Method and apparatus for power management of graphics processors and subsystems that allow the subsystems to respond to accesses when subsystems are idle

• US 6,938,176 B1
• Filed: 10/05/2001
• Issued: 08/30/2005
• Est. Priority Date: 10/05/2001
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Ma, Dennis Kd, Kelleher, Brian, Alben, Jonah
• Primary Examiner(s): Browne, Lynne H.
• Assistant Examiner(s): Trujillo, James K.
• Application Number:
  US09/972,414
• Time in Patent Office: 1,425 Days
• Field of Search: 713/300, 713/320, 713/322, 713/323, 713/324, 713/500, 713/600
• US Class Current: 713/323
• CPC Class Codes: G06F 1/10 Distribution of clock signals , e.g. skew
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3237 by disabling clock generation or distribution
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3296 by lowering the supply or operating voltage
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A graphics processing device implementing a set of techniques for power management, preferably at both a subsystem level and a device level, and preferably including peak power management, a system including a graphics processing device that implements such a set of techniques for power management, and the power management methods performed by such a device or system. In preferred embodiments, the device includes at least two subsystems and hardware mechanisms that automatically seek the lowest power state for the device that does not impact performance of the device or of a system that includes the device. Preferably, the device includes a control unit operable in any selected one of multiple power management modes, and system software can intervene to cause the control unit to operate in any of these modes.

Claims

1. A processing device, including:

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle; and

wherein the control circuitry is further configured to cause either of the first or second subsystems to respond to an access even though the first or second subsystem is idle.

2. The device of claim 1, wherein the control circuitry is coupled to the first subsystem, the first subsystem is configured to assert to the control circuitry a status signal indicative of whether said first subsystem is idle, the first subsystem clock branch includes logic circuitry having a first state allowing assertion of the first subsystem clock to the first subsystem and a second state preventing assertion of the first subsystem clock to the first subsystem, and the control circuitry is configured to assert a control signal to the logic circuitry in response to the status signal, wherein the control signal selects the first state when the status signal does not indicate that the first subsystem is idle and the control signal selects the second state when the status signal indicates that the first subsystem is idle.

3. The device of claim 1, wherein said device is an integrated circuit.

4. The device of claim 1, wherein said device is a graphics processing portion of an integrated circuit.

5. The device of claim 1, also including:

device clock generation circuitry configured to generate at least a first device clock, wherein the device clock generation circuitry is coupled to the subsystem clock circuitry, the first subsystem clock branch asserts the first subsystem clock to the first subsystem in response to the first device clock, the second subsystem clock branch asserts the second subsystem clock to the second subsystem in response to the first device clock, and the control circuitry and the device clock generation circuitry are configured to operate in a device clock management mode in which the control circuitry selectively disables and enables generation of the first device clock by the device clock generation circuitry.

6. The device of claim 5, wherein the control circuitry in the device clock management mode causes the device clock generation circuitry to disable generation of the first device clock when both the first subsystem and the second subsystem are idle.

7. The device of claim 1, wherein the control circuitry is also configured to operate in a peak power management mode, wherein when the control circuitry is in the peak power management mode, the control circuitry dynamically causes the frequency of at least one clock asserted at at least one node of the device to be lowered whenever power consumption by the device rises to a predetermined threshold.

8. The device of claim 1, also including:

a voltage regulator coupled to the device and configured to assert a supply voltage to the device,

wherein the control circuitry is configured to operate in a peak power management mode, wherein when the control circuitry is in the peak power management mode, the control circuitry asserts a voltage control signal to the voltage regulator when power consumption by the device rises to a predetermined threshold, and the voltage regulator responds to said voltage control signal by operating in such a manner that the supply voltage is reduced to a predetermined value.

9. A processing device, including:

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle;

multiplexing circuitry having inputs coupled to a first node at which a host clock is asserted and a second node at which a first device clock is asserted, and having at least one output coupled to the subsystem clock circuitry,

wherein the control circuitry and the multiplexing circuitry are configured to operate in a mode in which the control circuitry causes the multiplexing circuitry to assert a selected one of the host clock and the first device clock to the subsystem clock circuitry, and wherein the first subsystem clock branch asserts the first subsystem clock to the first subsystem in response to said selected one of the host clock and the first device clock, and the second subsystem clock branch asserts the second subsystem clock to the second subsystem in response to said selected one of the host clock and the first device clock.

11. The device of claim 9, also including:

host clock generation circuitry configured to generate a host clock;

device clock generation circuitry configured to generate at least one device clock including a first device clock; and

multiplexing circuitry having inputs coupled to the host clock generation circuitry and the device clock generation circuitry, and having at least one output coupled to the subsystem clock circuitry,

wherein the control circuitry and the multiplexing circuitry are configured to operate in a mode in which the control circuitry causes the multiplexing circuitry to assert a selected one of the host clock and the first device clock to the subsystem clock circuitry, and wherein the first subsystem clock branch asserts the first subsystem clock to the first subsystem in response to said selected one of the host clock and the first device clock, and the second subsystem clock branch asserts the second subsystem clock to the second subsystem in response to said selected one of the host clock and the first device clock.

10. A processing device, including:

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle;

a host slave bus, wherein each of the first subsystem and the second subsystem includes a host register connected along the host slave bus; and

a host slave unit coupled to the host slave bus, and configured to be coupled to a system bus so as to provide an interface between the system bus and the host slave bus.

12. The device of claim 10, wherein the device is configured to be coupled to a voltage regulator so as to receive a supply voltage generated by the voltage regulator, the control circuitry is coupled to the host slave bus, and the control circuitry is configured to operate in a power management mode in response to a control signal received over the host slave bus, wherein when the control circuitry is in the power management mode, said control circuitry asserts a voltage control signal capable of setting the supply voltage to a predetermined value.

13. A graphics processing device, including:

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem;

multiplexing circuitry having inputs coupled to a first node at which a host clock is asserted and a second node at which a first device clock is asserted, and having at least one output coupled to the subsystem clock circuitry;

control circuitry coupled to the subsystem clock circuitry and to the multiplexing circuitry;

a host slave bus, wherein each of the first subsystem and the second subsystem includes a host register connected along the host slave bus; and

a host slave unit coupled to the host slave bus, and configured to be coupled to a system bus so as to provide an interface between the system bus and the host slave bus,

wherein the control circuitry includes a host register array connected along the host slave bus, the control circuitry is configured to operate in a subsystem clock management mode in response to a first set of control bits in a first host register of the host register array, and the control circuitry is configured to operate in a device clock management mode in response to a second set of control bits in a second host register of the host register array.

14. The device of claim 13, wherein when the control circuitry operates in the subsystem clock management mode, the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle.

15. The device of claim 14, wherein when the control circuitry operates in the subsystem clock management mode, the control circuitry causes the multiplexing circuitry to assert the first device clock to the subsystem clock circuitry, so that the first device clock is asserted to the first subsystem clock branch and to the second subsystem clock branch.

16. The device of claim 14, wherein when the control circuitry operates in the device clock management mode,

the control circuitry causes the multiplexing circuitry to assert the host clock to the subsystem clock circuitry, so that the host clock is asserted to the first subsystem clock branch and to the second subsystem clock branch.

17. The device of claim 16, also including:

device clock generation circuitry configured to operate in a mode in which it generates the first device clock and asserts said first device clock to said second node,

and wherein when the control circuitry operates in the device clock management mode, the control circuitry causes the device clock generation circuitry to disable generation of the first device clock.

18. The device of claim 14, wherein the control circuitry is coupled to the first subsystem, the first subsystem is configured to assert to the control circuitry a status signal indicative of whether said first subsystem is idle, the first subsystem clock branch includes logic circuitry having a first state allowing assertion of the first subsystem clock to the first subsystem and a second state preventing assertion of the first subsystem clock to the first subsystem, and the control circuitry is configured to assert a control signal to the logic circuitry in response to the status signal during the subsystem clock management mode, wherein the control signal selects the first state when the status signal does not indicate that the first subsystem is idle and the control signal selects the second state when the status signal indicates that the first subsystem is idle.

19. The device of claim 13, wherein the control circuitry is configured to operate in a second device clock management mode in response to a third set of control bits in the second host register of the host register array.

20. The device of claim 19, also including:

device clock generation circuitry configured to operate in a mode in which it generates the first device clock and asserts said first device clock to said second node,

wherein when the control circuitry operates in the device clock management mode and in the second device clock management mode, the control circuitry causes the multiplexing circuitry to assert the host clock to the subsystem clock circuitry, so that the host clock is asserted to the first subsystem clock branch and to the second subsystem clock branch,

when the control circuitry operates in the device clock management mode, the control circuitry causes the device clock generation circuitry to disable generation of the first device clock, and

when the control circuitry operates in the second device clock management mode, the control circuitry allows the device clock generation circuitry to generate the first device clock.

21. The device of claim 13, wherein said device is an integrated circuit.

22. The device of claim 13, wherein said device is a graphics processing portion of an integrated circuit.

23. The device of claim 13, wherein the control circuitry is configured to operate in a power management mode in response to a third set of control bits in a third host register of the host register array, the device is configured to be coupled to a voltage regulator so as to receive a supply voltage generated by the voltage regulator, the control circuitry is coupled to the host slave bus, and the control circuitry is configured to operate in a power management mode in response to a control signal received over the host slave bus, and wherein when the control circuitry is in the power management mode, said control circuitry asserts a voltage control signal capable of setting the supply voltage to a predetermined value.

24. The device of claim 13, also including:

host clock generation circuitry coupled to the control circuitry and configured to operate in a mode in which it generates the host clock and asserts said host clock at said first node,

wherein the control circuitry is configured to operate in a host clock management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the host clock management mode, the control circuitry causes the host clock generation circuitry to disable generation of the host clock.

25. The device of claim 13, wherein the control circuitry is configured to operate in a peak power management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the peak power management mode, the control circuitry causes the frequency of at least one clock asserted at at least one node of the device to be lowered whenever power consumption by the device rises to a predetermined threshold.

26. A system, including:

a system bus;

a CPU connected along the system bus; and

a graphics processing device connected along the system bus, wherein the graphics processing device includes;

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry-coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle; and

wherein the control circuitry is further configured to cause either of the first or second subsystems to respond to an access even though the first or second subsystem is idle.

27. The system of claim 26, wherein the device also includes:

device clock generation circuitry configured to generate at least a first device clock, wherein the device clock generation circuitry is coupled to the subsystem clock circuitry, the first subsystem clock branch asserts the first subsystem clock to the first subsystem in response to the first device clock, the second subsystem clock branch asserts the second subsystem clock to the second subsystem in response to the first device clock, and the control circuitry and the device clock generation circuitry are configured to operate in a device clock management mode in which the control circuitry selectively disables and enables generation of the first device clock by the device clock generation circuitry.

28. The system of claim 26, also including:

at least one input device connected along the system bus, and

wherein the CPU and the graphics processing device are configured to operate in a frame generation mode in which frames of image data are generated by the graphics processing device at a selected frame rate, where the selected frame rate is a selected one of a set of predetermined frame rates, and the CPU is configured to respond to control data asserted from the input device over the system bus by causing the device to enter the frame generation mode, where the control data determines the selected frame rate.

30. The system of claim 28, also including:

a voltage regulator coupled to the device and configured to assert a supply voltage to the device, wherein the control circuitry is coupled to the host slave bus, the control circuitry is configured to operate in a power management mode in response to a control signal received over the host slave bus, wherein

when the control circuitry is in the power management mode, the control circuitry assets a voltage control signal to the voltage regulator, and the voltage regulator responds to said voltage control signal by operating in such a manner that the supply voltage has a predetermined value.

47. The system as in claim 28, wherein the input device is user operated to select the frame rate from a plurality of frame rates.

29. A system, including:

a system bus;

a CPU connected along the system bus; and

a graphics processing device connected along the system bus, wherein

the graphics processing device includes;

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle;

a host slave bus, wherein each of the first subsystem and the second subsystem includes a host register connected along the host slave bus; and

a host slave unit coupled between the host slave bus and the system bus so as to provide an interface between the system bus and the host slave bus.

31. A system, including:

a system bus;

a CPU connected along the system bus; and

a graphics processing device connected along the system bus, wherein

the graphics processing device includes;

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle;

host clock generation circuitry configured to generate a host clock;

device clock generation circuitry configured to generate at least one device clock including a first device clock; and

multiplexing circuitry having inputs coupled to the host clock generation circuitry and the device clock generation circuitry, and having at least one output coupled to the subsystem clock circuitry,

wherein the control circuitry and the multiplexing circuitry are configured to operate in a mode in which the control circuitry causes the multiplexing circuitry to assert a selected one of the host clock and the first device clock to the subsystem clock circuitry, and wherein the first subsystem clock branch asserts the first subsystem clock to the first subsystem in response to said selected one of the host clock and the first device clock, and the second subsystem clock branch asserts the second subsystem clock to the second subsystem in response to said selected one of the host clock and the first device clock.

32. A system, including:

a system bus;

a CPU connected along the system bus; and

a graphics processing device connected along the system bus, wherein the graphics processing device includes;

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem;

multiplexing circuitry having inputs coupled to a first node at which a host clock is asserted and a second node at which a first device clock is asserted, and having at least one output coupled to the subsystem clock circuitry;

control circuitry coupled to the subsystem clock circuitry and to the multiplexing circuitry;

a host slave bus, wherein each of the first subsystem and the second subsystem includes a host register connected along the host slave bus; and

a host slave unit coupled to the host slave bus, and configured to be coupled to a system bus so as to provide an interface between the system bus and the host slave bus,

wherein the control circuitry includes a host register array connected along the host slave bus, the control circuitry is configured to operate in a subsystem clock management mode in response to a first set of control bits in a first host register of the host register array, and the control circuitry is configured to operate in a device clock management mode in response to a second set of control bits in a second host register of the host register array.

33. The system of claim 32, wherein when the control circuitry operates in the subsystem clock management mode, the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle.

34. The system of claim 32, wherein when the control circuitry operates in the device clock management mode,

the control circuitry causes the multiplexing circuitry to assert the host clock to the subsystem clock circuitry, so that the host clock is asserted to the first subsystem clock branch and to the second subsystem clock branch.

35. The system of claim 34, also including:

device clock generation circuitry configured to operate in a mode in which it generates the first device clock and asserts said first device clock to said second node,

and wherein when the control circuitry operates in the device clock management mode, the control circuitry causes the device clock generation circuitry to disable generation of the first device clock.

36. The system of claim 32, wherein the control circuitry is configured to operate in a second device clock management mode in response to a third set of control bits in the second host register of the host register array.

37. The system of claim 36, wherein the device also includes:

device clock generation circuitry configured to operate in a mode in which it generates the first device clock and asserts said first device clock to said second node,

wherein when the control circuitry operates in the device clock management mode and in the second first device generation mode, the control circuitry causes the multiplexing circuitry to assert the host clock to the subsystem clock circuitry, so that the host clock is asserted to the first subsystem clock branch and to the second subsystem clock branch,

when the control circuitry operates in the device clock management mode, the control circuitry causes the device clock generation circuitry to disable generation of the first device clock, and

when the control circuitry operates in the second device clock management mode, the control circuitry allows the device clock generation circuitry to generate the first device clock.

38. The system of claim 32, also including:

a voltage regulator coupled to the device and configured to assert a supply voltage to the device,

wherein the control circuitry is configured to operate in a power management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the power management mode, the control circuitry asserts a voltage control signal to the voltage regulator, and the voltage regulator responds to said voltage control signal by operating in such a manner that the supply voltage has a predetermined value.

39. The system of claim 32, wherein the device also includes:

host clock generation circuitry coupled to the control circuitry and configured to operate in a mode in which it generates the host clock and asserts said host clock at said first node,

wherein the control circuitry is configured to operate in a host clock management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the host clock management mode, the control circuitry causes the host clock generation circuitry to disable generation of the host clock.

40. The system of claim 32, wherein the control circuitry is configured to operate in a peak power management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the peak power management mode, the control circuitry causes the frequency of at least one clock asserted at at least one node of the device to be lowered whenever power consumption by the device rises to a predetermined threshold.

41. The system of claim 32, also including:

a voltage regulator coupled to the device and configured to assert a supply voltage to the device,

wherein the control circuitry is configured to operate in a peak power management mode in response to a third set of control bits in a third host register of the host register array, wherein when the control circuitry is in the peak power management mode, the control circuitry asserts a voltage control signal to the voltage regulator when power consumption by the device rises to a predetermined threshold, and the voltage regulator responds to said voltage control signal by operating in such a manner that the supply voltage is reduced to a predetermined value.

42. The system of claim 32, also including:

at least one input device connected along the system bus, and

wherein the CPU and the graphics processing device are configured to operate in a frame generation mode in which frames of Image data are generated by the graphics processing device at a selected frame rate, where the selected frame rate is a selected one of a set of predetermined frame rates, and the CPU is configured to respond to control data asserted from the input device over the system bus by causing the device to enter the frame generation mode, where the control data determines the selected frame rate.

43. A graphics processing device, including:

at least two subsystems, including a first subsystem and a second subsystem;

subsystem clock circuitry including at least a first subsystem clock branch coupled and configured to assert a first subsystem clock to the first subsystem and a second subsystem clock branch coupled and configured to assert a second subsystem clock to the second subsystem; and

control circuitry coupled to the subsystem clock circuitry, wherein the control circuitry and the subsystem clock circuitry are configured to operate in a subsystem clock management mode in which the control circuitry prevents the first subsystem clock branch from asserting the first subsystem clock to the first subsystem when said first subsystem is idle, and the control circuitry prevents the second subsystem clock branch from asserting the second subsystem clock to the second subsystem when said second subsystem is idle;

a system bus;

a CPU connected along the system bus;

the graphics processing device being connected along the system bus; and

at least one input device connected along the system bus,

wherein the CPU and the graphics processing device are configured to operate in a frame generation mode in which frames of image data are generated by the graphics processing device at a selected frame rate, the selected frame rate is a selected one of a set of predetermined frame rates, and the CPU is configured to respond to control data asserted from the input device over the system bus by causing the device to enter the frame generation mode, where the control data determines the selected frame rate.

44. The device of claim 43, wherein the set of predetermined frame rates includes a maximum frame rate and a reduced frame rate, the graphics processing device generates-pixels of the image data at a first pixel rate when operating in the frame generation mode with the selected frame rate equal to the maximum frame rate, and the graphics processing device generates pixels of the image data at said first pixel rate but with idle time between generation of at least two subsets of the pixels when operating in the frame generation mode with the selected frame rate equal to the reduced frame rate.

45. The device as in claim 43, wherein the input device is user operated to select the frame rate from a plurality of frame rates.

46. The device as in claim 43, wherein at least one of the first subsystem clock and the second subsystem clock operate at a first frequency during each of the plurality of frame rates, the CPU controller, the GPU to alter a vertical blanking interval between subsets of pixels of a frame of video data, thereby altering the frame rate.