Trouble using bcm4318 compact flash with b43 driver

[Larry Finger <Larry.Finger@lwfinger.net>]

On 01/21/2011 09:51 AM, Dylan Cristiani wrote:
> probably i found a clue (maybe the point): when the b43 wlan interface
> comes up its rate is, at the beginning, setted to the lowest possible:
> 1Mbit, as i can see with iwconfig, and it seems that, at this low rates,
> some access points doesn't work, becuase of some handshake timeout
> failure happening or other different timeouts issue, like they can't
> 'deal' with such communication being too slow; if i set higher rates
> (i.e. 'iw set rate 24M') it associates to access point (WPA2
> encryption), it gets dhcp address and it is possible to ping other net's
> nodes, also if there are still some issue, like high percentage of
> packet lost and so on; furthermore, trying to force setting of the rate
> to highest possible 'iw set rate 54M', doesn't improve the performances
> but, at the opposite, it leads again to association failures; is this a
> normal behaviour? do you think that i'm doing something wrong? why is
> the starting rate setted to 1M (it's a wlan module policy or a driver
> choice?); which is the best way to solve this issue if any?
> 
> as usual thanks for you support and patience!!

Your finding may be a good clue, but I'm not sure how to interpret it. Any AP
must be able to handle traffic at 1 Mbps. Consider a station at an extreme
distance where rates no higher that 1M can be supported. In addition, all
management frames are sent at 1M to minimize the chances of packet loss.

You may have found a bug in the firmware of the AP, although that is not too
likely. What make and model is the AP and what firmware version is it using?

Fixing the transmission rate at too high a value will reduce throughput, just as
you see because of transmission errors. Any new connection always starts at 1M.
The rate-control algorithm will then increase the rate until the error rate
increases.

I think you must do the git bisection to find the kernel change that caused the
problem. I know that it is a lot of work, but at least you already know how to
compile a kernel.

Larry