+#ifdef CONFIG_DMA_RESTRICTED_POOL
+	if (swiotlb_free(dev, page, size))
+		return;
+#endif

Please avoid the ifdefs by either stubbing out the function to be a no-op
or by using IS_ENABLED.

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+	page = swiotlb_alloc(dev, size);
+	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+		__dma_direct_free_pages(dev, page, size);
+		page = NULL;
+	}
+#endif

Same here, for the stub it would just return NULL.