Low-power GPU states for reducing power consumption

Patent metadata

Field	Value
Publication number	US-9158367-B2
Application number	US-201514643911-A
Country	US
Kind code	B2
Filing date	Mar 10, 2015
Priority date	Aug 9, 2011
Publication date	Oct 13, 2015
Grant date	Oct 13, 2015

Abstract

The disclosed embodiments provide a system that drives a display from a computer system. During operation, the system detects an idle state in a first graphics-processing unit (GPU) used to drive the display. During the idle state, the system switches from using the first GPU to using a second GPU to drive the display and places the first GPU into a low-power state, wherein the low-power state reduces a power consumption of the computer system.

First claim

What is claimed is:

1. A method for driving a display in a computer, comprising:
switching from using a first graphics process unit (GPU) to drive the display to using a second GPU to drive the display;
transitioning the first GPU into a low-power state subsequent to the switching, wherein transitioning the first GPU into the low-power state comprises powering off the first GPU and an interface with the first GPU, and maintaining power to a video memory of the first GPU;
prior to transitioning the first GPU into the low-power state, saving a GPU configuration state of the first GPU in the video memory in the first GPU;
detecting that the first GPU is to drive the display subsequent to transitioning the first GPU to the low-power state;
powering on the first GPU responsive to the detecting;
restoring the GPU configuration state from the video memory subsequent to the powering on; and
driving the display with the first GPU subsequent to the restoring.

2. The method of claim 1 , further comprising:
detecting a disabling condition for the first GPU; and
based on detecting the disabling condition, performing the switching and transitioning operations.

3. The method of claim 2 , wherein the disabling condition is an idle state for the first GPU.

4. The method of claim 1 , further comprising:
when the first GPU is in the low-power state, intercepting a graphics call to the first GPU;
restoring the first GPU from the low-power state;
switching from using the second GPU to drive the display to using the first GPU to drive the display; and
directing the graphics call to the first GPU.

5. The method of claim 4 , wherein intercepting the graphics call to the first GPU comprises:
acquiring a lock for the graphics call to the first GPU; and
queuing the graphics call.

6. The method of claim 1 , further comprising:
saving an interface configuration state of the interface with the first GPU in a memory in the computer; and
concurrently restoring the interface configuration state from the memory when restoring the GPU configuration state from the video memory.

7. The method of claim 1 , wherein switching from using the first GPU to drive the display to using the second GPU to drive the display comprises:
copying pixel values from a first framebuffer for the first GPU to a second framebuffer for the second GPU; and
initiating a switch from the first framebuffer to the second framebuffer as a signal source for driving the display.

8. The method of claim 1 , wherein the first GPU is a high-power GPU and the second GPU is a low-power GPU.

9. The method of claim 1 , wherein the interface is separate from the GPU.

10. The method of claim 9 , wherein the interface is coupled between the GPU and a central processing unit (CPU) in the computer.

11. A computer system that drives a display, comprising:
the display;
a first graphics processing unit (GPU);
a second GPU; and
a switching mechanism configured to:
switch from using the first GPU to drive the display to using the second GPU to drive the display;
transition the first GPU into a low-power state, wherein transitioning the first GPU into the low-power state comprises powering off the first GPU and an interface with the first GPU, and maintaining power to a video memory of the first GPU;
prior to transitioning the first GPU into the low-power state, save a GPU configuration state of the first GPU in the video memory in the first GPU;
detect that the first GPU is to drive the display subsequent to transitioning the first GPU to the low-power state;
power on the first GPU responsive to detecting that the first GPU is to drive the display;
restore the GPU configuration state from the video memory subsequent to powering on the GPU; and
drive the display with the first GPU subsequent to the restoring.

12. The computer system of claim 11 , wherein the switching mechanism is further configured to:
detect a disabling condition for the first GPU; and
based on detecting the disabling condition, performing the switching and transitioning operations.

13. The computer system of claim 12 , wherein the disabling condition is an idle state for the first GPU.

14. The computer system of claim 11 , further comprising:
a processor that implements a shim, comprising:
when the first GPU is in the low-power state, intercepting a graphics call to the first GPU;
based on the intercepted graphics call, causing the switching mechanism to perform operations for:
restoring the first GPU from the low-power state; and
switching from using the second GPU to drive the display to using the first GPU to drive the display; and
forwarding the graphics call to the first GPU.

15. The computer system of claim 14 , wherein, when intercepting the graphics call to the first GPU, the processor:
acquires a lock for the graphics call to the first GPU; and
queues the graphics call in a queue that holds zero or more previous graphics calls for the first GPU.

16. The computer system of claim 11 , further comprising:
a memory;
wherein the processor:
saves an interface configuration state of an interface with the first GPU in the memory; and
concurrently restores the interface configuration state from the memory when restoring the GPU configuration state from the video memory.

17. The computer system of claim 11 , wherein, when switching from using the first GPU to drive the display to using the second GPU to drive the display, the switching mechanism:
copies pixel values from a first framebuffer for the first GPU to a second framebuffer for the second GPU; and
initiates a switch from the first framebuffer to the second framebuffer as a signal source for driving the display.

18. The computer system of claim 11 , the first GPU is a high-power GPU and the second GPU is a low-power GPU.

19. A non-transitory computer-readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method for driving a display in the computer, the method comprising:
switching from using the first GPU to drive the display to using a second GPU to drive the display;
transitioning the first GPU into a low-power state, wherein transitioning the first GPU into the low-power state comprises powering off the first GPU and an interface with the first GPU, and maintaining power to a video memory of the first GPU;
prior to transitioning the first GPU into the low-power state, saving a GPU configuration state of the first GPU in the video memory in the first GPU;
detecting that the first GPU is to drive the display subsequent to transitioning the first GPU to the low-power state;
powering on the first GPU responsive to the detecting;
restoring the GPU configuration state from the video memory subsequent to the powering on; and
driving the display with the first GPU again subsequent to the restoring.

20. The computer-readable storage medium of claim 19 , further comprising:
detecting a disabling condition for the first GPU; and
based on detecting the disabling condition, performing the switching and transitioning operations.

21. The computer-readable storage medium of claim 19 , further comprising:
when the first GPU is in the low-power state, intercepting a graphics call to the first GPU;
restoring the first GPU from the low-power state;
switching from using the second GPU to drive the display to using the first GPU to drive the display; and
directing the graphics call to the first GPU.

Assignees

• Apple Inc

Inventors

• Hendry Ian C
• Koduri Rajabali M

Classifications

• G06F1/3206 Primary

  Monitoring of events, devices or parameters that trigger a change in power modality · CPC title

• G09G5/003

  Details of a display terminal, the details relating to the control arrangement of the display terminal and to the interfaces thereto (specific for a CRT G09G1/165; for a flat panel G09G3/2092) · CPC title

• Y02B60/1242

  Cross-Sectional Technologies · mapped topic

• G06F1/3265

  Power saving in display device · CPC title

• G09G5/399

  using two or more bit-mapped memories, the operations of which are switched in time, e.g. ping-pong buffers · CPC title