diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index 42ce570812c1..f7706d722b39 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -214,6 +214,9 @@ struct machdep_calls {
 	/* Called after scan and before resource survey */
 	void (*pcibios_fixup_phb)(struct pci_controller *hose);
 
+	/* Called during PCI resource reassignment */
+	resource_size_t (*pcibios_window_alignment)(struct pci_bus *, unsigned long type);
+
 	/* Called to shutdown machine specific hardware not already controlled
 	 * by other drivers.
 	 */
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 2aa04f29e1de..43fea543d686 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -99,6 +99,26 @@ void pcibios_free_controller(struct pci_controller *phb)
 		kfree(phb);
 }
 
+/*
+ * The function is used to return the minimal alignment
+ * for memory or I/O windows of the associated P2P bridge.
+ * By default, 4KiB alignment for I/O windows and 1MiB for
+ * memory windows.
+ */
+resource_size_t pcibios_window_alignment(struct pci_bus *bus,
+					 unsigned long type)
+{
+	if (ppc_md.pcibios_window_alignment)
+		return ppc_md.pcibios_window_alignment(bus, type);
+
+	/*
+	 * PCI core will figure out the default
+	 * alignment: 4KiB for I/O and 1MiB for
+	 * memory window.
+	 */
+	return 1;
+}
+
 static resource_size_t pcibios_io_size(const struct pci_controller *hose)
 {
 #ifdef CONFIG_PPC64
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index b46e1dadc882..0e7eccc0f88d 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1139,6 +1139,44 @@ static void __devinit pnv_pci_ioda_fixup_phb(struct pci_controller *hose)
 	}
 }
 
+/*
+ * Returns the alignment for I/O or memory windows for P2P
+ * bridges. That actually depends on how PEs are segmented.
+ * For now, we return I/O or M32 segment size for PE sensitive
+ * P2P bridges. Otherwise, the default values (4KiB for I/O,
+ * 1MiB for memory) will be returned.
+ *
+ * The current PCI bus might be put into one PE, which was
+ * create against the parent PCI bridge. For that case, we
+ * needn't enlarge the alignment so that we can save some
+ * resources.
+ */
+static resource_size_t pnv_pci_window_alignment(struct pci_bus *bus,
+						unsigned long type)
+{
+	struct pci_dev *bridge;
+	struct pci_controller *hose = pci_bus_to_host(bus);
+	struct pnv_phb *phb = hose->private_data;
+	int num_pci_bridges = 0;
+
+	bridge = bus->self;
+	while (bridge) {
+		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE) {
+			num_pci_bridges++;
+			if (num_pci_bridges >= 2)
+				return 1;
+		}
+
+		bridge = bridge->bus->self;
+	}
+
+	/* We need support prefetchable memory window later */
+	if (type & IORESOURCE_MEM)
+		return phb->ioda.m32_segsize;
+
+	return phb->ioda.io_segsize;
+}
+
 /* Prevent enabling devices for which we couldn't properly
  * assign a PE
  */
@@ -1306,6 +1344,7 @@ void __init pnv_pci_init_ioda1_phb(struct device_node *np)
 	 */
 	ppc_md.pcibios_fixup_phb = pnv_pci_ioda_fixup_phb;
 	ppc_md.pcibios_enable_device_hook = pnv_pci_enable_device_hook;
+	ppc_md.pcibios_window_alignment = pnv_pci_window_alignment;
 	pci_add_flags(PCI_PROBE_ONLY | PCI_REASSIGN_ALL_RSRC);
 
 	/* Reset IODA tables to a clean state */
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index fb506137aaee..1e808ca338f8 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -697,6 +697,38 @@ static resource_size_t calculate_memsize(resource_size_t size,
 	return size;
 }
 
+resource_size_t __weak pcibios_window_alignment(struct pci_bus *bus,
+						unsigned long type)
+{
+	return 1;
+}
+
+#define PCI_P2P_DEFAULT_MEM_ALIGN	0x100000	/* 1MiB */
+#define PCI_P2P_DEFAULT_IO_ALIGN	0x1000		/* 4KiB */
+#define PCI_P2P_DEFAULT_IO_ALIGN_1K	0x400		/* 1KiB */
+
+static resource_size_t window_alignment(struct pci_bus *bus,
+					unsigned long type)
+{
+	resource_size_t align = 1, arch_align;
+
+	if (type & IORESOURCE_MEM)
+		align = PCI_P2P_DEFAULT_MEM_ALIGN;
+	else if (type & IORESOURCE_IO) {
+		/*
+		 * Per spec, I/O windows are 4K-aligned, but some
+		 * bridges have an extension to support 1K alignment.
+		 */
+		if (bus->self->io_window_1k)
+			align = PCI_P2P_DEFAULT_IO_ALIGN_1K;
+		else
+			align = PCI_P2P_DEFAULT_IO_ALIGN;
+	}
+
+	arch_align = pcibios_window_alignment(bus, type);
+	return max(align, arch_align);
+}
+
 /**
  * pbus_size_io() - size the io window of a given bus
  *
@@ -717,17 +749,12 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 	struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
 	unsigned long size = 0, size0 = 0, size1 = 0;
 	resource_size_t children_add_size = 0;
-	resource_size_t min_align = 4096, align;
+	resource_size_t min_align, io_align, align;
 
 	if (!b_res)
  		return;
 
-	/*
-	 * Per spec, I/O windows are 4K-aligned, but some bridges have an
-	 * extension to support 1K alignment.
-	 */
-	if (bus->self->io_window_1k)
-		min_align = 1024;
+	io_align = min_align = window_alignment(bus, IORESOURCE_IO);
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		int i;
 
@@ -754,8 +781,8 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 		}
 	}
 
-	if (min_align > 4096)
-		min_align = 4096;
+	if (min_align > io_align)
+		min_align = io_align;
 
 	size0 = calculate_iosize(size, min_size, size1,
 			resource_size(b_res), min_align);
@@ -785,6 +812,28 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
 	}
 }
 
+static inline resource_size_t calculate_mem_align(resource_size_t *aligns,
+						  int max_order)
+{
+	resource_size_t align = 0;
+	resource_size_t min_align = 0;
+	int order;
+
+	for (order = 0; order <= max_order; order++) {
+		resource_size_t align1 = 1;
+
+		align1 <<= (order + 20);
+
+		if (!align)
+			min_align = align1;
+		else if (ALIGN(align + min_align, min_align) < align1)
+			min_align = align1 >> 1;
+		align += aligns[order];
+	}
+
+	return min_align;
+}
+
 /**
  * pbus_size_mem() - size the memory window of a given bus
  *
@@ -864,19 +913,9 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 				children_add_size += get_res_add_size(realloc_head, r);
 		}
 	}
-	align = 0;
-	min_align = 0;
-	for (order = 0; order <= max_order; order++) {
-		resource_size_t align1 = 1;
 
-		align1 <<= (order + 20);
-
-		if (!align)
-			min_align = align1;
-		else if (ALIGN(align + min_align, min_align) < align1)
-			min_align = align1 >> 1;
-		align += aligns[order];
-	}
+	min_align = calculate_mem_align(aligns, max_order);
+	min_align = max(min_align, window_alignment(bus, b_res->flags & mask));
 	size0 = calculate_memsize(size, min_size, 0, resource_size(b_res), min_align);
 	if (children_add_size > add_size)
 		add_size = children_add_size;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 0d8718904e88..e52f16189cda 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1061,6 +1061,8 @@ int pci_cfg_space_size_ext(struct pci_dev *dev);
 int pci_cfg_space_size(struct pci_dev *dev);
 unsigned char pci_bus_max_busnr(struct pci_bus *bus);
 void pci_setup_bridge(struct pci_bus *bus);
+resource_size_t pcibios_window_alignment(struct pci_bus *bus,
+					 unsigned long type);
 
 #define PCI_VGA_STATE_CHANGE_BRIDGE (1 << 0)
 #define PCI_VGA_STATE_CHANGE_DECODES (1 << 1)