--- zzzz-none-000/linux-4.4.271/Documentation/DMA-attributes.txt	2021-06-03 06:22:09.000000000 +0000
+++ hawkeye-5590-750/linux-4.4.271/Documentation/DMA-attributes.txt	2023-04-19 10:22:27.000000000 +0000
@@ -100,3 +100,74 @@
 be mapped as contiguous chunk into device dma address space. By
 specifying this attribute the allocated buffer is forced to be contiguous
 also in physical memory.
+
+DMA_ATTR_STRONGLY_ORDERED
+-------------------------
+
+DMA_ATTR_STRONGLY_ORDERED allocates memory with a very restrictive type
+of mapping (no unaligned accesses, no re-ordering, no write merging, no
+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.
+
+DMA_ATTR_EXEC_MAPPING
+---------------------
+
+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_FORCE_COHERENT
+-----------------------
+
+When passed to a DMA map call the DMA_ATTR_FORCE_COHERENT DMA
+attribute can be used to force a buffer to be mapped as IO coherent.
+This DMA attribute is only currently supported for arm64 stage 1 IOMMU
+mappings.
+
+DMA_ATTR_FORCE_NON_COHERENT
+---------------------------
+When passed to a DMA map call the DMA_ATTR_FORCE_NON_COHERENT DMA
+attribute can be used to force a buffer to not be mapped as IO
+coherent.
+The DMA_ATTR_FORCE_NON_COHERENT DMA attribute overrides the buffer IO
+coherency configuration set by making the device IO coherent.
+
+This DMA attribute is only currently supported for arm64 stage 1 IOMMU
+mappings.
+
+DMA_ATTR_ALLOC_SINGLE_PAGES
+---------------------------
+
+This is a hint to the DMA-mapping subsystem that it's probably not worth
+the time to try to allocate memory to in a way that gives better TLB
+efficiency (AKA it's not worth trying to build the mapping out of larger
+pages).  You might want to specify this if:
+- You know that the accesses to this memory won't thrash the TLB.
+  You might know that the accesses are likely to be sequential or
+  that they aren't sequential but it's unlikely you'll ping-pong
+  between many addresses that are likely to be in different physical
+  pages.
+- You know that the penalty of TLB misses while accessing the
+  memory will be small enough to be inconsequential.  If you are
+  doing a heavy operation like decryption or decompression this
+  might be the case.
+- You know that the DMA mapping is fairly transitory.  If you expect
+  the mapping to have a short lifetime then it may be worth it to
+  optimize allocation (avoid coming up with large pages) instead of
+  getting the slight performance win of larger pages.
+Setting this hint doesn't guarantee that you won't get huge pages, but it
+means that we won't try quite as hard to get them.
+
+NOTE: At the moment DMA_ATTR_ALLOC_SINGLE_PAGES is only implemented on ARM,
+though ARM64 patches will likely be posted soon.