The “k10temp” Linux hardware monitoring driver is giving up support for reporting processor voltage and current information for AMD Zen-based processors due to a lack of documentation to properly support functionality.
In early 2020, this long-lasting AMD hwmon temperature driver added support for core / SoC current and voltage reporting with Zen processors based on community activity and best assumptions around the corresponding registers. But now the support is abandoned due to lack of precision in some configurations and the possibility of damaging the hardware.
Last week was the main hwmon pull request for the Linux 5.11 cycle, while it was sent today was a secondary update, the only change being the elimination of this k10temp current / voltage ratio.
The support is removed because “it turns out that [it] it was not worth the trouble. ”
The Git Committee that removes support from k10temp goes on to explain:
Voltages and current are reported by Zen processors. However, the means to do this are undocumented, they change from CPU to CPU and the raw data is not calibrated. Calibration information is available, but again not documented. This results in a less perfect user experience, to the point of concern that charging the driver could damage the hardware (by reporting out-of-range voltages). The actual voltage and current reporting support cannot be maintained. Let him.
For those who only want power values, the “AMD_Energy” driver is also available with the main kernel, but currently it exposes the power details of EPYC CPUs after the original Ryzen support was removed there. We hope that AMD will release the necessary documentation in 2021 to allow the correct restoration of this k10temp support.