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Diffstat (limited to 'u-boot/include/common.h')
| -rw-r--r-- | u-boot/include/common.h | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/u-boot/include/common.h b/u-boot/include/common.h index d8c912d..d5ec64d 100644 --- a/u-boot/include/common.h +++ b/u-boot/include/common.h @@ -750,4 +750,91 @@ int cpu_release(int nr, int argc, char * const argv[]); #define ALIGN(x,a) __ALIGN_MASK((x),(typeof(x))(a)-1) #define __ALIGN_MASK(x,mask) (((x)+(mask))&~(mask)) +/* + * 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> +#define ARCH_DMA_MINALIGN 64 // for ARM +#endif + +/* + * 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 ALLOC_ALIGN_BUFFER(type, name, size, align) \ +char __##name[ROUND(size * sizeof(type), align) + (align - 1)]; \ +\ +type *name = (type *) ALIGN((uintptr_t)__##name, align) +#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[roundup(size * sizeof(type), align)] \ +__attribute__((aligned(align))); \ +\ +static type *name = (type *)__##name +#define DEFINE_CACHE_ALIGN_BUFFER(type, name, size) \ +DEFINE_ALIGN_BUFFER(type, name, size, ARCH_DMA_MINALIGN) + +/* Pull in stuff for the build system */ +#ifdef DO_DEPS_ONLY +# include <environment.h> +#endif + + #endif /* __COMMON_H_ */ |