common: DMA-mapping: add WRITE_COMBINE attribute

DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
buffered to improve performance. It will be used by the replacement for
ARM/ARV32 specific dma_alloc_writecombine() function.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index b768cc0e402b8e6f1cfa8ae0b0f23c4e1c50168a..811a5d458dae79c9d557330793be45f53009ab68 100644 (file)
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -31,3 +31,13 @@ may be weakly ordered, that is that reads and writes may pass each other.
 Since it is optional for platforms to implement DMA_ATTR_WEAK_ORDERING,
 those that do not will simply ignore the attribute and exhibit default
 behavior.
+
+DMA_ATTR_WRITE_COMBINE
+----------------------
+
+DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
+buffered to improve performance.
+
+Since it is optional for platforms to implement DMA_ATTR_WRITE_COMBINE,
+those that do not will simply ignore the attribute and exhibit default
+behavior.

diff --git a/include/linux/dma-attrs.h b/include/linux/dma-attrs.h
index 71ad34eca6e3d124f9175e79d536a39379ee02fa..ada61e1abf2937d8705ffd0b2e2ffe0b42624a93 100644 (file)
--- a/include/linux/dma-attrs.h
+++ b/include/linux/dma-attrs.h
@@ -13,6 +13,7 @@
 enum dma_attr {
        DMA_ATTR_WRITE_BARRIER,
        DMA_ATTR_WEAK_ORDERING,
+       DMA_ATTR_WRITE_COMBINE,
        DMA_ATTR_MAX,
 };