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

• US 7,536,473 B2
• Filed: 08/23/2002
• Issued: 05/19/2009
• Est. Priority Date: 08/24/2001
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Fanning, Blaise, Ajanovic, Jasmin, Harriman, David, Lee, David M.
• Primary Examiner(s): Pwu; Jeffrey
• Assistant Examiner(s): Baturay; Alicia
• Application Number:
  US10/227,601
• Publication Number:
  US 20030158992A1
• Time in Patent Office: 2,461 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.

Claims

1. A method comprising:

initializing a flow control mechanism within an general input/output (GIO) interface of a transmitting device, the flow control mechanism initially associated with a first virtual channel upon initialization of the first virtual channel;

receiving, at the flow control mechanism from a GIO interface of a receiving device coupled with the GIO interface of the transmitting device via the virtual channel, an indication of a number of credits allocated for transmission of content from the transmitting device to the receiving device, wherein each credit indicates amount of content that can be transmitted;

dynamically tracking, by the flow control mechanism of the transmitting device, buffer availability associated with the GIO interface of the receiving device via the first virtual channel by monitoring the indication of the number of credits; and

selectively suspending, by the transmitting device, transmission of content to the remote GIO interface of the receiving device through the virtual channel when the GIO interface of the transmitting device determines that the receive buffer availability has reached a threshold amount;

wherein the flow control mechanism of the transmitting device dynamically tracks the buffer availability using a first register to track a number of credits consumed, a second register to track a credit limit, and a third register to track a number of credits allowed by the receiver; and

wherein the flow control mechanism of the transmitting device maintains and tracks separate indicators of credits for the following types of packet information for each virtual channel associated with the GIO interface;

posted request headers (PH), posted request data (PD), non-posted request headers (NPH), non-posted request data (NPD), read write and message completion headers (CPLH), and read and message completion data (CPLD).

2. A method according to claim 1, wherein the threshold amount is set to prevent a buffer overflow condition.

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

resuming transmission, by the transmitting device, 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.

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

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

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

6. 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.

7. A method according to claim 6, wherein the credit limit buffer is populated with an indication of credits allocated by the remote GIO interface of the receiving device.

8. A 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 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.

9. A method according to claim 8, 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.

10. A method according to claim 8, 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.

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

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

12. A method according to claim 11, 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.

13. A general input/output (GIO) interface in a transmitting device 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 first virtual channel between the GIO interface and a remote GIO interface of a receiving device, the flow control mechanism to;

populate a credit limit buffer of the flow control mechanism 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;

dynamically track additional buffer availability associated with a virtual channel between the GIO interfaces of the transmitting and receiving device using a first register to track a number of credits consumed, a second register to track a credit limit and a third register to track a number of credits allowed by the receiver; and

suspend the transmissions from the transmitting device via any one of the virtual channels if it is determined by the transmitting device that the buffer availability has reached a threshold amount;

wherein the flow control mechanism maintains and tracks separate indicators of credits for the following types of packet information for each virtual channel associated with the GIO interface;

posted request headers (PH), posted request data (PD), non-posted request headers (NPH), non-posted request data (NPD), read write and message completion headers (CPLH), and read and message completion data (CPLD).

14. A GIO interface according to claim 13, wherein the threshold amount is set to prevent an overflow condition at the remote GIO interface in the receiving device and suspension of transmission in any one of the virtual channels does not affect transmission on any other established virtual channels.

15. A GIO interface according to claim 14, wherein the credit limit buffer is 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.

16. A GIO interface according to claim 15, wherein the credits consumed buffer maintains a value associated with an amount of content transmitted to the remote GIO interface.

17. A GIO interface according to claim 16, 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.

18. A GIO interface according to claim 16, 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.

19. A GIO interface according to claim 18, wherein the threshold associated with the credit limit buffer is a number of credits denoted by the credit limit buffer.

20. A GIO interface according to claim 18, 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.

21. A GIO interface according to claim 20, 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.

22. An electronic component, suitable for use in an electronic device, comprising a GIO interface according to claim 13.

23. An electronic appliance comprising a plurality of electronic components according to claim 22.

24. 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 initially associated with a first virtual channel upon initialization of the first virtual channel;

receive, at the flow control mechanism from a GIO interface of a receiving device coupled with the GIO interface of the transmitting device via the first virtual channel, an indication of a number of credits allocated for transmission of content from the transmitting device to the receiving device, wherein each credit indicates amount of content that can be transmitted;

dynamically track, by the flow control mechanism of the transmitting device, buffer availability associated with the GIO interface of the receiving device via the first virtual channel by monitoring the indication of the number of credits; and

selectively suspend, by the transmitting device, transmission of content to the remote GIO interface of the receiving device through the first virtual channel when the GIO interface of the transmitting device determines that the receive buffer availability has reached a threshold amount;

wherein the flow control mechanism of the transmitting device dynamically track the buffer availability using a first register to track a number of credits consumed, a second register to track a credit limit, and a third register to track a number of credits allowed by the receiver; and

wherein the flow control mechanism of the transmitting device maintains and tracks separate indicators of credits for the following types of packet information for each virtual channel associated with the GIO interface;

posted request headers (PH), posted request data (PD), non-posted request headers (NPH), non-posted request data (NPD), read write and message completion headers (CPLH), and read and message completion data (CPLD).

25. A storage medium according to claim 24, the content to implement the GIO interface wherein the threshold amount is set to prevent a buffer overflow condition.

26. A storage medium according to claim 25, 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 of other virtual channels, 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.

27. A storage medium according to claim 26, 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.