dma-mapping: Introduce DMA_ATTR_IOMMU_USE_UPSTREAM_HINT
Add documentation for this new attribute. It will be used on the
skunk target for allowing smmu clients to set the bus attributes
required to use system cache.
Change-Id: Id0b0dc261e46082ac48accdeb949947dce375d28
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index 836d232..9fa070c 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -169,3 +169,10 @@
By default, the DMA mappings are non-executable. Some use cases might require
an executable mapping. This attribute can be used to indicate to the DMA
subsystem to create an executable mappings for the buffer.
+
+DMA_ATTR_IOMMU_USE_UPSTREAM_HINT
+--------------------------------
+
+DMA_ATTR_IOMMU_USE_UPSTREAM_HINT: Normally an smmu will override any bus
+attributes (i.e cacheablilty) provided by the client device. Some hardware
+may be designed to use the original attributes instead.