Methods and structure for assuring correct data order in SATA transmissions over a SAS wide port

• US 20060031612A1
• Filed: 08/03/2004
• Published: 02/09/2006
• Est. Priority Date: 08/03/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Day, Brian A., Bashford, Patrick R.
• Granted Patent: US 7,676,613 B2
• Time in Patent Office: Days
• US Class Current: 710/74
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

Methods and associated structure to assure correct order in delivery of SATA frames over a SAS wide port. In one aspect hereof, new connection requests from a SATA device are rejected until prior frames residing in receive buffers of the SAS/SATA controller are properly processed. In another aspect, when a device is already connected to the controller, the SAS/SATA controller may prevent return of a receiver ready primitive in response to a transmitter ready primitive until previously received frames are removed from the receive buffers.

Claims

1. A SAS/SATA controller for coupling a host system to one or more SATA devices via a SAS wide port, the SAS/SATA controller comprising:

a plurality of link layer processing elements collectively coupled to the SAS wide port wherein each link layer processing element is associated with connection status information regarding any SATA device communicatively coupled thereto;

a plurality of receive buffers each associated with a corresponding link layer processing element of the plurality of link layer processing elements wherein each receive buffer is associated with receive status information regarding one or more received frames stored therein; and

a transmission controller, coupled to the plurality of link layer processing elements and coupled to the plurality of receive buffers, to controllably prevent transmissions of frames from an identified SATA device wherein the transmission controller is adapted to use the receive status information of each receive buffer such that at any particular point in time only one receive buffer of the plurality of receive buffers stores any frames received from the identified SATA device.

2. The controller of claim 1 wherein the receive status information includes a received frame resident status indicia and an associated SATA device ID for a received frame and wherein each receive buffer of the plurality of receive buffers further comprises:

a frame received active indicator for storing a received frame resident status indicia indicating storage of a received frame in the corresponding receive buffer; and

a device ID indicator for storing the device ID of the SATA device that transmitted the corresponding received frame.

3. The controller of claim 2 wherein the transmission controller further comprises:

control logic to prevent transmissions of frames from a SATA device having a device ID equal to the device ID stored in the device ID indicator of any receive buffer that has its frame received active indicator indicative of a received frame present in the corresponding receive buffer.

4. The controller of claim 2 wherein the transmission controller designates for each link layer processing element a corresponding receive buffer as the native buffer for said each link layer processing element and designates all other receive buffers as foreign buffers for said each link layer processing element and wherein the transmission controller further comprises:

control logic to prevent transmissions of frames from a SATA device over a transmitting link layer processing element of the plurality of link layer processing elements where the device attempting to transmit a frame has a device ID value equal to the device ID value in the device ID indicator of any of the foreign buffers of the transmitting link layer processing element that have the corresponding frame received indicator set or where the device attempting to transmit a frame has a device ID value not equal to the device ID value in the device ID indicator of the native buffer of the transmitting link layer processing element and the native buffer has its received buffer indicator set.

5. The controller of claim 1 wherein the transmission controller is operable in response to the receive status information and connection status information associated with each of the plurality of link layer processing elements and wherein the connection status information includes a current connected device ID indicia, a connection request device ID indicia and a presently connected status indicia and wherein each link layer processing element of the plurality of link layer processing elements includes:

a current connected device ID indicator for storing the current connected device ID indicia associated with said each link layer processing element;

a connection request device ID indicator for storing the connection request device ID indicia associated with said each link layer processing element; and

a presently connected status indicator for storing the presently connected status indicia associated with said each link layer processing element.

6. The controller of claim 5 wherein the transmission controller further comprises:

control logic to prevent granting of a requested connection received on a link layer processing element where the connection request ID indicia associated with the link layer processing element is equal to the device ID indicia in any receive buffer of the plurality of receive buffers for which the frame received active indicator is set.

7. The controller of claim 5 wherein the transmission controller designates for each link layer processing element of the plurality of link layer processing elements a corresponding receive buffer as the native buffer for said each link layer processing element and designates all other receive buffers as foreign buffers with respect to said each link layer processing element and wherein the transmission controller further comprises:

control logic to prevent granting of a requested connection from a SATA device over a transmitting link layer processing element of the plurality of link layer processing elements where the device requesting a connection has a device ID value equal to the device ID value in the device ID indicator of any of the foreign buffers of the transmitting link layer processing element that have the corresponding frame received indicator set or where the device requesting a connection has a device ID value not equal to the device ID value in the device ID indicator of the native buffer of the transmitting link layer processing element and the native buffer has its received buffer indicator set.

8. A system comprising:

a host system;

a SAS/SATA controller within the host system;

a SATA device; and

a SAS expander coupled between the SAS/SATA controller and the SATA device,

wherein the SAS expander is coupled to the SAS/SATA controller via a SAS wide port, and

wherein the SAS/SATA controller further comprises;

a plurality of link layer processing elements coupling the SAS/SATA controller to the SAS wide port;

a plurality of receive buffers each associated with a corresponding link layer processing element of the plurality of link layer processing elements; and

a transmission blocker to prevent frame transmission from an identified SATA device using status information associated with each receive buffer such that at any particular point in time only one receive buffer of the plurality of receive buffers stores any frames received from the identified SATA device.

9. The system of claim 8 wherein the transmission blocker further comprises:

a flow control signal generator to controllably preclude transmission of a next frame in response to said status information.

10. The system of claim 8 wherein the transmission blocker further comprises:

a connection control element to controllably preclude opening of a connection in response to said status information.

11. The system of claim 8 wherein the status information includes connection status information relating to connections with SATA devices involving any of the plurality of link layer processing elements and wherein the transmission blocker further comprises:

a connection detector for detecting whether the SATA device associated with the earlier transmitted frame has a current connection to the host system;

a flow control signal generator, operable in response to detecting that the SATA device has a current connection to the host system, to controllably preclude transmission of frames in response to said status information; and

a connection control element, operable in response to detecting that the SATA device presently has no connection to the host system, to controllably preclude opening of a connection in response to said connection status information.

12. The system of claim 8 wherein the controller is operable to designate for each link layer processing element of the plurality of link layer processing elements a corresponding receive buffer as the native buffer for said each link layer processing element and is operable to designate all other receive buffers as foreign buffers for said each link layer processing element and wherein the transmission blocker further comprises:

comparison logic coupled to the plurality of receive buffers and coupled to the plurality of link layer processing elements wherein the comparison logic is operable to control the transmission blocker to prevent transmission of frames from the SATA device such that a next frame from an identified SATA device coupled to a transmitting link layer processing element of the plurality of link layer processing elements is held off if the native buffer associated with the transmitting link layer processing element presently stores a received frame from another SATA device or is held off if any of the foreign buffers associated with the transmitting link layer processing element presently store a received frame from the transmitting device.

13. The system of claim 12 wherein the status information includes connection status information relating to connections made with any of the plurality of link layer processing elements and wherein the comparison logic is operable prevent granting of a connection request from a requesting SATA device over the transmitting link layer processing element in response to a determination that the native buffer associated with the transmitting link layer processing element presently stores a received frame from another SATA device or prevents granting of the connection request if any of the foreign buffers associated with the transmitting link layer processing element presently store a received frame from the requesting device.

14. A method operable in a SAS/SATA controller adapted for coupling to a SATA device via a SAS wide port comprising multiple links and the controller having multiple receive buffers each associated with a corresponding one of the multiple links, the method comprising:

receiving a frame from a transmitting SATA device via a link layer processing element coupled to the SAS wide port;

storing the received frame in a receive buffer associated with the link layer processing element;

blocking frame transmissions from the transmitting SATA device such that at any particular point in time only one receive buffer of the plurality of receive buffers stores any frames received from the transmitting SATA device.

15. The method of claim 14 wherein the step of storing further comprises:

setting a received frame indicator associated with the receive buffer to indicate presence of a received frame in the corresponding receive buffer; and

setting a device ID indicator associated with the receive buffer to indicate the device ID of the transmitting SATA device that transmitted the received frame.

16. The method of claim 15 wherein the step of blocking further comprises:

holding off setting a receiver ready status on the SAS wide port to prevent transmission of another frame from the transmitting SATA device.

17. The method of claim 16 further comprising:

designating for each link of the multiple links a corresponding receive buffer as the native buffer for said each link; and

designating all other receive buffers as foreign buffers for said each link.

18. The method of claim 17 wherein the step of holding off further comprises:

holding off setting a receiver ready status on the SAS wide port to prevent transmission of another frame from the transmitting SATA device in response to detecting that the device ID of the SATA device attempting to transmit a next frame matches the device ID stored in the device ID indicator of any of the plurality of receive buffers where the associated received frame indicator is also set.

19. The method of claim 17 wherein the step of holding off further comprises:

preventing transmissions of frames from a SATA device over a transmitting link of the plurality of links where the device attempting to transmit a frame has a device ID value equal to the device ID value in the device ID indicator of any of the foreign buffers of the transmitting link that have the corresponding frame received indicator set or where the device attempting to transmit a frame has a device ID value not equal to the device ID value in the device ID indicator of the native buffer of the transmitting link and the native buffer has its received buffer indicator set.

20. The method of claim 15 wherein the step of blocking further comprises:

rejecting an open request from a transmitting device having a device ID matching the device ID stored in the device ID indicator of any of the plurality of receive buffers where the associated received frame indicator is also set.