diff --git a/drivers/acpi/atomicio.c b/drivers/acpi/atomicio.c
index 7489b89c3..f151afe 100644
--- a/drivers/acpi/atomicio.c
+++ b/drivers/acpi/atomicio.c
@@ -76,7 +76,7 @@
 {
 	struct acpi_iomap *map;
 
-	map = __acpi_find_iomap(paddr, size);
+	map = __acpi_find_iomap(paddr, size/8);
 	if (map)
 		return map->vaddr + (paddr - map->paddr);
 	else