diff --git a/drivers/rtc/rtc-pl031.c b/drivers/rtc/rtc-pl031.c
index 451fc13..f41873f 100644
--- a/drivers/rtc/rtc-pl031.c
+++ b/drivers/rtc/rtc-pl031.c
@@ -142,8 +142,7 @@
 		goto out;
 	}
 
-	ldata->base = ioremap(adev->res.start,
-			      adev->res.end - adev->res.start + 1);
+	ldata->base = ioremap(adev->res.start, resource_size(&adev->res));
 	if (!ldata->base) {
 		ret = -ENOMEM;
 		goto out_no_remap;