PCIe CLKREQ Emulator for L1 Sub-State Power Management
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Solution Overview
Problem
Current PCIe standards require all endpoint devices on a network to support L1 power sub-states for efficient power management, which is not universally adopted, leading to excessive power consumption when not all devices can transition to these sub-states.
Innovation Solution
Implementing a CLKREQ emulator in PCIe devices that initiates an L1 sub-state timer when an L1 idle state is detected, allowing devices to transition to L1.1 or L1.2 power sub-states even if not all devices on the network are configured for it, by de-asserting the CLKREQ_in signal and managing power states through a controller and signal detect circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If all endpoint devices on a PCIe network are required to support L1 power sub-states for efficient power management, then power consumption is reduced, but device compatibility and ease of operation deteriorate when not all devices can transition to these sub-states
Solution Approach 1:
A CLKREQ emulator is introduced as an intermediary component that generates clock request signals to enable L1 sub-state transitions. The emulator acts as a mediator between devices that support L1 sub-states and those that don't, allowing the former to enter low-power states while maintaining compatibility with the latter by providing the necessary clock signaling infrastructure.
Solution Approach 2:
The power management capability is segmented so that individual devices can independently transition to L1 sub-states based on their own capabilities and the presence of the CLKREQ emulator, rather than requiring universal support across all devices on the network. This allows mixed-configuration networks to achieve partial power savings.
2Use of energy by moving object
If L2 and L3 power states are used to reduce power consumption, then energy efficiency improves, but transition time increases significantly
Solution Approach 1:
The patent changes the power state parameters by introducing L1 sub-states (L1.1, L1.2) that offer intermediate power consumption levels between L0 and L2/L3. These sub-states provide a better balance between power savings and transition time, allowing devices to achieve significant power reduction without the millisecond-scale transition delays of deeper sleep states.
3Use of energy by moving object
If L1 power sub-states are enabled on a PCIe network, then power consumption is reduced, but reliability deteriorates if not all devices support the feature
Solution Approach 1:
The CLKREQ emulator serves as a reliability mechanism by providing clock request signaling that enables L1 sub-state transitions for capable devices while maintaining backward compatibility with devices that don't support the feature. This intermediary ensures that the network can operate reliably in mixed-configuration scenarios.
Solution Approach 2:
The system implements partial L1 sub-state enablement where only devices capable of entering these states do so, while other devices continue to operate in standard power states. This partial action approach allows the network to achieve power savings from capable devices without compromising overall network reliability or functionality.
Data Source
AI summary
The present disclosure describes methods and systems for data storage or other devices that are L1 sub-state capable, to be able to enter these sub-states while on the same network or bus as a device not enabled for transition to an L1 sub-state. In some embodiments, when an LTSSM circuit in a MAC of a PCIe device indicates an L1 idle state, an L1 sub-state (L1SS) timer is initiated in a CLKREQ on the device. Upon expiration of the timer, a CLKREQ_in emulator de-asserts its signal on the MAC, causing the MAC to enter an L1SS.