MPC8349 DMA

[jay_chen]

Hi,
 
I am using 2.6.14.5 and MPC8349.
I got some DMA problems with PCI devices.
So, I tried to understand the DMA stuff of linux.
 
I have one question about cache coherency.
In dma-mapping.h, I found some functions are defined as NULL.
For example:
#define dma_cache_inv(_start,_size)  do { } while (0)
#define dma_cache_wback(_start,_size)  do { } while (0)
#define dma_cache_wback_inv(_start,_size) do { } while (0)
 
#define __dma_alloc_coherent(gfp, size, handle) NULL
#define __dma_free_coherent(size, addr)  do { } while (0)
#define __dma_sync(addr, size, rw)  do { } while (0)
#define __dma_sync_page(pg, off, sz, rw) do { } while (0)

Does this mean that I don't need to take care of cache coherency in MPC83xx
platform?
So, I could use any range of memory for DMA transferring and the hardware
will take care of the cache coherency for me?
 
Thanks a lot.
 
                                    Jay Chen.
 
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