Re: USB_NET_AX8817X dependency on AX88796B_PHY

[Oleksij Rempel <o.rempel@pengutronix.de>]

Hi Maciej,

On Sun, Oct 15, 2023 at 02:55:29PM -0700, Maciej Żenczykowski wrote:
> I've received reports that an ethernet usb dongle doesn't work (google
> internal bug 304028301)...
> 
> Investigation shows that we have 5.10 (GKI) with USB_NET_AX8817X=y and
> AX88796B_PHY not set.
> I *think* this configuration combination makes no sense?
> [note: I'm unsure how many different phy's this driver supports...]

After porting part of this driver to PHYlib and then to PHYlink, the driver is
capable of supporting nearly all drivers/net/phy/*

I did this port for following USB Ethernet adapter which needs different PHY:
https://linux-automation.com/en/products/usb-t1l.html

> Obviously, we could simply turn it on 'manually'... but:
> 
> commit dde25846925765a88df8964080098174495c1f10
> Author: Oleksij Rempel <o.rempel@pengutronix.de>
> Date:   Mon Jun 7 10:27:22 2021 +0200
> 
>     net: usb/phy: asix: add support for ax88772A/C PHYs
> 
>     Add support for build-in x88772A/C PHYs
> 
>     Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
>     Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>     Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> includes (as a side effect):
> 
> drivers/net/usb/Kconfig
> @@ -164,6 +164,7 @@ config USB_NET_AX8817X
>         depends on USB_USBNET
>         select CRC32
>         select PHYLIB
> +       select AX88796B_PHY
>         default y
> 
> which presumably makes this (particular problem) a non issue on 5.15+
> 
> I'm guessing the above fix (ie. commit dde25846925765a88df8964080098174495c1f10)
> could (should?) simply be backported to older stable kernels?
> 
> I've verified it cherrypicks cleanly and builds (on x86_64 5.10 gki),
> ie.
> $ git checkout android/kernel/common/android13-5.10
> $ git cherry-pick -x dde25846925765a88df8964080098174495c1f10
> $ make ARCH=x86_64 gki_defconfig
> $ egrep -i ax88796b < .config
> CONFIG_AX88796B_PHY=y
> $ make -j50
> ./drivers/net/phy/ax88796b.o gets built

As far as i know, mainline kernel v5.10.198 do not supports ax88772A/C PHYs
within the ax88796b.c driver:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/net/phy/ax88796b.c?h=v5.10.198

There is no need to backport this patch to other stable kernels, except
they include porting of drivers/net/usb/asix_devices to PHYlink
framework.

> I've sourced a copy of the problematic hardware, but I'm hitting
> problems where on at least two (both my chromebook and 1 of the 2
> usb-c ports on my lenovo laptop) totally different usb
> controllers/ports it doesn't even usb enumerate (ie. nothing in dmesg,
> no show on lsusb), which is making testing difficult (unsure if I just
> got a bad sample)...

I use ax88772 based HW on different systems including on UCB-C ports (for
example on DELL XPS 13 developer edition)

Regards,
Oleksij
-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |