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