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RE: parport ECP & DMA



On Mon, 22 Jul 2002, Pieter Grimmerink wrote:

> I first thought of keeping the port in reverse mode all the
> time, allowing the peripheral to send its data whenever
> needed, and temporarily switching to forward whenever
> we have to send something out.
> But when we have to send a lot of data during a longer
> period of time, this would still mean we would have to
> switch between forward / reverse mode way to often.

Must you really switch between each byte?
Can't you send data in bulk when needed and then
switch to receive mode?
 
> We're currently considering to use the two parallel ports,
> one as dedicated input, the other as dedicated output.
> 
> I guess it won't be a problem, keeping a port in
> ecp_rev / ecp_forw and dma enabled all the time?

No, it shouldn't although you can't use DMA for
all serial ports since the DMA channels are shared
so you have to disable som serial ports (or make them 
interrupt driven if you really need them).
Check in arch/cris/drivers/lpslave/ where there is a driver
to communicate with another ETRAX chip using the two
parallel ports to get an additional network interface.
 
> Best regards,
> 
> Pieter
> 
Best regards
/Johan