On 06/12/2020 20.45, Vladimir Oltean wrote:

It would be interesting to see what is the ingress drop reason, if that
could be deduced from the drop counters that are incrementing in ethtool -S.

I don't see anything obvious from running ethtool -S before/during/after
ping.

Since you've already made the effort to boot kernel 5.9, you could make
the extra leap to try out the 5.10 rc's and look at the VTU using
Andrew's devlink based tool:
https://github.com/lunn/mv88e6xxx_dump

# devlink dev
mdio_bus/d0032004.mdio-mii:11
mdio_bus/d0032004.mdio-mii:12
mdio_bus/d0032004.mdio-mii:10
# ./mv88e6xxx_dump --device mdio_bus/d0032004.mdio-mii:10 --vtu
VTU:

Thanks for the hint. Unfortunately:

# uname -a
Linux (none) 5.10.0-rc7-00035-g66d777e1729d #194 Mon Dec 7 16:00:30 CET
2020 ppc GNU/Linux
# devlink dev
mdio_bus/mdio@e0102120:10
# mv88e6xxx_dump --device mdio_bus/mdio@e0102120:10 --vtu
VTU:
Error: devlink: The requested region does not exist.
devlink answers: Invalid argument
Unable to snapshot vtu

--atu, --global1 and --global2 does work, but the latter two say
"Unknown mv88e6xxx chip 186a" (and 186a is 6250 in hex, so I think that
should have been printed in decimal to reduce confusion). Whether that
has anything to do with --vtu not working I don't know - the global1/2
registers to seem to get printed correctly.

Rasmus