netdev - Re: network unstable on odroid-c1/meson8b.

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Date:   Thu, 20 Jun 2019 00:14:26 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Aymeric <mulx@...u.fr>, netdev@...r.kernel.org
Cc:     "linux-amlogic@...ts.infradead.org" 
        <linux-amlogic@...ts.infradead.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: network unstable on odroid-c1/meson8b.

On 19.06.2019 22:18, Aymeric wrote:
> 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].
> 
Kernel 3.10 didn't have a dedicated RTL8211F PHY driver yet, therefore
I assume the genphy driver was used. Do you have a line with
"attached PHY driver" in dmesg output of the vendor kernel?

The dedicated PHY driver takes care of the tx delay, if the genphy
driver is used we have to rely on what uboot configured.
But if we indeed had an issue with a misconfigured delay, I think
the connection shouldn't be fine with just another link partner.
Just to have it tested you could make rtl8211f_config_init() in
drivers/net/phy/realtek.c a no-op (in current kernels).

And you could compare at least the basic PHY registers 0x00 - 0x30
with both kernel versions, e.g. with phytool.

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