Method and apparatus for efficient command queuing within a serial ATA environment

• US 20040073719A1
• Filed: 09/30/2002
• Published: 04/15/2004
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Rakuten Group, Inc.
• Original Assignee: Intel Corporation
• Inventors: Royer, Robert J. Jr., Huffman, Amber D., Grimsrud, Knut S.
• Granted Patent: US 6,917,992 B2
• Time in Patent Office: Days
• US Class Current: 710/1
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method is described that involves sending a second command over a Serial ATA interface to a device before the device is able to execute a first command that was previously sent to the Serial ATA interface. In a further embodiment of the first command is tagged with a first reference number. In an even further embodiment of the method the second command is tagged with a second reference number.

Claims

1. A method, comprising:

sending a second command over a Serial ATA interface to a device before said device is able to execute a first command that was previously sent to said Serial ATA interface.

2. The method of claim 1 wherein said first command is tagged with a first reference number.

3. The method of claim 2 wherein said second command is tagged with a second reference number.

4. The method of claim 1 wherein said second command is a READ command.

5. The method of claim 4 wherein said second command involves a DMA transfer.

6. The method of claim 1 wherein said second command is WRITE command.

7. The method of claim 6 wherein said second command involves a DMA transfer.

8. The method of claim 1 wherein said device is a storage device.

9. The method of claim 8 wherein said storage device resides within the primary package of a computing system.

10. The method of claim 8 wherein said storage device is resides outside the primary package of a computing system, said Serial ATA interface assisting in coupling said storage device to said primary package.

11. The method of claim 10 wherein said storage device is a RAID box.

12. The method of claim 1 further comprising said device deciding to execute said second command before said first command.

13. A method, comprising:

a) receiving a command, said command tagged with a reference number;

b) sending said command and said reference number over a Serial ATA interface to a device and

setting a bit in order to indicate said Serial ATA interface is busy and

altering a field of information to reflect that said reference number is presently unavailable for tagging to another command;

c) receiving information from said Serial ATA interface that was sent from said device, said information indicating that said bit should be cleared in order to indicate that said Serial ATA interface is no longer busy and

clearing said bit so as to indicate that said Serial ATA interface is no longer busy; and

d) receiving additional information from said Serial ATA interface that was sent from said device, said additional information indicating that said field of information should again be altered to reflect that said reference number is presently available for tagging to another command because said command has been executed and

altering said field of information to reflect that said reference number is presently available for tagging to another command.

14. The method of claim 13 wherein said bit is a BSY bit within a host status register.

15. The method of claim 13 wherein said reference number is one reference number out of a plurality of reference numbers, said field of information further comprising one bit for each said reference numbers, each of said reference numbers for tagging to different commands, said field if information within an SDevice register.

16. The method of claim 13 wherein said information is sent within a Register packet.

17. The method of claim 13 wherein said additional information is sent within an SDevice packet.

18. The method of claim 13 further comprising sending an interrupt message to an entity that sent said command, as a consequence of said additional information having been received, so that said entity can recognize that said reference number is presently available for tagging to another command.

19. The method of claim 13 wherein said command is a READ command.

20. The method of claim 13 wherein said command is WRITE command.

21. The method of claim 13 further comprising receiving a DMA_Setup packet after said receiving of said information but prior to said receiving of said additional information, said DMA_Setup packet further comprising said reference number.

22. The method of claim 21 further comprising setting up a DMA engine in response to said receiving of said DMA_Setup packet.

23. The method of claim 22 wherein said setting up a DMA engine further comprises retrieving a scatter/gather table, said scatter/gather table referenced by said reference number.

24. The method of claim 23 further comprising setting up said scatter/gather table in response to said receiving of said command.

25. A method, comprising:

a) receiving a packet having a command and a reference number, said packet received from a Serial ATA interface that is coupled to a host;

b) queuing said command in a queue and

sending information to said host over said Serial ATA interface, said information indicating that a bit within said host should be cleared in order to indicate that said Serial ATA interface is no longer busy;

c) executing said command; and

d) sending additional information to said host over said Serial ATA interface, said additional information indicating that a field of information should be altered to reflect that said reference number is presently available for tagging to another command because said command was executed.

26. The method of claim 25 wherein said information is sent within a Register packet.

27. The method of claim 25 wherein said reference number is one reference number out of a plurality of reference numbers, said field of information further comprising one bit for each said reference numbers, each of said reference numbers for tagging to different commands, said field if information within an SDevice register within said host.

28. The method of claim 27 wherein said additional information is sent within an SDevice packet.

29. The method of claim 25 wherein said executing further comprises executing said command before another command is executed, said other command having been received before said command was said received.

30. The method of claim 25 wherein said executing further comprises executing said command after another command is executed, said other command having been received after said command was said received.

31. The method of claim 25 wherein said command is a READ command.

32. The method of claim 25 wherein said command is a WRITE command.

33. The method of claim 25 further comprising sending a DMA_Setup packet after said receiving of said packet in order to commence said execution of said command, said DMA_Setup packet further comprising said reference number.

34. An apparatus, comprising:

a) a host side functional unit that communicates over a Serial ATA interface;

b) a host status register, said host side functional unit to set a bit within said host status register in response to reception of a command and a reference number for said command, said command to be sent over said Serial ATA interface, said setting of said bit to indicate said Serial ATA interface is busy; and

c) an SDevice register to present a field of information, said field of information to indicate a status for each one of a plurality of commands, said host side functional unit to set said command'"'"'s status, in response to said reception, to indicate said command is both outstanding and unexecuted.

35. The apparatus of claim 34 further comprising a strorage device that is communicatively coupled to said host side functional unit.

36. The apparatus of claim 35 wherein said storage device and said host side functional unit reside within the same computing system package.

37. The apparatus of claim 36 wherein said computing system is a Personal Computer (PC).

38. The apparatus of claim 37 wherein said host side functional unit is at least partially implemented with software that is executed by said PC'"'"'s Central Processing Unit (CPU).

39. The apparatus of claim 35 wherein said storage device resides outside a computing system package that said host side functional unit resides within.

40. The apparatus of claim 39 wherein said computing system is a server.

41. The apparatus of claim 39 wherein said computing system is a workstation.

42. The apparatus of claim 39 wherein said storage device is a RAID box.

43. The apparatus of claim 34 wherein said host side functional unit is implemented with a semiconductor chip.

44. The apparatus of claim 34 wherein said host side functional unit is implemented with a software program.

45. The apparatus of claim 34 wherein said host side functional unit is further configured to clear said bit in response to a register packet being received at said Serial ATA interface.

46. The apparatus of claim 34 wherein said host side functional unit is also to change said command'"'"'s status, upon receipt of an SDevice packet from said Serial ATA interface, to indicate said command has been executed.

47. A machine readable medium having stored thereon a sequence of instructions which when executed by a processor or a controller, cause said processor or controller to implement a method, said method comprising:

a) receiving a command, said command tagged with a reference number;

b) sending said command and said reference number over a Serial ATA interface to a device and

setting a bit in order to indicate said Serial ATA interface is busy and

altering a field of information to reflect that said reference number is presently unavailable for tagging to another command;

c) receiving information from said Serial ATA interface that was sent from said device, said information indicating that said bit should be cleared in order to indicate that said Serial ATA interface is no longer busy and

clearing said bit so as to indicate that said Serial ATA interface is no longer busy; and

d) receiving additional information from said Serial ATA interface that was sent from said device, said additional information indicating that said field of information should again be altered to reflect that said reference number is presently available for tagging to another command because said command has been executed and

altering said field of information to reflect that said reference number is presently available for tagging to another command.

48. The machine readable medium of claim 47 wherein said bit is a BSY bit within a host status register.

49. The machine readable medium of claim 47 wherein said reference number is one reference number out of a plurality of reference numbers, said field of information further comprising one bit for each said reference numbers, each of said reference numbers for tagging to different commands, said field if information within an SDevice register.

50. The machine readable medium of claim 47 wherein said information is sent within a Register packet.

51. The machine readable medium of claim 47 wherein said additional information is sent within an SDevice packet.

52. The machine readable medium of claim 47 further comprising sending an interrupt message to an entity that sent said command, as a consequence of said additional information having been received, so that said entity can recognize that said reference number is presently available for tagging to another command.

53. The machine readable medium of claim 47 wherein said command is a READ command.

54. The machine readable medium of claim 47 wherein said command is WRITE command.