Intel's Dynamic Platform and Thermal Framework is a combination firmware/OS framework for allowing userland to implement more complex thermal policies in conjunction with the platform firmware. The rough gist is that the firmware exposes a set of information describing the relationships between various heat generating and heat removing components in the system, the OS makes a reasonable decision about what sort of policy will work best given the constraints the system is currently operating under and passes that decision back to the firmware, and the firmware does some magic (potentially including reprogramming various CPU MSRs) to match the OS policy. Depending on the policy, the OS may then be responsible for ensuring that the system stays within the appropriate thermal envelope.
Linux already has a driver that exposes the firmware interface for setting the policy, but it's somewhat broken - it only exposes a very small subset of the defined policies, and most new systems don't intersect with the exposed ones (strangely, support for some policies was actively removed in 31908f45a583e8f21db37f402b6e8d5739945afd). It also doesn't actually /work/ on any new systems, since the PASSIVE_1 policy seems to have been replaced by the PASSIVE_2 policy and therefore it's impossible to actually trigger a new UUID write. The consequence of this right now is that various new systems (such as most current Thinkpads) default to a safe policy that throttles the CPU at a low temperature, dramatically reducing system performance. Since Linux provides no mechanism to set any of the other policies the platform supports, users are stuck. This patchset adds all the UUIDs I've been able to find from scraping various ACPI tables, and fixes the mode setting in order to make it possible to actually set the new modes. It should be noted that this is nowhere near an actual solution - doing this properly requires appropriate userspace management tooling, and Intel haven't documented most of the ACPI information required to make it possible to write such tooling. However, this is a first step in making it possible to do that work.
