Unexpected busfree in Data-in phase (aic7xxx 6.2.1 .. 6.2.5 with linux kernel 2.4.7 .. 2.4.18)

[C R Ritson]

I have been seeing intermittent "Unexpected busfree in Data-in pahse"
errors using a Dell PV120T and an adaptec 2944. The Dell device is a
tape changer based on a Quantum DLT7000.

The errors are seen when using Amanda's amcheck script to read the tape
back and verify that there are no obious read errors and sometimes when
attempting a restore which is worrying. It is most easily triggered if
attempting a restore when there is any significant delay in the output
pipeline, so it would appear to be a problem caused by attempting to
stall the tape read when running out of buffer space somewhere.

Reducing the maximum transfer speed in the scsi bios to 13 Mb/sec has
helped a little.

I am currently running with "aic7xxx=verbose,tag_info:{,{,,,255}}" as a
boot option.

Any suggestions as to what to try to work round this or fix it (if it is
a fault or a bug) would be most welcome. All hardware except the tape
unit itself has been exchanged with no effect, so it does not appear to
be a card/cable/termination problem.

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