Breaking a multiple type command sequence

gop at us.ibm.com gop at us.ibm.com
Fri Dec 17 13:49:06 PST 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* gop at us.ibm.com
*
Sriram,
I believe your every wish has been fulfilled in rev 12 of SPI-3 which is on
the web site but has not been moved to the place where everyone can get at
it.

Bye for now,
George Penokie

Dept Z9V  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880



Sriram Srinivasan <srirams at propwash.co.lsil.com> on 12/17/99 12:44:31 PM

Please respond to Sriram Srinivasan <srirams at propwash.co.lsil.com>

To:   t10 at t10.org
cc:
Subject:  Breaking a multiple type command sequence




* From the T10 Reflector (t10 at t10.org), posted by:
* Sriram Srinivasan <srirams at propwash.co.lsil.com>
*
George:

     I have some questions regarding the issue of breaking a multiple type
command sequence.

     Let's take a case where a target chip has the ability to accept, say,
4
commands in a high speed register file and, after receiving 4 multiple type
commands, would like to break out into  actions other than queue full (such
as
sending out staged data/status as Bill pointed out).  The reason queue full
is
not an option is that the queue is not managed real-time (i.e. could be
managed
in firmware) and the queue may not be even close to full.  In order to
break a
sequence of multiple type command IUs, if we are required to send a STATUS
IU
(w/ say a TASK SET FULL status) ONLY for the multiple commands just
received,
then the target has to pause on the SCSI bus while the queue check is
performed
(non-real time).  Also in case the target has alrady queued up data/status
for
the same initiator we dont want to pause while the target rearranges the
queued
events to send TASK SET FULL first to break the sequence of multiple
commands.

     In this regard, the two SPI-3 clarifications/changes that we would
like
to see are the following:

1. The target is allowed to transition at the end of a
command multiple to any of these options:
   - BUS FREE
     (so that we can send out the TASK SET FULL on a future bus connection
      for these command multiples received)

   - SPI L-Q followed by Data IU
   - SPI L_Q followed by Status IU
     (w/ status other than QUEUE FULL for some other L_Q for the same
initiator)

   - continue w/ receiving Command IUs from initiator

2. There is no restriction on when or if a TASK SET FULL
status is sent for any of the commands received on this
or any previous bus connection (as long as the data for
the command has not started).  Target can send TASK
SET FULL for L_Qs other than the ones received from the
initiator during the existing DT DATA OUT (CMD IU) phase
and may defer sending the TASK SET FULL STATUS IU
(if required) for the current stream of multiple commands
to a future bus connection w/ the same initiator.

Sriram

----------------------------------------------------------------------------


Sriram Srinivasan,                 Sriram.Srinivasan at lsil.com
ASIC Design Engineer, LSI Logic,         Phone : (970) 206 5847
2001 Danfield Ct., Ft. Collins, CO 80525      FAX   : (970) 206 5244
-----------------------------------------------------------------------------



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