Re: [PATCH 0/5] usb: typec: ps883x: fixes for older Thunderbolt 4 / USB4 docks

["Dr. David Alan Gilbert" <dave@treblig.org>]

* Sebastian Reichel (sre@kernel.org) wrote:
> Hello,
> 
> 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.
> > 
> > This series addresses the issue with two main changes:
> > 
> > - Add a new optional DT property "parade,disable-usb4". When present,
> >   the PS883x driver rejects USB4 mode (-EOPNOTSUPP). This forces the
> >   Type-C stack to fall back to USB3 + DP Alt Mode, which works
> >   reliably with the 40B0.
> > 
> > - Refactor DP altmode handling to also support the legacy
> >   TYPEC_DP_STATE_F request (deprecated since DP Alt Mode 1.0b) sent by
> >   the 40B0 and other docks (e.g. SSK SC220).
> > 
> > - Add a short delay after writing configuration registers, which
> >   improves hotplug reliability.
> > 
> > This is a temporary workaround until full USB4 DP tunneling support is
> > available in the X1E USB4 controller and qmp-combo PHY stack.
> > 
> > Note: The DT patch adds the new property to all currently upstream
> > boards using the PS883x retimer (15 files). Happy to split it on v2
> > if requested.
> 
> I don't think a kernel driver limitation is a good reason for the DT
> property. I suggest to add something like this in the ps883x driver
> instead:
> 
> /*
>  * Hamoa does not yet support USB4, disable it for now to gracefully
>  * fall back to USB3 + DP AltMode. This should be removed once USB4
>  * support landed for X1E.
>  */
> if (of_machine_is_compatible("qcom,x1e80100"))
>     disable_usb4 = true;

It seems a bit of a weird abstraction break to put a machine type check
down in a device that's not specific to qcom.
I'd bet it's not just qcom's suffering from this as well.

Dave

> Greetings,
> 
> -- Sebastian
> 
> > As an additional observation, the same dock with type-c cable works well
> > on Thinkpad X13s, Thinkbook 16 G7 QOY, Ideapad 5 14Q8X9, but doesn't need
> > the ps883x changes (naturally). 
> > 
> > Signed-off-by: Jens Glathe <jens.glathe@oldschoolsolutions.biz>
> > ---
> > Jens Glathe (5):
> >       dt-bindings: usb: parade,ps8830: Add parade,disable-usb4 property
> >       usb: typec: ps883x: Return -EOPNOTSUPP for USB4 when parade,disable-usb4 is set
> >       usb: typec: mux: ps883x: refactor DP altmode handling and support TYPEC_DP_STATE_F
> >       usb: typec: mux: ps883x: add a delay after writing config regs
> >       arm64: dts: qcom: x1: disable ps883x USB4 capability
> > 
> >  .../devicetree/bindings/usb/parade,ps8830.yaml     |  6 +++
> >  arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts         |  4 ++
> >  .../qcom/hamoa-lenovo-ideacentre-mini-01q8x10.dts  |  2 +
> >  arch/arm64/boot/dts/qcom/purwa-iot-evk.dts         |  6 +++
> >  arch/arm64/boot/dts/qcom/x1-asus-vivobook-s15.dtsi |  4 ++
> >  arch/arm64/boot/dts/qcom/x1-asus-zenbook-a14.dtsi  |  4 ++
> >  arch/arm64/boot/dts/qcom/x1-crd.dtsi               |  6 +++
> >  arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi        |  4 ++
> >  arch/arm64/boot/dts/qcom/x1-hp-omnibook-x14.dtsi   |  2 +
> >  arch/arm64/boot/dts/qcom/x1-microsoft-denali.dtsi  |  4 ++
> >  arch/arm64/boot/dts/qcom/x1e001de-devkit.dts       |  6 +++
> >  .../dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi    |  4 ++
> >  .../boot/dts/qcom/x1e80100-dell-xps13-9345.dts     |  4 ++
> >  .../boot/dts/qcom/x1e80100-lenovo-yoga-slim7x.dts  |  6 +++
> >  .../dts/qcom/x1e80100-medion-sprchrgd-14-s1.dts    |  2 +
> >  .../boot/dts/qcom/x1e80100-microsoft-romulus.dtsi  |  4 ++
> >  drivers/usb/typec/mux/ps883x.c                     | 47 +++++++++++++++-------
> >  17 files changed, 100 insertions(+), 15 deletions(-)
> > ---
> > base-commit: 0718283ab28bc3907e10b61a6b4be6fefa1cbb2f
> > change-id: 20260718-ps883x-disable-usb4-19b0fc13b5ab
> > 
> > Best regards,
> > -- 
> > Jens Glathe <jens.glathe@oldschoolsolutions.biz>
> > 
> > 
> > 


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