AMD Revises WiFi RFI Mitigation Feature For Linux

Besides Bcachefs missing out on Linux 6.5, another patch series that didn't get buttoned up in time for the v6.5 merge window was AMD's work on radio frequency interference (RFI) mitigation between WiFi 6/6e/7 hardware and AMD's newest SoCs with RDNA3 graphics.

As I wrote about back in May, AMD's Linux engineers have been working on WiFi RFI interference mitigation for Linux with new Ryzen laptops. With their latest SoCs bearing RDNA3 graphics (SMU13) there can be interference from the (G)DDR memory clocks and with the local radio module frequency bands used by WiFi 6 / 6e / 7 chipsets. The mitigation approach is to advertise the frequencies in use and then the WiFi hardware can avoid those frequencies for sensitive features.

The AMD work on ACPI WBRF support for Linux has the AMD Radeon graphics driver power management code reporting the frequency information. This support is wired up for SoCs with SMU 13.0.0 / 13.0.7 (RDNA3) IP. Earlier iterations of the WiFi RFI mitigation patches were focused on adapting the wireless drivers Qualcomm ath12k and MediaTek mt76 WiFi to make use of that information in their frequency selection decisions. With more recent versions of the patches this ACPI WBRF support is wired into the mac80211/cfg80211 driver code for easier re-use by different WiFi drivers.

The patches don't note how many AMD Ryzen laptop designs are affected by these electrical and mechanical constraints to need this radio frequency interference mitigation, but if you believe you are affected, today brought the v6 patch series while we wait to see if this work will be ready in time for the next kernel cycle.