SAS rate matching - ALIGNs in OPEN

Jim.Coomes at seagate.com Jim.Coomes at seagate.com
Thu Feb 20 09:01:46 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Jim.Coomes at seagate.com
*
The option of rate matching during the OPEN should be removed. It is
unneeded as the OPEN frames have to be buffered and validate before action
is taken on them.

There should be no requirement to place an ALIGN following the EOAF. The
expander phy that is performing the rate match is not buffering the dword
stream following the OPEN. The dwords following the EOAF may fall on the
ground before an OPEN-ACCept.

How about the following wording to remove the word immediate:

The source phy shall start rate matching at the selected connection rate
with the first dword following EOAF.

Dword covers both idle dwords and primitives.

----- Forwarded by Jim Coomes/Seagate on 02/20/03 10:39 AM -----
                                                                                                                                       
                      "Elliott, Robert                                                                                                 
                      (Server                  To:      "Seto, Pak-lung" <pak-lung.seto at intel.com>, "Hoglund, Tim"                     
                      Storage)"                <thoglund at lsil.com>, "T10 Reflector" <t10 at t10.org>                                      
                      <Elliott at hp.com>         cc:                                                                                     
                      Sent by:                 Subject: RE: SAS rate matching - ALIGNs in OPEN                                         
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                      02/19/03 06:54                                                                                                   
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* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
The important rule is that rate matching begins sometime during the
first idle dwords - it must already be rate matching when the expander
forwards an OPEN_ACCEPT.

There's nothing special about rate matching ALIGNs vs. other ALIGNs.
They don't get forwarded through an expander like normal dwords -
they're deleted and added back as needed.

The January SAS WG thought it would be better to specify exactly when
the rate matching starts to reduce testing variety.

Nobody is commenting on whether I should remove that sentence about rate
matching during the OPEN or not.

If I go with Brian's wording:
Immediately after transmitting the EOAF of the OPEN address frame, the
source phy shall start rate matching at the selected connection rate.

George will complain about "immediately" and this prohibits rate
matching during the OPEN itself (do we want to prohibit that?).

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




> -----Original Message-----
> From: Seto, Pak-lung [mailto:pak-lung.seto at intel.com]
> Sent: Wednesday, February 19, 2003 4:22 PM
> To: 'Hoglund, Tim'; T10 Reflector
> Subject: RE: SAS rate matching - ALIGNs in OPEN
>
>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Seto, Pak-lung" <pak-lung.seto at intel.com>
> *
> I agree and I don't know what is the reason to put in such
> requirements?
>
> Pak
>
>
>
> -----Original Message-----
> From: Hoglund, Tim [mailto:thoglund at lsil.com]
> Sent: Wednesday, February 19, 2003 12:19 PM
> To: T10 Reflector
> Subject: Re: SAS rate matching - ALIGNs in OPEN
>
>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Hoglund, Tim" <thoglund at lsil.com>
> *
> I do not agree with imposing a requirement to send a
> rate-matching ALIGN immediately following EOAF - this is a
> needless constraint on implementations.
>
> The OPEN address frame is not delivered through the topology,
> rather is store/forward through expanders, therefore it
> should not matter whether the rate matching ALIGNs begin as
> EOAF/ALIGN/idle dword or as EOAF/idle dword/ALIGN.
>
> TimH
>
> ~~~~~~~~~~~~~~~~~~~~~~~
> Tim.Hoglund at lsil.com
> 719/533-7450 (Voice)
> 719/533-7480 (Fax)
> ~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
> -----Original Message-----
> From: Elliott, Robert (Server Storage) [mailto:Elliott at hp.com]
> Sent: Tuesday, February 18, 2003 2:40 PM
> To: t10 at t10.org
> Subject: SAS rate matching - ALIGNs in OPEN
>
>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Elliott, Robert (Server Storage)" <Elliott at hp.com>
> *
> sas-r03 7.15 Rate matching says:
>     The OPEN address frame itself may or may not have ALIGNs
> interspersed.
>
> A letter ballot comment asked that we be very precise in
> mandating that the first dword after the OPEN address frame
> shall be an ALIGN,
> yielding:
>
>     After transmitting the OPEN address frame, the source phy
> shall start rate matching at the selected connection rate.
> The first dword after the EOF shall be an ALIGN or NOTIFY for
> rate matching.
>
> Should I keep or delete the sentence about ALIGNs (and
> NOTIFYs) in the OPEN address frame?  It's true, but might
> lead someone to think they should start rate matching in the
> OPEN (there's probably no reason to do so).
>
>
> --
> Rob Elliott, elliott at hp.com
> Hewlett-Packard Industry Standard Server Storage Advanced
> Technology https://ecardfile.com/id/RobElliott
>
>
>
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