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bus_dma(9): Correct arm64 BUS_DMA_COHERENT implementation note

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BUS_DMA_COHERENT isn't supported in bus_dmamap_create but bus_dma_tag_create.
Document it properly.

Submitted by:	andrew
This commit is contained in:
Emmanuel Vadot 2018-05-22 13:45:24 +00:00
parent a3c7cd11d2
commit 435b87a99b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=334041
1 changed files with 10 additions and 1 deletions
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11
share/man/man9/bus_dma.9
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@ -446,6 +446,15 @@ allocated with
Also, due to resource sharing with other tags, this flag does not guarantee
that resources will be allocated or reserved exclusively for this tag.
It should be treated only as a minor optimization.
.It Dv BUS_DMA_COHERENT
Indicate that the DMA engine and CPU are cache-coherent.
Cached memory may be used to back allocations created by
.Fn bus_dmamem_alloc .
For
.Fn bus_dma_tag_create ,
the
.Dv BUS_DMA_COHERENT
flag is currently implemented on arm64.
.El
.It Fa lockfunc
Optional lock manipulation function (may be
@ -504,7 +513,7 @@ For
.Fn bus_dmamap_create ,
the
.Dv BUS_DMA_COHERENT
flag is currently implemented on arm64 and sparc64.
flag is currently implemented on sparc64.
.El
.It Fa mapp
Pointer to a