Hello all,

I've an ODROID-C1 board (a meson8b/S805) and I've some network
unstablity with current mainline kernel; as time of writting, tested
5.0.y, 5.1.y, 5.2-rc4 and didn't try with any others versions.

After a few talks on linux-amlogic mailing list, I've been pointed here
to find and, hoppefully, fix the issue.
The whole thread on linux-amlogic is available here: [¹]

A short summary:
1. With Kernel 3.10.something made by Hardkernel (the one from the board
vendor), the network link is working at 1 gigabit and stay at 1 gigabit.
2. With Kernel 5.0.y, 5.1.y, mainline, the network link goes from up to
down every few seconds at 1 gigabit (making the board unusable) but is
working fine when forced at 100Mb (using ethtool command).
3. The ethernet cable is not the cause of the issue (see #4).
4. After a few more check, I was able to narrow the problem. It's only
present when the board is connected to my "internet box" (a Livebox
3/Sagemcom) but not with a "stupid" d-link switch (both have gigabit
capability).
5. With the help from Martin on linux-amlogic I've tried to disable EEE
in the dtb but it didn't change anything.
6. An extract of the dmesg output grepping ethernet and meson is here
when the issue is occuring: [²].


And the last comment from Martin and why I'm sending a mail here:
- the Amlogic SoCs use a DesignWare MAC (Ethernet controller, the driver
is called stmmac) with a Relatek RTL8211F Ethernet PHY.
- there's little Amlogic specific registers involved: they mostly
control the PHY interface (enabling RMII or RGMII) and the clocks so
it's very likely that someone on the netdev list has an idea how to
debug this because a large part of the Ethernet setup is not Amlogic SoC
specific

So if you've got any idea to fix this issue.. :)

Thanks in advance,

Aymeric.


[¹]:
http://lists.infradead.org/pipermail/linux-amlogic/2019-June/012341.html
[²]:
https://paste.aplu.fr/?b5eb6df48a9c95b6#sqHk8xhWGwRfagWNpL+u7mIsPGWVWFn2d7xBqika8Kc=