8.5. Developing Ethernet based applications with Linux + RTOS

8.5.1. Introduction

Common Port Switch (CPSW) provides Ethernet packet communication for the device. The total ports includes the following:

  • Internal Host Port which provides the packet streaming interface to the device cores

  • External MAC Port supporting the following:

    • Reduced Media Independent Interface (RMII)

    • Reduced Gigabit Media Independent Interface (RGMII)

Note that the MII modes supported vary based on device variant, please refer to the device’s TRM for the MII modes supported for each CPSW instance..

  • J721S2 has 2 instances

    • 2-port (CPSW2G) in MCU domain (MCU_CPSW0)

    • 2-port (CPSW2G) in Main domain (CPSW2)

Note

CPSW instance is commonly referred with number of ports suffixed to the CPSW. 2 port instances are referred to as CPSW2G.

8.5.2. CPSW Support Software

  • Enet LLD is low level driver residing in the PDK. It supports both CPSW2G instances in the SoC and provides HAL layer for higher level stacks.

  • TCP/IP Stack - Open source lwIP stack.

    • lwIP network interface driver (lwipif) is adaptation layer connecting Enet LLD to lwIP stack. This lwIP adaptation layer is part of Enet LLD and supports both CPSW2G instances with lwIP TCP/IP applications.

  • PTP Stack - PDK includes a test PTP stack used mainly to validate and demonstrate time synchronization integration with CPSW.

    • Note that this is not a production stack.

The scope of this developer note is to point to various documentation and source code resources available within the SDK (RTOS) to understand and use CPSW2G using Enet LLD in an user application.

8.5.3. Documentation References

SDK Component

Documentation

Description

Section

PDK

LINK

Enet API guide

Enet Driver

PDK

LINK

Enet Module User’s Guide - driver, examples

Full document

PDK

LINK

Enet Integration Guide - further details about Enet LLD initialization

Full document

PDK

LINK

lwIP network interface User’s Guide and Migration Guide

Full document

PDK

LINK

PHY integration guide - to help integrating new PHY with Enet LLD

Implementing a New PHY Driver

PDK

LINK

Link Configuration Guidelines

Link Configuration Guidelines

8.5.4. Source Code References

8.5.4.1. Enet LLD

SDK Component

File / Folder

Description

PDK

pdk/packages/ti/drv/enet/enet.h

Enet LLD interface for both CPSW2G instances

PDK

pdk/packages/ti/drv/enet/include/phy/enetphy.h

PHY LLD driver interface

PDK

pdk/packages/ti/drv/enet/lwipif/inc/lwipif2enet_appif.h

App interface of the Enet-based lwIP network interface driver

PDK

pdk/packages/ti/drv/board/

Board drivers for GESI board

8.5.4.2. lwIP

SDK Component

File / Folder

Description

PDK

pdk/packages/ti/transport/lwip/lwip-stack/src/include

lwIP TCP/IP header files

PDK

pdk/packages/ti/transport/lwip/lwip-contrib/apps

lwIP contrib application header files

8.5.4.3. Example applications

SDK Component

File / Folder

Decription

PDK

pdk/packages/ti/drv/enet/examples/enet_loopback_test

MCU CPSW2G internal loopback example mcu1_0, and Main CPSW2G on mcu2_0

PDK

pdk/packages/ti/drv/enet/examples/enet_lwip_example

lwIP integration example for MCU CPSW2G on mcu1_0 and Main CPSW2G on mcu2_0

The MAC port allocation in TI J721S2 EVM is as follows:

  • MCU CPSW2G - use the Ethernet port located in the J7X Common Processor Board labeled as MCU_ENET.

  • Main CPSW2G - use the Ethernet port located in the GESI board labeled as PRG0_RGMII1_B.

Make sure that the correct port is used when running the Enet LLD example applications.

8.5.5. Getting started on CPSW

  • Refer to Enet module documentation [LINK] for information about Enet LLD key APIs and the Examples section for available examples on this platform.

  • Refer to Enet LLD integration guide [LINK] for a further details about the initialization of an Ethernet peripheral via Enet LLD.

8.5.5.1. Configuring Ethernet port mode

Based on your board configuration, port can be in RMII, RGMII etc. mode. You need to do below to configure port in required mode.

  • Configure port ENET control to required mode using board library.

  • Configure CPSW interface.

    For RMII, it should be configured to below:

    interface->layerType    = ENET_MAC_LAYER_MII;
interface->sublayerType = ENET_MAC_SUBLAYER_REDUCED;
interface->variantType  = ENET_MAC_VARIANT_NONE;

    For RGMII, it should be configured to below:

    interface->layerType    = ENET_MAC_LAYER_GMII;
interface->sublayerType = ENET_MAC_SUBLAYER_REDUCED;
interface->variantType  = ENET_MAC_VARIANT_NONE;

8.5.5.2. Run Enet loopback example

  • We recommend running Enet loopback example first as this doesn’t have any dependency on board/EVM set up

  • See PDK user guide [LINK], section Build Steps for build steps

8.5.5.3. Run Enet lwIP example (TCP/IP example)

  • Once loopback example is run, you can run enet_lwip_example which uses lwIP stack for TCP/IP applications.

  • You need to connect EVM to PC running DHCP server. You should see IP printed on UART after running the example. The PDK Enet examples uses UART based on core it is running. Refer to PDK documentation for core-to-UART mapping. If you want to use static IP configuration, edit enet_lwip_example/lwipcfg.h to enable static IP.

  • You can ping to board using this IP address

  • You can also run iperf2 test (Enet LLD app is server, external PC is client).

8.5.5.4. Integrate new PHY in Enet

  • You need to add new PHY driver if existing PHY drivers present in enet/src/phy/* does not support PHY present on your Board.

  • Refer to PHY integration guide [LINK] which has details for adding support for new PHY in Enet LLD.

8.5.5.5. Modify the examples to support your board configuration

  • Modify examples to change PHY address, speed (10M/100M/1G etc.) setting, mode (RMII/RGMII etc.) settings.

  • Rebuild the example and run on your board. You should be able to see data transfer happening.