DWS State transition during SNW

Elliott, Robert (Server Storage) Elliott at hp.com
Fri Nov 16 14:01:39 PST 2007


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
Once D.C. idle begins, SP_DWS detects a slew of invalid dwords (maybe based
on some kind of loss of signal detect logic) and declares dword
synchronization to be lost.  It transitions to SP_DWS0:AcquireSync and waits
for Start DWS from SP before looking for valid dwords again.
--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Mona
> Sent: Wednesday, October 31, 2007 5:17 AM
> To: t10 at t10.org
> Subject: DWS State transition during SNW
>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Mona <monika.talwar at nsysinc.com>
> *
>
>
> What state DWS state machine will be when device is receivig
> D.C idle on bus
> .
>
> For example, during Speed negotiation window, consider that
> SNW1 passed
> successfuly and DWS state machine is in SP_DWS3,SyncAcquired
> state. Now
> device will enter SNW-2. During RCDT both connected phys will
> transmit D.C.
> idle. At this point of time the receiver will not be able to latch the
> characters from the bus and hence will not generate any dword received
> message. The DWS state machine will keep waiting for
> dword_received message
> which it will not get.
>
> [-------------------------------------------------------------
> ----------------
> (As is mentioned on page# 314 if SAS2r11:
>      Upon receiving a Find Dword message, the SP_DWS receiver
> shall monitor
>      the input data stream and force each K28.5 character
> detected into the
> first character position of a  possible dword. If the next
> three characters
> are data characters with correct disparity, it shall send the
> dword as a
> Dword Received (Primitive) message to the SP_DWS state
> machine. Until it
> receives another Find Dword message, for every four
> characters it receives it
> shall:
> a) send a Dword Received (Invalid) message to the SP_DWS
> state machine if the
> dword is an invalid dword (see 3.1.112);
> b) send a Dword Received (Primitive) message to the SP_DWS
> state machine if
> the dword is a primitive  (i.e., the dword contains a K28.5
> character in the
> first character position followed by three data characters); or
> c) send a Dword Received (Data Dword) message to the SP_DWS
> state machine if
> the dword is a data dword (i.e., it is not an invalid dword
> or a primitive).
> Upon receiving a Find Dword message, the SP_DWS receiver
> shall monitor the
> input data stream and force
> each K28.5 character detected into the first character
> position of a possible
> dword. If the next three characters
> are data characters with correct disparity, it shall send the
> dword as a
> Dword Received (Primitive) message to
> the SP_DWS state machine. Until it receives another Find
> Dword message, for
> every four characters it
> receives it shall:
> a) send a Dword Received (Invalid) message to the SP_DWS
> state machine if the
> dword is an invalid
> dword (see 3.1.112);
> b) send a Dword Received (Primitive) message to the SP_DWS
> state machine if
> the dword is a primitive
> (i.e., the dword contains a K28.5 character in the first
> character position
> followed by three data
> characters); or
> c) send a Dword Received (Data Dword) message to the SP_DWS
> state machine if
> the dword is a data
> dword (i.e., it is not an invalid dword or a primitive).
> --------------------------------------------------------------
> ---------------]
>
>  Instead it will received start_dws message from SP state
> machine(when SP
> state machine enters SP10:SAS_AwaitALIGN). DWS state machine
> will ignore this
> message and will keep waiting for dword_received message.
>
> But As per the specification, DWS shall restart everytime new
> SNW executes.
>
> Please suggest me the correct behaviour of sas receiver in
> case D.C. idle is
> detected on bus.
>
>
> I will be thankful for the help provided.
>
> Thanks
> Mona
> *
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