Hi Bruce,
This isn't really a Linux PPC question, but this is the smartest mailing
list I know for asking PPC hardware questions, so here goes.
We're using an MPC8308 and want to use the DMA engine to move data in and
out of an FPGA hanging on the local bus. Our bandwidth/local bus burden
calculations were done assuming that we could use bursting. So I've setup
a UPM to do single beat and burst reads/writes. I've also configured my
DMA TCD to use a data transfer size of 32-bytes when accessing the FPGA.
The problem I'm having is I can't seem to get the UPM to ever trigger the
burst write sequence using the DMA. Single beat reads and writes work
okay, but no bursting. In fact, the only thing I've been able to find in
the manual that causes a burst transaction is a cache line miss, which is
wholly in the purview of the core and really does me no good.
Does anyone know of any way (short of issuing a run command to the UPM via
MxMR) to force a burst transaction on the 8308? Am I just being dumb and
missing something totally fundamental?
Read my MPC8349EA UPM setup notes and see if you have used
similar settings (I assume the local bus UPMs are similar):
http://www.ovro.caltech.edu/~dwh/carma_board/carma_sys.pdf
Do you have a Modelsim simulation of your interface?
I have a VHDL bus-functional-model I wrote that I can
send you.
Cheers,
Dave
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