Tuomas,
You guessed right about memory failing me - it wasn't about DMA in
the end (for some reason, I seem to have DMA stuck in my mind at the
moment), Do you see any other avenues to try and enable tagged
commands in the ESP chip? We tried one config register only so far...
I think I've tested almost all possible register settings for the
chip, but it occurred to me that it is not enough to enable some chip
features by flipping bits. The code in esp_scsi would need to be
modified to handle the behaviour of these enabled features also.
So, rethinking the code in esp_scsi would be one option.
Other versions of ESP SCSI cards do appear to handle TCQ correctly with
the default configuration of the chip, i.e. pass on the additional
message bytes without any problem. From that I'd guess reading the tag
message works OK in the current esp_scsi code. Other features (target
mode) we are not really interested in, and without a second initiator on
the bus, nothing should ever try to select our ESP host. What else is
there to look out for?
The second possibility is that I have a buggy chip in my setup.
Removing a sticker from my SCSI-board revealed the chip to be an AMD
AM53CF94.
There are different versions of the SCSI-boards out there with
different chips; NCR, AMD, and QLogic, so if we had more people
testing the driver we would find out if the chip is actually the
problem. (Is anyone even testing the ISA/PCI cards that use esp_scsi?)
Some Macs/PowerMacs use esp_scsi IIRC - I suspect we would have heard if
the driver was broken altogether.
Those are my suggestions at the TCQ problem.
But do we really need TCQ?
Maybe not - if no one's missed the feature in the original Amiga ESP
drivers, we probably shouldn't worry.
Cheers,
Michael
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