General input/output architecture, protocol and related methods to implement flow control

• US 8,566,473 B2
• Filed: 02/27/2009
• Issued: 10/22/2013
• Est. Priority Date: 08/24/2001
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Ajanovic, Jasmin, Harriman, David, Fanning, Blaise, Lee, David M.
• Primary Examiner(s): Baturay, Alicia
• Application Number:
  US12/395,497
• Publication Number:
  US 20090193164A1
• Time in Patent Office: 1,698 Days
• Field of Search: 709/234, 370/229, 370231-233, 370/235
• US Class Current: 709/234
• CPC Class Codes: G06F 13/124 where hardware is a sequential transfer control unit, e.g. microprocessor, peripheral processor or state-machine
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 13/4059 where the synchronisation uses buffers, e.g. for speed matching between buses
• CPC Class Codes: G06F 13/42 Bus transfer protocol, e.g. handshake; Synchronisation
• CPC Class Codes: G06F 13/4221 being an input/output bus, e.g. ISA bus, EISA bus, PCI bus, SCSI bus
• CPC Class Codes: G06F 13/4252 using a handshaking protocol
• CPC Class Codes: G06F 13/4265 on a point to point bus G06F13/4247, G06F13/4282 take precedence
• CPC Class Codes: G06F 13/4269 using a handshaking protocol, e.g. Centronics connection
• CPC Class Codes: G06F 13/4282 on a serial bus, e.g. I2C bus, SPI bus on daisy chain buses G06F13/4247
• CPC Class Codes: G06F 5/06 for changing the speed of data flow, i.e. speed regularising or timing, e.g. delay lines, FIFO buffers; over- or underrun control therefor G06F7/78 takes precedence
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes

Abstract

An enhanced general input/output communication architecture, protocol and related methods are presented. In one embodiment, a method for an enhanced general input/output communication architecture includes initializing a flow control mechanism within an general input/output (GIO) interface associated with a virtual channel upon initialization of the virtual channel, and tracking receive buffer availability in a remote GIO interface coupled with the GIO interface by the virtual channel by monitoring an indication associated with an amount of content transmitted from the GIO interface to the remote GIO interface.

Claims

1. A method, comprising:

initializing a flow control mechanism within a general input/output interface of a transmitting device associated with a virtual channel upon initialization of the virtual channel; and

tracking buffer availability in a remote receiving device having a general input/output interface coupled with the general input/output interface of the transmitting device via the virtual channel by monitoring an indication associated with an amount of content transmitted from the general input/output interface of the transmitting device to the remote general input/output interface of the receiving device;

selectively suspending transmission to the remote general input/output interface of the receiving device through the virtual channel when the general input/output interface of the transmitting device determines that the receive buffer availability has reached a threshold; and

,

determining according to ordering rules what types of packets should be permitted to bypass a packet not yet transmitted.

2. A method according to claim 1, further comprising:

tagging transactions by adding a transaction descriptor to a packet including an ordering attribute including the type of ordering.

3. A method according to claim 2, wherein the threshold is set to prevent a buffer overflow condition.

4. A method according to claim 2, further comprising:

resuming transmission of content through the virtual channel when the GIO interface of the transmitting device receives an indication from the remote GIO interface of the receiving device of receive buffer availability.

5. A method according to claim 4, wherein the received indication is an update flow control packet.

6. A method according to claim 2, further comprising:

resuming transmission of content through the virtual channel after a period of time has lapsed.

7. A method according to claim 1, the element of initializing the flow control mechanism comprising:

receiving an indication from the remote GIO interface of the receiving device of a number of credits allocated to transmission to the remote GIO from the transmitting device, wherein a credit is associated with an amount of content.

8. A method according to claim 7, the element of initializing further comprising:

establishing one or more of a credit consumed buffer and a credit limit buffer in the GIO interface of the transmitting device, wherein the credit limit buffer is populated with an indication of credits allocated by the remote GIO interface of the receiving device.

9. A method according to claim 7, further comprising:

determining a number of credits to be consumed by a prospective transmission of content from the GIO interface of the transmitting device to the remote GIO interface of the receiving device; and

selectively transmitting the content to the remote GIO interface of the receiving device if when added to the credit consumed buffer by the transmitting device, the determined number of credits to be consumed by the prospective transmission does not exceed indication of credits allocated in the credit limit buffer.

10. A method according to claim 9, further comprising:

updating the credits consumed buffer with the transmitting device with an indication of the credits consumed by a transmission if the transmission is effected.

11. A method according to claim 9, further comprising:

suspending transmission of the content if it is determined by the transmitting device that the credits to be consumed by the prospective transmission would send the credits consumed buffer over that permitted by the credit limit buffer.

12. A method according to claim 11, further comprising:

receiving an indication from the remote GIO interface denoting a credit availability.

13. A method according to claim 12, further comprising:

updating the credit consumed register in the GIO interface of the transmitting device to reflect the credit availability denoted in the received indication from the remote GIO interface.

14. A general input/output interface in a transmitting device, comprising:

a physical layer to couple the general input/output interface to a general input/output interface communication link; and

a transaction layer coupled with the physical layer through a data link layer, the transaction layer including a flow control mechanism dynamically established upon initialization of a virtual channel between the general input/output interface and a remote general input/output interface of a receiving device, to monitor an ability of the remote general input/output interface to receive transmissions from the general input/output interface, and to suspend further transmissions if it is determined that further transmission would result in an overflow condition at the remote general input/output interface in the receiving device, and where, the transmitting device determines according to ordering rules what types of packets should be permitted to bypass a packet not yet transmitted.

15. A general input/output interface according to claim 14, wherein the transaction layer tags transactions by adding a transaction descriptor to a packet including an ordering attribute including the type of ordering.

16. A GIO interface according to claim 15, wherein suspension of transmission in any one of a plurality of virtual channels does not affect transmission on any other established virtual channels.

17. A GIO interface according to claim 16, the flow control mechanism further comprising:

a credit limit buffer, populated with a value received from the remote GIO interface denoting a number of flow control credits allocated to the virtual channel during initialization of the virtual channel.

18. A GIO interface according to claim 17, the flow control mechanism further comprising:

a credits consumed buffer, to maintain a value associated with an amount of content transmitted to the remote GIO interface.

19. A GIO interface according to claim 18, wherein the flow control mechanism of the transmitting device determines whether the remote GIO interface of the receiving device can receive a prospective transmission of content by adding flow control credits to be consumed by the prospective transmission to the credits consumed buffer to identify whether the prospective transmission would cause the credits consumed buffer to exceed a threshold associate with the credit limit buffer.

20. A GIO interface according to claim 18, wherein the flow control mechanism suspends further transmission along a virtual channel if the credits consumed buffer reaches the threshold associated with the credit limit buffer.

21. A GIO interface according to claim 20, wherein the threshold associated with the credit limit buffer is a number of credits denoted by the credit limit buffer.

22. A GIO interface according to claim 20, wherein the flow control mechanism resumes transmission along the virtual channel upon receipt of an update message denoting that the remote GIO interface is ready to receive additional transmissions.

23. A GIO interface according to claim 22, wherein the update message includes an indication of credit availability of the receive buffer, wherein the flow control mechanism updates the credit consumed buffer with the indication of credit availability of the update message.