Raspberry Pi Close To Seeing CPUFreq Support

Nicolas Saenz Julienne of SUSE has been working on CPUFreq support for the Raspberry Pi single board computers to allow for the Linux kernel to provide CPU frequency scaling controls.

This CPUFreq support communicates with firmware running on a dedicated processor on the Raspberry Pi that is responsible for adjusting the CPU frequencies as well as that of the VPU and related blocks. The driver can request changes to the CPU frequencies though isn't necessarily honored depending upon thermal factors and other criteria. The firmware also offers the ability to request a turbo mode, but that can boost up other clocks and appears to be causing issues at least with the current state of the Raspberry Pi kernel drivers.

On Monday the SUSE developer sent out the latest patches for this Raspberry Pi CPUFreq support that amounts to almost 400 lines of new code. Feedback is looking good so far and up to now has been tested with a Raspberry Pi 3 Model B+ but will be tested on more Raspberry Pi hardware soon. Hopefully this support could be tuned up in time for the Linux 5.3 kernel in the late summer.