RPi 3b + Ar9271 low bandwidth on v5 kernel.

[lukolszewski]

For various reasons (including that it doesn't work on RPi Zero2W) I compiled wifibroadcast from the project subfolder on couple of my existing OS images. I've applied all ath9k driver patches and module options. I haven't applied the dwc otg kernel patch.

I've tried running it on RPi 3b, RPi Zero2W and an amd64 VM. All running kernel 5.13 (Pi's run 5.13.19, the VM runs 5.13.0).

The result of running tx_measure always shows less than 1Mbit. On the VM it is pretty close to 1Mbit. On RPis it is closer to 850kbit. Same RPi with the same dongle running the EZ-WifiBroadcast image reports slightly over 7Mbit so the hardware is definitely capable.

I also tried the other Wifibroadcast project with similar results.

I've tried to get everything as close as possible on my systems to the image. I believe the issue is caused by v5 kernel. I'm logging this issue to let the devs know this is happening also hoping for tips how to troubleshoot this further.

The WiFi adapter is Tl-wn722n v1. Firmware is open firmware same version as in EZ-WifiBroadcast image (1.4). CPU usage was few % at most during the test.

[lukolszewski]

Turns out Ar9271 based usb adapters need a firmware patch to run in monitor mode faster than 1Mbit. As of now there is no such patch present in the github repo, but openhd have few examples in their repo so I took a firmware image (set to 24Mbit) from them.

With this image I'm getting 11Mbits on RPi Zero2W (on raspbian kernel 5.15).