SoC Display Controller Drives Frames with CPUs Powered Down
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Solution Overview
Problem
Mobile devices face challenges in reducing power consumption while maintaining display functionality, especially when central processing units (CPUs) are powered down.
Innovation Solution
A system on a chip (SoC) that includes a display controller, a memory controller, and a power management circuit, allowing the display controller and memory controller to remain powered on while CPUs are powered off, enabling the display of prerendered frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the display controller and CPUs are powered on together, then the system can provide full functionality and user interaction, but power consumption increases
Solution Approach 1:
The system divides power domains into separate controllable units: CPUs, display controller, and memory controller can be independently powered on or off. This segmentation allows the display controller to remain operational while CPUs are powered down, reducing overall power consumption while maintaining display functionality.
Solution Approach 2:
Frames are prerendered and stored in memory before the CPUs are powered down. The display controller reads these pre-rendered frames from memory and displays them autonomously without requiring CPU intervention, enabling the system to maintain display output with minimal power consumption.
2Duration of action of moving object
If the display controller remains powered on while CPUs are powered off, then battery life is extended, but the system cannot perform real-time processing
Solution Approach 1:
The system performs frame rendering in advance while CPUs are active, storing completed frames in memory. When CPUs are powered down to extend battery life, the display controller continuously reads and displays these pre-rendered frames, maintaining visual output without requiring real-time CPU processing.
Solution Approach 2:
The display controller reads frame data from memory and generates display output independently of CPU activity. This copying mechanism allows the display system to operate autonomously using pre-prepared frame data, decoupling display functionality from real-time CPU processing requirements.
3Speed
If all components are powered on continuously, then the system responds immediately to user input, but power consumption is maximized
Solution Approach 1:
The system implements separate power domains that allow selective powering of components. The display controller maintains operation independently of CPU power state, enabling continuous display functionality with minimal power consumption while CPUs can be powered down when not needed for processing.
Solution Approach 2:
The display controller autonomously reads frames from memory and drives the display without requiring continuous CPU intervention. This self-service capability allows the display subsystem to operate independently, maintaining system responsiveness for display-related tasks while minimizing overall power consumption.
Data Source
AI summary
In an embodiment, a system may include one or more processors forming central processing units (CPUs) in the system, a display controller configured to display frames on a display device, a memory controller configured to control a memory, and a power management circuit. The power management circuit may be configured to establish one of a plurality of power states in the system. In a first power state, the display controller and the memory controller are powered on while the CPUs are powered off. The display controller may be configured to read a plurality of prerendered frames from the memory and display the plurality of prerendered frames at times specified for each of the plurality of prerendered frames.