Re: [PATCH net-next v19 00/13] ax88179_178a: Add support for AX88179A-based chips

[Birger Koblitz <mail@birger-koblitz.de>]

Thanks so much Emir for testing!

On 29/10/2026 1:58 am, Emir Beganovic wrote:
> Hi Birger,
> 
> I tested v19 on a Dell DA305 USB-C adapter. It has an AX88179A
> (0b95:1790, bcdDevice 0x0200, FW 1.0.7.131) behind a VIA VL822 hub,
> plugged into a Dell XPS 16 (Panther Lake). The peer is an Intel I225-V
> behind a switch.
> 
> I built ax88179, libphy, phylink and ax88796b as modules for a 7.2.8
> kernel. v19 needed two things on that base: a4e22e9253e7 and a backport
> of genphy_{read,write}_mmd_c45() from the adin1140 series.
> 
> With the current driver in configuration 1 this adapter never gets a
> link ("Failed to read reg index 0x0040: -32"). With v19:
> 
> - 1000/full link with flow control
> - download 940-941 Mbit/s in nine runs. Upload was 937-941 in five of
>    nine and lower in the other four, and I couldn't find why. Eight
>    later runs with tracing on all averaged about 932.
I have seen similar behaviour with iperf3 for an AX88279 and a 2.5GBit 
link: in the first round, some 4-10 packets get dropped by the 
RTL8372-switch as a link partner and then no further frame drops happen. 
Looking into the switch's error counts, the drops are due to Flow 
Control. I was not able to investigate further, but I have seen the same 
behaviour with RTL8156/7/9-adapters using the r8152 driver and that 
switch. So that seems to be "normal" and the speed of the adapter in 
iperf3 is very close (about 2.35Mbit/s) to the theoretical limit.

> - 1-byte TCP request/response around 190-200 us, against about 1.46 ms
>    with cdc_ncm on the same port (its default 400 us TX timer)
> - switching itself to configuration 1 when the device comes up in the
>    CDC configuration
> - 100M and 10M links
> - VLAN with rx-vlan-offload on and off, and rx-vlan-filter dropping a
>    VID that isn't configured
> - multicast filtering and allmulti
> - suspend/resume (s2idle) and wake-on-LAN with a magic packet
> 
> Two small things I noticed:
> 
> - "Switching to vendor mode" is printed twice, once per CDC interface,
>    and before the netdev is registered, so it shows up as
>    "(unnamed net_device) (uninitialized)".
The device can be registered only once it has been switched from CDC to 
the vendor mode, that is why you see the message for the unregistered 
device. That you see it twice can be due to the fact that it has 2 
active interfaces, see the explanation given in commit c67cc43 for Anker 
adapters.
The devices I have print it only once and that also disappears once the 
device has been switched and stays plugged even if the module is 
loaded/unloaded.

> - After a WoL wake the link goes down and up twice within about 2.5 s,
>    where a normal resume shows a single link up. It comes back fine
>    either way.
I see this, too. It is not triggered in any way by the host or the link 
partner, I checked. It appears that this is due to the firmware on the 
device trying to optimize the link settings further, the out-of tree 
ASIX driver displays the same behaviour, although it works very differently.

> 
> I only have this one adapter, so nothing on the other chips.
> 
> Tested-by: Emir Beganovic <beganovic.emir@gmail.com>
Will add in upcoming v20.

Birger