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

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Message-ID: <aW7sW91DrgZ6FMrv@pie>
Date: Tue, 20 Jan 2026 02:45:47 +0000
From: Yao Zi <me@...ao.cc>
To: Georg Gottleuber <ggo@...edocomputers.com>,
	"Russell King (Oracle)" <linux@...linux.org.uk>
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,
	Christoffer Sandberg <cs@...edocomputers.com>
Subject: Re: [PATCH RESEND net-next v6 0/3] Add DWMAC glue driver for
 Motorcomm YT6801

On Mon, Jan 19, 2026 at 06:57:48PM +0100, Georg Gottleuber wrote:
> Am 19.01.26 um 18:45 schrieb Georg Gottleuber:
> > Hi,
> > 
> > thanks for the quick reply.
> > 
> > Am 19.01.26 um 16:43 schrieb Russell King (Oracle):
> >> 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:
> >>>
> > ...
> >>>
> >>> 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
> > 
> > That looks good (after iperf):
> > 
> > 2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
> > mode DEFAULT group default qlen 1000
> >     link/ether ba:90:88:24:49:4f brd ff:ff:ff:ff:ff:ff
> >     RX:  bytes packets errors dropped  missed   mcast
> >        2091654   31556      0       0       0       0
> >     TX:  bytes packets errors dropped carrier collsns
> >       88532451    1518      0       0       0       0
> > 
> > 
> >> - 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.
> > 
> > That looks also good, I think. I saved it before and after the test with
> > iperf. See attachments.
> 
> Oh, there was something else interesting in dmesg. See attachment.
> 
> > Regards,
> > Georg

> [    0.933480] dwmac-motorcomm 0000:02:00.0: error -ENOENT: failed to read maca0lr from eFuse
> [    0.933483] dwmac-motorcomm 0000:02:00.0: eFuse contains no valid MAC address
> [    0.933485] dwmac-motorcomm 0000:02:00.0: fallback to random MAC address

Some vendors didn't write a MAC address to the eFuse. With these YT6801
chips, the failure is expected.

Which DKMS driver do you use? Could you read out a permanent address
with your DKMS driver? If not, this piece of log should have nothing to
do with the rate problem.

Note some out-of-tree driver derived from the vendor one fallback to a
static MAC address[1], so it doesn't mean your eFuse has MAC address
written if you only observe the MAC address doesn't change between
reboots.

Best regards,
Yao Zi

[1]: https://github.com/ziyao233/yt6801-vendor-driver/blob/0efb3e86702ad2b19e7f9d19172a8e1df143e8c7/fuxi-gmac-common.c#L17-L32