Re: Porting to Snapdragon 8cx SoC

On 1/12/26 12:57, Gabe Bauer wrote:
> Hello, community! I am reaching out because I have a Thinkpad X13s with
> a Snapdragon 8cx Gen 3 SoC. I have been unable to get any operating
> system to work so far on this machine. I have done a fair amount of
> coding and debugging in C. However, I have never ported an operating
> system before. I am in my senior year at university and I would like to
> undertake this as a project. I have an x86_64 machine running FreeBSD
> which I can use to help me in this endeavour. However, since I have
> never done this before, I lack the domain specific knowledge on what I
> will need in order to be successful. Any tips on how to get started
> would be greatly appreciated. Thank you very much!!


Well, the Windows Dev Kit 2023 used(/uses) a Snapdragon 8cx Gen 3 SoC
and has a UEFI/ACPI that FreeBSD boots just fine. But FreeBSD does not
support the 2 USB-C ports in the result. It does support the 3 USB-A
ports, including booting from USB-A ports. (Some UEFI configuration
required to make that the default. I leave the internal drive with
Windows 11 Pro, forming the local Windows on aarch64 example when booted
that way.)

But, in the FreeBSD based Dev Kit 20023 context, the UEFI/ACPI that is
built-in has the Snapdragon 8cx Gen 3 SoC related magic in it instead of
in the FreeBSD kernel, if I understand right.

The UEFI/ACPI source code is not public as far as I know.


The Snapdragon 8cx Gen 3 SoC presents as having:

4 Cortex-A78C
and
4 Cortex-X1C


FreeBSD does report the following relative to the ACPI and what FreeBSD
does not handle:

ACPI Error: AE_NOT_FOUND, While resolving a named reference package
element - \134_SB_.UBF0.PRT0 (20251212/dspkginit-605)
ACPI Error: AE_NOT_FOUND, While resolving a named reference package
element - \134_SB_.UBF0.PRT1 (20251212/dspkginit-605)
. . .
ACPI Warning: \134_SB.GPU0._CLS: Return Package is too small - found 1
elements, expected 3 (20251212/nsprepkg-511)
can't fetch resources for \134_SB_.ADC1 - AE_AML_INVALID_RESOURCE_TYPE
acpi0: Could not update all GPEs: AE_NOT_CONFIGURED

The 2 "ACPI Error" messages may well be tied to the 2 USB-C ports.


-- 
===
Mark Millard
marklmi at yahoo.com