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BCM53125S Configured as a 7 Port Switch - RGMII ports not working

  • 1.  BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-17-2019 09:51 PM
    Hi,

    We are trying to design a 7 Port Ethernet Switch using the BCM53125S. 


    The 5 integrated PHY Ethernet Transceivers are working fine. We verified this by having the upstream ethernet connection connected to one of the PHY ports, and had a downstream device connected on a different PHY port, and the downstream device was able to get a proper IP address (DHCP was able to resolve), and ping 8.8.8.8. 


    Here's the issue, we're struggling with configuring the IMP and WAN ports (in RGMII mode) to operate as data ports. To test these, we did something similar - we had the upstream ethernet connection connected to the IMP port, and a downstream device connected on one of the PHY ports. The downstream device was unable to get a proper IPaddress.


    We have connected the IMP and WAN ports to external PHYs (Atheros AR8035) following Figure 2 on the BCM53125 Application Note(53125-AN102-R.pdf) - running the RGMII at 2.5V. LED[0] is pulled high on boot, because we wanted to have the switch work in unmanaged mode. LED[5:4] are pulled to GND (to set RGMII mode for the WAN port), and LED[7:6] are also pulled to GND to set IMP to RGMII mode as well. LED[9] is pulled high to have traffic forwarding without any register settings. We've also connected the SPI bus to a processor, and we're able to read and write to the BCM53125S registers. Hardware-wise, we believe we've connected it correctly. 


    What we've observed so far, the BCM53125S RGMII RX signals have activity (probed with oscilloscope) when ethernet is connected to that respective port (expected behaviour). However, there is no life on the RGMII TX data signals (TXCLK signal shows life when a downstream device is connected to one of the PHYs). I've had to manually enable the IMP and WAN ports (by writing into registers via SPI) - I can provide a more detailed explanation of which registers I've written to if necessary. At this point, the downstream device (using tcpdump) can see outside traffic, whereas before, tcpdump would only show ARP requests that the downstream device was sending out, and no outside traffic. It seems we've gotten to a point where we are unable to successfully send data out via the RGMII TX data lines (even though they show activity)- does anyone have any ideas on why this may be happening?


    Another question maybe, are register changes truly necessary to operate the BCM53125S as a 7 port switch? Or should the boot strapping configure the switch properly upon boot up?



  • 2.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-23-2019 01:52 AM

    Hi,

    Thanks the input.

    By double checking your issue descriptions, I believe this case issue is how to configure to make BCM53125S port5 WAN port and port8 IMP port work.

    The BCM53125S strap pins setting in your description are correct.

    Right, it requires to do registers write for BCM53125S port5 WAN port and port8 IMP port usage because they are phy-less interface port.

    Please find the following registers write for port5 WAN port and port8 IMP port:

    1. For port5 WAN port,

    Set Reg(0x00: 0x5d)=0x4b; force link up port5 at 1000Mbps for example

    Set reg(0x00: 0x65)=0x03; set port5 RGMII delay mode if your external gphy did not set RGMII delay mode

    1. For port8 IMP port,

    Set Reg(0x00: 0x0b)=0x06; configure IMP port as unmanaged mode

    Set Reg(0x00: 0x0e)=0x8b; force link up port8 IMP port at 1000Mbps for example

    Set Reg(0x00: 0x60)=0x03; set port8 IMP port RGMII delay mode if your external gphy did not set RGMII delay mode

     

    Please double check it and let me know if there is question.

     

    Thanks,

    Ryan



    ------------------------------
    Master R&D Applications Engineer
    Broadcom
    ------------------------------



  • 3.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-24-2019 05:31 PM
    "I believe this case issue is how to configure to make BCM53125S port5 WAN port and port8 IMP port work." --> That is correct!

    I've tried implementing the register changes you've suggested - I can see the IMP and WAN port have life on the RGMII_TX lines. However, I still can't get DHCP to resolve - and from using tcpdump on a downstream device connected to one of the PHYs, I can't see outside traffic (on the downstream PHY) from just changing those registers you've suggested.

    Are there any other registers that need to be set? Or at this point, should packets be already forwarded to all ports?




  • 4.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-24-2019 11:05 PM
    Hi Michael,
    From your descriptions last time, your BCM53125 Port5 and IMP port are connected with external gphy chip.
    Suggest could you use the traffic generator (such like IXIA) to do the port pair traffic test on your platform? And make sure the traffic rx/tx no problems including your external gphy.

    Thanks,
    Ryan


    ------------------------------
    Master R&D Applications Engineer
    Broadcom
    ------------------------------



  • 5.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-25-2019 09:19 PM
    Hi Ryan,

    With upstream ethernet connection connected to the IMP port, and a downstream device connected on one of the PHY ports, I was able to get a proper IP address on the downstream device, and I was able to ping 8.8.8.8.

    The key was to follow your register settings (as you've mentioned), but ONLY enabling EN_RGMII_TX_CLK for both the WAN and IMP ports (page 00h, addr 60h and 65h). Whereas I was previously enabling both the EN_RGMII_RX_CLK delay as well.

    Now, if I connect the upstream ethernet connectiong to one of the PHYs and connect the downstream device to the one of the RGMII ports (IMP or WAN), I cannot get a proper IP address. Is this expected behaviour?

    Thanks so much!
    -Michael



  • 6.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 09-26-2019 04:39 AM
    Hi Michael,
    No and not sure.
    - becasue the BCM53125 is switch to receive/forward the packet, no matter the upstream and downstream port.
    As I replied in your message, could you provide your IP packet ping diagram on your platform?
    It will be very helpful to know your BCM53125 and external gphy connection configuration to do analysis.

     

    Thanks,

    Ryan



    ------------------------------
    Master R&D Applications Engineer
    Broadcom
    ------------------------------



  • 7.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 10-03-2019 05:22 PM

    Hi Ryan, 


    Apologies for the delayed response. 


    We were able to get the RGMII ports working as normal data ports last week! We were testing with a downstream device that ran at 100Mbps, and I was forcing the BCM53125S IMP+WAN port to run at 1000Mbps. When I forced the IMP and WAN ports to run at 100Mbps, I could get a proper IP address on my downstream device, and I was able to ping 8.8.8.8. 


    The last thing for us to chase down is to have the external PHYs communicate the link speed to the IMP and WAN port, and have the IMP and WAN ports change their link speeds to match the external PHYs. I would think this happens through the MDIO bus. Is it possible to have the IMP and WAN ports automatically able to change their speeds after they've been set to to a certain link speed in the registers?




  • 8.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 10-08-2019 10:59 AM
    Hi Michael,
    Sounds great, good progress.
    Per your question, since BCM53125 does not support automatically polling external phy status through MDC/MDIO so it requires the following two approach.
    1. External CPU MDC/MDIO connect with external phy
    Use external CPU SW link scan task to polling external phy status via CPU MDC/MDIO then update BCM53125 IMP port/WAN port link speed(Reg(0x00: 0x0e) for IMP port and Reg(0x00: 0x5d) for WAN port) via SPI  interface to sync up with external phy.
    2. Use BCM53125 internal 8051
    Implement 8051 SW link scan task to polling external phy status via BCM53125 MDC/MDIO then update BCM53125 IMP port/WAN port link speed. It requires external serial flash device to store the 8051 SW image.

    Thanks,
    Ryan

    ------------------------------
    Master R&D Applications Engineer
    Broadcom
    ------------------------------



  • 9.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 10-15-2019 12:13 PM
    Thanks for the clarification and advice - it's super helpful!

    For suggestion 2), Do you have any source code, or application notes to create an 8051 SW image?


  • 10.  RE: BCM53125S Configured as a 7 Port Switch - RGMII ports not working

    Posted 10-17-2019 02:35 AM

    Hi Michael,

    1. For our BCM53125 updated 8051 SW image, it requires to apply and download it through our docSAFE. Could you double check with your local distributor FAE to help you to apply it?
    2. There is application note of Programmer's Reference Guide for 8051 "53125-PG104-RDS" already in this community site. Could you double check it and download through [Ethernet Switches Community1] folder in this community site?

    Please let me know if there is question.

    Thanks,

    Ryan



    ------------------------------
    Master R&D Applications Engineer
    Broadcom
    ------------------------------