[SRU][N][PATCH v2 0/1] cpufreq amd-pstate: cpuinfo_max_freq reports incorrect value

[Manuel Diewald]

BugLink: https://bugs.launchpad.net/bugs/2109609

SRU Justification:

[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/18882bfe-4ca5-495c-ace5-b9bcab796ae5@amd.com/
[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

[Fix]

Revert the revert commit that was erroneously included in noble via a
stable update including patches from linux-6.6.y.

[Test Plan]

(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

[Where problems could occur]

If regressions were to occur they would manifest as cpu frequencies
being reported in incorrect frequency units.

[Other Info]
v2:
 - Fix threading of patch submission

Manuel Diewald (1):
  UBUNTU: SAUCE: Revert "Revert "cpufreq: amd-pstate: Fix the
    inconsistency in max frequency units""

 drivers/cpufreq/amd-pstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.34.1