Hi,

On Wed, Jul 22, 2026 at 10:27:57AM +0200, Konrad Dybcio wrote:
> On 7/22/26 1:34 AM, Sebastian Reichel wrote:
> > On Tue, Jul 21, 2026 at 04:24:06PM +0000, Dr. David Alan Gilbert wrote:
> >> * Sebastian Reichel (sre@kernel.org) wrote:
> >>> On Sat, Jul 18, 2026 at 07:06:28PM +0200, Jens Glathe via B4 Relay wrote:
> >>>> On Qualcomm X1E80100 platforms (e.g. Lenovo ThinkPad T14s Gen 6)
> >>>> using the Parade PS883x retimer, connecting USB4-capable docks such
> >>>> as the Lenovo 40B0 via a regular Type-C cable (which forces the dock
> >>>> into Type-C fallback mode) often results in working USB but no
> >>>> DisplayPort output.
> 
> [...]
> 
> > AFAIK only Qcom and Apple M series support it. A quick search
> > suggsts Apple used an Intel retimer in the past and a custom one
> > nowadays. From the looks of it the x86 world cannot use this driver
> > either and probably handles retimers transparently in ACPI, so it's
> > effectively Qcom specific until other vendors start adding USB4
> > support. The only thing announced potentially running into this
> > would be the Nvidia RTX Spark, which first needs to be released,
> > then find a bunch of people motivated to implement upstream support.
> > Nothing with USB4 capabilities has been announced from Mediatek or
> > Rockchip. So I wouldn't hold my breath for another user and still
> > suggested adding the machine check instead of simply disabling USB4
> > for everyone ;)
> 
> The PS883x is used on x86 machines too.

In context of x86 I was more talking about the driver than the chip
itself. The driver can only be loaded via DT. Any quirks and hacks
in the driver are unrelevant if the driver is not used by a
platform.

> Apart from I2C, it also ""speaks thunderbolt"" - the bus has a way
> for retimers to enumerate and communicate with the routers
> (controllers) through a sideband UART-like interface. But for
> that, it still probably needs the platform firmware to program it
> into the right mode over I2C, which Linux is unaware of (as it
> effectively should be).
>
> FWIW, we do the same on X2. An MCU takes care of setting it up.

Thanks for the info.

Greetings,

-- Sebastian