AMD Prepares PMF Linux Driver For "Smart PC Solutions Builder"
AMD Linux engineers on Friday posted a set of fifteen patches for extending the AMD PMF Linux driver to support this new "Smart PC Solutions Builder" functionality. It's described by the patches as:
"Smart PC Solutions Builder allows for OEM to define a large number of custom system states to dynamically switch to. The system states are referred to as policies, and multiple policies can be loaded onto the system at any given time, however only one policy can be active at a given time.
Policy is a combination of PMF input and output capabilities. The inputs are the incoming information from the other kernel subsystems like LID state, Sensor info, GPU info etc and the actions are the updating the power limits of SMU etc."
Basically it's around allowing OEMs more control over the power/performance/thermal behavior of the laptop/desktop based on more environment factors and not limited to just the CPU/SoC subsystem. But where it may be a bit controversial among the open-source/Linux crowd comes down to the authentication and restrictions put in place by AMD. The patch series goes on to explain:
"The policy binary is signed and encrypted by a special key from AMD. This policy binary shall have the inputs and outputs which the OEMs can build for the platform customization that can enhance the user experience and system behavior.
This series adds the initial support for Smart PC solution to PMF driver.
Note that, on platforms where CnQF and Smart PC is advertised, Smart PC shall have higher precedence and same applies for Auto Mode."
So to benefit from this extra tuning, a signed and encrypted blob is needed on the system. Thus similar to the recently-merged AMD Dynamic Boost Control functionality that depends upon integration with the PSP/CCP security and not allowing users unfettered access for tuning. The AMD PMF authentication for this new "Smart PC" functionality also ties into the AMD Security Processor's Trusted Execution Environment (TEE). The AMD PMF "policy" binary blob is to be distributed as part of the system BIOS. But with these patches is also the ability to side-load the binaries via DebugFS for debugging purposes but for end-users it's expected these binaries will just be loaded from the BIOS.
At least from looking through the patches, it appears only AMD will be signing these blobs on behalf of the OEMs/ODMs. These policies are shared regardless of operating system in use and AMD will be reviewing each policy before signing/encrypting them -- presumably to ensure they don't push the Ryzen SoCs out-of-spec or other abnormal state.
The AMD PMF patches also provide the integration with the AMDGPU kernel graphics driver, human presence detection (HPD), and ambient light sensor (ALS) bits.
See the patch series for those interested in this AMD PMF Smart PC Solution Builder feature being worked on for the Linux kernel.
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