Intel AX200 - Station Mode - TX drops

Installing and Using OpenWrt
1

Hi there

I'm using a heavily patched 21.02 based OpenWRT build on Gateworks Ventana platform (imx6). I'm at the moment testing Intel AX200 based MPCIE-cards (Alfa Networks AX200U) for station mode. RX traffic seems to be no problem, but within the TX traffic I see appr. 15% of the frames missing (captured on the AP). The AP is a Cisco Catalyst 9300 with an SSID with WPA2-PSK, 80 MHz channel on non DFS-channels.

The weird thing is, that enabling power for the bluetooth-device (via bluetoothctl -> power on) results in less loss (appr. 7%). The results where measured with iperf3 in udp mode. And missing frames have been verified by a packet capture on the AP.

I already tested using the iwlwifi from backports 5.15.8 and firmware version 66. Still the same. Does anybody know some hints, how to get more advanced debug logs, than the known one from the log buffer and the kernel log buffer? Or does somebody maybe have some hints, what I can try to tackle the error down?

Kind regards
Sebastian

2

I tried to go ahead to see if it as an already known code bug ... So I'm running on OpenWRT trunk with backported iwlwifi driver from iwlwifi-next kernel git (Firmware 71, as 72 is not released by Intel yet).
Still the same. Now I will enable debugfs and try if I see something with the trace scripts.

Any help/hint would be still appreciated.
Kind regards
Sebastian

3

Now I did some debug tracing on 21.02. I used the following trace command and ran iperf on a second session:

trace-cmd record -e iwlwifi -e iwlwifi_msg -e iwlwifi_io -e tcp -e iwlwifi_ucode -e net -e sock

The output typically looks like this:

          iperf3-11001 [002]  2634.186937: net_dev_queue:        dev=wlan1 skbaddr=0xe6835bb0 len=55
          iperf3-11001 [002]  2634.186941: net_dev_start_xmit:   dev=wlan1 queue_mapping=0 skbaddr=0xe6835bb0 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 len=55 data_len=1 network_offset=14 transport_offset_valid=1 transport_offset=34 tx_flags=0 gso_size=0 gso_segs=1 gso_type=0x1
          iperf3-11001 [002]  2634.186954: iwlwifi_dbg:          TX to [0|0] Q:3 - seq: 0x2fc len 75
          iperf3-11001 [002]  2634.186962: iwlwifi_dev_tx:       [0000:07:00.0] TX 1c (101 bytes) skbaddr=0xe6835bb0
          iperf3-11001 [002]  2634.186968: iwlwifi_dbg:          Q:3 WR: 0xfd
          iperf3-11001 [002]  2634.186971: iwlwifi_dev_iowrite32: [0000:07:00.0] write io[0x460] = 0x300fd)
          iperf3-11001 [002]  2634.186976: iwlwifi_dbg:          TXQ of sta 0c:75:bd:b6:96:40 tid 0 is now empty
          iperf3-11001 [002]  2634.186980: net_dev_xmit:         dev=wlan1 skbaddr=0xe6835bb0 len=55 rc=0

The complete trace-report looks good.

Maybe somebody has a hint, where to search next
Kind regards