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Differential D55925

axe: fix spurious link flaps from MII
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Authored by rkitover_gmail.com on Wed, Mar 18, 7:04 PM.
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imp
sanpei

Details

Reviewers
adrian
pouria
zlei
Summary

A race condition in the MII layer causes spurious link down events, see:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252165

. In statchg, on link down, check if the PHY reports the link as
actually down using the BMSR register, if not, force the status of the
link to back up. Do the same in a MII linkchg handler.

I have tested this patch with an ASIX AX88772B USB 2.0 interface, and it
fixes the link flaps.

Differential Review:

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

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Event Timeline

rkitover_gmail.com created this revision.Wed, Mar 18, 7:04 PM
Herald added a subscriber: imp. · View Herald TranscriptWed, Mar 18, 7:04 PM
rkitover_gmail.com requested review of this revision.Wed, Mar 18, 7:04 PM
rkitover_gmail.com added a parent revision: D55631: axge: fix spurious link down from MII, frozen TX.
Harbormaster completed remote builds in B71492: Diff 173865.Wed, Mar 18, 7:05 PM
rkitover_gmail.com updated this revision to Diff 173866.Wed, Mar 18, 7:06 PM

Add Differential Revision

Harbormaster completed remote builds in B71493: Diff 173866.Wed, Mar 18, 7:06 PM
rkitover_gmail.com added projects: USB, desktop.Wed, Mar 18, 7:07 PM
rkitover_gmail.com added reviewers: adrian, pouria, zlei.
rkitover_gmail.com mentioned this in D55631: axge: fix spurious link down from MII, frozen TX.
sanpei added a subscriber: sanpei.Tue, Mar 24, 9:05 PM
sanpei added a comment.Tue, Mar 24, 9:52 PM

Environment:

Hardware: ASIX Electronics Corp. AX88772 (BUFFALO LUA3-U2-ATX, 100Base Ethernet)
Tested on: Raspberry Pi 4(16-current), Raspberry Pi Zero 2W(15.0-RELEASE), Pine64(15.0-RELEASE)

Description:
I am experiencing a "link flapping" issue where the connection repeatedly toggles between UP and DOWN. Unfortunately, this issue persists even after applying the latest patch.

The logs show frequent "spurious link down" messages[OK] and link state changes[NG], as seen below:

Log Output:

Mar 23 16:01:29 generic syslogd: last message repeated 9 times
Mar 23 16:01:29 generic kernel: ue0: link state changed to DOWN
Mar 23 16:01:29 generic kernel: ue0: link state changed to UP
Mar 23 16:01:30 generic kernel: axe0: spurious link down (PHY link up), overriding
Mar 23 16:01:31 generic syslogd: last message repeated 1 times
Mar 23 16:01:31 generic kernel: ue0: link state changed to DOWN
Mar 23 16:01:31 generic kernel: axe0: spurious link down (PHY link up), overriding
Mar 23 16:01:31 generic syslogd: last message repeated 2 times
Mar 23 16:01:31 generic kernel: ue0: link state changed to UP
Mar 23 16:01:31 generic kernel: ue0: link state changed to DOWN
Mar 23 16:01:31 generic kernel: axe0: spurious link down (PHY link up), overriding
Mar 23 16:01:31 generic kernel: ue0: link state changed to UP
Mar 23 16:01:32 generic kernel: axe0: spurious link down (PHY link up), overriding
Mar 23 16:01:40 generic syslogd: last message repeated 10 times
Mar 23 16:01:40 generic kernel: ue0: link state changed to DOWN
Mar 23 16:01:40 generic kernel: ue0: 3 link states coalesced
Mar 23 16:01:40 generic kernel: ue0: link state changed to UP
Mar 23 16:01:42 generic kernel: axe0: spurious link down (PHY link up), overriding

Notes:
I also use a ure driver dongle (Lenovo USB-C to LAN). In that case, the similar issue was successfully resolved by the ure patch, but the axe driver (AX88772) still exhibits this behavior.

Please let me know if you need any further debug information.

sanpei added a comment.Tue, Mar 24, 10:07 PM

FYI: My testing methodology

Setup:

  • Machine A (Remote): Run ping [Unassigned Local IP].
  • Machine B (Target): Run the route -n monitor command in four separate instances.

Note: In my environment, the link issue only occurs while route -n monitor is running. If the command is not active, the connection remains stable.

rkitover_gmail.com added a comment.Thu, Mar 26, 4:03 AM

Thank you for testing,

I'll run some tests and try to find the issue.

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sys/
dev/
usb/
net/
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Diff 173865

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sys/dev/usb/net/if_axe.c

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