/* * Copyright (c) 2015 Google, Inc * * SPDX-License-Identifier: GPL-2.0+ */ #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 */