AMD Zen 2 Temperature Monitoring Changes Sent In For Linux 4.21

When AMD Zen CPUs originally rolled out, the ability to monitor the CPU core temperatures under Linux didn't roll out until months later. Fortunately, for Zen 2 the AMD Linux CPU temperature driver looks like it will be ready in time.

Back in November when patches first emerged I commented on AMD already working on temperature driver support for Zen 2, or AMD Family 17 Model 30h and newer. Special changes are needed with the new processors having multiple roots per Data Fabric / SMN interface.

That code is now sent in as x86/amd-nb changes for the Linux 4.21 kernel.

Updates the data fabric/system management network code needed to get k10temp working for M30h. Since there are now processors which have multiple roots per DF/SMN interface, there needs to some logic which skips N-1 root complexes per DF/SMN interface. This is because the root complexes per interface are redundant (as far as DF/SMN goes). These changes shouldn't effect past processors and, for F17h M0Xh, the mappings stay the same.

This temperature monitoring support is on top of other "Zen 2" Linux patches we've begun seeing in Q4'2018 for ensuring these next-gen AMD processors will be fully supported by Linux by the time they officially launch in 2019.