From: Bill.Martin@emulex.com To: <Bill.Martin@emulex.com>, <Brian.Day@lsi.com>, <t10@t10.org> Date: Wed, 5 Nov 2008 17:41:21 -0800 Subject: RE: Response to 08-425r0 X-Message-Number: 9274 Formatted message: HTML-formatted message Brian: I will agree that there are situations due to ambiguities in when the training completed message, Sync Acquired message, and TRAIN_DONE received messages are received that make item d necessary to ensure that there are no implementations that fall through the crack here. Bill Martin Emulex Office of Technology Industry Standards 916 772-3658 916 765-6875 (Cell) bill.martin@emulex.com ________________________________ From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Bill.Martin@emulex.com Sent: Wednesday, November 05, 2008 3:17 PM To: Brian.Day@lsi.com; t10@t10.org Subject: RE: Response to 08-425r0 Brian: The two questions that have to be answered are: 1) When and how is training completed generated? This is not specified in the standard; however the next question is more pertinent to how you guarantee reception of the TRAIN_DONE at the same time as Sync Acquired. 2) SAS2 states "When the SP_DWS receiver receives a Sync Acquired message, it shall send the most recently received primitive." Since it requires three primitives to acquire sync, does this not send the TRAIN_DONE received message along with the Sync Acquired Message? Bill Martin Emulex Office of Technology Industry Standards 916 772-3658 916 765-6875 (Cell) bill.martin@emulex.com ________________________________ From: Day, Brian [mailto:Brian.Day@lsi.com] Sent: Wednesday, November 05, 2008 3:08 PM To: Martin, Bill; t10@t10.org Subject: RE: Response to 08-425r0 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@Emulex.Com [mailto:Bill.Martin@Emulex.Com] Sent: Wednesday, November 05, 2008 3:43 PM To: Day, Brian; t10@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@emulex.com ________________________________ From: Day, Brian [mailto:Brian.Day@lsi.com] Sent: Wednesday, November 05, 2008 2:28 PM To: Martin, Bill; t10@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@Emulex.Com [mailto:Bill.Martin@Emulex.Com] Sent: Wednesday, November 05, 2008 12:16 PM To: Day, Brian; t10@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@emulex.com