LPC burst accesses

Kári Davíðsson kari.davidsson at marel.is
Tue Dec 11 20:46:57 EST 2007


I am in the process of optimizing read accesses to an FPGA in one of our custom mpc5200b boards.

I have attempted to do this in two ways, i.e.

1) With the the general SDMA task. Also used by the AC97 audio codec driver.
2) Trought the SCLPC fifo offered in relation with the LP bus.

The documentation on freescales site is somehow very vague and even though they talk about
read burst accesses they also seem not to be able to guarantee under what conditions
burst accesses are generated/not generated. The result that I am seeing is that even though 
that the DMA task and fifo is working as expected (transfering data from the FPGA to memory/fifo)
burst reads are _never_ generated (short burst/long burst).

Is there any enlightened soul out there that might shed a litle light on this issue or point me into 
the right direction where I can find more concrete documentation.

I am using linux 2.6.23 as base for these experiments.


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