James Bottomley wrote:
This seems to be a bug in sym_prepare_nego(), yes ... it should do
either a PPR or WDTR/SDTR sequence ... there is a case where it won't do
anything when asked.
- The patch deletes code from sym_sir_task_recovery()/M_RESET branch. It's
unnecessary to reset negotiation status there, since any reset eventually
triggers S_CHECK_COND.
It looks like a reasonable safety feature against problem drives ... I'd
be hesitant to remove it.
To me, the code looked like it was added there to compensate the bug
mentioned above. Anyway, it probably does no harm to leave it there.
- It seems that the SPI "domain validation" consists solely of INQUIRY
commands.
Actually, no. DV uses Inquiry solely for non DT negotiations because of
potential echo buffer problems in certain drives but it uses the echo
buffer for DT verification.
Yes, you are correct.
As a result, if (b) is followed, targets that support PPR would
never get to the point of doing PPR transfers during domain validation
(but immediately after on the next command following the dv), since each
INQUIRY re-starts the negotiation cycle. This patch solves this by making
it possible to do the negotiation cycle WIDE -> SYNC -> PPR during a
single SCSI command.
I don't quite follow this. The way SPI DV works is that we start out
fully async for the first INQUIRY, then move to wide async (to check no
bus width domain problems, which are the most common) then jump to the
highest speed supported by the device and transport. i.e. we always do
async -> WDTR -> SDTR
or
async -> WDTR -> PPR
we never go
async -> WDTR -> SDTR -> PPR.
What's the actual problem you are seeing?
If you consider this patch, the WDTR message will be resent when the DV
jumps to the highest speed, and then, if you look at the code in
sym_wide_nego(), the driver will also send SDTR after the target
responds to WDTR since the goal offset is now set. So what you will get
is WDTR -> SDTR -> PPR.
But now that I think of it, perhaps the code in sym_wide_nego() should
already check whether to send PPR instead of SDTR if the goals are
appropriate.
A.
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