Dear Maintainer,

USB-C DisplayPort output does not work on my Lenovo Chromebook
(board name TANIKS) with the stock Debian amd64 kernel.

The system uses MrChromebox UEFI firmware and Debian 14. The internal
display works normally, but an external monitor connected through a
USB-C DisplayPort Alt Mode adapter is not detected.

The stock Debian 7.1.8+deb14.1-amd64 kernel configuration contains:

    # CONFIG_TYPEC_MUX_INTEL_PMC is not set
    CONFIG_INTEL_SCU_IPC=y
    # CONFIG_INTEL_SCU_PLATFORM is not set

The machine exposes the following relevant ACPI devices:

    INTC1026:00
    INTC105C:00

With the stock kernel, /sys/class/typec is empty and the deferred-device
list contains:

    INTC105C:00
    GOOG0014:00    cros-ec-typec: Failed to register port 0

The DRM connectors for the external outputs also remain disconnected:

    card0-DP-1: disconnected
    card0-DP-2: disconnected

I rebuilt the exact Debian 7.1.8 source using the stock Debian kernel
configuration and performed the following tests.

Test 1:

    CONFIG_TYPEC_MUX_INTEL_PMC=m
    # CONFIG_INTEL_SCU_PLATFORM is not set

Result: intel_pmc_mux was present and loaded, but INTC105C remained
deferred, cros_ec_typec could not register port 0, and USB-C DisplayPort
still did not work.

Test 2:

    CONFIG_TYPEC_MUX_INTEL_PMC=m
    CONFIG_INTEL_SCU_PLATFORM=m

Kconfig also selected:

    CONFIG_INTEL_SCU=y

CONFIG_INTEL_SCU_IPC=y was already enabled in the Debian configuration.

Result: after booting this kernel, the USB-C Type-C stack initializes
correctly and the external DisplayPort monitor works.

No kernel source changes were required. The only required changes were
enabling the existing upstream kernel configuration options.

This appears to be a Debian amd64 kernel configuration issue. Please
consider enabling:

    CONFIG_TYPEC_MUX_INTEL_PMC=m
    CONFIG_INTEL_SCU_PLATFORM=m

in the default Debian amd64 kernel configuration.

The controlled results were:

    stock Debian configuration:
        USB-C DisplayPort broken

    + CONFIG_TYPEC_MUX_INTEL_PMC=m:
        still broken

    + CONFIG_INTEL_SCU_PLATFORM=m:
        USB-C DisplayPort works

Expected result:
USB-C DisplayPort Alt Mode should work with the stock Debian kernel on
TANIKS without requiring a custom kernel.

We believe that the bug you reported is fixed in the latest version of
linux, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1145131@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Salvatore Bonaccorso <carnil@debian.org> (supplier of updated linux package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Fri, 04 Sep 2026 06:14:59 +0200
Source: linux
Architecture: source
Version: 7.2.3-1~exp1
Distribution: experimental
Urgency: medium
Maintainer: Debian Kernel Team <debian-kernel@lists.debian.org>
Changed-By: Salvatore Bonaccorso <carnil@debian.org>
Closes: 1145131
Changes:
 linux (7.2.3-1~exp1) experimental; urgency=medium
 .
   * New upstream stable update:
https://www.kernel.org/pub/linux/kernel/v7.x/ChangeLog-7.2.3
 .
   [ Salvatore Bonaccorso ]
   * [amd64] drivers/usb/typec/mux: Enable TYPEC_MUX_INTEL_PMC as module
     (Closes: #1145131)
   * [amd64] drivers/platform/x86: Enable INTEL_SCU_PLATFORM as module
     (Closes: #1145131)
   * linux-image: Bump Pre-Depends version on linux-base (>= 4.17~)
 .
   [ Aurelien Jarno ]
   * [riscv64] Backport support for SpacemiT K1 cpufreq from 7.3
 .
   [ Sjoerd Simons ]
   * [amd64] drivers/hwmon: Enable SENSORS_LENOVO_EC as module
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 e1f39859fd60589fc95cde4a741ed0275ca2c519 1458732 linux_7.2.3-1~exp1.debian.tar.xz
 df625dd72e01832c31912aef93555c4ebc036536 6929 linux_7.2.3-1~exp1_source.buildinfo
Checksums-Sha256:
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