common: DMA-mapping: add NO_DELAYED_UNMAP attribute
DMA_ATTR_NO_DELAYED_UNMAP specifies to the msm lazy mapping
driver that this buffer should be immediately unmapped once
it is freed.
Change-Id: I43e6a6058705502cf91bf5f0c530c3099cba06ae
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index d0f97c3..c0b673c 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -135,3 +135,13 @@
buffering, no pre-fetching). This has severe performance penalties and
should not be used for general purpose DMA allocations. It should only
be used if one of the restrictions on strongly ordered memory is required.
+
+DMA_ATTR_NO_DELAYED_UNMAP
+-------------------------
+
+DMA_ATTR_NO_DELAYED_UNMAP is used only by the msm specific lazy mapping
+feature. By default, the lazy mapping and unmapping holds an additional
+reference so that when the buffer is freed, the mapping is not destroyed
+and can be re-used. By specifying this attribute, an additional reference
+will NOT be held by the lazy mapping code and it will be released as soon
+as the buffer is freed.