linux-kernel - Re: ath9k becon loss messages

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Date:	Mon, 06 Apr 2009 13:23:53 +0300
From:	Kalle Valo <kalle.valo@....fi>
To:	Michael Buesch <mb@...sch.de>
Cc:	Helmut Schaa <helmut.schaa@...glemail.com>,
	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Sujith <Sujith.Manoharan@...eros.com>,
	wireless <linux-wireless@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: ath9k becon loss messages

Michael Buesch <mb@...sch.de> writes:

>> NetworkManager typically scans every 120 seconds and I can also trigger
>> the messages by a manual scan with iwlist. I did not dig any further but
>> the messages seem to appear right at the end of the scan. Tried with iwlagn
>> and both sw_scan and hw_scan.
>
> Yeah OK. While scanning it's expected to lose some frames.
>
> However, the driver should probably protect against this by using the
> scan notification callbacks. It could disable beacon-loss reporting
> while scanning.

That case is already covered. In sw_scan mac80211 will disable power
save and hence beacon filter is also disabled. With hw_scan the firmware
should be clever enough to not emit beacon loss events when scanning.

But ath9k nor iwlwifi don't support beacon filtering and this is a
problem in mac80211. We need to disable the beacon loss check in
mac80211, most probably by stopping the associated timer whenever
scanning.

-- 
Kalle Valo
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