[Make-wifi-fast] [RFC/RFT 5/5] ath9k: Count RX airtime in airtime deficit

[Toke Høiland-Jørgensen]

Toke Høiland-Jørgensen <toke at toke.dk> writes:

>> [snip]
>>
>> I also found one of my notes in my version of this - how can we
>> estimate the duration of an A-MPDU, when we only get hardware
>> de-encapsulated frames?
>
> Well in my case I'm sidestepping this by getting the TX duration from
> a register in the hardware. There seems to be registers containing the
> duration spent on each step in the retry chain; I simply sum these.

Ah, but you're still talking RX? Hmm, I'm using ath_pkt_duration() to
compute the RX time, which does take into account MIMO (I think) but
expects the size to include padding. Which is probably not included in
the rs_datalen field of struct ath_rx_status that I'm using.

So yeah, how to account for that?

I initially thought that using the timestamp put into the frame by the
hardware could be a way to get timing. But there's only a timestamp of
the first symbol in rs_tstamp, and getting a time to compare it with is
difficult; by the time the frame is handled in the rx tasklet, way too
much time has been spent on interrupt handling etc for the current time
to be worth comparing with.

-Toke