SAS-2: Notify Power Loss

Stephen FINCH steve.finch at st.com
Tue Oct 24 09:18:59 PDT 2006


* From the T10 Reflector (t10 at t10.org), posted by:
* Stephen FINCH <steve.finch at st.com>
*
Section 7.2.5.10.3 states:
"If a SAS target device supports NOTIFY (POWER LOSS EXPECTED) and receives
NOTIFY (POWER LOSS
EXPECTED) on an SSP target port, then each SAS phy within the target device
shall:
a) if there is an SSP connection, then transmit a BREAK on that connection;
and
b) respond to SSP connection requests with OPEN_REJECT (RETRY) until the
power loss timeout
timer expires or power is lost.
If any frames are received by the SAS target device after receiving NOTIFY
(POWER LOSS EXPECTED)
before a connection is closed, then the SAS target device shall discard the
received frames."
Since it is the CC state machine that transmits BREAK primitives, I looked to
that state machine to see where and how this is accomplished.  
There is no inputs to that state machine indicating the reception of a NOTIFY
(POWER LOSS EXPECTED).
That being the case, I thought maybe the SSP state machine had an input for
the NOTIFY (POWER LOSS EXPECTED) and, in turn, would issue a Request Break to
the CC state machine.
SURPRISE! SURPRISE!
The SSP state machine doesn't have such an input either.  And there is no
input to the SSP state machine from higher levels that can generate a BREAK.
SO, how are NOTIFY (POWER LOSS EXPECTED) supposed to be handled?
I think we need state machine changes in the Link Layer to handle the
requirements above, or we need to remove the requirements.
Regards,
Steve Finch
STMicroelectronics
303 381-3587
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