1*01c0aa79SMauro Carvalho Chehab===================== 2*01c0aa79SMauro Carvalho ChehabCMA Debugfs Interface 3*01c0aa79SMauro Carvalho Chehab===================== 4*01c0aa79SMauro Carvalho Chehab 517e0db82SSasha LevinThe CMA debugfs interface is useful to retrieve basic information out of the 617e0db82SSasha Levindifferent CMA areas and to test allocation/release in each of the areas. 717e0db82SSasha Levin 817e0db82SSasha LevinEach CMA zone represents a directory under <debugfs>/cma/, indexed by the 917e0db82SSasha Levinkernel's CMA index. So the first CMA zone would be: 1017e0db82SSasha Levin 1117e0db82SSasha Levin <debugfs>/cma/cma-0 1217e0db82SSasha Levin 1317e0db82SSasha LevinThe structure of the files created under that directory is as follows: 1417e0db82SSasha Levin 1517e0db82SSasha Levin - [RO] base_pfn: The base PFN (Page Frame Number) of the zone. 1617e0db82SSasha Levin - [RO] count: Amount of memory in the CMA area. 1717e0db82SSasha Levin - [RO] order_per_bit: Order of pages represented by one bit. 1817e0db82SSasha Levin - [RO] bitmap: The bitmap of page states in the zone. 19*01c0aa79SMauro Carvalho Chehab - [WO] alloc: Allocate N pages from that CMA area. For example:: 2017e0db82SSasha Levin 2117e0db82SSasha Levin echo 5 > <debugfs>/cma/cma-2/alloc 2217e0db82SSasha Levin 2317e0db82SSasha Levinwould try to allocate 5 pages from the cma-2 area. 2417e0db82SSasha Levin 2517e0db82SSasha Levin - [WO] free: Free N pages from that CMA area, similar to the above. 26