General Input/Output Architecture, Protocol and Related Methods to Implement Flow Control

• US 20090193164A1
• Filed: 02/27/2009
• Published: 07/30/2009
• Est. Priority Date: 08/24/2001
• Status: Active Grant

• Current Assignee: Blaise fanning, David Harriman, David M. Lee, Jasmin Ajanovic
• Original Assignee: Blaise fanning, David Harriman, David M. Lee, Jasmin Ajanovic
• Inventors: Fanning, Blaise, Ajanovic, Jasmin, Harriman, David, Lee, David M.
• Granted Patent: US 8,566,473 B2
• Time in Patent Office: Days
• US Class Current: 710/107
• 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 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.

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

selectively suspending transmission of content to the remote GIO interface through the virtual channel when the GIO interface determines that the receive buffer availability has reached a threshold set to prevent a buffer overflow condition.

3. The method according to claim 2, further comprising:

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

4. The method according to claim 3, wherein the received indication is an update flow control packet.

5. The method according to claim 2, further comprising:

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

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

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

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

7. The method according to claim 6, further comprising:

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

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

8. The method according to claim 6, further comprising:

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

9. The method according to claim 6, further comprising:

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

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

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

10. A general input/output (GIO) interface comprising:

a physical layer, to couple the GIO interface to a GIO 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 GIO interface and a remote GIO interface, to monitor an ability of a remote GIO interface to receive transmissions from the GIO interface, and to suspend further transmissions if it is determined that further transmission would result in an overflow condition at the remote GIO interface.

11. The GIO interface according to claim 10, wherein a flow control mechanism is initialized and associated with each of a plurality of virtual channels established in the GIO link between the GIO interface and the remote GIO interface.

12. The GIO interface according to claim 11, 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; and

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

13. The GIO interface according to claim 12, wherein the flow control mechanism determines whether the remote GIO interface 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.

14. The GIO interface according to claim 12, 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.

15. The GIO interface according to claim 14, wherein the threshold associated with the credit limit buffer is a number of credits denoted by the credit limit buffer.

16. The GIO interface according to claim 14, 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, and 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.

17. A storage medium comprising content which, when executed by an accessing device, causes the device to implement a general input/output interface (GIO) to initialize a flow control mechanism associated with a virtual channel upon initialization of the virtual channel, and to track receive buffer availability in a remote GIO interface coupled with the device by the virtual channel by monitoring an indication associated with an amount of content already transferred from the GIO interface to the remote GIO interface.

18. The storage medium according to claim 17, the content to implement the GIO interface further comprising content to selectively suspend transmission of content to the remote GIO interface when the flow control mechanism determines that the receive buffer availability has reached a threshold.

19. The storage medium according to claim 18, wherein the content to implement the flow control mechanism of the GIO interface employs a flow control credit as a measure of content, wherein the flow control mechanism establishes a credit consumed buffer and a credit limit buffer associated with each virtual channel, wherein the credit limit buffer is populated with a value associated with an availability of a receive buffer in the remote GIO interface to receive content from the GIO interface, and the credit consumed buffer is updated by the GIO interface to reflect an amount of content transmitted to the remote GIO interface.

20. The storage medium according to claim 19, wherein the flow control mechanism suspends transmission of content to the remote GIO interface if the value of the credit consumed buffer exceeds a threshold associated with the credit limit buffer until an update message is received from the remote GIO interface.