powerpc/PCI: Override pcibios_window_alignment()

This patch implements pcibios_window_alignment() so powerpc platforms can
force P2P bridge windows to be at larger alignments than the PCI spec
requires.

[bhelgaas: changelog]
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

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.
 	 */

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