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DMA Channel Sharing
I am trying to figure out how to get a parallel port DMA driver working. I
understand that the DMA channel for the parallel port 0 is multiplexed with
the Asynchronous Serial Port 2 (along with the ATA and SCSI-8) interface. I
believe that in order to get the parallel port working with DMA, I will have
to disable the serial port 2, and configure the R_GEN_CONFIG register to
properly control the mux into the DMA channel.
As configured, the developer board utilizes the serial port 2, and has
allocated the DMA IRQ and resources for the serial driver for tty2. I used
make xconfig to turn off serial port #2, but when I flashed the new
configuration, the board never came out of "programming" mode. I was able
to return the board to original condition by turning the serial port #2 on
and reflashing. Is there a known procedure for disabling the serial port
#2? What more would I need to do to allow my parallel port driver to gain
access to its DMA channel?