diff --git a/[refs] b/[refs]
index a79164638e12..50bc9cec16fe 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 168a328f30e9d1a8bc6ff55c0501e0bdc08bee60
+refs/heads/master: f4d2e2d87eac0338884b2c26f6bafed115dbac5e
diff --git a/trunk/drivers/acpi/motherboard.c b/trunk/drivers/acpi/motherboard.c
index ec6b7f9ede34..2e17ec75af03 100644
--- a/trunk/drivers/acpi/motherboard.c
+++ b/trunk/drivers/acpi/motherboard.c
@@ -48,6 +48,12 @@ ACPI_MODULE_NAME("acpi_motherboard")
  * the io ports if they really know they can use it, while
  * still preventing hotplug PCI devices from using it.
  */
+
+/*
+ * When CONFIG_PNP is enabled, pnp/system.c binds to PNP0C01
+ * and PNP0C02, redundant with acpi_reserve_io_ranges().
+ * But acpi_reserve_io_ranges() is necessary for !CONFIG_PNP.
+ */
 static acpi_status acpi_reserve_io_ranges(struct acpi_resource *res, void *data)
 {
 	struct resource *requested_res = NULL;