text: /* SPDX-License-Identifier: GPL-2.0+ */
  /*
   * Copyright (c) 2015 Google, Inc
   */
  
  #ifndef __ALIGNMEM_H
  #define __ALIGNMEM_H
  
  /*
   * ARCH_DMA_MINALIGN is defined in asm/cache.h for each architecture.  It
   * is used to align DMA buffers.
   */
  #ifndef __ASSEMBLY__
  #include <asm/cache.h>
  #include <malloc.h>
  
  /*
   * The ALLOC_CACHE_ALIGN_BUFFER macro is used to allocate a buffer on the
   * stack that meets the minimum architecture alignment requirements for DMA.
   * Such a buffer is useful for DMA operations where flushing and invalidating
   * the cache before and after a read and/or write operation is required for
   * correct operations.
   *
   * When called the macro creates an array on the stack that is sized such
   * that:
   *
   * 1) The beginning of the array can be advanced enough to be aligned.
   *
   * 2) The size of the aligned portion of the array is a multiple of the minimum
   *    architecture alignment required for DMA.
   *
   * 3) The aligned portion contains enough space for the original number of
   *    elements requested.
   *
   * The macro then creates a pointer to the aligned portion of this array and
   * assigns to the pointer the address of the first element in the aligned
   * portion of the array.
   *
   * Calling the macro as:
   *
   *     ALLOC_CACHE_ALIGN_BUFFER(uint32_t, buffer, 1024);
   *
   * Will result in something similar to saying:
   *
   *     uint32_t    buffer[1024];
   *
   * The following differences exist:
   *
   * 1) The resulting buffer is guaranteed to be aligned to the value of
   *    ARCH_DMA_MINALIGN.
   *
   * 2) The buffer variable created by the macro is a pointer to the specified
   *    type, and NOT an array of the specified type.  This can be very important
   *    if you want the address of the buffer, which you probably do, to pass it
   *    to the DMA hardware.  The value of &buffer is different in the two cases.
   *    In the macro case it will be the address of the pointer, not the address
   *    of the space reserved for the buffer.  However, in the second case it
   *    would be the address of the buffer.  So if you are replacing hard coded
   *    stack buffers with this macro you need to make sure you remove the & from
   *    the locations where you are taking the address of the buffer.
   *
   * Note that the size parameter is the number of array elements to allocate,
   * not the number of bytes.
   *
   * This macro can not be used outside of function scope, or for the creation
   * of a function scoped static buffer.  It can not be used to create a cache
   * line aligned global buffer.
   */
  #define PAD_COUNT(s, pad) (((s) - 1) / (pad) + 1)
  #define PAD_SIZE(s, pad) (PAD_COUNT(s, pad) * pad)
  #define ALLOC_ALIGN_BUFFER_PAD(type, name, size, align, pad)		\
  	char __##name[ROUND(PAD_SIZE((size) * sizeof(type), pad), align)  \
  		      + (align - 1)];					\
  									\
  	type *name = (type *)ALIGN((uintptr_t)__##name, align)
  #define ALLOC_ALIGN_BUFFER(type, name, size, align)		\
  	ALLOC_ALIGN_BUFFER_PAD(type, name, size, align, 1)
  #define ALLOC_CACHE_ALIGN_BUFFER_PAD(type, name, size, pad)		\
  	ALLOC_ALIGN_BUFFER_PAD(type, name, size, ARCH_DMA_MINALIGN, pad)
  #define ALLOC_CACHE_ALIGN_BUFFER(type, name, size)			\
  	ALLOC_ALIGN_BUFFER(type, name, size, ARCH_DMA_MINALIGN)
  
  /*
   * DEFINE_CACHE_ALIGN_BUFFER() is similar to ALLOC_CACHE_ALIGN_BUFFER, but it's
   * purpose is to allow allocating aligned buffers outside of function scope.
   * Usage of this macro shall be avoided or used with extreme care!
   */
  #define DEFINE_ALIGN_BUFFER(type, name, size, align)			\
  	static char __##name[ALIGN(size * sizeof(type), align)]	\
  			__aligned(align);				\
  									\
  	static type *name = (type *)__##name
  #define DEFINE_CACHE_ALIGN_BUFFER(type, name, size)			\
  	DEFINE_ALIGN_BUFFER(type, name, size, ARCH_DMA_MINALIGN)
  
  /**
   * malloc_cache_aligned() - allocate a memory region aligned to cache line size
   *
   * This allocates memory at a cache-line boundary. The amount allocated may
   * be larger than requested as it is rounded up to the nearest multiple of the
   * cache-line size. This ensured that subsequent cache operations on this
   * memory (flush, invalidate) will not affect subsequently allocated regions.
   *
   * @size:	Minimum number of bytes to allocate
   *
   * @return pointer to new memory region, or NULL if there is no more memory
   * available.
   */
  static inline void *malloc_cache_aligned(size_t size)
  {
  	return memalign(ARCH_DMA_MINALIGN, ALIGN(size, ARCH_DMA_MINALIGN));
  }
  #endif
  
  #endif /* __ALIGNMEM_H */
  