mt7921 & mt7922 Losing Carrier After DFS Strike

[Mike Silva]

I and other users are having with the following error on the mt7921 & mt7921 after a DFS strike. This has seemed to be an issue since the chipsets were released.

I am experiencing this on:
uname -a
Linux Vancouver 6.2.0-1008-raspi #10-Ubuntu SMP PREEMPT Fri Jun 30 12:20:13 UTC 2023 aarch64 aarch64 aarch64 GNU/Linux

However, you can see that this is a common issue for people running on other linux OSes and architectures, here:
https://github.com/morrownr/USB-WiFi/issues/283

I am running the latest driver in the git.kernel.org repository.
kernel: mt7921u 2-2.4:1.3: WM Firmware Version: ____010000, Build Time: 20230526130958
kernel: mt7921u 2-2.4:1.3: HW/SW Version: 0x8a108a10, Build Time: 20230526130917a

However, as I said this has been an issue for months, so it’s also effected previous kernel and mt76 driver versions. It also is an issue whether I use wpa_supplicant or iwd to manage my WiFi connection.

Where I live, DFS strikes seem fairly common, so I see this on at least a daily basis. And, not infrequently multiple times in a day. Typical log output is here:
Jul 18 06:58:23 Vancouver kernel: wlxe0e1a9368b21: driver doesn't support chan-switch with channel contexts
Jul 18 06:58:23 Vancouver systemd-networkd[1033]: wlxe0e1a9368b21: Lost carrier
Jul 18 07:02:40 Vancouver systemd-resolved[1058]: wlxe0e1a9368b21: Bus client set DNS server list to: 50.0.1.1, 50.0.2.2
Jul 18 09:21:20 Vancouver NetworkManager[1229]: <info>  [1689697280.5776] dhcp4 (wlxe0e1a9368b21): activation: beginning transaction (timeout in 45 seconds)
Jul 18 09:21:20 Vancouver NetworkManager[1229]: <info>  [1689697280.5779] dhcp4 (wlxe0e1a9368b21): state changed no lease
Jul 18 09:21:21 Vancouver avahi-daemon[1183]: Withdrawing address record for 192.168.4.26 on wlxe0e1a9368b21.
Jul 18 09:21:21 Vancouver avahi-daemon[1183]: Leaving mDNS multicast group on interface wlxe0e1a9368b21.IPv4 with address 192.168.4.26.
Jul 18 09:21:21 Vancouver avahi-daemon[1183]: Interface wlxe0e1a9368b21.IPv4 no longer relevant for mDNS.
Jul 18 09:22:05 Vancouver systemd-resolved[1058]: wlxe0e1a9368b21: Bus client set default route setting: no
Jul 18 09:22:05 Vancouver systemd-resolved[1058]: wlxe0e1a9368b21: Bus client reset DNS server list.

In short, DFS strike, AP changes channel, then the mt7921 loses carrier, and my headless machine becomes unresponsive.

I’m happy to provide more detailed logging, if you can suggest a debug mode to run in and how to activate it. This is quite repeatable.