vc4.ko causes another misterious error

[Ryutaroh Matsumoto]

Hi Stefan, thank you for your continued interest in this topic.

>> sorry, this error description isn't helpful. Wifi especially 802.11ac
>> has a little bit more than a simple on/off switch.
>> Which wifi channel do you use?
>> Can you provide the output of "iw reg get", "iw list" and "ifconfig
>> wlan0" in case the issue occurs?
>> Is it still correct that the wifi connection is established, but higher
>> communication like IP doesn't work?
>> Can you please provide the content of
>> "/lib/firmware/brcm/brcmfmac43455-sdio.raspberrypi,4-model-b.txt"
> 
> I recheck the situation with Debian kernel 5.10.24 and
> Debian firmware-brcm80211 20201218-3.
> 5GHz WiFi works fine with vc4 and without vc4.

It was incorrect. Actually, 5GHz WiFi with vc4 fails with 5260 MHz.
I run the following script:
#!/bin/sh
set -x
dpkg-query -W | fgrep firmware
lsmod | fgrep vc4
iw reg get
iw list
iw wlan0 scan
ip l
ip a
ping -c 10 192.168.1.2
cat /lib/firmware/brcm/brcmfmac43455-sdio.raspberrypi,4-model-b.txt
journalctl -b

The output of the above script is attached.
I hope this is sufficient information for investigating the issue.

I removed ifupdown and ifconfig as they are obsolete.
Network config. is solely done by NetworkManager.

With vc4.ko loaded, association to an SSID of 5260 MHz fails with high probabilty
(very rarely succeeds). We have lots of lots of

NetworkManager[556]: <warn>  [1616654312.2203] device (wlan0): Activation: failed for connection 'Yamashita9_203'

Without vc4.ko, the same SSID of 5260 MHz is used with no problem.

in the attached log with vc4.ko loaded.

Best regards, Ryutaroh
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