DP routing from iGPU to discrete Barlow Ridge TB5 on HP ZBook Fury G1i

DP routing from iGPU to discrete Barlow Ridge TB5 on HP ZBook Fury G1i

[Francesco Orro]

Hi,

Setup:
  HP ZBook Fury G1i 16 inch, BIOS X96 01.03.04
  Intel Arrow Lake-HX + Nvidia RTX PRO 1000 Blackwell (hybrid graphics)
  Kernel 6.19.13

The laptop exposes Thunderbolt 5 on both the integrated MTL iTBT (right
USB-C, domain0, 00:0d.2) and a discrete Intel Barlow Ridge (left USB-C,
domain1, 00:06.1 -> 05:00.0).

- Right port: i915 drives a DP tunnel over the iTBT host without issues.
- Left port: no i915 connector ever sees the external monitor. The TB
  driver allocates a DP tunnel on demand but DPRX reads time out, no DP
  source is feeding the Barlow DP_IN adapter.
- With nvidia-drm.modeset=1, a DP-MST connector on the Nvidia DRM device
  sees the monitor via the left port (EDID readable, modes negotiated).
  The path Nvidia -> Barlow DP_IN is functional.

Current hypothesis: on this board the discrete Barlow Ridge DP_IN is
either hardwired to a Nvidia output or behind a firmware-programmed mux
that BIOS latches to Nvidia at POST and is not exposed to the OS. i915
would therefore have no path to drive the left ports, by design.

Tests done that did not surface an OS-visible lever:
- i2cdetect across all SMBus/i801 busses: no DP mux/retimer at plausible
  addresses (0x60-0x7F).
- DSDT/SSDT dump (iasl -d): no Device/Method referring to DP routing,
  DPMUX, retimer programming, or dock display source selection.
- HP WMI + /sys/devices/virtual/firmware-attributes/hp-bioscfg attribute
  enumeration: nothing switching dock display source. "Graphics"
  attribute only offers Hybrid/Discrete.
- PCI config dump of Barlow Ridge: standard USB4 NHI, no vendor-specific
  capability hinting at source selection.
- acpi.no_usb4_osc kernel param (locally patched) to opt out of OSC USB4
  native support: no change in i915 visibility of the dock.

Is there any known way to route an Intel DDI output to a PCIe-attached
Barlow Ridge DP_IN adapter, or is this strictly a design where the dGPU
is the only valid DP source for the discrete TB controller on this class
of HP workstations?

Happy to share the DSDT dump, lspci -vvv, full dmesg, or run any test.

Regards,
Francesco Orro

Re: DP routing from iGPU to discrete Barlow Ridge TB5 on HP ZBook Fury G1i

[Rodrigo Vivi]

On Mon, Apr 20, 2026 at 04:04:02PM +0000, Francesco Orro wrote:
> Hi,
> 
> Setup:
>   HP ZBook Fury G1i 16 inch, BIOS X96 01.03.04
>   Intel Arrow Lake-HX + Nvidia RTX PRO 1000 Blackwell (hybrid graphics)
>   Kernel 6.19.13
> 
> The laptop exposes Thunderbolt 5 on both the integrated MTL iTBT (right
> USB-C, domain0, 00:0d.2) and a discrete Intel Barlow Ridge (left USB-C,
> domain1, 00:06.1 -> 05:00.0).
> 
> - Right port: i915 drives a DP tunnel over the iTBT host without issues.
> - Left port: no i915 connector ever sees the external monitor. The TB
>   driver allocates a DP tunnel on demand but DPRX reads time out, no DP
>   source is feeding the Barlow DP_IN adapter.
> - With nvidia-drm.modeset=1, a DP-MST connector on the Nvidia DRM device
>   sees the monitor via the left port (EDID readable, modes negotiated).
>   The path Nvidia -> Barlow DP_IN is functional.
> 
> Current hypothesis: on this board the discrete Barlow Ridge DP_IN is
> either hardwired to a Nvidia output or behind a firmware-programmed mux
> that BIOS latches to Nvidia at POST and is not exposed to the OS. i915
> would therefore have no path to drive the left ports, by design.

yes, that is usually the case.

> 
> Tests done that did not surface an OS-visible lever:
> - i2cdetect across all SMBus/i801 busses: no DP mux/retimer at plausible
>   addresses (0x60-0x7F).
> - DSDT/SSDT dump (iasl -d): no Device/Method referring to DP routing,
>   DPMUX, retimer programming, or dock display source selection.
> - HP WMI + /sys/devices/virtual/firmware-attributes/hp-bioscfg attribute
>   enumeration: nothing switching dock display source. "Graphics"
>   attribute only offers Hybrid/Discrete.
> - PCI config dump of Barlow Ridge: standard USB4 NHI, no vendor-specific
>   capability hinting at source selection.
> - acpi.no_usb4_osc kernel param (locally patched) to opt out of OSC USB4
>   native support: no change in i915 visibility of the dock.
> 
> Is there any known way to route an Intel DDI output to a PCIe-attached
> Barlow Ridge DP_IN adapter, or is this strictly a design where the dGPU
> is the only valid DP source for the discrete TB controller on this class
> of HP workstations?

I believe this is physically connected or static mux without any way to
re-route this. But I might be wrong.

So, bringing some more folks to the discussion.

> 
> Happy to share the DSDT dump, lspci -vvv, full dmesg, or run any test.
> 
> Regards,
> Francesco Orro

Re: DP routing from iGPU to discrete Barlow Ridge TB5 on HP ZBook Fury G1i

[Mika Westerberg]

On Mon, Apr 20, 2026 at 04:47:25PM -0400, Rodrigo Vivi wrote:
> On Mon, Apr 20, 2026 at 04:04:02PM +0000, Francesco Orro wrote:
> > Hi,
> > 
> > Setup:
> >   HP ZBook Fury G1i 16 inch, BIOS X96 01.03.04
> >   Intel Arrow Lake-HX + Nvidia RTX PRO 1000 Blackwell (hybrid graphics)
> >   Kernel 6.19.13
> > 
> > The laptop exposes Thunderbolt 5 on both the integrated MTL iTBT (right
> > USB-C, domain0, 00:0d.2) and a discrete Intel Barlow Ridge (left USB-C,
> > domain1, 00:06.1 -> 05:00.0).
> > 
> > - Right port: i915 drives a DP tunnel over the iTBT host without issues.
> > - Left port: no i915 connector ever sees the external monitor. The TB
> >   driver allocates a DP tunnel on demand but DPRX reads time out, no DP
> >   source is feeding the Barlow DP_IN adapter.
> > - With nvidia-drm.modeset=1, a DP-MST connector on the Nvidia DRM device
> >   sees the monitor via the left port (EDID readable, modes negotiated).
> >   The path Nvidia -> Barlow DP_IN is functional.
> > 
> > Current hypothesis: on this board the discrete Barlow Ridge DP_IN is
> > either hardwired to a Nvidia output or behind a firmware-programmed mux
> > that BIOS latches to Nvidia at POST and is not exposed to the OS. i915
> > would therefore have no path to drive the left ports, by design.
> 
> yes, that is usually the case.
> 
> > 
> > Tests done that did not surface an OS-visible lever:
> > - i2cdetect across all SMBus/i801 busses: no DP mux/retimer at plausible
> >   addresses (0x60-0x7F).
> > - DSDT/SSDT dump (iasl -d): no Device/Method referring to DP routing,
> >   DPMUX, retimer programming, or dock display source selection.
> > - HP WMI + /sys/devices/virtual/firmware-attributes/hp-bioscfg attribute
> >   enumeration: nothing switching dock display source. "Graphics"
> >   attribute only offers Hybrid/Discrete.
> > - PCI config dump of Barlow Ridge: standard USB4 NHI, no vendor-specific
> >   capability hinting at source selection.
> > - acpi.no_usb4_osc kernel param (locally patched) to opt out of OSC USB4
> >   native support: no change in i915 visibility of the dock.
> > 
> > Is there any known way to route an Intel DDI output to a PCIe-attached
> > Barlow Ridge DP_IN adapter, or is this strictly a design where the dGPU
> > is the only valid DP source for the discrete TB controller on this class
> > of HP workstations?
> 
> I believe this is physically connected or static mux without any way to
> re-route this. But I might be wrong.
> 

This is my understanding too based on the systems I've seen.