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AM335x 10BASE-T support for SMSC LAN8820

Steve Turza
Prodigy 220 points
Other Parts Discussed in Thread: AM3358

I have designed a AM335x board using the SMSC LAN8820 RGMII PHY.
1G and 100M mode seem to work fine, but I cannot get a 10M connection working.
When connecting to 10M, the PHY confirms a 10M link via MDIO.

I recently noticed a RGMII disclaimer in the AM335x datasheet stating;
"If RGMII is used, and a 10Mbit operation is desired, in-band mode must be used and an ethernet PHY
that supports in-band status signaling must be selected."
I have reviewed the datasheet of the LAN8820 and it does not mention in-band status support.

I have experimented with the software, writing different patterns to the MACCONTROL register.
For a 10M connection I have tried both forced and in-band mode, without any luck.

Is there any way I can get 10M mode working if I use the LAN8820 PHY.

Thanks,
Steve

  • 0
    TI__Guru 60955 points

    No, you must use a RGMII PHY that supports the optional in-band status to get the MAC to operate in 10Mbit mode.

    Regards,
    Paul

  • 0 in reply to peaves
    TI__Guru 60955 points

    I just realized it may be helpful to clarify my reference to optional in-band status.  In-band status is a function defined in the RGMII specification and is listed as an optional function for RGMII PHYs.  However, AM335x requires a PHY to support this feature to operate in 10Mbit mode.

    Regards,
    Paul

  • 0 in reply to peaves
    Prodigy 220 points

    Thanks for your answer.

    Does TI have a list of RGMII PHYs that are compatible with the AM335x processors ?

    Our application requires boot-up from Etherent, and I have yet to find a PHY that can be strapped for RX and TX clock ID mode and also support in-band status.

    Thanks,

    Steve

  • 0 in reply to Steve Turza
    TI__Mastermind 27890 points

    I'm not aware of one offhand. I'd inquire at Micrel and Marvell. The Micrel KSZ9031 integrates both delays and in-band signalling, but the delays cannot be programmed via HW strapping so that won't work for RGMII Boot. They may have a version that does both.

    Marvell probably is your best bet, but most of their product line technical info is unavailable to me.

  • 0
    Prodigy 145 points
    hey steve,

    I have custom board running on am3358 with LAN8820 PHY chip for LAN, I am working on linux v4.1.6. I am stuck at driver changes for LAN8820. Can you please share your findings on driver changes. I have raised a questionnaire here in this regard e2e.ti.com/.../467681

    thanks and regards,
    Satish