diff --git a/include/linux/usb/of.h b/include/linux/usb/of.h
index e460a24115ca..a0ef405368b8 100644
--- a/include/linux/usb/of.h
+++ b/include/linux/usb/of.h
@@ -10,19 +10,23 @@
 #include <linux/usb/otg.h>
 #include <linux/usb/phy.h>
 
-#ifdef CONFIG_OF
-enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np);
+#if IS_ENABLED(CONFIG_OF)
 enum usb_dr_mode of_usb_get_dr_mode(struct device_node *np);
 #else
-static inline enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np)
-{
-	return USBPHY_INTERFACE_MODE_UNKNOWN;
-}
-
 static inline enum usb_dr_mode of_usb_get_dr_mode(struct device_node *np)
 {
 	return USB_DR_MODE_UNKNOWN;
 }
 #endif
 
+#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_USB_PHY)
+enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np);
+#else
+static inline enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np)
+{
+	return USBPHY_INTERFACE_MODE_UNKNOWN;
+}
+
+#endif
+
 #endif /* __LINUX_USB_OF_H */