Can anyone provide a quick summary (sorry if this is a FAQ, but I
couldn't find any real explanation of this in the archives) of what
'FIFO is stuck' means? I am in the unfortunate situation of not
knowing whether (A) the PC hardware has a problem (B) the target at
the other end of the cable has a problem (C) the driver has a problem,
(D) everything is working normally, but just seems strange, or (E) my
brain has a problem.
Feb 28 14:00:51 linux kernel: parport0: In mode 0x10
Feb 28 14:00:51 linux kernel: parport0: ECP direction: forward
Feb 28 14:00:51 linux kernel: parport0: Using ECP mode
Feb 28 14:00:51 linux kernel: parport0: ECP direction: reverse
Feb 28 14:00:51 linux kernel: parport0: Using ECP mode
Feb 28 14:00:56 linux kernel: parport0: FIFO is stuck
Feb 28 14:00:56 linux kernel: parport0: wrote 0/7 bytes
Feb 28 14:00:56 linux kernel: parport0: Using ECP mode
Feb 28 14:00:56 linux kernel: parport0: wrote 7/7 bytes
I've looked at the source code and at the National PC87332 datasheets
(only ECP hardware docs I've tracked down so far). This only occurs
when I've switched from reverse mode (by using read()) to forward mode
(by using write()), and it also seems a little odd that I never get
the "ECP direction: forward" that ought to correspond to the
ecp_reverse_to_forward(). One time (after adding some debugging code
to the parport_pc module and recompiling and reinstalling it) I got
something different:
Feb 28 13:58:43 linux kernel: parport0: In mode 0x10
Feb 28 13:58:43 linux kernel: parport0: ECP direction: forward
Feb 28 13:58:43 linux kernel: parport0: Using ECP mode
Feb 28 13:58:43 linux kernel: parport0: ECP direction: reverse
Feb 28 13:58:43 linux kernel: parport0: Using ECP mode
Feb 28 13:58:43 linux kernel: parport0: ECP direction: forward
Feb 28 13:58:43 linux kernel: parport0: wrote 7/7 bytes
I don't know if this had to do with DMA being disabled, or something
else, but the debugging lines I added to
parport_pc_fifo_write_block_dma() never showed up.
If anyone can explain this difference in behavior, or when I should or
shouldn't expect this FIFO stuck timeout to occur, or what it means, I
would really appreciate it.
Thanks,
Greg Nelson
Princeton Gamma-Tech, Inc.
ghn@qtmsys.com
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