cache: add ALLOC_CACHE_ALIGN_BUFFER macro
This macro is used to allocate cache line size aligned stack buffers for use with DMA hardware. Signed-off-by: Anton Staaf <robotboy@chromium.org> Cc: Lukasz Majewski <l.majewski@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Aneesh V <aneesh@ti.com> Cc: Albert ARIBAUD <albert.u.boot@aribaud.net> Cc: Wolfgang Denk <wd@denx.de>
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@ -40,6 +40,8 @@ Buffer Requirements:
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- If the buffer is not cache-line aligned invalidation will be restricted
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- If the buffer is not cache-line aligned invalidation will be restricted
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to the aligned part. That is, one cache-line at the respective boundary
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to the aligned part. That is, one cache-line at the respective boundary
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may be left out while doing invalidation.
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may be left out while doing invalidation.
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- A suitable buffer can be alloced on the stack using the
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ALLOC_CACHE_ALIGN_BUFFER macro.
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Cleanup Before Linux:
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Cleanup Before Linux:
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- cleanup_before_linux() should flush the D-cache, invalidate I-cache, and
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- cleanup_before_linux() should flush the D-cache, invalidate I-cache, and
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@ -843,6 +843,64 @@ int cpu_release(int nr, int argc, char * const argv[]);
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#include <asm/cache.h>
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#include <asm/cache.h>
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#endif
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#endif
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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 ALLOC_CACHE_ALIGN_BUFFER(type, name, size) \
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char __##name[ROUND(size * sizeof(type), ARCH_DMA_MINALIGN) + \
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ARCH_DMA_MINALIGN - 1]; \
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\
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type *name = (type *) ALIGN((uintptr_t)__##name, ARCH_DMA_MINALIGN)
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/* Pull in stuff for the build system */
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/* Pull in stuff for the build system */
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#ifdef DO_DEPS_ONLY
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#ifdef DO_DEPS_ONLY
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# include <environment.h>
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# include <environment.h>
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