All of the power management feature updates for the in-development Linux 6.14 kernel were sent out earlier this week and subsequently merged. As we’ve been seeing with recent Linux kernel releases, AMD continues investing a lot into their AMD P-State CPU frequency scaling driver for better power efficiency on Ryzen processors and since the prior kernel also now being used with the new 5th Gen AMD EPYC server processors too.
Linux power management subsystem maintainer Rafael Wysocki of Intel described the PM pull request for Linux 6.14 as:
“The majority of changes here are cpufreq updates which are dominated by amd-pstate driver changes, like in the previous cycle. Moreover, changes related to amd-pstate are also the majority of cpupower utility updates.
Included are some pieces of new hardware support, like the addition of Clearwater Forest processors support to intel_idle, new cpufreq driver for Airoha SoCs, and Apple cpufreq driver extensions to support more SoCs. The intel_pstate driver is also extended to be able to support new platforms by using ACPI CPPC to compute scaling factors between HWP performance states and frequency.”
On the AMD side there is a regression fix for the preferred core rankings not being utilized, ftrace event support for the amd-pstate driver within active mode, code clean-ups / fixes, and changing the EPP policy for Ryzen CPUs to help with power savings. The Ryzen change is about using “balance_performance” as the Energy Performance Preference default while “performance” will be the default on EPYC server processors. The cpupower utility within the Linux kernel source tree is also extended to support more AMD CPU features.
Over on the Intel side the ACPI CPPC is being used for reading the scaling factors between hardware P-State (HWP) performance levels and frequency and making use of that for Intel Arrow Lake processors. The Intel Idle driver has also added support for next-gen Clearwater Forest E-core server processors.
The Airoha CPUFreq driver that’s new to the Linux 6.14 kernel is for supporting the Airoha EN7581 SoC CPU frequency via the SMC APIs. The extended Apple SoC CPUFreq support is for covering older Apple A7 through A8X SoCs.
More details on the many power management updates for Linux 6.14 via this pull request that is already within Linux Git. Linux 6.14 benchmarks on modern Intel and AMD platforms will begin in the coming days at Phoronix.
