Re: iwn(4) hangs after r257133

On Sat, Nov 9, 2013 at 8:46 PM, Adrian Chadd <adrian_at_freebsd.org> wrote:
> Hi!
>
> On 9 November 2013 18:29, Brandon Gooch <jamesbrandongooch_at_gmail.com> wrote:
>> Turns out that not enabling MRR causes my Intel Ultimate N WiFi Link
>> 5300 to hang after only a few moments of use.
>
> That's .. odd. Ok.
>
>> For now, I've just reverted only those aspects of r257133, enabling
>> MRR and keeping the rate index lookup, which seems to do something on
>> my hardware at least (I assume it's not the right thing based on
>> Adrian's analysis, but it works never-the-less).
>>
>> Has anyone else hit this with Intel WiFi hardware?
>>
>> Also, what needs to be done to have MRR working properly?
>
> So, it could be a fall out of how utterly crap AMRR is at 11n rates.
>
> Please compile with IWN_DEBUG, then do this before you associate:
>
> sysctl dev.iwn.0.debug=0x1
>
> (that's IWN_DEBUG_XMIT in sys/dev/iwn/if_iwn_debug.h)
>
> You can do the same on a kernel with and without the MRR stuff enabled.
>
> I'd like to see what the actual rate selection looks like and what the
> final rate selection is. We may have to patch the kernel to print out
> the contents of 'rate' and 'tx->rate' in iwn_tx_data() to get that.

I've attached the log output, both with and without MRR.

The output looks very much the same within iwn_tx_data(); in
iwn5000_tx_done() things are
clearly different.

If I'm reading the rate conversion bits correctly, I see anywhere from
6 Mbps to 60 Mbps, with the
the non-MRR module "getting stuck" -- I really don't know what has
happened when it does this.

Is there any further debugging output that would be helpful?

-Brandon

> The MRR stuff is a bit special. I don't know how the link table works
> in great depth yet. I know it's broken for 11n; it's plainly using the
> wrong indexes now. That's why I disabled it. It shouldn't take that
> much work to get it in the tree again; it'll just be fiddly. The easy
> bit is populating the table. The hard bit is knowing which index to
> set linkq to when transmitting a frame.
>
>
>
> -adrian