diff --git a/arch/arm/mach-omap2/mailbox.c b/arch/arm/mach-omap2/mailbox.c
index c035ad3..ef57b38 100644
--- a/arch/arm/mach-omap2/mailbox.c
+++ b/arch/arm/mach-omap2/mailbox.c
@@ -300,7 +300,7 @@
 		dev_err(&pdev->dev, "invalid mem resource\n");
 		return -ENODEV;
 	}
-	mbox_base = ioremap(res->start, res->end - res->start);
+	mbox_base = ioremap(res->start, resource_size(res));
 	if (!mbox_base)
 		return -ENOMEM;