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DP83867IR: fix to 10/100 when RGMII was connected.

Sung-IL
Mastermind 31050 points
Part Number: DP83867IR
Other Parts Discussed in Thread: AM3352

Dear Champs,

In my customer's custom board, DP83867 was connected to AM3352 through RGMII, but they found packet loss in their test at 1Gbps.

So, they want to fix it to 10/100 mode in DP83867, but failed. 

Could you please let me know how DP83867 can be set to 100Mbps limit mode with RGMII I/F?

The OS on AM3352 is Linux.(Linux Processor SDK 4.0)

Thanks and Best Regards,

SI.

  • 0
    TI__Genius 11725 points

    Hi SI,

    You may use register 9 disable the 1Gbps speed advertisement. This will still allow auto-negotiation for 10/100 Mbps speeds.

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    TI__Mastermind 31050 points

    Hi Nikhil,

    I already tried it, but failed when it was connected to PC.

    Even when I disabled 1Gbps speed advertisement in register 9 as you said, it was connected to PC at 1Gbps speed.

    Also, I tried to change register 0 and I disabled 'Auto-negotiation enable' and set 'SPEED SELECTION' to 100 Mbps('01'), but still connected with PC at 1Gbps speed.

    Is there any other method to connect with PC at 100Mbps?

    Thanks and Best Regards,

    SI.

  • 0 in reply to Sung-IL
    TI__Genius 11725 points

    Hi SI,

    Can you read back register 0 to confirm you are correctly disabling auto-negotiation and setting your speed to 100Mbps? If the register has been set to force a speed, the device should not link at any other speed, you would not see a link. Additionally, please read registers 2 and 3 to confirm that you are programming the correct PHY. 

  • 0 in reply to Nikhil Menon
    TI__Mastermind 31050 points

    Hi Nikhil,

    we found the registers(0 and 9) were not updated even when we set it in dts file.

    Can you guess why the settings in dts file of linux were not applied to DP83867 registers?

    Thanks and Best Regards,

    SI.

  • 0 in reply to Sung-IL
    TI__Genius 11725 points

    Hi SI,

    Can you read registers 0, 2, 3, and 9 and let me know the results? Can you also share you schematic with me?

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    TI__Mastermind 31050 points

    Hi Nikhil,

    I'm sorry for late. My customer implemented workaround in to force 10/100 link in the ethtool application SW and it works well.

    I could not response you because they have not provided registers dump and only shared schematic.

    Please check attached below their HW schematic and let me know if you find any strange thing.

    Thanks and Best Regards,

    SI.