Linux Gets New Thermal Driver Code Ahead of Alder Lake

The thermal subsystem updates for the Linux 5.14 kernel include more work on Intel's int340x driver that is used by newer Intel laptops for dealing with their varying thermal control capabilities and exposing more thermal information to user-space for use by Intel's Thermal Daemon (Thermald). This cycle the work includes a new driver that will be used by next-gen Alder Lake SoCs.

Among the Intel int340x thermal work for Linux 5.14 is the introduction of a new processor_thermal PCI MMIO-based driver. This PCI driver registers a thermal zone and the temperatures and trip points are using PCI MMIO rather than ACPI methods for communication. This PCI MMIO thermal driver is set so far just to be used for upcoming Alder Lake SoCs and isn't used by already supported int340x-using hardware.

Also for this next kernel the Intel int340x code exports more attributes via sysfs. The current DDR memory data rate is exposed as a new "ddr_data_rate" attribute on sysfs for those wondering if the DDR speed is being set lower for thermal reasons.

The other new attribute on sysfs for int340x is "rfi_restriction" for showing or setting the Radio Frequency Interference (RFI) protection state. This is part of Intel's recent work around radio frequency interference mitigation on Linux.

The Intel thermal work and other new code in this subsystem can be found via this pull request. The work though hasn't landed as it looks like the thermal code will be re-submitted but without the NVIDIA Tegra changes due to build breakage.