We have a problem with the MT7915 radio. Sometimes it switches to the 6 GHz band instead of the selected channel. I find this issue in the HE20/HE40/HE80 MHz modes, across different regions and channels that I have tested. I tested it using the command ubus hostapd switch_chan, as well as through the config file. I discovered that the AM region is mostly garbaged. I mainly use the KZ and CN regions, and everything is almost fine there.
I also conducted some experiments with the mt76 driver and tried to disable the transition to 6 GHz wherever it seemed possible to me. And I feel that it sometimes works, but not always. But with the given config, I always get 6 GHz:
config wifi-device 'radio1'
...
option channel '36'
option band '5g'
option htmode 'HE40'
option txpower '20'
option country 'AM'
...
I also noticed a strange way to achieve operation at the required frequency, bandwidth, and region. If you make many attempts to switch (ubus hostapd switch_chan) to random channels, at some point it is possible to set the desired configuration. I stumbled upon this while running my script, which switches to a random channel with bandwidth every 2 seconds.
Forexample:
ubus call hostapd.wlan1 switch_chan "{'freq':5180,'bcn_count':10,'bandwidth':40,'sec_channel_offset':0,'ht':true,'he':true}"
I even tried to ban 6GHz via device tree. But it doesn't work for me.
&pcie0 {
wifi@0,0 {
compatible = "mediatek,mt76";
reg = <0x0000 0 0 0 0>;
mediatek,mtd-eeprom = <&factory 0x0>;
nvmem-cells = <&macaddr_factory_e00c>;
nvmem-cell-names = "mac-address";
ieee80211-freq-limit = <5000000 6000000>;
};
};
The issue with switching to 6 GHz occurs in all versions of OpenWRT v21.02.0-rc1 and later.
Is there anyone in the community who cares, understands this, and can help?
Maybe you have a firmware fix, ideas or some workaround?
link to open issue on github.