Public bug reported:
# HP ZBook Ultra G1a — Linux UCSI ACPI initialization failure (version
0x0000)
**Summary**
Native USB-C DisplayPort Alt Mode fails under Ubuntu 24.04 LTS on an HP
ZBook Ultra G1a, despite functioning correctly under Windows 11 Pro on
the same hardware.
The Linux `ucsi_acpi` driver detects and probes the ACPI UCSI device,
but the firmware mailbox returns UCSI version `0x0000`. The kernel
rejects controller registration with `-ENODEV`, leaving
`/sys/class/typec/` empty.
## Hardware and software
- Device: HP ZBook Ultra G1a
- Processor: AMD Ryzen AI MAX+ PRO 395
- Graphics: AMD Radeon 8060S
- BIOS: X89 01.06.02 (August 26, 2026)
- OS: Ubuntu 24.04 LTS, dual-boot Windows 11 Pro
- Kernels tested: `6.17.0-1032-oem`, `7.0.0-38-generic`
- External display: XREAL One Pro, connected directly over USB-C
- Secure Boot: Enabled
## Expected behavior
Linux initializes the UCSI controller, registers USB-C ports, negotiates
DisplayPort Alt Mode, and detects the external display.
## Actual behavior
- USB device `3318:0436` (XREAL One Pro) enumerates.
- No DisplayPort connector becomes connected.
- `/sys/class/typec/` remains empty.
- `USBC000:00` exists but does not bind to `ucsi_acpi`.
- Explicit driver binding returns `ENODEV`.
- Windows 11 successfully drives the same glasses over the same USB-C
connection.
## Kernel tracing evidence
The driver reaches `ucsi_acpi_probe()`, maps the ACPI resource, and
invokes `_DSM` function 2.
Return probes establish:
```
ucsi_acpi_dsm() = 0
ucsi_acpi_read_version() = 0
UCSI version = 0x0000
ucsi_acpi_probe() = -19
```
The `read_version()` return value is a successful operation status; the
version itself is zero.
The matching Ubuntu source in `drivers/usb/typec/ucsi/ucsi.c` rejects a
zero version:
```c
if (!ucsi->version)
return -ENODEV;
```
## ACPI firmware evidence
- Device: `\_SB.UBTC`
- Hardware ID: `USBC000`
- Compatible ID: `PNP0CA0`
- Shared-memory mailbox: `0x48F94000`
- Resource size: `0x1000`
- `_CRS` and `_STA` are defined.
- HP firmware implements EC communication through `UOTE`, `UDHX`, `UCRT`, and
`UETO`.
- `UETO` copies UCSI version bytes from EC fields `UB00`/`UB01` into mailbox
fields `VER1`/`VER2`.
- The normal Linux `_DSM` read function does not appear to initiate this
response-transfer sequence.
## Troubleshooting performed
1. Verified the XREAL and USB-C video connection work under Windows 11.
2. Updated HP BIOS from X89 01.05.07 to 01.06.02.
3. Tested Ubuntu OEM 6.17 and generic HWE 7.0 kernels.
4. Confirmed UCSI is enabled in BIOS.
5. Tested the BIOS High Resolution USB-C DP Alt Mode option, then restored its
original disabled setting.
6. Verified driver matching, platform-device registration, and absence of
deferred probing.
7. Captured function-graph and return-probe traces.
8. Reproduced the failure after more than 30 minutes of uptime.
## Requested engineering investigation
Please investigate whether HP's embedded controller requires a firmware
initialization handshake before Linux reads the UCSI version.
In particular:
- Why does the UCSI mailbox version remain zero?
- Is an HP-specific initialization step missing?
- Does firmware need to populate the UCSI mailbox before OS driver registration?
- Can this be corrected through HP firmware or a narrowly scoped Linux UCSI
driver quirk?
Please avoid bypassing the version check or assuming a UCSI protocol
version without confirming controller compatibility.
**Impact:** Native USB-C DisplayPort functionality is unavailable under
Linux on an otherwise working workstation.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-38-generic 7.0.0-38.38~24.04.4
ProcVersionSignature: Ubuntu 7.0.0-38.38~24.04.4-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Mon Oct 19 17:51:48 2026
InstallationDate: Installed on 2026-08-10 (70 days ago)
InstallationMedia: Ubuntu 24.04.4 LTS "Noble Numbat" - Release amd64 (20260210)
IwConfig:
lo no wireless extensions.
wlp193s0 no wireless extensions.
docker0 no wireless extensions.
MachineType: HP HP ZBook Ultra G1a 14 inch Mobile Workstation PC
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-38-generic
root=UUID=e60a6fbb-ecf1-4b82-9c69-011acab19baf ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-7.0.0-38-generic N/A
linux-backports-modules-7.0.0-38-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.27
SourcePackage: linux-hwe-7.0
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/26/2026
dmi.bios.release: 6.2
dmi.bios.vendor: HP
dmi.bios.version: X89 Ver. 01.06.02
dmi.board.name: 8D01
dmi.board.vendor: HP
dmi.board.version: KBC Version 35.36.00
dmi.chassis.type: 10
dmi.chassis.vendor: HP
dmi.ec.firmware.release: 53.54
dmi.modalias:
dmi:bvnHP:bvrX89Ver.01.06.02:bd08/26/2026:br6.2:efr53.54:svnHP:pnHPZBookUltraG1a14inchMobileWorkstationPC:pvrSBKPFV3:rvnHP:rn8D01:rvrKBCVersion35.36.00:cvnHP:ct10:cvr:skuB90JKUAR:pfa103C_5336ANHPZBook:
dmi.product.family: 103C_5336AN HP ZBook
dmi.product.name: HP ZBook Ultra G1a 14 inch Mobile Workstation PC
dmi.product.sku: B90JKUAR
dmi.product.version: SBKPFV3
dmi.sys.vendor: HP
** Affects: linux-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug kernel-daily-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2171452
Title:
HP ZBook Ultra G1a — Linux UCSI ACPI initialization failure (version
0x0000)
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