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AM5726: MII interface with a 10/100 PHY

Roger McCalman51
Intellectual 335 points
Part Number: AM5726

I have a embedded board loosly derived from the Am572x EVM. We have changed the PHY for the ethernet to be an MII rather RGMII as we only need ethernet for debug/initialisation. I'm having problems getting SPL (from am57xx-evm-linux-sdk-src-03.00.00.04/u-boot-2016.05+gitAUTOINC+b4e185a8c3-gb4e185a8c3) to configure the CPSW/GEMAC to operate in MII 100Mbps mode. The PHY is detected by the SPL and also by u-boot (when loaded from the UART) and the mii dump shows the correct configuration. However when looking at the other end of the ethernet cable I see no packets. The MII_TXCLK is 25MHz bu the bit timings on the MII_TXDn look like 5MHz i.e. 2.5MHz x 2 i.e. 10Mhz RMII How is the AM57x ethernet configured for MII?

  • 0
    TI__Guru**** 393215 points
    The software team have been notified. They will respond here.
  • 0 in reply to Biser Gatchev-XID
    TI__Mastermind 40080 points
    A dts file will set the interface mode. Depending on how u-boot was ported to your platform you may have or may not have modified the dts file.

    I am guessing here, but if you based your custom board on the TI EVM then most likely arch/arm/dts/am57xx-beagle-x15.dts was the dts file used in the build if evm defconfig was used. In this file is a structure cpsw_mac0. Assuming interface 0 since that is the default interface in u-boot phy-mode field is the one to change.

    &cpsw_emac0{
    ......
    phy-mode = "rgmii";
    ......
    }

    Trying changing the to phy-mode to "mii" and rebuild, make sure the am57xx-beagle-x15.dts file is compiles to a newer am57xx-beagle-x15.dtb
  • 0 in reply to Schuyler Patton
    Intellectual 335 points
    Thanks for the suggestion. I will try that for u-boot. I'm also wanting to load u-boot from the SPL via the network and i'm using the SPL with no dtb as it makes the image smaller and faster to load via the UART I also find the details of how to create a DTS to understand. There seem to be a lot of 'magic' words and numbers used as references.