Roaming problems on NVIDIA Jetson TX2

[Steve deRosier]

Hi Manuel,

On Tue, Jun 15, 2021 at 8:25 AM Manuel Wagesreither <ManWag at fastmail.fm> wrote:
>
> Hello all,
>
> I'm working on a project which is using wpa_supplicant 2.9 with NetworkManager 1.22.10 on a NVIDIA Jetson TX2 system-on-module using a CYW4354=BCM4354. The GNU/Linux distribution is a custom one created with Yocto; the kernel used is 4.9.140-l4t-r32.4+g3924d6fccfbf provided by NVIDIA.
>

I expect you aren't going to get a lot of help here.  You're asking
about a 5+ year old vendor kernel with a Broadcom vendor driver, ie
not fully open source and upstream stuff.  And you're asking about
largely driver oriented stuff on the hostapd list.  Granted, a lot of
the same people are on multiple lists, so you'll hit a subset of the
linux-wireless folk too.  Since your stuff is provided by NVIDIA, I'd
suggest asking them for support.


> I observed the following behaviour:
> 1. The error message `Failed to enable signal strength monitoring` shows up in our logs.

It's not necessarily an error message.  Do you need to enable "signal
strength monitoring"?  The drivers often output lots of information,
you still need to evaluate if you actually care.  I'm guessing
everything works fine and you don't care.

> 2. When roaming to a access point with a similar SSID, roaming works. (WebRTC video stream stutters but doesn't break.)
> 3. When roaming to an access point with a different SSID, the "Dongle Host Driver" (which is a kernel module I guess?) restarts.

Typically switching to a different SSID is not considered "roaming."
And thus would typically have a more intense change. Indeed, if you
look at your kernel log above your marked point, it's clear that the
stack is being fully torn down and it looks like the WiFi chip's bus
is being powered down, which usually results in an unload of the
driver. And then powered back up reloads the driver which reloads the
firmware.

DHD or "Dongle Host Driver" is the Broadcom proprietary vendor driver
for their WiFi chips.

I hope that helps you understand at least a little bit.

- Steve