Power Condition Mode Select interpretation of intent

Penokie, George George.Penokie at lsi.com
Mon Aug 25 11:16:01 PDT 2008

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See my comments below.
There appears to be a small bug in the power condition state machine. In the
case were:
a) The idle condition timer is active;
b) The idle condition timer is zero.
c) The standby condition timer is active; and
d) The standby condition timer is zero.
There is no description of which transition should be used from the
PC1:Active.state.  I realize that in the end, if the PC1:Active to PC2:Idle
transitions is taken there will be a transition from PC2:Idle to PC3:Standby
right away which would have the same effect as a PC1:Active to PC3: Standby
but it would be clearer to the reader if a single clear active was defined
for this case.
Bye for now,
George Penokie
LSI Corporation
3033 41st St. NW
Suite 100
Rochester, MN 55901
george.penokie at lsi.com
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Kevin D Butt
Sent: Monday, August 25, 2008 10:58 AM
To: t10 at t10.org
Cc: Hirokazu Nakayama
Subject: Power Condition Mode Select interpretation of intent
I have a question of the intent of the Power Condition mode parameters.
The following text is from SPC-4r16.
7.4.12 Power Condition mode page
The Power Condition mode page provides an application client with methods to
control the power condition of a
logical unit (see 5.10). These methods include:
a) Specifying that the logical unit transition to a power condition without
delay; and
b) Activating and setting of idle condition and standby condition timers to
specify that the logical unit wait for a period of inactivity before
transitioning to a specified power condition.
Item a) implies to me that there is a method of telling the target to "go to
specified power condition immediately (i.e., now)".
Item b) implies to me that there is a method of specifying a timer value for
when to transition to the power condition.
Is the intent of listing a) separately to infer that a timer value of zero is
the "go immediately" command and that it is a one time event?	(GP - No,
although this could be subject to interpretation. If you look in the power
conditions state machine you will see it is not a one time change. When the
power condition is active (i.e., the bit is set) and the timer is zero the
transitions occur.)  Or is the intent that the timer value is modified to be
zero and the side effect of that modification is that the power condition is
immediately transitioned to?   (GP - No)  Stated differently, does a mode
select specifying a power condition timer of zero modify that timer until the
next mode select (or event that changes mode parameters) thereby causing a
device to transition out of and back into that state on the receipt and
completion of each command that causes a transition (e.g., write)  (GP - Yes,
the power transitions would occur any time there is no active command.) ?
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com

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