Public bug reported:
[Target]
Jammy kernel branch: hwe-6.8-next & Noble kernel
[Impact]
After the revert [0] of upstream commit e4731baaf294 ("cpufreq: amd-
pstate: Fix the inconsistency in max frequency units") [1], pushed in
Ubuntu-6.8.0-48.48 / Ubuntu-hwe-6.8-6.8.0-48.48_22.04.1, incorrect value
of cpuinfo_max_freq has been seen when disabling the cpufreq boost in
passive mode (when amd_pstate=passive is passed to the kernel in the
boot command line). This revert was originally introduced to address a
regression observed in older stable kernels (precisely on 6.6.y, see
[2]). However, this regression is linked to the absence of the linux
upstream commit 5547c0ebfc2e ("cpufreq: amd-pstate: Unify computation of
{max,min,nominal,lowest_nonlinear}_freq") that is not backported on
6.6.y but it is present in both 6.9.y [3] and linux-hwe-6.8 [4].
Thus, the revert should not have been applied to linux-hwe-6.8.
[0]
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?id=d76c1093e3fc
[1]
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?id=342e57b2330b
[2] https://lore.kernel.org/all/[email protected]/
[3]
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d10692ac4a4a2
[4]
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?id=7a7da95b1e7c
[Test Case]
(Activating the boost)
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/boost; do echo 1 > $cpu ; done
(Deactivating the boost)
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/boost; do echo 0 > $cpu ; done
$ cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
[Expected behavior]
2151000
[Actual behavior]
2151
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2109609
Title:
cpufreq amd-pstate: cpuinfo_max_freq reports incorrect value (kHz
instead of MHz)
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