USB Host Controller Context Preservation for Fast Wake

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Solution Overview

Problem

Mobile computing devices face significant delays when waking up from deep sleep due to the need for USB controller re-enumeration, which resets and loses connection information, leading to slow device recovery and potential issues with downstream devices like modems.

Innovation Solution

A method where a USB driver receives sleep and resume commands, stores and restores the USB host controller context, and manages power and clock states to maintain connection information, allowing for seamless wake-up without re-enumeration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the USB controller is reset during deep sleep wake-up, then the processor can be fully activated, but the connection information is lost and re-enumeration is required causing delay

Engineering Contradiction:

Improveprocessor activationVSAvoidwake-up delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The USB controller context is saved before the deep sleep state is entered, so that when wake-up occurs, the context is already preserved and can be restored immediately without requiring re-enumeration. This preliminary preservation of context eliminates the need for time-consuming re-detection and re-initialization of USB devices.

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the USB controller is kept on during sleep mode, then connection information is maintained, but power consumption increases

Engineering Contradiction:

Improvewake-up timeVSAvoidpower consumption

Core Design Contradiction:

Loss of timeVSUse of energy by moving object

Solution Approach 1:

The invention extracts only the essential USB controller context (configuration data, connection information, and state parameters) from the full system state and preserves it separately in non-volatile memory. This allows the USB controller to be powered down completely during deep sleep while its critical context remains preserved, enabling fast wake-up without maintaining continuous power consumption.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If complete re-enumeration is performed after deep sleep, then all USB devices are detected, but the process takes 1-2 seconds adding significant delay

Engineering Contradiction:

Improvedevice detectionVSAvoidwake-up speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Instead of discarding the USB controller context during deep sleep and recovering it through re-enumeration, the invention preserves the context intact and restores it directly upon wake-up. This recovery approach eliminates the need for time-consuming re-detection and re-initialization of USB devices, significantly improving wake-up speed while maintaining reliable device detection.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS8850252B2USB host wake from sleep state for mobile devices

Publication Date: 2014.09.30 NVIDIA CORP

AI summary

A USB host for wakeup from a sleep state includes a hold memory, a USB host controller, and a USB driver. When going to sleep, the USB driver sends a suspend command to the USB host controller in response to receiving a sleep command. The USB driver also reads a controller context from the USB host controller and saves the controller context in the hold memory. Thereafter, the USB driver turns off one or more supply potentials and one or more clocks in the host controller, and returns a sleep acknowledgement. While in sleep, the interface pins are placed in a hold state and notification to the operating system are disabled.