Issue #623 has been updated by herme herme.
Hi Ivi, many thanks for taking an interest in this issue! I was able to obtain the following files: - A dump using the method described in the first post, for a T480S motherboard; Bios Version: N22ET62W (1.39), CPU: i5-8350U. Courtesy of [cepawiel at the Libreboot issue tracker](https://codeberg.org/libreboot/lbmk/issues/394#issuecomment-10420088). The files are here: [https://codeberg.org/attachments/f669fca0-90d2-48c9-9602-c9aa20102440](https://www.thinkwiki.org/wiki/Category:T480s) - One dump for T480 (Model: [20L5000UUS](https://github.com/linuxhw/ACPI/tree/d6d30c6ef6f45506567f25a302c64f009d8f5f4e/Notebook/Lenovo/ThinkPad/ThinkPad%20T480%2020L5000UUS)) and two dumps for T480S (Models: [20L7S00600](https://github.com/linuxhw/ACPI/tree/d6d30c6ef6f45506567f25a302c64f009d8f5f4e/Notebook/Lenovo/ThinkPad/ThinkPad%20T480s%2020L7S00600) and [20L8S7PP06](https://github.com/linuxhw/ACPI/tree/d6d30c6ef6f45506567f25a302c64f009d8f5f4e/Notebook/Lenovo/ThinkPad/ThinkPad%20T480s%2020L8S7PP06)). These dumps are part of the repo for the [https://linux-hardware.org/](https://linux-hardware.org/) project, which provides their own tool for dumping the ACPI tables. The actual data is uploaded by anonymous volunteers. There is some variation across T480/S models (e.g [several different CPU models](https://www.thinkwiki.org/wiki/Category:T480s) and [dozens of device models](https://devicehd.com/laptops/en/model/lenovo-thinkpad-t-t480s)). I didn't know if this makes a difference, which is why I tried to include more than one source. Please let me know in case you think additional dumps might be useful and I'll try to find more volunteers. ---------------------------------------- Bug #623: On T480/S, missing P-state data from ACPI tables prevents Xen from performing frequency scaling https://ticket.coreboot.org/issues/623#change-2213 * Author: herme herme * Status: New * Priority: Normal * Target version: none * Start date: 2026-01-16 * Affected versions: main * Affected hardware: T480/S * Affected OS: QubesOS ---------------------------------------- Hello Currently, P-state data is missing from ACPI tables on T480/S. On my T480S running libreboot, this was confirmed by using the iasl command to decompile the tables at `/sys/firmware/acpi/tables/`; grepping for `_PSS`, `_PCT` and `_PPC` didn't return any results. [Another user](https://codeberg.org/libreboot/lbmk/issues/394) has confirmed that this is also the case for the similar T480 device, with latest release build of libreboot (26.01 RC1). Meanwhile, in the vendor T480S BIOS, this data is present (contributed by @henk on #coreboot IRC channel): ``` # grep -r -e _PCT -e _PPC -e _PSS *.dsl DSDT.dsl: If (CondRefOf (\_PR.PR00._PPC)) DSDT.dsl: If ((CondRefOf (\_PR.PR00._PSS) && CondRefOf (\_PR.PR00._PPC))) SSDT1.dsl: External (_PR_.PR00._PSS, MethodObj) // 0 Arguments SSDT1.dsl: Name (_PPC, Zero) // _PPC: Performance Present Capabilities SSDT1.dsl: If (CondRefOf (\_PR.PR00._PSS)) SSDT1.dsl: Method (_PSS, 0, NotSerialized) // _PSS: Performance Supported States SSDT1.dsl: If (CondRefOf (\_PR.PR00._PSS)) SSDT1.dsl: Return (\_PR.PR00._PSS ()) SSDT1.dsl: If (CondRefOf (\_PR.PR00._PSS)) SSDT8.dsl: If (CondRefOf (\_PR.PR00._PSS)) ``` The Linux kernel doesn't rely on this data to perform frequency scaling, because native support is provided by the intel_pstate driver. However, the Xen kernel lacks this native support. When the data is missing, as in my case, the Xen-based QubesOS runs underclocked and is only barely usable. -- You have received this notification because you have either subscribed to it, or are involved in it. To change your notification preferences, please click here: https://ticket.coreboot.org/my/account _______________________________________________ coreboot mailing list -- [email protected] To unsubscribe send an email to [email protected]
