mt76: MT7921K monitor mode not working

[Jan Fuchs]

Hi,

we are not able to obtain any packets when packet capturing with the 
Mediatek MT7921K in monitor mode on 2.4, 5 and 6 GHz.
tcpdump will show you 0 recorded packets. When doing a "iw dev wls1 
scan" on a parallel running managed interface on the same phy, the 
packet capture will contain beacons and probe responses from the scan 
though.
Can anyone confirm that?

mt76 (https://github.com/openwrt/mt76/commits/master): commit 
6fad970893dd26ef6e6c8344b958344254f6362a (HEAD -> master, origin/master, 
origin/HEAD)
Kernel: 5.16.0-rc2-next-20211124+
WM Firmware Version: ____010000, Build Time: 20211014150922

Steps to reproduce:
sudo iw dev wls1 del
sudo iw phy phy0 interface add mon0 type monitor
sudo ip link set dev mon0 up
sudo iw dev mon0 set freq 6115
sudo tcpdump -i mon0 -w 6g-capture.pcap

Kinds regards, Jan