|author||Simon Glass <email@example.com>||2015-09-02 17:24:58 -0600|
|committer||Tom Rini <firstname.lastname@example.org>||2015-09-11 17:15:20 -0400|
Move ALLOC_CACHE_ALIGN_BUFFER() to the new memalign.h header
Now that we have a new header file for cache-aligned allocation, we should move the stack-based allocation macro there also. Signed-off-by: Simon Glass <email@example.com>
Diffstat (limited to 'include/memalign.h')
1 files changed, 92 insertions, 1 deletions
diff --git a/include/memalign.h b/include/memalign.h
index f78b9dd9dc..a960039083 100644
@@ -13,9 +13,100 @@
+ * 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;
+ * 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));