Re: Porting to Snapdragon 8cx SoC

On 1/12/26 15:09, Mark Millard wrote:
> 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.
> 
> 

Looking around, the following are the commits that reference the Windows
Dev Kit 2023. The older ones may give hints at what was required to get
the FreeBSD kernel to boot based on the UEFI/ACPI involved.


Commit message
Author	Age	Files	Lines
Commit URL

lib/libmd: add optimised SHA1 implementations for aarch64
Robert Clausecker	2025-05-14	2	-0/+514
https://cgit.freebsd.org/src/commit/?id=f6210541f9e3c6cfda321e0ad98f277fb98a625b

libc/aarch64: fix strlen() when flush-to-zero is set
Robert Clausecker	2025-01-16	1	-2/+1
https://cgit.freebsd.org/src/commit/?id=521c1fe0e2002dfd7d8db86eb7144b7865229912

arm64: Enable the Hyper-V keyboard driver
Andrew Turner	2023-06-21	1	-0/+2
https://cgit.freebsd.org/src/commit/?id=3a1bfe881a24a76ff8d6406476461924a027ea8a

arm64: Disable PAC when booting on a Windows Dev Kit 2023
Mark Johnston	2023-04-23	1	-1/+30
https://cgit.freebsd.org/src/commit/?id=4b39a12830feaf2ac49b157ed079c04114b1a3ca

Add CPU Ident for Qualcomm Kryo 400 (used in MS Dev Kit)
Allan Jude	2023-01-18	2	-1/+14
https://cgit.freebsd.org/src/commit/?id=fd5e9210598cfafbecc05b5ec03da25483833f90

Add the fixed memory type to the pci ecam driver
Andrew Turner	2023-01-18	1	-3/+20
https://cgit.freebsd.org/src/commit/?id=896f556205c8d87ef842dc844752daa7d2385336

loader.efi: make sure kernel image is executable
Robert Clausecker	2023-01-05	1	-4/+4
https://cgit.freebsd.org/src/commit/?id=95fa2e0aee5b7259cf4bcdea7396c4dff3241173

Add Windows Dev Kit 2023 support to if_ure
Andrew Turner	2023-01-04	2	-0/+2
https://cgit.freebsd.org/src/commit/?id=e5b9b5ee8c3a4f3bff348cd94e3555e6b69585f6

Check for more XHCI ACPI IDs
Andrew Turner	2023-01-04	1	-4/+7
https://cgit.freebsd.org/src/commit/?
id=8793196ca28f7b78f04ca479fe60b7d7af6b20e1


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