SAS SSP Receive Frame state confusing credit and balance

Elliott, Robert (Server Storage) Elliott at hp.com
Sun Feb 16 08:53:55 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
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The SSP receive frame state machine has a problem:=20

7.16.7.9 SSP_RF1 Receive Frame state  (sas-r03):=20
"If the frame CRC is good and the frame contained no invalid data
dwords, this state shall send the Frame Received (Successful) parameter
to the SSP_TAN1:Idle state and:

a) if the last Rx Credit Status parameter received had an argument of
Credit Extended send the Frame Received (ACK/NAK Balanced) confirmation
to the port layer; or

b) if the last Rx Credit Status parameter received had an argument of
Credit Exhausted send a Frame Received (ACK/NAK Unbalanced) =
confirmation
to the port layer."

This is confusing the concepts of credit (RRDY granted or not, giving
permission to transmit a frame) with balance (ACK/NAKs matching or not =
-
required to match for "non-interlocked" frames). =20

If there is no credit available, a frame cannot be received (the =
purpose
of credit is indicating a frame could be accepted into a buffer) and
cannot be passed up.  That is already mentioned earlier.  This =
paragraph
needs to determine if the frame was received while ACK/NAKs were
balanced or not, so it can mark the frame and pass that up, so the
transport layer can discard something like a non-interlocked command
frame.

--=20
Rob Elliott, elliott at hp.com=20
Hewlett-Packard Industry Standard Server Storage Advanced Technology=20
 <https://ecardfile.com/id/RobElliott>
https://ecardfile.com/id/RobElliott=20




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SAS SSP Receive Frame state confusing credit and balance The SSP receive frame state machine = has a problem: 7.16.7.9 SSP_RF1 Receive Frame = state  (sas-r03): 
;If the frame CRC is good and = the frame contained no invalid data dwords, this state shall send the = Frame Received (Successful) parameter to the SSP_TAN1:Idle state = and: a) if the last Rx Credit Status = parameter received had an argument of Credit Extended send the Frame = Received (ACK/NAK Balanced) confirmation to the port layer; = or b) if the last Rx Credit Status = parameter received had an argument of Credit Exhausted send a Frame = Received (ACK/NAK Unbalanced) confirmation to the port = layer.; This is confusing the concepts of = credit (RRDY granted or not, giving permission to transmit a frame) = with balance (ACK/NAKs matching or not - required to match for = ;non-interlocked; frames).  If there is no credit available, a = frame cannot be received (the purpose of credit is indicating a frame = could be accepted into a buffer) and cannot be passed up.  That is = already mentioned earlier.  This paragraph needs to determine if = the frame was received while ACK/NAKs were balanced or not, so it can = mark the frame and pass that up, so the transport layer can discard = something like a non-interlocked command frame. -- 
Rob Elliott, elliott at hp.com 
Hewlett-Packard Industry Standard = Server Storage Advanced Technology 
https://ecardfile.com/id/RobElliott 


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