Hi Johannes,
Niel bisected the probe timeouts with iwlagn to your commit
47afbaf5af9454a7a1a64591e20cbfcc27ca67a8 . I too was getting probe
timeouts but with ath9k and tried reverting the above commit which
made the problem disappear.
It is not yet reverted from mainline and compat-wireless - just wanted
to bring it to your notice that it impacts both iwlagn and ath9k.
Thanks
Parag