[RFC 0/2] ath10k spectral scan support

[Michal Kazior]

On 16 July 2014 10:38, Simon Wunderlich <sw at simonwunderlich.de> wrote:
>
>> On Wednesday 16 July 2014 08:24:58 Michal Kazior wrote:
>> > >  * So far, we always get 64 bins of fft data in the samples, even if we
>> > >
>> > >    are in HT40 or VHT80 mode. That doesn't seem right, as there should
>> > >    be more bins for wider channels (e.g. 128 or 256 bins). Is there any
>> > >    parameter to change in the configuration to get the output from
>> > >    multiple channels / higher bandwidth?
>> >
>> > Hmm.. I suspect this may be because you use scan command. Scanning
>> > uses channel list which is programmed with legacy modes a and g
>> > (implying 20Mhz). Perhaps that's the limiting factor now. Using other
>> > (wider) modes breaks scan from what I remember but it might be worth
>> > checking out if it impacts fft bin sizes.
>>
>> I did the HT80 and HT40 stuff on a single channel in the spectral
>> "background" mode. They reports from the firmware (10.1) still only had 64
>> bins. The HT80 stuff wasn't tested with the "main" firmware because it
>> refused to switch to HT80 mode as AP/Sta.
>
> Just to clarify this a little more, we tried AP (running hostapd) as well a
> STA in 40 and 80 MHz modes. We always got 64 bins returned.

It seems the number of bins is 2^ (fft_size - bin_scale) = 2^(7-1) =
64. Changing fft_size to 9 yields 256 bins.

Perhaps fft reports are (implicitly) relative to the mode the hw is in
at a given time and if you want a reasonable bin resolution for, e.g.
VHT80 you need to increase fft_size?


Michał