Hi Wolfgang,
I think I'd like to see a macro that can be used like this:
void *dma_buffer_pointer = DMA_BUFFER(size_in_bytes);
Frankly speaking I don't know any easy way to define buffer this way in a macro (at least without digging deep enough to C preprocessor programming tricks). Maybe Mike or Anton knows.
The void *dma_buffer_pointer = DMA_BUFFER(size_in_bytes); approach needs to do following things in macro:
#define DMA_BUFFER(100) \ char buf[100 + get_dcache_line_size]; \ unsigned long tmp = (unsigned long) buf; \ void* buf_out = (void*) ((tmp + (get_dcache_line_size() - 1)) & ~(get_dcache_line_size() - 1))
The problem here is to assign the buf_out pointer to the void *dma_buffer_pointer. How can we "return" the void *buf_out?
For comparison please look to this solution:
#define ALIGN_ADDR(addr) ((void *)(((unsigned long) addr + get_dcache_line_size() - 1)\ & ~(get_dcache_line_size() - 1)))
#define DMA_DECLARE_BUFFER(type, name, size) \ char *__##name[size + get_dcache_line_size()]; \ type *name = ALIGN_ADDR(__##name);
int mmc_startup(struct mmc *mmc) { /* Some declarations */ /* char ext_csd[512]; */ DMA_DECLARE_BUFFER(char, ext_csd, 512);
printf("%s: ptr:%p\n", __func__, ext_csd);
/* rest of the code */ }
Here the DMA_DECLARE_BUFFER really defines the buffer as an automatic variable with this function scope. This is tested and works :-)
- get_dcache_line_size() can be simply defined as
#define get_dcache_line_size() CONFIG_SYS_CACHE_LINE_SIZE if we _really_ want to save a few bytes.
Actually I fail to understand why we would ever need get_dcache_line_size() in a boot loader.
If I can ask for clarification here.
Shall not u-boot read on fly the cache line size (as it is now done) or you don't like the get_cache_line_size defined as function?
Going further shall the get_cache_line_size be removed completely and replaced with CONFIG_SYS_CACHE_LINE_SIZE?
Best regards,
Wolfgang Denk