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 #include <linux/device.h>
  57
  58 struct cma;
  59 struct page;
  60
  61 #ifdef CONFIG_DMA_CMA
  62
  63 extern struct cma *dma_contiguous_default_area;
  64
  65 static inline struct cma *dev_get_cma_area(struct device *dev)
  66 {
  67         if (dev && dev->cma_area)
  68                 return dev->cma_area;
  69         return dma_contiguous_default_area;
  70 }
  71
  72 static inline void dev_set_cma_area(struct device *dev, struct cma *cma)
  73 {
  74         if (dev)
  75                 dev->cma_area = cma;
  76 }
  77
  78 static inline void dma_contiguous_set_default(struct cma *cma)
  79 {
  80         dma_contiguous_default_area = cma;
  81 }
  82
  83 void dma_contiguous_reserve(phys_addr_t addr_limit);
  84
  85 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
  86                                        phys_addr_t limit, struct cma **res_cma,
  87                                        bool fixed);
  88
  89 /**
  90  * dma_declare_contiguous() - reserve area for contiguous memory handling
  91  *                            for particular device
  92  * @dev:   Pointer to device structure.
  93  * @size:  Size of the reserved memory.
  94  * @base:  Start address of the reserved memory (optional, 0 for any).
  95  * @limit: End address of the reserved memory (optional, 0 for any).
  96  *
  97  * This function reserves memory for specified device. It should be
  98  * called by board specific code when early allocator (memblock or bootmem)
  99  * is still activate.
 100  */
 101
 102 static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 103                                          phys_addr_t base, phys_addr_t limit)
 104 {
 105         struct cma *cma;
 106         int ret;
 107         ret = dma_contiguous_reserve_area(size, base, limit, &cma, true);
 108         if (ret == 0)
 109                 dev_set_cma_area(dev, cma);
 110
 111         return ret;
 112 }
 113
 114 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 115                                        unsigned int order);
 116 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 117                                  int count);
 118
 119 #else
 120
 121 static inline struct cma *dev_get_cma_area(struct device *dev)
 122 {
 123         return NULL;
 124 }
 125
 126 static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { }
 127
 128 static inline void dma_contiguous_set_default(struct cma *cma) { }
 129
 130 static inline void dma_contiguous_reserve(phys_addr_t limit) { }
 131
 132 static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 133                                        phys_addr_t limit, struct cma **res_cma,
 134                                        bool fixed)
 135 {
 136         return -ENOSYS;
 137 }
 138
 139 static inline
 140 int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 141                            phys_addr_t base, phys_addr_t limit)
 142 {
 143         return -ENOSYS;
 144 }
 145
 146 static inline
 147 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 148                                        unsigned int order)
 149 {
 150         return NULL;
 151 }
 152
 153 static inline
 154 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 155                                  int count)
 156 {
 157         return false;
 158 }
 159
 160 #endif
 161
 162 #endif
 163
 164 #endif