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Date: Mon, 11 Nov 2013 16:03:59 +0100
From: Lars Engels <lars.engels@0x20.net>
To: freebsd-current@freebsd.org
Subject: Re: iwn(4) hangs after r257133
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Am 11.11.2013 09:18, schrieb Stefan Farfeleder:
> On Sun, Nov 10, 2013 at 02:01:12PM -0800, Adrian Chadd wrote:
>> Yes. So one of the.. unfortunately broken things in iwn is the ampdu 
>> tx
>> code doesn't do retransmits. So if amrr picks a rate that fails to 
>> transmit
>> everything, the driver doesn't retransmit them. It frees them.
>> 
>> Now when amrr is enabled the hardware will retry at lower rates until
>> something succeeds. But it still doesn't retransmit things. I believe 
>> it
>> should be.
>> 
>> So yes its more broken with Mrr disabled. But enabling mrr doesn't fix 
>> it.
>> It just makes it less broken. Someone needs to implement ampdu 
>> retransmit.
>> 
>> The latest iwn code in head at least tells the rate selection code 
>> that a
>> total ampdu tx failure occured. This BTW is one of the hangs I fixed - 
>> if
>> you hit a point where you never successfully transmitted an ampdu at a 
>> rate
>> the rate would never be decreased.
>> 
>> Now to be clear. I won't be in implementing ampdu retransmit. I'll 
>> maybe
>> fix last multi rate retry once the new hardware support is in. I would
>> really appreciate help here with these. Everyone with iwn hardware 
>> will
>> appreciate it :)
> 
> In the mean time, wouldn't it make sense to disable ampdu tx in iwn
> then? Or to disallow the combination Mrr + ampdu?


Yes, please. I'm also encountering this.