Unusable Realtek NIC after upgrading to NetBSD 9

[Rocky Hotas <rockyhotas%firemail.cc@localhost>]

Hello!
Using NetBSD 8.1 in a laptop, both its Ethernet and WiFi NICs worked.
Then, I made a NetBSD 9 (formal release) fresh install and the
Ethernet NIC is almost unusable.

Here, the relevant dmesg part:

[     1.055234] re0 at pci3 dev 0 function 0: RealTek
8100E/8101E/8102E/8102EL PCIe 10/100BaseTX (rev. 0x05)
[     1.055234] re0: interrupting at msix3 vec 0
[     1.055234] re0: Ethernet address 28:92:4a:29:53:5a
[     1.055234] re0: using 256 tx descriptors
[     1.055234] rlphy0 at re0 phy 7: RTL8201E 10/100 media interface,
rev. 2
[     1.055234] rlphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX,
auto

The card is detected and configured by the system, but it is extremely
slow: a Google ping may take up to 10 seconds (yes, 10000 ms). An ssh
connection is extremely slow, making it unusable.

It seems that, if I use the card, the dmesg gets populated by this
repeated message:

[ 20690.751223] re0: watchdog timeout
[ 20695.773292] re0: watchdog timeout
[ 20706.809817] re0: watchdog timeout
[ 20720.853570] re0: watchdog timeout
[ 20730.887686] re0: watchdog timeout

I also tried to boot disabling rlphy(4) (`userconf disable rlphy' from
the boot prompt), and ukphy(4) is used instead, but nothing changed.
The same happens with netbsd-9 (stable).
This problem did not appear with NetBSD 8.1, so it is a regression.
Is there anything I can do?
Bye!

Rocky


P.S.1
From `ifconfig -a' (note that the Ethernet cable is currently
disconnected, because I can't use the card):

re0: flags=0x8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500

capabilities=3f80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx>
        capabilities=3f80<UDP4CSUM_Rx,UDP4CSUM_Tx>
        enabled=0
        ec_capabilities=3<VLAN_MTU,VLAN_HWTAGGING>
        ec_enabled=0
        address: 28:92:4a:29:53:5a
        media: Ethernet autoselect (none)
        status: no carrier
        inet 192.168.1.27/24 broadcast 192.168.1.255 flags 0x4<DETACHED>
        inet6 fe80::2a92:4aff:fe29:535a%re0/64 flags 0x8<DETACHED>
scopeid 0x1


P.S.2

Note that this is not the same issue as the previous thread:

 <http://mail-index.netbsd.org/netbsd-users/2020/02/29/msg024128.html>

which has been solved.