Re: iwn(4) hangs after r257133

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.

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