Re: [BUG] ucsi_acpi: Fails to bind on USBC000 devices, version=0 in NVS blocks probe

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi Daniel,

On Tue, Apr 21, 2026 at 11:15:56AM +0000, Daniel Dev wrote:
> Hello everyone,
> 
> I am reporting two related issues in ucsi_acpi that prevent it from binding on Lenovo ThinkPad T14 Gen 2a (AMD) platforms. The result is that /sys/class/typec/ is empty and USB-C display hotplug is non-functional unless a manual workaround is applied.
> 
> Hardware:
> - Machine: Lenovo ThinkPad T14 Gen 2a (20XLS10M00)
> - CPU: AMD Ryzen 7 PRO 5850U
> - Kernel: 6.19.12-200.fc43.x86_64 (Reproduced on 6.19.12, 6.19.9, and 6.18.19)
> - Distros tested: Fedora 43, CachyOS (Arch-based), Arch and Kubuntu (Debian-based)
> 
> ---
> 
> ### Bug 1: HID Mismatch (USBC000 vs PNP0CA0)
> The ACPI device uses "USBC000" as its primary HID, with "PNP0CA0" as a Compatible ID (CID).
> ```bash
> $ cat /sys/bus/platform/devices/USBC000:00/modalias
> acpi:USBC000:PNP0CA0:
> ```
> Because ucsi_acpi only matches on PNP0CA0, the ACPI bus does not automatically bind the driver. Adding USBC000 to the acpi_device_id table is required for automatic discovery on these platforms.

This sounds really odd? Why would this become a problem now, and not
before?

I'll see if I can reproduce this.

> ---
> 
> ### Bug 2: UCSI NVS Version = 0x0000 blocks probe
> Even when forced to bind (via driver_override), the probe fails because the BIOS does not populate the VERSION field in the UCSI ACPI NVS region at runtime.
> 
> Actual probe failure log:
> ```text
> Apr 21 11:29:37 fedora kernel: platform USBC000:00: bus: 'platform': __driver_probe_device: matched device with driver ucsi_acpi
> Apr 21 11:29:37 fedora kernel: platform USBC000:00: bus: 'platform': really_probe: probing driver ucsi_acpi with device
> Apr 21 11:29:39 fedora kernel: ucsi_acpi USBC000:00: probe with driver ucsi_acpi rejects match -19
> ```
> 
> Actual Raw NVS Dump (from UCSI region 0xCBC37000):
> ```text
> Apr 21 11:41:28 fedora kernel: ucsi_peek: version=0x0000 cci=0x00000002
> Apr 21 11:41:28 fedora kernel: ucsi_peek: raw NVS dump:
>                                  +00: 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00
>                                  +10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>                                  +20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ```

Again with the missing version. Please contact Lenovo. This is a bug
in their firmware. The version field must supply the actual ucsi
version.

thanks,

-- 
heikki