linux-kernel - Re: [PATCH RESEND net-next v6 0/3] Add DWMAC glue driver for Motorcomm YT6801

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Message-ID: <aW5RMKqwpYTZ9uFH@shell.armlinux.org.uk>
Date: Mon, 19 Jan 2026 15:43:44 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Georg Gottleuber <ggo@...edocomputers.com>
Cc: Yao Zi <me@...ao.cc>, andrew+netdev@...n.ch, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	Frank.Sae@...or-comm.com, hkallweit1@...il.com,
	vladimir.oltean@....com, wens@...e.org, jszhang@...nel.org,
	0x1207@...il.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, jeffbai@...c.io, kexybiscuit@...c.io
Subject: Re: [PATCH RESEND net-next v6 0/3] Add DWMAC glue driver for
 Motorcomm YT6801

On Mon, Jan 19, 2026 at 04:33:17PM +0100, Georg Gottleuber wrote:
> Hi,
> 
> I tested this driver with our TUXEDO InfinityBook Pro AMD Gen9. Iperf
> revealed that tx is only 100Mbit/s:
> 
> ## YT6801 TX
> 
> [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
> [  5]   0.00-1.00   sec  8.75 MBytes  73.3 Mbits/sec    0    164 KBytes
> 
> [  5]   1.00-2.00   sec  8.62 MBytes  72.4 Mbits/sec    0    164 KBytes
> 
> [  5]   2.00-3.00   sec  8.62 MBytes  72.4 Mbits/sec    0    164 KBytes
> 
> [  5]   3.00-4.00   sec  8.12 MBytes  68.2 Mbits/sec    0    164 KBytes
> 
> [  5]   4.00-5.00   sec  8.62 MBytes  72.3 Mbits/sec    0    164 KBytes
> 
> [  5]   5.00-6.00   sec  8.50 MBytes  71.3 Mbits/sec    0    164 KBytes
> 
> [  5]   6.00-7.00   sec  8.25 MBytes  69.2 Mbits/sec    0    164 KBytes
> 
> [  5]   7.00-8.00   sec  8.62 MBytes  72.4 Mbits/sec    0    164 KBytes
> 
> [  5]   8.00-9.00   sec  8.50 MBytes  71.3 Mbits/sec    0    164 KBytes
> 
> [  5]   9.00-10.00  sec  8.62 MBytes  72.3 Mbits/sec    0    164 KBytes
> 
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  85.2 MBytes  71.5 Mbits/sec    0             sender
> [  5]   0.00-10.05  sec  84.4 MBytes  70.5 Mbits/sec
> receiver
> 
> 
> ## YT6801 RX
> 
> [ ID] Interval           Transfer     Bitrate
> [  5]   0.00-1.00   sec   112 MBytes   939 Mbits/sec
> [  5]   1.00-2.00   sec   112 MBytes   941 Mbits/sec
> [  5]   2.00-3.00   sec   112 MBytes   941 Mbits/sec
> [  5]   3.00-4.00   sec   112 MBytes   942 Mbits/sec
> [  5]   4.00-5.00   sec   112 MBytes   942 Mbits/sec
> [  5]   5.00-6.00   sec   112 MBytes   943 Mbits/sec
> [  5]   6.00-7.00   sec   112 MBytes   941 Mbits/sec
> [  5]   7.00-8.00   sec   112 MBytes   942 Mbits/sec
> [  5]   8.00-9.00   sec   112 MBytes   942 Mbits/sec
> [  5]   9.00-10.00  sec   112 MBytes   941 Mbits/sec
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.04  sec  1.10 GBytes   941 Mbits/sec   88             sender
> [  5]   0.00-10.00  sec  1.10 GBytes   941 Mbits/sec
> receiver
> 
> With our normally used DKMS module, Ethernet works with full-duplex and
> gigabit. Attached are some logs from lspci and dmesg. Do you have any
> idea how I can debug this further?

My suggestion would be:

- Look at the statistics, e.g.

   ip -s li sh dev enp2s0

- apply
  https://lore.kernel.org/r/E1vgtBc-00000005D6v-040n@rmk-PC.armlinux.org.uk
  to enable more statistics to work, and check the network driver
  statistics:

   ethtool --statistics enp2s0

to see if there's any clues for what is going on.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!