bitmap *bmp, unsigned int offset,
+			    unsigned int num);
+void msi_bitmap_reserve_hwirq(struct msi_bitmap *bmp, unsigned int hwirq);
+
+int msi_bitmap_reserve_dt_hwirqs(struct msi_bitmap *bmp);
+
+int msi_bitmap_alloc(struct msi_bitmap *bmp, unsigned int irq_count,
+		     struct device_node *of_node);
+void msi_bitmap_free(struct msi_bitmap *bmp);
+
+#endif /* _POWERPC_SYSDEV_MSI_BITMAP_H */
diff --git a/arch/powerpc/sysdev/Kconfig b/arch/powerpc/sysdev/Kconfig
index 72fb35b..3965828 100644
--- a/arch/powerpc/sysdev/Kconfig
+++ b/arch/powerpc/sysdev/Kconfig
@@ -6,3 +6,9 @@
 	bool
 	depends on PCI && 4xx
 	default n
+
+config PPC_MSI_BITMAP
+	bool
+	depends on PCI_MSI
+	default y if MPIC
+	default y if FSL_PCI
diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
index a90054b..b6c269e 100644
--- a/arch/powerpc/sysdev/Makefile
+++ b/arch/powerpc/sysdev/Makefile
@@ -5,6 +5,7 @@
 mpic-msi-obj-$(CONFIG_PCI_MSI)	+= mpic_msi.o mpic_u3msi.o mpic_pasemi_msi.o
 obj-$(CONFIG_MPIC)		+= mpic.o $(mpic-msi-obj-y)
 fsl-msi-obj-$(CONFIG_PCI_MSI)	+= fsl_msi.o
+obj-$(CONFIG_PPC_MSI_BITMAP)	+= msi_bitmap.o
 
 obj-$(CONFIG_PPC_MPC106)	+= grackle.o
 obj-$(CONFIG_PPC_DCR_NATIVE)	+= dcr-low.o
diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c
new file mode 100644
index 0000000..f84217b
--- /dev/null
+++ b/arch/powerpc/sysdev/msi_bitmap.c
@@ -0,0 +1,247 @@
+/*
+ * Copyright 2006-2008, Michael Ellerman, IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2 of the
+ * License.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/bitmap.h>
+#include <asm/msi_bitmap.h>
+
+int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num)
+{
+	unsigned long flags;
+	int offset, order = get_count_order(num);
+
+	spin_lock_irqsave(&bmp->lock, flags);
+	/*
+	 * This is fast, but stricter than we need. We might want to add
+	 * a fallback routine which does a linear search with no alignment.
+	 */
+	offset = bitmap_find_free_region(bmp->bitmap, bmp->irq_count, order);
+	spin_unlock_irqrestore(&bmp->lock, flags);
+
+	pr_debug("msi_bitmap: allocated 0x%x (2^%d) at offset 0x%x\n",
+		 num, order, offset);
+
+	return offset;
+}
+
+void msi_bitmap_free_hwirqs(struct msi_bitmap *bmp, unsigned int offset,
+			    unsigned int num)
+{
+	unsigned long flags;
+	int order = get_count_order(num);
+
+	pr_debug("msi_bitmap: freeing 0x%x (2^%d) at offset 0x%x\n",
+		 num, order, offset);
+
+	spin_lock_irqsave(&bmp->lock, flags);
+	bitmap_release_region(bmp->bitmap, offset, order);
+	spin_unlock_irqrestore(&bmp->lock, flags);
+}
+
+void msi_bitmap_reserve_hwirq(struct msi_bitmap *bmp, unsigned int hwirq)
+{
+	unsigned long flags;
+
+	pr_debug("msi_bitmap: reserving hwirq 0x%x\n", hwirq);
+
+	spin_lock_irqsave(&bmp->lock, flags);
+	bitmap_allocate_region(bmp->bitmap, hwirq, 0);
+	spin_unlock_irqrestore(&bmp->lock, flags);
+}
+
+/**
+ * msi_bitmap_reserve_dt_hwirqs - Reserve irqs specified in the device tree.
+ * @bmp: pointer to the MSI bitmap.
+ *
+ * Looks in the device tree to see if there is a property specifying which
+ * irqs can be used for MSI. If found those irqs reserved in the device tree
+ * are reserved in the bitmap.
+ *
+ * Returns 0 for success, < 0 if there was an error, and > 0 if no property
+ * was found in the device tree.
+ **/
+int msi_bitmap_reserve_dt_hwirqs(struct msi_bitmap *bmp)
+{
+	int i, j, len;
+	const u32 *p;
+
+	if (!bmp->of_node)
+		return 1;
+
+	p = of_get_property(bmp->of_node, "msi-available-ranges", &len);
+	if (!p) {
+		pr_debug("msi_bitmap: no msi-available-ranges property " \
+			 "found on %s\n", bmp->of_node->full_name);
+		return 1;
+	}
+
+	if (len % (2 * sizeof(u32)) != 0) {
+		printk(KERN_WARNING "msi_bitmap: Malformed msi-available-ranges"
+		       " property on %s\n", bmp->of_node->full_name);
+		return -EINVAL;
+	}
+
+	bitmap_allocate_region(bmp->bitmap, 0, get_count_order(bmp->irq_count));
+
+	spin_lock(&bmp->lock);
+
+	/* Format is: (<u32 start> <u32 count>)+ */
+	len /= 2 * sizeof(u32);
+	for (i = 0; i < len; i++, p += 2) {
+		for (j = 0; j < *(p + 1); j++)
+			bitmap_release_region(bmp->bitmap, *p + j, 0);
+	}
+
+	spin_unlock(&bmp->lock);
+
+	return 0;
+}
+
+int msi_bitmap_alloc(struct msi_bitmap *bmp, unsigned int irq_count,
+		     struct device_node *of_node)
+{
+	int size;
+
+	if (!irq_count)
+		return -EINVAL;
+
+	size = BITS_TO_LONGS(irq_count) * sizeof(long);
+	pr_debug("msi_bitmap: allocator bitmap size is 0x%x bytes\n", size);
+
+	bmp->bitmap = zalloc_maybe_bootmem(size, GFP_KERNEL);
+	if (!bmp->bitmap) {
+		pr_debug("msi_bitmap: ENOMEM allocating allocator bitmap!\n");
+		return -ENOMEM;
+	}
+
+	/* We zalloc'ed the bitmap, so all irqs are free by default */
+	spin_lock_init(&bmp->lock);
+	bmp->of_node = of_node_get(of_node);
+	bmp->irq_count = irq_count;
+
+	return 0;
+}
+
+void msi_bitmap_free(struct msi_bitmap *bmp)
+{
+	/* we can't free the bitmap we don't know if it's bootmem etc. */
+	of_node_put(bmp->of_node);
+	bmp->bitmap = NULL;
+}
+
+#ifdef CONFIG_MSI_BITMAP_SELFTEST
+
+#define check(x)	\
+	if (!(x)) printk("msi_bitmap: test failed at line %d\n", __LINE__);
+
+void test_basics(void)
+{
+	struct msi_bitmap bmp;
+	int i, size = 512;
+
+	/* Can't allocate a bitmap of 0 irqs */
+	check(msi_bitmap_alloc(&bmp, 0, NULL) != 0);
+
+	/* of_node may be NULL */
+	check(0 == msi_bitmap_alloc(&bmp, size, NULL));
+
+	/* Should all be free by default */
+	check(0 == bitmap_find_free_region(bmp.bitmap, size,
+					   get_count_order(size)));
+	bitmap_release_region(bmp.bitmap, 0, get_count_order(size));
+
+	/* With no node, there's no msi-available-ranges, so expect > 0 */
+	check(msi_bitmap_reserve_dt_hwirqs(&bmp) > 0);
+
+	/* Should all still be free */
+	check(0 == bitmap_find_free_region(bmp.bitmap, size,
+					   get_count_order(size)));
+	bitmap_release_region(bmp.bitmap, 0, get_count_order(size));
+
+	/* Check we can fill it up and then no more */
+	for (i = 0; i < size; i++)
+		check(msi_bitmap_alloc_hwirqs(&bmp, 1) >= 0);
+
+	check(msi_bitmap_alloc_hwirqs(&bmp, 1) < 0);
+
+	/* Should all be allocated */
+	check(bitmap_find_free_region(bmp.bitmap, size, 0) < 0);
+
+	/* And if we free one we can then allocate another */
+	msi_bitmap_free_hwirqs(&bmp, size / 2, 1);
+	check(msi_bitmap_alloc_hwirqs(&bmp, 1) == size / 2);
+
+	msi_bitmap_free(&bmp);
+
+	/* Clients may check bitmap == NULL for "not-allocated" */
+	check(bmp.bitmap == NULL);
+
+	kfree(bmp.bitmap);
+}
+
+void test_of_node(void)
+{
+	u32 prop_data[] = { 10, 10, 25, 3, 40, 1, 100, 100, 200, 20 };
+	const char *expected_str = "0-9,20-24,28-39,41-99,220-255";
+	char *prop_name = "msi-available-ranges";
+	char *node_name = "/fakenode";
+	struct device_node of_node;
+	struct property prop;
+	struct msi_bitmap bmp;
+	int size = 256;
+	DECLARE_BITMAP(expected, size);
+
+	/* There should really be a struct device_node allocator */
+	memset(&of_node, 0, sizeof(of_node));
+	kref_init(&of_node.kref);
+	of_node.full_name = node_name;
+
+	check(0 == msi_bitmap_alloc(&bmp, size, &of_node));
+
+	/* No msi-available-ranges, so expect > 0 */
+	check(msi_bitmap_reserve_dt_hwirqs(&bmp) > 0);
+
+	/* Should all still be free */
+	check(0 == bitmap_find_free_region(bmp.bitmap, size,
+					   get_count_order(size)));
+	bitmap_release_region(bmp.bitmap, 0, get_count_order(size));
+
+	/* Now create a fake msi-available-ranges property */
+
+	/* There should really .. oh whatever */
+	memset(&prop, 0, sizeof(prop));
+	prop.name = prop_name;
+	prop.value = &prop_data;
+	prop.length = sizeof(prop_data);
+
+	of_node.properties = &prop;
+
+	/* msi-available-ranges, so expect == 0 */
+	check(msi_bitmap_reserve_dt_hwirqs(&bmp) == 0);
+
+	/* Check we got the expected result */
+	check(0 == bitmap_parselist(expected_str, expected, size));
+	check(bitmap_equal(expected, bmp.bitmap, size));
+
+	msi_bitmap_free(&bmp);
+	kfree(bmp.bitmap);
+}
+
+int msi_bitmap_selftest(void)
+{
+	printk(KERN_DEBUG "Running MSI bitmap self-tests ...\n");
+
+	test_basics();
+	test_of_node();
+
+	return 0;
+}
+late_initcall(msi_bitmap_selftest);
+#endif /* CONFIG_MSI_BITMAP_SELFTEST */