5 * Contiguous Memory Allocator for DMA mapping framework
6 * Copyright (c) 2010-2011 by Samsung Electronics.
8 * Marek Szyprowski <m.szyprowski@samsung.com>
9 * Michal Nazarewicz <mina86@mina86.com>
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License as
13 * published by the Free Software Foundation; either version 2 of the
14 * License or (at your optional) any later version of the license.
18 * Contiguous Memory Allocator
20 * The Contiguous Memory Allocator (CMA) makes it possible to
21 * allocate big contiguous chunks of memory after the system has
26 * Various devices on embedded systems have no scatter-getter and/or
27 * IO map support and require contiguous blocks of memory to
28 * operate. They include devices such as cameras, hardware video
31 * Such devices often require big memory buffers (a full HD frame
32 * is, for instance, more then 2 mega pixels large, i.e. more than 6
33 * MB of memory), which makes mechanisms such as kmalloc() or
34 * alloc_page() ineffective.
36 * At the same time, a solution where a big memory region is
37 * reserved for a device is suboptimal since often more memory is
38 * reserved then strictly required and, moreover, the memory is
39 * inaccessible to page system even if device drivers don't use it.
41 * CMA tries to solve this issue by operating on memory regions
42 * where only movable pages can be allocated from. This way, kernel
43 * can use the memory for pagecache and when device driver requests
44 * it, allocated pages can be migrated.
48 * CMA should not be used by the device drivers directly. It is
49 * only a helper framework for dma-mapping subsystem.
51 * For more information, see kernel-docs in drivers/base/dma-contiguous.c
63 * There is always at least global CMA area and a few optional device
64 * private areas configured in kernel .config.
66 #define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS)
68 extern struct cma *dma_contiguous_def_area;
70 void dma_contiguous_reserve(phys_addr_t addr_limit);
72 int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t *res_base,
73 phys_addr_t limit, const char *name);
75 int dma_contiguous_add_device(struct device *dev, phys_addr_t base);
78 * dma_declare_contiguous() - reserve area for contiguous memory handling
79 * for particular device
80 * @dev: Pointer to device structure.
81 * @size: Size of the reserved memory.
82 * @base: Start address of the reserved memory (optional, 0 for any).
83 * @limit: End address of the reserved memory (optional, 0 for any).
85 * This function reserves memory for specified device. It should be
86 * called by board specific code when early allocator (memblock or bootmem)
90 static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
91 phys_addr_t base, phys_addr_t limit)
94 ret = dma_contiguous_reserve_area(size, &base, limit, NULL);
96 ret = dma_contiguous_add_device(dev, base);
100 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
102 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
107 #define MAX_CMA_AREAS (0)
109 static inline void dma_contiguous_reserve(phys_addr_t limit) { }
112 int dma_declare_contiguous(struct device *dev, phys_addr_t size,
113 phys_addr_t base, phys_addr_t limit)
119 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
126 bool dma_release_from_contiguous(struct device *dev, struct page *pages,