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AM6441: AM6441

Part Number: AM6441
Other Parts Discussed in Thread: AM3358,

Dear TI experts,

I'm currently migrating from a design based on AM3358 to one based on the newest family AM64x (in detail AM6441), and I'm facing a problem related to the ETH interface section.

In the previous design I interconnected ETH PHYs through MII interface (allowed by AM3358), but now it seems that AM64 Sitara processor family allows only RGMII or RMII interfaces, but NOT the MII one. Is this correct?

To support this theory I found out (in the datasheet) that AM6441 pins only refer to RGMII_xxx or RMII_xxx:

After that, I read also the AM64x TRM and I found this PRU_ICSSG section, which instead refers to MII ports:

So, the question is "Is MII interface supported even in AM64x processor family or not"? And if the answer is YES, which are the pins to be connected with ETH PHYS for a complete MII setup? RMII_xxx pins are only two (RXD0/RXD1 and TXD0/TXD1), so it seems they are not the right ones...

Thank you in advance for your help.

Flavio

  • Hello Flavio,

    Thank you for posting. It looks like we need to clarify the datasheet documentation.

    I expect CPSW Ethernet to support RMII and RGMII. I will need to take a couple days to research about PRU Ethernet. The rest of my reply will discuss PRU Ethernet.

    INTRODUCTION

    Just because the pin signals are named after a particular interface, does not mean that other interfaces are not possible. For example, AM65x PRU pin names only reference RGMII, but the hardware can support RGMII, MII, SGMII depending on which ICSSG is used.

    Keep in mind there are two things to consider here:

    1) What is the hardware physically capable of? (this is what you would see in the datasheet)

    2) What can TI support? We might not have the software resources and hardware boards to write code and test it for every PRU Ethernet interface combination. So even if the hardware can support MII, we may not have current plans to write software that works with MII.

    OK, WHAT IS SUPPORTED? 

    The AM64x general purpose EVM (TMDS64GPEVM) User Guide indicates that the EVM was designed to allow RGMII or MII signals to connect to the PRU Ethernet. The RGMII and MII signals go to the same PRU pins. So it looks like the hardware should support MII.

    I need a couple of days to take a look at whether we have plans to support PRU Ethernet MII in software.

    Regards,

    Nick

  • Hello Nick,

    thank you very much for your kind reply. You couldn't be clearer than this! 

    I'll wait for you to verify whether TI plans to support SW for MII communication or not.

    Again, thank you for your exhaustive answer.

    Flavio

  • Hello Flavio,

    Are you looking at controlling the PRU Ethernet from Linux A53 or RTOS / bare metal R5?

    We will add PRU Ethernet support on AM64x in SDK 8.0 (which will be out next month). PRU Ethernet will be supported on all three OS options.

    On Linux, that PRU Ethernet support will be tested on RGMII. I am submitting a request to add MII support as well. I expect the request to get approved, but I do not have a timeline for when it will get added (probably late 2021 or 2022 if the feature request goes through).

    I have not yet checked on the details of AM64x RTOS/bare metal PRU Ethernet as of SDK 8.0, but I should have another update next week.

    Regards,

    Nick

  • Hello Nick,

    As for AM3385 (ti-processor-sdk-linux-rt-am335x-evm-07.03.00.005) we expect to control PRU Ethernet through Linux over A53. 

    Good to hear that SDK8.0 will add PRU ETH support for AM64x family. In practical terms, what do you mean with "PRU Ethernet support will be tested on RGMII" on Linux?? Does it mean that MII support is provided with the new SDK but not yet tested? 

    If you have any update regarding your request to add MII support, please let me know.

    Thank you.

    Flavio

  • Hello Flavio,

    I am on vacation for the next couple days. I will respond with more information next week.

    Regards,

    Nick

  • Hello Flavio,

    Thanks for your patience. My understanding is that the Linux driver that adds PRU Ethernet RGMII support in SDK 8.0 will require some modifications to support both RGMII and MII. However, I am double checking with the developers. I will correct this post if anything is wrong.

    Regards,

    Nick