Re: Lynx 10G SerDes Driver on my kernel

Tanjeff Moos
2025-12-05T11:38:39Z

On 12/4/25 20:34, Vladimir Oltean wrote:
> On Thu, Dec 04, 2025 at 08:01:10PM +0100, Tanjeff Moos wrote:
>> This worked for SGMII and 2.5SGMII, but I never managed to switch between SGMII to XFI.
>
> Yes, the SoC architecture on devices with the 10G Lynx didn't initially
> target the use case of switching between SGMII and XFI, so you won't find
> documentation on how to do that. We've since validated that the use case
> works on LS1088A, LS2088A and LS1046A by implementing a procedure called
> "RCW override", where you use undocumented SoC features in drivers/soc/fsl/guts.c
> to essentially change the RCW[SRDS_PRTCL_S1] value to something different
> than what was originally loaded at boot time. We've tested the feature
> on the above SoCs and it is seamlessly integrated in the lynx-10g driver
> (it is not invasive, the user is essentially unaware that this is taking
> place).
Sounds promising!

>
> As mentioned earlier, lynx-10g is in our upstreaming queue, but it may
> take a while to reach it. You can get the driver with the RCW override
> support from Linux Factory, though.
I'm still unsure how to get it. Probably I'm completely off track...

I tried flexbuild (https://github.com/nxp/flexbuild) to get sources, but
didn't find the patches.

I also tried
repo init -u https://github.com/nxp-imx/imx-manifest -b imx-linux-walnascar -m imx-6.12.34-2.1.0.xml
to get the Yocto repo (LF is yocto-based, right?). The "IMX" looks suspicious,
since we are talking about qoriq, but I didn't find LF for qoriq.

The repo https://github.com/nxp-qoriq/linux.git has a branch net/phy which was
merged with commit 0229b2500383. So I will try to "extract" this branch with
"git format-patch" so I can apply its commits to my OpenWRT-Repo.

BTW, I'm still working on getting my board running again after I upgraded to
kernel 6.12.34 (by merging the corresponding OpenWRT commit).

>>> By switching from 10GBase-R to SGMII it would support them all,
>>> wouldn't it?
>> I don't think so. SGMII does only support 100M and 1G. Tell me if I'm wrong.
>
> I hope I didn't confuse you by naming XFI "10GBase-R". This is what the
> 10GbE SerDes protocol should truly be called - XFI is the name of an
> electrical standard.
I did grasp the meaning. But yeah, the terms are confusing, even data sheets mix
them up. It took me some time to understand that my PHY does no SGMII (i.e. no
in-band autoneg) despite its manual claiming that it does.

Anyhow, thanks for clarifying it.