diff options
Diffstat (limited to 'include/memalign.h')
| -rw-r--r-- | include/memalign.h | 93 |
1 files changed, 92 insertions, 1 deletions
diff --git a/include/memalign.h b/include/memalign.h index f78b9dd9dc7..a9600390839 100644 --- a/include/memalign.h +++ b/include/memalign.h @@ -13,9 +13,100 @@ */ #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)); |