SAS2 SNW-3 SP29:SAS_Train

Stephen FINCH steve.finch at st.com
Wed Jan 24 09:54:31 PST 2007


Formatted message: <A HREF="r0701243_f.htm">HTML-formatted message</A>

Here are my comments/thoughts:
Training Complete is generated by the physical layer receiver.	How, why,
when is implementation specific and probably will not be defined by the PHY
working group (although my comment here is not binding on the WG).
Training Completed is not a function of any received dword or primitive, so
it does not _require_ dword synchronization to occur.
06-515r0 (this is the latest revision) requires SP_DWS Sync Acquired and
Training Completed to move forward in the state machine.  The order of these
two events is not specified.
Regards,
Steve
  _____  
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Craig Stoops
Sent: Wednesday, January 24, 2007 9:17 AM
To: t10 at t10.org
Subject: RE: SAS2 SNW-3 SP29:SAS_Train
Hi Rob and Steve,
I see the receiver is supposed to send this message, but I do not see any
definition of what the conditions are for generating this message.
It also doesn't say that the message is only sent after DWS has obtains
synchronization as it does with ALIGN Receieved and TRAIN_DONE Received.
It would seem to me, that Training Completed is the same as SP_DWS Sync
Aquired. The point being to lock the rx pll, then the dws will sync. 
I am refering to 06-515R0 as I don't see a revision posted on t10.
Can you point me the way to which section has the definition of Training
Completed? I particularly want to know if this message generation requires a
certain number of patterns and of what type to be seen to qualify it.
Thanks,
Craig
ExpertIO, Inc
www.expertio.com
805-428-0839
-----Original Message-----
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Elliott,
Robert (Server Storage)
Sent: Wednesday, January 24, 2007 6:53 AM
To: t10 at t10.org
Subject: RE: SAS2 SNW-3 SP29:SAS_Train
That state is waiting for the SP receiver to report Training Completed
(meaning the receiver itself is satisfied with the incoming data stream),
not that it has detected any particular incoming TRAIN or TRAIN_DONE
(indicating the state of the other phy).
Training Completed is in the list of messages defined earlier in the
proposal, but is never used again; it was supposed to have been used here.
That correction will be incorporated into sas2r08.
  _____  
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Craig Stoops
Sent: Tuesday, January 23, 2007 4:24 PM
To: t10 at t10.org
Subject: SAS2 SNW-3 SP29:SAS_Train
Steve, Rob and other interested parties,
Per the latest 6Gb SNW-3 proposal pasted below, the TRAIN Completed message
is not defined in the document. Based on my read of other parts, I think
this should be "TRAIN Transmitted message" as the requirement per
6.7.4.2.3.3 is to send at least 1 TRAIN pattern and after achieving receiver
sync, then transition to sending TRAIN_DONE. 
6.8.4.12.4 Transition SP29:SAS_Train to SP30:SAS_TrainingDone
This transition shall occur if:
a) this state receives a TRAIN Completed message before the TLT timer
expires; and
b) dword synchronization is acquired.
Second point - becuase one end device may be capable of acheiving rx sync
faster than the other, it is possible (as seen by our modeling) for the
slower device to be in SP29 and before that device gains sync the faster
device starts sending TRAIN_DONE.
So it can not be a condition of SP29 -> SP30 to receive a TRAIN pattern, but
rather either TRAIN or a TRAIN_DONE pattern This is implied by aquiring
receiver synchronization.. Currently, as it is undefined, some people may
consider the TRAIN Completed message to be TRAIN Received messsage.
I think it should be further clarified, as I beleive was the original
intention, that both TRAIN and TRAIN_DONE serve to allow a receiver to gain
synchronization. If true, then the slow device will transition from SP29 to
SP30 when gaining rx sync even though it is receiving TRAIN_DONE and not
TRAIN.
Basically, in summary, rewording 6.8.4.12.4 to:
  This transition shall occur after:  
    a) Transmitting at least 1 complete TRAIN pattern (or said the spec way,
after having received at least one TRAIN Transmitted message)
   b) Receiver DWORD synchronization is acquired
Thoughts?
Craig Stoops
ExpertIO, Inc
www.expertio.com
805-428-0839



More information about the T10 mailing list