Async Channel Bandwith, mt7915, mt7916.

I noticed at 5ghz when i look in openwrt in the wireless client list that, tx bandwith gets stuck at 20Mhz and rx stays at 80mhz or 160mhz. So the chip only uses 20mhz bandwith for tx despite best conditions. Result 250mbit down and 800mbit at 80mhz and 1400mbit upload at 160mhz. At first i suspected a DFS event, but there is noting in the logs and i also looked in the air with my spectrum analyzer, nothing that would/should ever trigger a DFS event. Same result on a completly empty channel.

Happens with: mt7921, ax210, S23 and iPhone 12 as STA

Openwrt: 23.05.4 build today and todays snap.

Edit: the mt7915, mt7916 and mt7976c ( bpi r3 ) seem to work perfectly, if I copy the eeprom files from this git to /lib/firmware/meditek.

Edit: did some further tests, mt7976c is also affected on bpi r3. This happens when, the client roams on a DBDC version from the phy of 2,4ghz to 5ghz. To me it looks like the driver/DBDC does not notice that the STA is now on the other phy with 80/160mhz bandwith. Also tried all branches from 22-now. copied the firmware binaries to /lib/firmware/mediatek. Tested with x86/mt7915/16 and bpi r3. It takes a couple of hours, sometimes a day or more before I see clients beeing connected that way ( tx 20mhz | rx 80/160mhz ).

Start by reproducing the intermittent 20 MHz TX-width state with the listed mt7915, mt7916, or mt7976c hardware, especially after a DBDC roam from 2.4 GHz to 5 GHz. Compare behavior across the mentioned OpenWrt versions and firmware files. Done means TX width correctly reflects the connected client's 80/160 MHz capability after roaming without requiring copied firmware binaries.