diff --git a/drivers/isdn/hardware/mISDN/mISDNinfineon.c b/drivers/isdn/hardware/mISDN/mISDNinfineon.c
index fa9c491f9c38b..88d592bafdb02 100644
--- a/drivers/isdn/hardware/mISDN/mISDNinfineon.c
+++ b/drivers/isdn/hardware/mISDN/mISDNinfineon.c
@@ -630,17 +630,19 @@ static void
 release_io(struct inf_hw *hw)
 {
 	if (hw->cfg.mode) {
-		if (hw->cfg.p) {
+		if (hw->cfg.mode == AM_MEMIO) {
 			release_mem_region(hw->cfg.start, hw->cfg.size);
-			iounmap(hw->cfg.p);
+			if (hw->cfg.p)
+				iounmap(hw->cfg.p);
 		} else
 			release_region(hw->cfg.start, hw->cfg.size);
 		hw->cfg.mode = AM_NONE;
 	}
 	if (hw->addr.mode) {
-		if (hw->addr.p) {
+		if (hw->addr.mode == AM_MEMIO) {
 			release_mem_region(hw->addr.start, hw->addr.size);
-			iounmap(hw->addr.p);
+			if (hw->addr.p)
+				iounmap(hw->addr.p);
 		} else
 			release_region(hw->addr.start, hw->addr.size);
 		hw->addr.mode = AM_NONE;
@@ -670,9 +672,12 @@ setup_io(struct inf_hw *hw)
 				(ulong)hw->cfg.start, (ulong)hw->cfg.size);
 			return err;
 		}
-		if (hw->ci->cfg_mode == AM_MEMIO)
-			hw->cfg.p = ioremap(hw->cfg.start, hw->cfg.size);
 		hw->cfg.mode = hw->ci->cfg_mode;
+		if (hw->ci->cfg_mode == AM_MEMIO) {
+			hw->cfg.p = ioremap(hw->cfg.start, hw->cfg.size);
+			if (!hw->cfg.p)
+				return -ENOMEM;
+		}
 		if (debug & DEBUG_HW)
 			pr_notice("%s: IO cfg %lx (%lu bytes) mode%d\n",
 				  hw->name, (ulong)hw->cfg.start,
@@ -697,9 +702,12 @@ setup_io(struct inf_hw *hw)
 				(ulong)hw->addr.start, (ulong)hw->addr.size);
 			return err;
 		}
-		if (hw->ci->addr_mode == AM_MEMIO)
-			hw->addr.p = ioremap(hw->addr.start, hw->addr.size);
 		hw->addr.mode = hw->ci->addr_mode;
+		if (hw->ci->addr_mode == AM_MEMIO) {
+			hw->addr.p = ioremap(hw->addr.start, hw->addr.size);
+			if (!hw->addr.p)
+				return -ENOMEM;
+		}
 		if (debug & DEBUG_HW)
 			pr_notice("%s: IO addr %lx (%lu bytes) mode%d\n",
 				  hw->name, (ulong)hw->addr.start,