AMD's New PMF CPU Linux Driver Now Preparing For "CnQF"

Written by Michael Larabel in AMD on 23 August 2022 at 03:30 PM EDT. 2 Comments
AMD --
As I've written about the past several weeks, AMD engineers have been preparing a Platform Management Framework (PMF) driver for Linux. The AMD Platform Management Framework for future hardware appears similar to Intel's Dynamic Platform and Thermal Framework (DPTF) and designed to enhance the thermal/power performance of future platforms.

The initial AMD PMF code is coming with Linux 6.1 with an intent on "making AMD PCs smarter, quieter, power efficient by adapting to user behavior and environment."

While that initial AMD PMF code is now ready to go with Linux 6.1 by way of the x86 platform drivers tree, there is already some follow-up functionality being worked on for the Platform Management Framework. Sent out today is support for a new PMF feature: CnQF, or Cool n Quiet Framework. (There were some CnQF mentions as part of the original PMF posting, but now today's CnQF patches are split out as their own series for this feature.)

AMD Cool 'n Quiet itself has been around for nearly two decades while we don't hear much talk of that branding these days... Cool 'n Quiet going back to the Athlon XP days has been around dynamic frequency scaling for AMD processors to improve energy efficiency. Linux has long supported Cool n Quiet for dynamic frequency scaling going back to the Linux 2.6 days.


The hardware days at Phoronix when testing the original AMD Cool 'n' Quiet functionality on Linux. Now based on new Linux driver code, for future AMD CPUs it looks like Cool n Quiet (Framework) branding is becoming part of their Platform Management Framework umbrella.


AMD is now renewing the Cool n Quiet branding as part of their Platform Management Framework:
Cool n Quiet Framework (CnQF) is an extension to the static slider, where the system power can be boosted or throttled independent of the selected slider position. On the fly, the CnQF can be turned on/off via a sysfs knob.

The new AMD PMF CnQF patch comments goes on to summarize:
CnQF (a.k.a Cool and Quiet Framework) extends the static slider concept. PMF dynamically manages system power limits and fan policy based on system power trends which is representative of workload trend.

Static slider and CnQF controls are mutually exclusive for system power budget adjustments. CnQF supports configurable number of modes which can be unique for AC and DC. Every mode is representative of a system state characterized by unique steady state and boost behavior.

OEMs can configure the different modes/system states and how the transition to a mode happens. Whether to have CnQF manage system power budget dynamically in AC or DC or both is also configurable. Mode changes due to CnQF don’t result in slider position change.

CnQF can be toggled by the BIOS or at the Linux run-time via the "/sys/devices/platform/AMDI0102\:00/cnqf/feat" sysfs interface.

This patch series is preparing for the Cool n Quiet Framework in the new AMD PMF world. For now the patches are under review on the kernel mailing list but still have time to be reviewed and potentially mainlined for Linux 6.1 later this year when the initial PMF code is set to be introduced.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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