[Bug 2156713] [NEW] Core Ultra 7 258V (Lunar Lake) pinned to minimum frequency — BD PROCHOT stuck asserted (ASUS Zenbook S14 UX5406SA)

Public bug reported: What I expected to happen: CPU scales up to its rated frequency (up to 4.8 GHz) under load. What actually happened: All cores are pinned at the hardware minimum under full load — P-cores 400 MHz, E-cores 200 MHz — while the package is cold (~45 C). Governor and EPP set to "performance", scaling_max_freq = 4.8 GHz, no_turbo = 0, so the OS is requesting full speed. thermal_throttle/package_throttle_count does NOT increment during the clamp, so it is not thermal throttling. RAM/swap/load are all fine. Root cause — BD PROCHOT asserted with no thermal reason: $ sudo rdmsr -a 0x1FC e4005b # MSR_POWER_CTL bit0 = 1 -> BD PROCHOT enabled $ sudo rdmsr -a 0x1B1 8837000c # IA32_PACKAGE_THERM_STATUS, ...0c -> bit2 = 1 PROCHOT actively asserted # digital readout shows the CPU is cold Key behaviour: - A normal reboot does NOT clear it; PROCHOT stays asserted across warm reboots (the EC appears to retain the state). - A full shutdown + EC reset (power off, unplug charger, hold power button ~40 s, replug, power on) DOES clear it; the CPU then runs at full speed (3.8 GHz P-cores / 3.7 GHz E-cores under load). - The usual userspace workaround (sudo wrmsr -a 0x1FC 0xe4005a, clearing BD PROCHOT enable bit) is blocked by kernel lockdown because Secure Boot is enabled: Lockdown: wrmsr: raw MSR access is restricted; see man kernel_lockdown.7 - NOT reproducible on Windows on the same machine/BIOS, which points to a Linux-specific driver/firmware interaction. Steps to reproduce: 1. Boot Ubuntu on an ASUS Zenbook S14 UX5406SA (Core Ultra 7 258V), Secure Boot enabled. 2. Suspend (close lid) and resume — or simply observe after a warm reboot. 3. Run a CPU load and check: cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq -> pinned at 400000/200000. 4. sudo rdmsr -a 0x1B1 -> value ends in 0c (bit2 = PROCHOT asserted) while the CPU is cold. System: - ASUS Zenbook S14 UX5406SA - Intel Core Ultra 7 258V (Lunar Lake), family 6 model 189 stepping 1 - BIOS UX5406SA.308 (2025-06-05, latest available) - Ubuntu 26.04 LTS, kernel 7.0.0-22-generic - intel_pstate (HWP active), Secure Boot ON (lockdown=integrity) Question: should an ASUS platform driver (asus-nb-wmi / asus_armoury) or a Lunar Lake power/thermal driver be de-asserting this PROCHOT source on resume/boot? Is there a fix that does not require disabling Secure Boot? ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-22-generic 7.0.0-22.22 ProcVersionSignature: Ubuntu 7.0.0-22.22-generic 7.0.0 Uname: Linux 7.0.0-22-generic x86_64 ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: ricardo-reis 4575 F.... pipewire ricardo-reis 4600 F.... wireplumber /dev/snd/controlC1: ricardo-reis 4600 F.... wireplumber /dev/snd/seq: ricardo-reis 4575 F.... pipewire CasperMD5CheckResult: unknown CurrentDesktop: ubuntu:GNOME Date: Sun Jun 14 13:52:13 2026 InstallationDate: Installed on 2026-04-24 (51 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) MachineType: ASUSTeK COMPUTER INC. ASUS Zenbook S 14 UX5406SA_UX5406SA ProcEnviron: LANG=pt_BR.UTF-8 PATH=(custom, no user) SHELL=/bin/bash XDG_RUNTIME_DIR=<set> ProcFB: 0 xedrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-22-generic root=UUID=95b909ce-2bd9-461b-88f7-b44bcb954f4b ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 06/05/2025 dmi.bios.release: 5.32 dmi.bios.vendor: American Megatrends International, LLC. dmi.bios.version: UX5406SA.308 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: UX5406SA dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.ec.firmware.release: 3.19 dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvrUX5406SA.308:bd06/05/2025:br5.32:efr3.19:svnASUSTeKCOMPUTERINC.:pnASUSZenbookS14UX5406SA_UX5406SA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX5406SA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:sku:pfaASUSZenbookS14: dmi.product.family: ASUS Zenbook S 14 dmi.product.name: ASUS Zenbook S 14 UX5406SA_UX5406SA dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug resolute wayland-session -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2156713 Title: Core Ultra 7 258V (Lunar Lake) pinned to minimum frequency — BD PROCHOT stuck asserted (ASUS Zenbook S14 UX5406SA) Status in linux package in Ubuntu: New Bug description: What I expected to happen: CPU scales up to its rated frequency (up to 4.8 GHz) under load. What actually happened: All cores are pinned at the hardware minimum under full load — P-cores 400 MHz, E-cores 200 MHz — while the package is cold (~45 C). Governor and EPP set to "performance", scaling_max_freq = 4.8 GHz, no_turbo = 0, so the OS is requesting full speed. thermal_throttle/package_throttle_count does NOT increment during the clamp, so it is not thermal throttling. RAM/swap/load are all fine. Root cause — BD PROCHOT asserted with no thermal reason: $ sudo rdmsr -a 0x1FC e4005b # MSR_POWER_CTL bit0 = 1 -> BD PROCHOT enabled $ sudo rdmsr -a 0x1B1 8837000c # IA32_PACKAGE_THERM_STATUS, ...0c -> bit2 = 1 PROCHOT actively asserted # digital readout shows the CPU is cold Key behaviour: - A normal reboot does NOT clear it; PROCHOT stays asserted across warm reboots (the EC appears to retain the state). - A full shutdown + EC reset (power off, unplug charger, hold power button ~40 s, replug, power on) DOES clear it; the CPU then runs at full speed (3.8 GHz P-cores / 3.7 GHz E-cores under load). - The usual userspace workaround (sudo wrmsr -a 0x1FC 0xe4005a, clearing BD PROCHOT enable bit) is blocked by kernel lockdown because Secure Boot is enabled: Lockdown: wrmsr: raw MSR access is restricted; see man kernel_lockdown.7 - NOT reproducible on Windows on the same machine/BIOS, which points to a Linux-specific driver/firmware interaction. Steps to reproduce: 1. Boot Ubuntu on an ASUS Zenbook S14 UX5406SA (Core Ultra 7 258V), Secure Boot enabled. 2. Suspend (close lid) and resume — or simply observe after a warm reboot. 3. Run a CPU load and check: cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq -> pinned at 400000/200000. 4. sudo rdmsr -a 0x1B1 -> value ends in 0c (bit2 = PROCHOT asserted) while the CPU is cold. System: - ASUS Zenbook S14 UX5406SA - Intel Core Ultra 7 258V (Lunar Lake), family 6 model 189 stepping 1 - BIOS UX5406SA.308 (2025-06-05, latest available) - Ubuntu 26.04 LTS, kernel 7.0.0-22-generic - intel_pstate (HWP active), Secure Boot ON (lockdown=integrity) Question: should an ASUS platform driver (asus-nb-wmi / asus_armoury) or a Lunar Lake power/thermal driver be de-asserting this PROCHOT source on resume/boot? Is there a fix that does not require disabling Secure Boot? ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-22-generic 7.0.0-22.22 ProcVersionSignature: Ubuntu 7.0.0-22.22-generic 7.0.0 Uname: Linux 7.0.0-22-generic x86_64 ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: ricardo-reis 4575 F.... pipewire ricardo-reis 4600 F.... wireplumber /dev/snd/controlC1: ricardo-reis 4600 F.... wireplumber /dev/snd/seq: ricardo-reis 4575 F.... pipewire CasperMD5CheckResult: unknown CurrentDesktop: ubuntu:GNOME Date: Sun Jun 14 13:52:13 2026 InstallationDate: Installed on 2026-04-24 (51 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) MachineType: ASUSTeK COMPUTER INC. ASUS Zenbook S 14 UX5406SA_UX5406SA ProcEnviron: LANG=pt_BR.UTF-8 PATH=(custom, no user) SHELL=/bin/bash XDG_RUNTIME_DIR=<set> ProcFB: 0 xedrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-22-generic root=UUID=95b909ce-2bd9-461b-88f7-b44bcb954f4b ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 06/05/2025 dmi.bios.release: 5.32 dmi.bios.vendor: American Megatrends International, LLC. dmi.bios.version: UX5406SA.308 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: UX5406SA dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.ec.firmware.release: 3.19 dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvrUX5406SA.308:bd06/05/2025:br5.32:efr3.19:svnASUSTeKCOMPUTERINC.:pnASUSZenbookS14UX5406SA_UX5406SA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX5406SA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:sku:pfaASUSZenbookS14: dmi.product.family: ASUS Zenbook S 14 dmi.product.name: ASUS Zenbook S 14 UX5406SA_UX5406SA dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. 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