Public bug reported:
On some GB10 OEM platforms the firmware brings up USB4. DGX Spark does
not currently plan to support USB4, so it must be disabled from the OS
side on these platforms. Disabling USB4 at the firmware level also lets
any connected USB4 device fall back to USB3 so it remains usable.
The OEM firmware exposes an NVIDIA vendor _DSM on the UCSI device (UUID
58ee92f1-76ca-48da-92f0-d548e83e80ea, rev 0) with three functions: 0 =
query supported-functions bitmap, 1 = enable USB4, 2 = disable USB4. The
method returns a Buffer(1) whose byte 0 is 0x01 on success and 0x00 on
failure.
Invoke the disable function (index 2) at ucsi_acpi probe time. Running
before ucsi_register() avoids a race where the asynchronous partner
discovery kicked off by the UCSI core could read the USB4 capabilities
from the partner before the firmware has gated USB4 off. The call is
gated on acpi_check_dsm() so hardware without this vendor DSM is
unaffected, and is best-effort: probe never fails on a DSM error.
** Affects: linux-nvidia-bos (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2167862
Title:
usb: typec: ucsi: acpi: disable USB4 via vendor _DSM
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