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 Checksums-Sha1: 38c88621f5b6415ddc346afff60e8ffbebc97619 177068 linux_7.2.3-1~exp1.dsc 3becad2c2b321052721cddd23f64e45d0a2fb2a6 163367692 linux_7.2.3.orig.tar.xz e1f39859fd60589fc95cde4a741ed0275ca2c519 1458732 linux_7.2.3-1~exp1.debian.tar.xz df625dd72e01832c31912aef93555c4ebc036536 6929 linux_7.2.3-1~exp1_source.buildinfo Checksums-Sha256: d914448e45e12a0b121d5e17f238f0f96ab4a92eb04597b79953dd063df99547 177068 linux_7.2.3-1~exp1.dsc 93e9469bbd366ba119f5b36e061ea413cdbbe07dd76cc73df816ef044e9ce74a 163367692 linux_7.2.3.orig.tar.xz 6230c5a91744008b37488df463e2e5ee643e05640840260ccb0bace8bdff96e9 1458732 linux_7.2.3-1~exp1.debian.tar.xz d0ca10198b9221c633740bc5dfd4270ca646698050255d7d3c3ea91a850adf28 6929 linux_7.2.3-1~exp1_source.buildinfo Files: 8bc0151424d61caa8883e32c538e0b70 177068 kernel optional linux_7.2.3-1~exp1.dsc 68a758463823d75c8fe0f237bc2bd063 163367692 kernel optional linux_7.2.3.orig.tar.xz 96d7aa1f81c0f1d1089503d682c7b536 1458732 kernel optional linux_7.2.3-1~exp1.debian.tar.xz b7ca53018294b3b9691512eec11f9b63 6929 kernel optional linux_7.2.3-1~exp1_source.buildinfo -----BEGIN PGP SIGNATURE----- iQKmBAEBCgCQFiEERkRAmAjBceBVMd3uBUy48xNDz0QFAmqaSfpfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldDQ2 NDQ0MDk4MDhDMTcxRTA1NTMxRERFRTA1NENCOEYzMTM0M0NGNDQSHGNhcm5pbEBk ZWJpYW4ub3JnAAoJEAVMuPMTQ89EkC4P/A+16PPosweLvIEp9Ch/lL2VxBk6pQdi 4GW6UcUyEsK1ScFLkFqeMrDI6Lw+JEubIcETcnw9KIDif93TOqw0fKAXa+hIm+3K eBlxoV3y07U4YcxGB3+VW/nBtYiziUtaG6sXReYMLg1RspWvfMomoZPMwVLtJ5yD yWaglfcMAl13XYDINTVHCaXtH8GmQKuEI4dAxso0GLjzyKmYbZAsx5W87DZzb3JT ifdMDKAIWg+l17/nTVVPC/8XKez26M2OCsa9JDA0IPne+gxyJobtjCBcFX/G/F6n yCEJ0l5wJCCykeOstunoUYoKzguTZbPBDSOJfKYMOqwRETm/xTqD9RXP3+VfykG7 QUAHSx9CBwCubPLTYl8qM0TadqYs6eWbZsK2NittsFXC49Dx7Qb8b4Wv+1W8h/KK NFQ/P0phiyMNCd6AZGYcOJG+F/p6s/xq/2eB0HmYSy7hrJKqr2ox3E5Fd9Oho0WC mjEvEkFPBEl0s7g5k9nCDr7REb+V+AG2k+TegmOogtxKdXjar6QJunM3PHp8/hl+ g5nOVyXLVXShG7OWjaSnpQJf5mkXDjNPRAU37Y4YVyI8VOu6QEqwzAqBFB3L2XIC DBUS2mGCsBd4Tt1/ecrtFXaiZGOObEELGvRCkiV5fvdaQre27bVtX46lNGqKqLQ6 wtly0xpRUROA =s8q9 -----END PGP SIGNATURE-----
Dear Debian kernel maintainers, I have the same problem as the original reporter: I attach my laptop to a beamer via the USB-C Display Port and nothing happens. This worked in bookworm, so this is a regression from bookworm to trixie. Could you please enable the TYPEC_MUX_INTEL_PMC and INTEL_SCU_PLATFORM kernel modules in the trixie stable series kernel as well? Many thanks for maintaining the kernels!!! *t
Hi Tomas, Were you able to test this fixes your problem? Regards, Salvatore
Ciao Salvatore, thanks a lot for replying... contains those modules, but it requires linux-base from unstable and that maybe pulls in other stuff... which made me back off from that. I've also compiled those modules for my current trixie kernel from Debian sources but I can't insmod those due missing Secure Boot signatures. I have no idea about Secure Boot, so I've backed off from this as well for the moment. In case I'd be trivial for you to flip those two config flags, type `make` and send those two modules to me then I could test those - see below. FWIW symptoms: when I plug in a display into the Display Port then there's no reaction at all from the kernel. No message in `dmesg` at all. I want to re-test with the bookworm kernel since it does contain the modules in question ... $ dpkg -L linux-image-6.1.0-53-amd64 | grep pmc | grep intel /lib/modules/6.1.0-53-amd64/kernel/drivers/mfd/intel_pmc_bxt.ko /lib/modules/6.1.0-53-amd64/kernel/drivers/platform/x86/intel/pmc /lib/modules/6.1.0-53-amd64/kernel/drivers/platform/x86/intel/pmc/intel_pmc_core.ko /lib/modules/6.1.0-53-amd64/kernel/drivers/platform/x86/intel/pmc/intel_pmc_core_pltdrv.ko ... just to make sure it's not a broken hardware port. However I can't test at the moment, since I do not own a Display Port device myself - the problem occured at a location where I had to give a presentation. Hopefully I'll get a hand on a Display Port to HDMI adapter this weekend, then I'll be able to test. Otherwise I'll be at the same presentation location next Tuesday and I'll be able to test there for maybe an hour... Thank you & best greetings! *t