Re: [PATCH ath-next] wifi: ath9k_htc: fix beacon slot selection once TSF exceeds 2^42 us

["Toke Høiland-Jørgensen" <toke@toke.dk>]

"Felix K." <fk@mutemail.de> writes:

> ath9k_htc_choose_bslot() derives the beacon slot from the TSF reported
> in the SWBA event as
>
> 	tsftu = TSF_TO_TU(tsf >> 32, tsf);
> 	slot = ((tsftu % intval) * ATH9K_HTC_MAX_BCN_VIF) / intval;
>
> TSF_TO_TU() truncates its result to 32 bits, so tsftu is
> (tsf / 1024) mod 2^32 and wraps every 2^42 us (~50.9 days). 2^32 is not
> a multiple of the beacon interval (2^32 mod 100 = 96 for the default
> of 100 TU), so every wrap shifts the computed position within the
> beacon interval by 4 TU. Depending on where in the interval the SWBA
> event arrives, the wrong slot is chosen after one or more wraps. The
> state only recovers when the TSF is reset.
>
> Compute the offset within the beacon interval from the 64-bit TSF
> instead. For TSF values below 2^42 us and an even beacon interval the
> result is identical to the old calculation. TSF_TO_TU() in htc.h has no
> other user and is removed.
>
> This is the same issue as in ath9k_beacon_choose_slot(), which is fixed
> separately. Compile tested only, I do not have ath9k_htc hardware.
>
> Fixes: 832f6a18fc2a ("ath9k_htc: Add beacon slots")
> Cc: stable@vger.kernel.org
> Signed-off-by: Felix K. <fk@mutemail.de>

Mehmet, any chance you could test this one? :)

Thanks!

-Toke