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

[Stefan Bader]

On 20.05.25 15:25, Manuel Diewald wrote:
> 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(-)
> 

Acked-by: Stefan Bader <stefan.bader at canonical.com>
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