LXR uboot/include/memalign.h

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