LXR uboot/include/memalign.h

   1/*
   2 * Copyright (c) 2015 Google, Inc
   3 *
   4 * SPDX-License-Identifier:    GPL-2.0+
   5 */
   6
   7#ifndef __ALIGNMEM_H
   8#define __ALIGNMEM_H
   9
  10/*
  11 * ARCH_DMA_MINALIGN is defined in asm/cache.h for each architecture.  It
  12 * is used to align DMA buffers.
  13 */
  14#ifndef __ASSEMBLY__
  15#include <asm/cache.h>
  16#include <malloc.h>
  17
  18/*
  19 * The ALLOC_CACHE_ALIGN_BUFFER macro is used to allocate a buffer on the
  20 * stack that meets the minimum architecture alignment requirements for DMA.
  21 * Such a buffer is useful for DMA operations where flushing and invalidating
  22 * the cache before and after a read and/or write operation is required for
  23 * correct operations.
  24 *
  25 * When called the macro creates an array on the stack that is sized such
  26 * that:
  27 *
  28 * 1) The beginning of the array can be advanced enough to be aligned.
  29 *
  30 * 2) The size of the aligned portion of the array is a multiple of the minimum
  31 *    architecture alignment required for DMA.
  32 *
  33 * 3) The aligned portion contains enough space for the original number of
  34 *    elements requested.
  35 *
  36 * The macro then creates a pointer to the aligned portion of this array and
  37 * assigns to the pointer the address of the first element in the aligned
  38 * portion of the array.
  39 *
  40 * Calling the macro as:
  41 *
  42 *     ALLOC_CACHE_ALIGN_BUFFER(uint32_t, buffer, 1024);
  43 *
  44 * Will result in something similar to saying:
  45 *
  46 *     uint32_t    buffer[1024];
  47 *
  48 * The following differences exist:
  49 *
  50 * 1) The resulting buffer is guaranteed to be aligned to the value of
  51 *    ARCH_DMA_MINALIGN.
  52 *
  53 * 2) The buffer variable created by the macro is a pointer to the specified
  54 *    type, and NOT an array of the specified type.  This can be very important
  55 *    if you want the address of the buffer, which you probably do, to pass it
  56 *    to the DMA hardware.  The value of &buffer is different in the two cases.
  57 *    In the macro case it will be the address of the pointer, not the address
  58 *    of the space reserved for the buffer.  However, in the second case it
  59 *    would be the address of the buffer.  So if you are replacing hard coded
  60 *    stack buffers with this macro you need to make sure you remove the & from
  61 *    the locations where you are taking the address of the buffer.
  62 *
  63 * Note that the size parameter is the number of array elements to allocate,
  64 * not the number of bytes.
  65 *
  66 * This macro can not be used outside of function scope, or for the creation
  67 * of a function scoped static buffer.  It can not be used to create a cache
  68 * line aligned global buffer.
  69 */
  70#define PAD_COUNT(s, pad) (((s) - 1) / (pad) + 1)
  71#define PAD_SIZE(s, pad) (PAD_COUNT(s, pad) * pad)
  72#define ALLOC_ALIGN_BUFFER_PAD(type, name, size, align, pad)            \
  73        char __##name[ROUND(PAD_SIZE((size) * sizeof(type), pad), align)  \
  74                      + (align - 1)];                                   \
  75                                                                        \
  76        type *name = (type *)ALIGN((uintptr_t)__##name, align)
  77#define ALLOC_ALIGN_BUFFER(type, name, size, align)             \
  78        ALLOC_ALIGN_BUFFER_PAD(type, name, size, align, 1)
  79#define ALLOC_CACHE_ALIGN_BUFFER_PAD(type, name, size, pad)             \
  80        ALLOC_ALIGN_BUFFER_PAD(type, name, size, ARCH_DMA_MINALIGN, pad)
  81#define ALLOC_CACHE_ALIGN_BUFFER(type, name, size)                      \
  82        ALLOC_ALIGN_BUFFER(type, name, size, ARCH_DMA_MINALIGN)
  83
  84/*
  85 * DEFINE_CACHE_ALIGN_BUFFER() is similar to ALLOC_CACHE_ALIGN_BUFFER, but it's
  86 * purpose is to allow allocating aligned buffers outside of function scope.
  87 * Usage of this macro shall be avoided or used with extreme care!
  88 */
  89#define DEFINE_ALIGN_BUFFER(type, name, size, align)                    \
  90        static char __##name[ALIGN(size * sizeof(type), align)] \
  91                        __aligned(align);                               \
  92                                                                        \
  93        static type *name = (type *)__##name
  94#define DEFINE_CACHE_ALIGN_BUFFER(type, name, size)                     \
  95        DEFINE_ALIGN_BUFFER(type, name, size, ARCH_DMA_MINALIGN)
  96
  97/**
  98 * malloc_cache_aligned() - allocate a memory region aligned to cache line size
  99 *
 100 * This allocates memory at a cache-line boundary. The amount allocated may
 101 * be larger than requested as it is rounded up to the nearest multiple of the
 102 * cache-line size. This ensured that subsequent cache operations on this
 103 * memory (flush, invalidate) will not affect subsequently allocated regions.
 104 *
 105 * @size:       Minimum number of bytes to allocate
 106 *
 107 * @return pointer to new memory region, or NULL if there is no more memory
 108 * available.
 109 */
 110static inline void *malloc_cache_aligned(size_t size)
 111{
 112        return memalign(ARCH_DMA_MINALIGN, ALIGN(size, ARCH_DMA_MINALIGN));
 113}
 114#endif
 115
 116#endif /* __ALIGNMEM_H */
 117