PCI DMA support on the MPC8250

Callebaut Benoit callebaut at mailandnews.com
Thu Jun 26 00:24:45 EST 2003

>===== Original Message From Allen Curtis <acurtis at onz.com> =====
>>But the DMA transfers are working and are 5 time faster. You must only
>>them. It is just 5 registers to configure. You buffers in RAM must be
>>allocated with consistent_alloc to avoid caching on them and you must always
>>write physical addresses in the DMA registers( use virt_to_phys).
>>Note For  PCI addresses virt_to_phys doesn't work well. You must take the
>>addresses from the "remap" function code. I did it and it works very well.
>Do you have a patch for you DMA support?

No, but I will make one for the physical address lookup code, the small
changes to support DMA in the kernel (access of EUMBAR base address) and the
snippet of my code that I use in my driver.

It will be against a 2.4.17 Kernel( sorry )

Note : I have A generic DMA driver but it has a big setup time of 25000 cycles
making it interesting (better than memcpy) only for blocks larger than

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