1. SOP Queuing Layer T10/11-127r0 SOP: Inbound & Outbound Queues
Tim Symons, PMC-Sierra
Ie-Wei Njoo, PMC-Sierra and
Neil Wanamaker, PMC-Sierra
8 March,2011
T10/11-127r0 SOP: Inbound & Outbound Queues

2. Inbound – the direction from the host to the controller
Definitions
Inbound – the direction from the host to the controller
IQ – Inbound Queue
Outbound – the direction from the controller to the host
OQ – Outbound Queue
IU – Information Unit
The unit of information where the SOP requests, responses and events are transferred
Represented by one or more queue element(s)
T10/11-127r0 SOP: Inbound & Outbound Queues

3. Circular Queue Mechanics
Circular queues are arrays in host memory with two associated indices, a Producer Index (PI) and a Consumer Index (CI).
The queue is empty when the PI and CI are equal.
The queue is full when the PI is exactly one position behind the CI.
Unidirectional
Handshaking via posted writes only
PI resides in consumer space and is cached by producer
CI resides in producer space and is cached by consumer
T10/11-127r0 SOP: Inbound & Outbound Queues

4. Inbound Queue (IQ) and Outbound Queue (OQ) Example
Host prepares request IU using the IQ element
Host increments IQPI in controller
Controller consumes request IU
Controller increments IQCI in host
Outbound Queue
Controller prepares and DMAs response IU to the OQ element
Controller increments OQPI in host
Controller triggers interrupt to host
Host consumes response IU
Host increments OQCI in controller
T10/11-127r0 SOP: Inbound & Outbound Queues

5. Administrator Queue Operational Queue Queue Types
Management of the controller functionalities
Initialized using the controller register set
One administrator IQ
One administrator OQ
Highest priority
Create operational queues
Operational Queue
SCSI operations
Compact IU
Extended IU
X:Y ratio of IQs and OQs
Initiator mode and target mode
Configurable:
Priority
Queue element size
Number of queue elements
T10/11-127r0 SOP: Inbound & Outbound Queues

6. Queue Element Size vs. IU Size
One queue element for one IU
Multiple queue elements for one IU
Additional reference to other memory

7. IU Header
Byte\ Bit 7 6 5 4 3 2 1
IU TYPE
OBID
COMMAND PRIORITY
CHAINING COUNT
OPC
IU specific content … n
The IU TYPE specifies the type of IU in the queue: administrator, SCSI initiator, SCSI target, events, etc.
The OBID field specifies the Outbound Queue ID where controller sends the response/event to.
The CHAINING COUNT field specifies the number of queue elements used by the IU/operation.
The COMMAND PRIORITY field is defined in SAM-5 Command Priority.
The OPC field specifies the command, response or event code that the function.
T10/11-127r0 SOP: Inbound & Outbound Queues

8. Inbound-Outbound Message Mapping
Multiple Queues per direction
Minimum one IQ and one OQ
Host selects the Inbound Queue to post any message to.
No requirements imposed by controller
Host may want to map COMMAND PRIORITY with the corresponding Inbound Queue QUEUE PRIORITY
The Inbound Message header allows the host to specify the Outbound Queue ID (OQID) to be used for posting any response IUs
Asynchronous events (including target mode, hot plug) are mapped to a specific Outbound Queue configured by administrator function during host driver initialization
T10/11-127r0 SOP: Inbound & Outbound Queues

9. T10/11-127r0 SOP: Inbound & Outbound Queues