Issue #623 has been reported by herme herme. ---------------------------------------- Bug #623: On T480/S, missing P-state data from ACPI tables prevents Xen from performing frequency scaling https://ticket.coreboot.org/issues/623
* 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]
