[FS#896] mt7620 - dropping frames (WiFi)

[LEDE Bugs]

The following task has a new comment added:

FS#896 - mt7620 - dropping frames (WiFi)
User who did this - svobodavac (svobodavac)

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I have experienced the same problem not only on ramips/mt7620 platform (ZBT-WE2026)
but also on lantiq/xway platform (ZyXEL P-2812HNU-F1).
Both platforms use rt2x00 driver for their WLAN.

There are at least two different issues with the rt2x00 driver.
 - log messages
 - WLAN hangs

HOWTO simply reproduce WLAN hangs:
1) Heavy load on WLAN - in my case:
  3x Samsung S4 mini connected to AP, WPA2 PSK
  AP in 802.11n mode
  1x iperf3 stream per phone against iperf3 servers on LAN, RECEIVING data TO phones

2) Turn off WLAN on one phone (iperf3 receiver)

3) There is approx. 50% chance that AP stops receiving packetsi mmediately from all clients after sudden client disassociation under heavy load.

4) The only solution: rmmod kernel modules and insmod them again. (or reboot).

AP in 802.11g mode is stable.
Latest tested firmware: LEDE 17.01.2

PLEASE, PLEASE, help us with the hanging AP in N mode.
I'm able to help with testing.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=896#comment4040