--- zzzz-none-000/linux-2.6.39.4/arch/arm/mm/dma-mapping.c	2011-08-03 19:43:28.000000000 +0000
+++ puma6-atom-6490-729/linux-2.6.39.4/arch/arm/mm/dma-mapping.c	2021-11-10 13:38:14.000000000 +0000
@@ -665,3 +665,28 @@
 	return 0;
 }
 fs_initcall(dma_debug_do_init);
+
+
+/*
+ * Make an area consistent for devices.
+ */
+void consistent_sync(void *vaddr, size_t size, int direction)
+{
+	unsigned long start = (unsigned long)vaddr;
+	unsigned long end   = start + size;
+
+	switch (direction) {
+	case DMA_FROM_DEVICE:		/* invalidate only */
+		dmac_inv_range((void*)start, (void*)end);
+		break;
+	case DMA_TO_DEVICE:		/* writeback only */
+		dmac_clean_range((void*)start, (void*)end);
+		break;
+	case DMA_BIDIRECTIONAL:		/* writeback and invalidate */
+		dmac_flush_range((void*)start, (void*)end);
+		break;
+	default:
+		BUG();
+	}
+}
+EXPORT_SYMBOL(consistent_sync);