L- and H-tile Avalon® Streaming and Single Root I/O Virtualization (SR-IOV) Intel® FPGA IP for PCI Express* User Guide

ID 683111
Date 3/07/2022
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents

4.6.5. Power Management

Table 22.  Power Management Parameters

Parameter

Value

Description

Endpoint L0s acceptable latency

Maximum of 64 ns

Maximum of 128 ns

Maximum of 256 ns

Maximum of 512 ns

Maximum of 1 us

Maximum of 2 us

Maximum of 4 us

No limit

This design parameter specifies the maximum acceptable latency that the device can tolerate to exit the L0s state for any links between the device and the root complex. It sets the read-only value of the Endpoint L0s acceptable latency field of the Device Capabilities Register (0x084).

This Endpoint does not support the L0s or L1 states. However, in a switched system there may be links connected to switches that have L0s and L1 enabled. This parameter is set to allow system configuration software to read the acceptable latencies for all devices in the system and the exit latencies for each link to determine which links can enable Active State Power Management (ASPM). This setting is disabled for Root Ports.

The default value of this parameter is 64 ns. This is a safe setting for most designs.

Endpoint L1 acceptable latency

Maximum of 1 us

Maximum of 2 us

Maximum of 4 us

Maximum of 8 us

Maximum of 16 us

Maximum of 32 us

Maximum of 64 ns

No limit

This value indicates the acceptable latency that an Endpoint can withstand in the transition from the L1 to L0 state. It is an indirect measure of the Endpoint’s internal buffering. It sets the read-only value of the Endpoint L1 acceptable latency field of the Device Capabilities Register.

This Endpoint does not support the L0s or L1 states. However, a switched system may include links connected to switches that have L0s and L1 enabled. This parameter is set to allow system configuration software to read the acceptable latencies for all devices in the system and the exit latencies for each link to determine which links can enable Active State Power Management (ASPM). This setting is disabled for Root Ports.

The default value of this parameter is 1 µs. This is a safe setting for most designs.

The Intel L-/H-Tile Avalon-ST for PCI Express and Intel L-/H-Tile Avalon-MM for PCI Express IP cores do not support the L1 or L2 low power states. If the link ever gets into these states, performing a reset (by asserting pin_perst, for example) allows the IP core to exit the low power state and the system to recover.

These IP cores also do not support the in-band beacon or sideband WAKE# signal, which are mechanisms to signal a wake-up event to the upstream device.