Re: IWD 1.27 with brcmfmac not working for roaming

[Denis Kenzior <denkenz@gmail.com>]

Hi Martin,

> 
> I think the regulatory domain issue is fixed. It seems that 99 is correct 
> (because it is handled in firmware). We see far better signal and data rates at 
> a site where we had problems. It seems the general setup is far better now for 
> simple setups. We removed the configuration from device tree and then it may 
> have used the configuration from brcmfmac4339-sdio.txt (device tree stuff was 
> something the SOM vendor added for some reason).

Sounds like you're getting somewhere.

> 
> However, I have now already seen at one of our testing sites, that it connected 
> to the router instead of the repeater (which is far closer and has far far 
> better signal: -67 vs. -29 dBm). It also did not switch to the repeater after

You may have to revise your expectations here.  Most implementations do not 
trigger roaming unless signal quality reaches a certain threshold.  This 
includes many of the firmware roaming implementations I've seen.

For iwd this threshold is -70 dbm on 2.4G and -76 dbm on 5/6G by default. 
Parking at the AP with good signal (-67 is good) is just fine and I see nothing 
inherently wrong here.  And remember, the firmware is responsible for roaming in 
the case of brcmfmac.

One may question why -67 AP was preferred over -29 one?  We'd need logs to 
answer that question.  It could be the -29 one was simply not seen in the scan 
results at the time of the initial scan / connection.

> several hours (both FritzBox - so consumer grade and we don't know the exact 
> configuration). After a reboot, it connected to the repeater and until now it 

So that's... good?

> remains there. I will switch to more complex roaming environment, however, this 
> is more sensitive because it is at a clients site. This first impression gave me 
> not much confidence...
> 
> What do you think about the idea to disable roaming in the firmware / driver? 
> (if I understand Arend right, this is setting "roam_off" in brcmfmac4339-sdio.txt)

You can certainly give it a try.  It is not something we have tested explicitly, 
but it should (mostly?) work.  However, note that trying to make a FullMAC card 
roam from userspace in such a manner is inherently limited.  iwd cannot utilize 
advanced roaming features such as FT with such a setup (I can get into the 
technical details if you care).  Having said that, roaming behavior is a 
frequent complaint for many fullmac implementations.

> 
> Will IWD smoothly take over the roaming? How can I check who is handling the 
> roaming?

iwd looks at the NL80211_ATTR_ROAM_SUPPORT flag.  If such a flag is reported by 
the wifi driver, iwd will let the firmware handle roaming.  Otherwise it will 
try to handle roaming itself with the (rather limited in the case of fullmac) 
tools that it has access to.  Taking a peek at the brcmfmac driver, looks like 
it is doing the right thing in setting/not setting this flag based on the 
"roam_off" parameter.

Regards,
-Denis