Periodic Link State Querying

Oct 13, 2025 by thesweetdesigns.com 133 views

Introduction

In modern embedded systems, efficient communication between components is crucial for optimal performance. The Ethernet configuration interface (Ethernet_cfg_if) plays a vital role in facilitating communication between the MAC (Media Access Controller) and PHY (Physical Layer) drivers. However, the current implementation of XC interface based notifications in Ethernet_cfg_if is channel-heavy, leading to potential performance issues. In this article, we will explore the existing solution, its limitations, and propose an alternative solution that is optimal in terms of channel usage, does not compromise the MAC speed, and is always enabled.

Current Implementation

The MII Ethernet server (mii_ethernet_server()) uses the [[ notification ]] and [[ clears_notification ]] functions to initiate communication with the client. Specifically, the mac_started() notification is used to inform the MAC that it has started, and the ack_mac_start() notification is used to acknowledge this event. This notification is essential for the MAC to receive the current link state after it restarts after an exit() command.

However, the current implementation has a limitation. The PHY driver shares the link state with the MAC only when there is a change to the link state. As a result, when the MAC restarts after an exit() command, it continues to see the link as down, leading to incorrect link state queries from clients.

The Need for a Channel-Efficient Solution

The current implementation of XC interface based notifications is channel-heavy, using one extra channel per client on the Ethernet_cfg_if interface. This is far from ideal, especially in dual MAC scenarios. To address this issue, we have wrapped the notification mechanism in a #if ENABLE_MAC_START_NOTIFICATION directive, allowing it to be enabled selectively for applications. However, this is not an optimal solution, as it does not translate well to dual MAC cases.

Alternative Solutions

There are two alternative solutions that can be explored to address the channel-inefficiency of the current implementation:

Periodic Link State Querying: The PHY driver can query the link state from the MAC periodically and update it if it sees the link state saved in the MAC is different from the current link state. However, this approach would cause unnecessary interruptions to the MAC from the PHY driver, which is not ideal.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state. However, this would require an API change for both the MII Ethernet server and the dual DP83826E PHY driver.

Optimal Solution

To address the channel-inefficiency of the current implementation, we propose an alternate solution that is optimal in terms of channel usage, does not compromise the MAC speed, and is always enabled. The proposed solution involves the following steps:

MAC-Initiated Link State Query: The MAC can initiate a link state query to the PHY driver, which will respond with the current link state.
PHY Driver-Initiated Link State Update: The PHY driver can periodically query the link state from the MAC and update it if it sees the link state saved in the MAC is different from the current link state.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state.

Implementation

To implement the proposed solution, the following changes can be made:

MAC-Initiated Link State Query: The MAC can be modified to initiate a link state query to the PHY driver using a new API call (e.g., get_link_state()).
PHY Driver-Initiated Link State Update: The PHY driver can be modified to periodically query the link state from the MAC and update it if it sees the link state saved in the MAC is different from the current link state.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state.

Conclusion

In conclusion, the current implementation of XC interface based notifications in Ethernet_cfg_if is channel-heavy, leading to potential performance issues. To address this issue, we have proposed an alternate solution that is optimal in terms of channel usage, does not compromise the MAC speed, and is always enabled. The proposed solution involves the MAC-initiated link state query, PHY driver-initiated link state update, and dedicated channel. By implementing these changes, we can ensure efficient communication between the MAC and PHY drivers, leading to optimal performance in embedded systems.

Future Work

Future work can focus on implementing the proposed solution and testing its performance in various scenarios. Additionally, further optimization of the channel usage can be explored to ensure that the solution is optimal in terms of channel usage.

References

[1] MII Ethernet Server (mii_ethernet_server()) API documentation.
[2] Dual DP83826E PHY Driver (dual_dp83826e_phy_driver()) API documentation.
[3] Ethernet configuration interface (Ethernet_cfg_if) documentation.
Frequently Asked Questions (FAQs) on Optimizing XC Interface Based Notifications in Ethernet_cfg_if =====================================================================================

Q: What is the current implementation of XC interface based notifications in Ethernet_cfg_if?

A: The current implementation of XC interface based notifications in Ethernet_cfg_if uses the [[ notification ]] and [[ clears_notification ]] functions to initiate communication with the client. Specifically, the mac_started() notification is used to inform the MAC that it has started, and the ack_mac_start() notification is used to acknowledge this event.

Q: What is the limitation of the current implementation?

A: The current implementation has a limitation. The PHY driver shares the link state with the MAC only when there is a change to the link state. As a result, when the MAC restarts after an exit() command, it continues to see the link as down, leading to incorrect link state queries from clients.

Q: Why is the current implementation channel-heavy?

A: The current implementation of XC interface based notifications is channel-heavy, using one extra channel per client on the Ethernet_cfg_if interface. This is far from ideal, especially in dual MAC scenarios.

Q: What are the alternative solutions proposed to address the channel-inefficiency of the current implementation?

A: There are two alternative solutions proposed to address the channel-inefficiency of the current implementation:

Periodic Link State Querying: The PHY driver can query the link state from the MAC periodically and update it if it sees the link state saved in the MAC is different from the current link state.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state.

Q: What is the proposed optimal solution to address the channel-inefficiency of the current implementation?

A: The proposed optimal solution involves the following steps:

MAC-Initiated Link State Query: The MAC can initiate a link state query to the PHY driver, which will respond with the current link state.
PHY Driver-Initiated Link State Update: The PHY driver can periodically query the link state from the MAC and update it if it sees the link state saved in the MAC is different from the current link state.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state.

Q: How can the proposed solution be implemented?

A: To implement the proposed solution, the following changes can be made:

MAC-Initiated Link State Query: The MAC can be modified to initiate a link state query to the PHY driver using a new API call (e.g., get_link_state()).
PHY Driver-Initiated Link State Update: The PHY driver can be modified to periodically query the link state from the MAC and update it if it sees the link state saved in the MAC is different from the current link state.
Dedicated Channel: A dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be established, allowing the server to query the link state.

Q: What are the benefits of the proposed solution?

A: The proposed solution has several benefits, including:

Optimal channel usage: The proposed solution optimizes channel usage by reducing the number of channels required for communication between the MAC and PHY drivers.
Improved performance: The proposed solution improves performance by reducing the latency associated with periodic link state querying.
Increased reliability: The proposed solution increases reliability by ensuring that the link state is updated correctly and consistently.

Q: What are the next steps for implementing the proposed solution?

A: The next steps for implementing the proposed solution include:

Implementing the MAC-Initiated Link State Query: Modify the MAC to initiate a link state query to the PHY driver using a new API call (e.g., get_link_state()).
Implementing the PHY Driver-Initiated Link State Update: Modify the PHY driver to periodically query the link state from the MAC and update it if it sees the link state saved in the MAC is different from the current link state.
Establishing a Dedicated Channel: Establish a dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) to allow the server to query the link state.

Q: What are the potential challenges associated with implementing the proposed solution?

A: The potential challenges associated with implementing the proposed solution include:

API changes: The proposed solution requires API changes to the MAC and PHY drivers, which can be challenging to implement.
Channel establishment: Establishing a dedicated channel between the MII Ethernet server (mii_ethernet_server()) and the dual DP83826E PHY driver (dual_dp83826e_phy_driver()) can be challenging.
Testing and validation: Testing and validating the proposed solution can be challenging due to the complexity of the system.