Hi Finn,
got sidetracked once again ...
Where? In esp_reconnect, we don't get to that point when returning from
esp_reconnect_with_tag() after timeout.
Well, the point is, we potentially release ACK (either after the
Information Transfer command or after the Accept Message command) with ATN
still asserted.
Who asserts ATN in case of reselection? I always thought that the
target, by initiating reselection, assumes the role of initiator and is
in charge of driving bus phase changes (including control of ATN).
How does the target signal end of message in phase? Stop handshaking, or
change phase?
Either would do. To stop handshaking would imply entering bus free phase.
ATN going false?
AIUI, only the initiator can drive ATN.
So the initiator would have to read two tag message bytes if a target
reselects that had a tagged command disconnected? From the initiator
side, that should work (if an untagged commmand has been issued, no
tagged commands are sent so we expect either tagged or untagged
reselections).
With the DMA programmed for two tag bytes, and the reselection
originating from a tagged command, I would expect the target to send the
two tag bytes.
Sure, but I think the initator is messing it up along the way.
Can't see how - reconnect_with_tag() is only used if no untagged command
is on record for the target.
Would it help to do the message transfer without DMA?
I would, just to see more clearly what was going on (command queue,
control lines, bus phase).
Not sure we can get control lines read - bus phases are available IIRC.
Recall that Tuomas said he tried PIO for this with zorro_esp without any
improvement. And I first saw this bug on a Quadra 660av, on which mac_esp
uses PIO for all transfers.
PIO does get set up for the expected number of message bytes though. Is
there a check for phase mismatch during PIO?
What use could an initiator have for the QTAG Control bit
(ESP_CONFIG3_TBMS) when the target never controls /ATN? (I only
remembered this yesterday, so please ignore my earlier comments about
reselection and SEL-with-ATN.)
I had thought the reselection process similar to selection. But if the
target does not signal further message bytes by keepin ATN asserted,
that bit might not matter here.
If only the initator drives ATN, the documentation can only be referring
to an ESP device in target mode.
The documentation mentions a command descriptor block to be transferred
- would only apply to ESP in target mode again.
My recollection from 2009 is that this particular disk did work with
mac_esp on one of my Quadras, but not on my 660av. And three people have
reported the problem now (to my knowledge) so I don't blame the disks.
What ESP versions are used in the Quadras vs 660av?
Cheers,
Michael
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