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cma: debug: document new debugfs interface

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Document the structure and files under the new debugfs interface.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Sasha Levin 2015-04-14 15:45:08 -07:00 committed by Linus Torvalds
parent 875abdb6d4
commit 17e0db822b
1 changed files with 21 additions and 0 deletions
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Documentation/cma/debugfs.txt Normal file
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The CMA debugfs interface is useful to retrieve basic information out of the
different CMA areas and to test allocation/release in each of the areas.
Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
kernel's CMA index. So the first CMA zone would be:
<debugfs>/cma/cma-0
The structure of the files created under that directory is as follows:
- [RO] base_pfn: The base PFN (Page Frame Number) of the zone.
- [RO] count: Amount of memory in the CMA area.
- [RO] order_per_bit: Order of pages represented by one bit.
- [RO] bitmap: The bitmap of page states in the zone.
- [WO] alloc: Allocate N pages from that CMA area. For example:
echo 5 > <debugfs>/cma/cma-2/alloc
would try to allocate 5 pages from the cma-2 area.
- [WO] free: Free N pages from that CMA area, similar to the above.