use generic DMA mapping code in powerpc V4

[Christoph Hellwig]

Hi Christian,

can you check if the debug printks in this patch trigger?

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 355d16acee6d..e46c9b64ec0d 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -118,8 +118,11 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 			page = NULL;
 		}
 	}
-	if (!page)
+	if (!page) {
 		page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
+		if (!page)
+			pr_warn("failed to allocate memory with gfp 0x%x\n", gfp);
+	}
 
 	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 		__free_pages(page, page_order);
@@ -139,6 +142,10 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 		}
 	}
 
+	if (!page) {
+		pr_warn("failed to allocate DMA memory!\n");
+		dump_stack();
+	}
 	return page;
 }