include/linux/dma-contiguous.h

   1 #ifndef __LINUX_CMA_H
   2 #define __LINUX_CMA_H
   3
   4 /*
   5  * Contiguous Memory Allocator for DMA mapping framework
   6  * Copyright (c) 2010-2011 by Samsung Electronics.
   7  * Written by:
   8  *      Marek Szyprowski <m.szyprowski@samsung.com>
   9  *      Michal Nazarewicz <mina86@mina86.com>
  10  *
  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.
  15  */
  16
  17 /*
  18  * Contiguous Memory Allocator
  19  *
  20  *   The Contiguous Memory Allocator (CMA) makes it possible to
  21  *   allocate big contiguous chunks of memory after the system has
  22  *   booted.
  23  *
  24  * Why is it needed?
  25  *
  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
  29  *   coders, etc.
  30  *
  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.
  35  *
  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.
  40  *
  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.
  45  *
  46  * Driver usage
  47  *
  48  *   CMA should not be used by the device drivers directly. It is
  49  *   only a helper framework for dma-mapping subsystem.
  50  *
  51  *   For more information, see kernel-docs in drivers/base/dma-contiguous.c
  52  */
  53
  54 #ifdef __KERNEL__
  55
  56 struct cma;
  57 struct page;
  58 struct device;
  59
  60 #ifdef CONFIG_DMA_CMA
  61
  62 /*
  63  * There is always at least global CMA area and a few optional device
  64  * private areas configured in kernel .config.
  65  */
  66 #define MAX_CMA_AREAS   (1 + CONFIG_CMA_AREAS)
  67
  68 extern struct cma *dma_contiguous_default_area;
  69
  70 static inline struct cma *dev_get_cma_area(struct device *dev)
  71 {
  72         if (dev && dev->cma_area)
  73                 return dev->cma_area;
  74         return dma_contiguous_default_area;
  75 }
  76
  77 static inline void dev_set_cma_area(struct device *dev, struct cma *cma)
  78 {
  79         if (dev)
  80                 dev->cma_area = cma;
  81 }
  82
  83 static inline void dma_contiguous_set_default(struct cma *cma)
  84 {
  85         dma_contiguous_default_area = cma;
  86 }
  87
  88 void dma_contiguous_reserve(phys_addr_t addr_limit);
  89
  90 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
  91                                        phys_addr_t limit, struct cma **res_cma);
  92
  93 /**
  94  * dma_declare_contiguous() - reserve area for contiguous memory handling
  95  *                            for particular device
  96  * @dev:   Pointer to device structure.
  97  * @size:  Size of the reserved memory.
  98  * @base:  Start address of the reserved memory (optional, 0 for any).
  99  * @limit: End address of the reserved memory (optional, 0 for any).
 100  *
 101  * This function reserves memory for specified device. It should be
 102  * called by board specific code when early allocator (memblock or bootmem)
 103  * is still activate.
 104  */
 105
 106 static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 107                                          phys_addr_t base, phys_addr_t limit)
 108 {
 109         struct cma *cma;
 110         int ret;
 111         ret = dma_contiguous_reserve_area(size, base, limit, &cma);
 112         if (ret == 0)
 113                 dev_set_cma_area(dev, cma);
 114
 115         return ret;
 116 }
 117
 118 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
 119                                        unsigned int order);
 120 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 121                                  int count);
 122
 123 #else
 124
 125 #define MAX_CMA_AREAS   (0)
 126
 127 static inline struct cma *dev_get_cma_area(struct device *dev)
 128 {
 129         return NULL;
 130 }
 131
 132 static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { }
 133
 134 static inline void dma_contiguous_set_default(struct cma *cma) { }
 135
 136 static inline void dma_contiguous_reserve(phys_addr_t limit) { }
 137
 138 static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 139                                        phys_addr_t limit, struct cma **res_cma) {
 140         return -ENOSYS;
 141 }
 142
 143 static inline
 144 int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 145                            phys_addr_t base, phys_addr_t limit)
 146 {
 147         return -ENOSYS;
 148 }
 149
 150 static inline
 151 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
 152                                        unsigned int order)
 153 {
 154         return NULL;
 155 }
 156
 157 static inline
 158 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 159                                  int count)
 160 {
 161         return false;
 162 }
 163
 164 #endif
 165
 166 #endif
 167
 168 #endif