Response to 08-425r0

Day, Brian Brian.Day at lsi.com
Wed Nov 5 15:07:50 PST 2008


Formatted message: <a href="r0811055_f.htm">HTML-formatted message</a>

Without item d) taken into consideration, this an example sequence I am
trying to describe:
Received Dwords 	     DWS state	  SP state
invalid 		  DWS0	      SP29
TRAIN_DONE(3rd)
TRAIN_DONE(4th) 	  DWS1
TRAIN_DONE(5th) 	  DWS2
TRAIN_DONE(6th) 	  DWS3	-->   SP30 (dword sync acquired here)
zero scrambled(58 times)
random scrambled "forever"
This is how I interpret the state machine flow without the new d) item.  I
think where we may be seeing things differently is based on your comment
about being in SP29 for the duration of the training pattern.  My assumption
was that SP transmitter enforces the training pattern "wholeness", and
perhaps your assumption is that the SP state machine enforces the "wholeness"
of the pattern. (Not I'm kinda guessing here at where we're not together in
thought)
I think I would agree with your concept of nothing getting missed if the SP
state machine only transitioned at the pattern boundaries... but that's not
how I read the wording.  Am I forgetting/missing a statement in the spec that
indicates that?
Brian
________________________________
From: Bill.Martin at Emulex.Com [mailto:Bill.Martin at Emulex.Com]
Sent: Wednesday, November 05, 2008 3:43 PM
To: Day, Brian; t10 at t10.org
Subject: RE: Response to 08-425r0
Brian:
The TRAIN_DONE received message is sent by the SP Receiver to the SP state
machine.  The SP Receiver is responsible for recognizing the three
primitives, so this will either be seen in the SP29 or SP30 state of the SP
state machine, but it will not be missed since detecting three is not up to
the SP state machine.  The device will be in the SP29 state for at least one
full TRAIN or TRAIN_DONE pattern in order to complete training.  If any time
during that process a TRAIN_DONE received message is received it will set the
variable that is sent to the SP30 state.  I do not see any way that this
message will be missed.  The previous problem was that SP29 was not looking
for the TRAIN_DONE received message, so if it was sent just before the
transition to SP30 then there would not be another one.
Bill Martin
Emulex
Office of Technology
Industry Standards
916 772-3658
916 765-6875 (Cell)
bill.martin at emulex.com
________________________________
From: Day, Brian [mailto:Brian.Day at lsi.com]
Sent: Wednesday, November 05, 2008 2:28 PM
To: Martin, Bill; t10 at t10.org
Subject: RE: Response to 08-425r0
Hi Bill...
I'm suggesting the new item d) is required so we don't have the exact same
race condition issue when the "slower" trained device acquires dword sync on
the 4th, 5th, or 6th dword of a TRAIN_DONE (i.e. there aren't enough of the
TRAIN_DONE dwords left to detect 3 out of 6 redundant rule in the primitive
sequence)
Without item d), it would be possible to then transition to SP30 without
detecting the TRAIN_DONE, and have the faster device move to SAS_PHY_Ready,
and we've got the same problem again.
Essentially, I'm suggesting a device doesn't say TRAIN_DONE until it's
reached the point where it's actually seeing/decoding the other devices
primitives, instead of just acquiring dword sync as the gating factor.
Brian
________________________________
From: Bill.Martin at Emulex.Com [mailto:Bill.Martin at Emulex.Com]
Sent: Wednesday, November 05, 2008 12:16 PM
To: Day, Brian; t10 at t10.org
Subject: Response to 08-425r0
Brian:
I understood the need to detect the TRAIN_DONE primitive in the training
state; however, I do not see the reason that a TRAIN or TRAIN_DONE has to be
received before exiting this state.  The device will continue sending
TRAIN_DONE until a TRAIN_DONE is received, so the device that is later
entering the training sequence will see a TRAIN or TRAIN_DONE sequence during
its training process, and should be able to train on either pattern.
I would like to see the new item d) in 6.8.4.12.5.
I am sorry that I did not catch this part of your proposal in our discussions
on Monday.
Bill Martin
Emulex
Office of Technology
Industry Standards
916 772-3658
916 765-6875 (Cell)
bill.martin at emulex.com



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