I found the "BIOS and Kernel Developer’s Guide (BKDG) for AMD Family 16h Models 30h-3Fh Processors" on the AMD website that contains information about the Hardware Thermal Control (HTC) feature. Here it is possible to configure the HTC temperature limit (HtcTmpLmt) using the PCI configuration space. This allows the CPU to automatically limit the maximum p-state once the temperature limit is reached, so the CPU temperature does not further increase.
This feature is exactly what I need to limit the maximum temperature that my CPU reaches without using fans. However, I don't have a family 16h CPU, but an "AMD Ryzen 5 5560U", which is family 19h. I was not able to find any documentation about the HTC feature for this family and trying to use the PCI configuration space addresses from the family 16h documentation did not work for my CPU.
My question is whether the HTC feature is still present in family 19h CPUs and if it is possible to configure the temperature limit from the kernel.
If the HTC feature is no longer present, is there some alternative way to configure a maximum temperature from the kernel, that throttles the CPU?
Of course there is the possibility to use a user space program like thermald to control the maximum pstate based on the temperature, but I would prefer if the controller runs directly on the CPU like it does with HTC. For intel CPUs I am currently using the "Thermal Control Circuit" feature for this, which worked way better than thermald, so it would be great if such a configuration option is still present on AMD CPUs.
