--- zzzz-none-000/linux-4.4.60/arch/arm/mm/dma-mapping.c	2017-04-08 07:53:53.000000000 +0000
+++ dragonfly-4020-701/linux-4.4.60/arch/arm/mm/dma-mapping.c	2018-11-08 13:36:17.000000000 +0000
@@ -225,7 +225,8 @@
 	return mask;
 }
 
-static void __dma_clear_buffer(struct page *page, size_t size)
+static void __dma_clear_buffer(struct page *page, size_t size,
+				struct dma_attrs *attrs)
 {
 	/*
 	 * Ensure that the allocated pages are zeroed, and that any data
@@ -236,7 +237,8 @@
 		phys_addr_t end = base + size;
 		while (size > 0) {
 			void *ptr = kmap_atomic(page);
-			memset(ptr, 0, PAGE_SIZE);
+			if (!dma_get_attr(DMA_ATTR_SKIP_ZEROING, attrs))
+				memset(ptr, 0, PAGE_SIZE);
 			dmac_flush_range(ptr, ptr + PAGE_SIZE);
 			kunmap_atomic(ptr);
 			page++;
@@ -245,7 +247,8 @@
 		outer_flush_range(base, end);
 	} else {
 		void *ptr = page_address(page);
-		memset(ptr, 0, size);
+		if (!dma_get_attr(DMA_ATTR_SKIP_ZEROING, attrs))
+			memset(ptr, 0, size);
 		dmac_flush_range(ptr, ptr + size);
 		outer_flush_range(__pa(ptr), __pa(ptr) + size);
 	}
@@ -271,7 +274,7 @@
 	for (p = page + (size >> PAGE_SHIFT), e = page + (1 << order); p < e; p++)
 		__free_page(p);
 
-	__dma_clear_buffer(page, size);
+	__dma_clear_buffer(page, size, NULL);
 
 	return page;
 }
@@ -293,7 +296,8 @@
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
-				     const void *caller, bool want_vaddr);
+				     const void *caller, bool want_vaddr,
+					struct dma_attrs *attrs);
 
 static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 				 pgprot_t prot, struct page **ret_page,
@@ -361,7 +365,7 @@
 
 	if (dev_get_cma_area(NULL))
 		ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
-					      &page, atomic_pool_init, true);
+					      &page, atomic_pool_init, true, NULL);
 	else
 		ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
 					   &page, atomic_pool_init, true);
@@ -530,7 +534,8 @@
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
-				     const void *caller, bool want_vaddr)
+				     const void *caller, bool want_vaddr,
+				     struct dma_attrs *attrs)
 {
 	unsigned long order = get_order(size);
 	size_t count = size >> PAGE_SHIFT;
@@ -541,7 +546,12 @@
 	if (!page)
 		return NULL;
 
-	__dma_clear_buffer(page, size);
+	/*
+	 * skip completely if we neither need to zero nor sync.
+	 */
+	if (!(dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs) &&
+	      dma_get_attr(DMA_ATTR_SKIP_ZEROING, attrs)))
+		__dma_clear_buffer(page, size, attrs);
 
 	if (!want_vaddr)
 		goto out;
@@ -591,7 +601,7 @@
 #define __get_dma_pgprot(attrs, prot)				__pgprot(0)
 #define __alloc_remap_buffer(dev, size, gfp, prot, ret, c, wv)	NULL
 #define __alloc_from_pool(size, ret_page)			NULL
-#define __alloc_from_contiguous(dev, size, prot, ret, c, wv)	NULL
+#define __alloc_from_contiguous(dev, size, prot, ret, c, wv, a)	NULL
 #define __free_from_pool(cpu_addr, size)			0
 #define __free_from_contiguous(dev, page, cpu_addr, size, wv)	do { } while (0)
 #define __dma_free_remap(cpu_addr, size)			do { } while (0)
@@ -653,7 +663,7 @@
 		addr = __alloc_simple_buffer(dev, size, gfp, &page);
 	else if (dev_get_cma_area(dev) && (gfp & __GFP_DIRECT_RECLAIM))
 		addr = __alloc_from_contiguous(dev, size, prot, &page,
-					       caller, want_vaddr);
+					       caller, want_vaddr, attrs);
 	else if (is_coherent)
 		addr = __alloc_simple_buffer(dev, size, gfp, &page);
 	else if (!gfpflags_allow_blocking(gfp))
@@ -1146,7 +1156,7 @@
 		if (!page)
 			goto error;
 
-		__dma_clear_buffer(page, size);
+		__dma_clear_buffer(page, size, NULL);
 
 		for (i = 0; i < count; i++)
 			pages[i] = page + i;
@@ -1190,7 +1200,7 @@
 				pages[i + j] = pages[i] + j;
 		}
 
-		__dma_clear_buffer(pages[i], PAGE_SIZE << order);
+		__dma_clear_buffer(pages[i], PAGE_SIZE << order, NULL);
 		i += 1 << order;
 		count -= 1 << order;
 	}
@@ -2140,6 +2150,7 @@
 
 	set_dma_ops(dev, dma_ops);
 }
+EXPORT_SYMBOL(arch_setup_dma_ops);
 
 void arch_teardown_dma_ops(struct device *dev)
 {