DP83867E: SGMII PHY not always detected after reboot (Zynq + Linux)

Hello again,

Following up on my previous post regarding the intermittent issue with the DP83867E in SGMII mode, I would like to share some additional observations based on our debugging.

When the PHY is in the non-working (KO) state, we observe the following:

• MDIO is functional: The MAC address is correctly retrieved and visible from Linux. For example, the output of ip a shows:

  4: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq qlen 1000
      link/ether 00:0a:35:00:01:23 brd ff:ff:ff:ff:ff:ff

  However, no physical link is detected on the interface:

• The PHY does not detect any valid signal on the physical layer. Possible causes could be: no cable plugged, a defective cable, or an inactive switch port.

We’ve confirmed that the cable and switch are functional in normal cases

Any insight into potential causes (e.g., link detection logic, PHY auto-negotiation behavior in SGMII mode, known errata) would be very helpful.

Thanks again for your support!

Hi Sébastien,

user5867317 said:

However, no physical link is detected on the interface:

Does this mean the PHY does not detect the link when the cable is plugged in? Like the LED is not on when the cable is plugged in? Or, does this mean the Linux does not detect the link?

Since MDIO is functional, could you provide register dump (0x00 to 0x1F + 0x31 + 0x37) when the ethernet cable is plugged in?

In addition, have you looked at this document? 

Please let me know. 

Best,
J

Hello thanks J for you answer. I really appreciate this.

PHY LEDs (Link/Activity) are always ON, regardless of link status. This occurs even when Linux reports NO-CARRIER.
However, when the link is functional, the LEDs turn off if we unplug the cables.

Here are some registers dumps

Link up :
  reg 0x00 -> 0x1140
  reg 0x01 -> 0x796d
  reg 0x02 -> 0x2000
  reg 0x03 -> 0xa231
  reg 0x04 -> 0x01e1
  reg 0x05 -> 0xc5e1
  reg 0x06 -> 0x006f
  reg 0x07 -> 0x2001
  reg 0x08 -> 0x6801
  reg 0x09 -> 0x0300
 
Link Fail : 
  reg 0x00 -> 0x1140
  reg 0x01 -> 0x796d
  reg 0x02 -> 0x2000
  reg 0x03 -> 0xa231
  reg 0x04 -> 0x01e1
  reg 0x05 -> 0xc5e1
  reg 0x06 -> 0x006d
  reg 0x07 -> 0x2001
  reg 0x08 -> 0x6801
  reg 0x09 -> 0x0300

I need to perform extra tests to complete with the missing values. I expect to do this on monday. 

Meanwhile I'll check the document.

Regards,

Sébastien

Hi Sébastien, 

Based on your description, it could be either the PHY or the RJ45 connector is bad. Would you be able to perform ABA swap on the PHY and the RJ45 connector and see if the issue disappears?

Best,
J

Hello, Thanks for your inputs.

We don't have the full view over the registers but here is what I can give so far:

reg 0x00 -> 0x0140
reg 0x01 -> 0x7949
reg 0x02 -> 0x2000
reg 0x03 -> 0xa231
reg 0x04 -> 0x01e1
reg 0x05 -> 0x0000
reg 0x06 -> 0x0064
reg 0x07 -> 0x2001
reg 0x08 -> 0x0000
reg 0x09 -> 0x1300
reg 0x0a -> 0x0000
reg 0x0b -> 0x0000
reg 0x0c -> 0x0000
reg 0x0d -> 0x0000
reg 0x0e -> 0x0000
reg 0x0f -> 0x3000
reg 0x10 -> 0x5c48
reg 0x11 -> 0xa802
reg 0x12 -> 0x0000
reg 0x13 -> 0x0040
reg 0x14 -> 0x29c7
reg 0x15 -> 0x0000
reg 0x16 -> 0x0000
reg 0x17 -> 0x0040
reg 0x18 -> 0x6150
reg 0x19 -> 0x4444
reg 0x1a -> 0x0002
reg 0x1b -> 0x0000
reg 0x1c -> 0x0000
reg 0x1d -> 0x0000
reg 0x1e -> 0x0002
reg 0x1f -> 0x0000

Regarding your comment, we are still working on having a second board for tests. I was wondering if you are ok if I share with the interesting parts of the schematics for quick review?

Thanks.

Sebastien

Hi Sébastien,

I would be happy to review the schematic. You can attach it on your post or you can directly send it to me via message after accepting my friend request.

What state the PHY is in when this register dump was produced? It doesnt look like the PHY is in the problematic state. If you can, please send me the register dump when the PHY enters the unresponsive state.

Best,

J

Hello,

Thanks for the help.

I would rather send it through messages if you don't mind. I'll wait for your friend request. :-)

Hi I just sent the friend request. 

Hi, 
Schematic looks good. Please see attached. Please update me on the register dump.

Copy of DP83867_Schematic_Checklist_Commented.xlsx

Best,
J