cpu frequency stuck below min frequency with power_save governor

[Rocko]

Sometimes my laptop will be very sluggish after rebooting from prime-select = nvidia back into intel and it's because the cpu frequency is stuck in the range approx 450-750 MHz instead of its normal range of 800 MHz to 3.8 GHz. Switching to use the performance governor restores performance, but if I switch back to powersave, the frequency gets stuck again below the minimum.

I've attached dumps of /sys/cpuinfo and /sys/devices/system/cpu/cpu0/cpufreq/* to show the current frequency is below 750 MHz even though the minimum frequency is 800 MHz.

Usually this resolves after a second reboot but this time it has persisted over several reboots (and it doesn't matter whether I boot into linux 5.2 or 5.3-rc6).

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: linux-image-5.2.0-10-generic 5.2.0-10.11
ProcVersionSignature: Ubuntu 5.2.0-10.11-generic 5.2.4
Uname: Linux 5.2.0-10-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu7
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: gdm 1400 F.... pulseaudio
                      rocko 1829 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 27 16:46:08 2019
InstallationDate: Installed on 2019-07-01 (56 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Alpha amd64 (20190606)
MachineType: Dell Inc. XPS 15 9560
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-5.2.0-10-generic root=UUID=f5a24957-19c2-4a22-acc0-3776c6300bf5 ro rootflags=subvol=@ quiet splash scsi_mod.use_blk_mq=1 vt.handoff=7
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: XDG_RUNTIME_DIR (/run/user/1001) is not owned by us (uid 0), but by uid 1001! (This could e.g. happen if you try to connect to a non-root PulseAudio as a root user, over the native protocol. Don't do that.)
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-5.2.0-10-generic N/A
 linux-backports-modules-5.2.0-10-generic N/A
 linux-firmware 1.181
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/23/2019
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.15.0
dmi.board.name: 05FFDN
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.15.0:bd05/23/2019:svnDellInc.:pnXPS159560:pvr:rvnDellInc.:rn05FFDN:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: XPS
dmi.product.name: XPS 15 9560
dmi.product.sku: 07BE
dmi.sys.vendor: Dell Inc.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Kai-Heng Feng (kaihengfeng)]

Does this issue happen under v5.3?

[Rocko (rockorequin)]

I've not had a chance to test it recently - I haven't seen it happen for a while, but I'm not switching between the nvidia and intel cards, either, so I don't expect to. If I get a chance to try it on the weekend I'll report back.